1

CHAPTER 1

INTRODUCTION

Petro-based polymers and polymeric composite materials have

helped human kind in many ways such as aerospace, automotive, marine,

infrastructure, military, sports and industrial fields. These light weight

materials exhibit excellent mechanical properties, high corrosion resistance,

dimensional stability and low assembly costs.

However, petroleum resources are finite and the prices are likely to

continue to rise in the future. In addition, global warming, caused in part by

carbon dioxide released by the process of fossil fuel combustion has become

an increasingly important problem and the disposal of items made of

petroleum-based plastics, such as fast-food utensils, packaging materials and

trash bags also creates an environmental problem. Petroleum-based or

synthetic solvents are also contributing to air pollution.

It is necessary to find new ways to secure sustainable development.

Renewable bio-materials that can be used for both bio-energy and bio-

products are a possible alternative to petroleum-based products. Recent

advances in development of polymers from bio-based materials, natural fiber

development, genetic engineering and composite science offer significant

opportunities for improved materials from renewable resources with enhanced

support for global sustainability.

2

1.1 CLASSIFICATION OF BIO POLYMERS

Bio polymers are classified into three major types

1) Renewable Resource based

a) Poly Lactic acid polymer

b) Cellulose plastics

c) Soy-based plastics

d) Starch plastics

2) Microbial synthesized

a) Poly hydroxyl alkonates (PHA’S)

b) Poly hydroxyl butyrate co-valerate (PHBV)

3) Petro – bio (mixed) sources

a) Sorona

b) Bio based polyurethane

c) Bio based epoxy

d) Blends, etc.

1.2 BIO POLYMERS

Poly (lactic acid), PLA is derived from renewable resources like

corn or sugar beads. PLA is a hydrophobic polymer because of the

incorporation of –CH3 side group and it is synthesized by the condensation

polymerization of D- or L-Lactic acid or ring opening polymerization of

lactide. Advanced industrial technologies have been developed to obtain high

molecular weight pure PLA which leads to a potential for structural materials

with enough life time to maintain mechanical properties without rapid

hydrolysis even under humid environmental conditions. PLA is primarily

used for medical applications including sutures, drug delivery, vascular grafts,

artificial skin, and orthopedic implants (Mayer and Kaplan 1994).

3

Cellulose plastics are derived from cellulose esters, e.g., cellulose

acetate (CA) are considered as potentially useful polymers in biodegradable

applications. CA is a modified polysaccharide synthesized by the reaction of

acetic anhydride with cotton linters or wood pulp. CA can also be produced

from recycled paper and sugar cane (G.R. Elion, US patent 2, 244, 945,

1993). The studies on biodegradation of CA have been given much attention

in recent times. It was generally accepted that cellulose esters with a degree

substitution (DS) less than 0.1 will degrade from the attack of microorganisms

(Kasulke et al 1983 and Perlin 1971). CA of various DS is now being widely

used as films and coatings. CA is also used to produce clear adhesive tapes,

tool handles, eye glass frames, textiles and related materials.

Starch is one of the least expensive biodegradable materials

available. Corn is the primary source of starch, although potato, wheat and

rice starch are other sources. Starch is produced by plants and is a mixture of

linear amylase (poly- α-1, 4-D-glucopyranoside) and branched amylo-pectin

(poly- α-1,4-D-glucopyranoside and α-1,6-D-glucopyranoside). The amount

of amylase and amylopectin varies with the nature of source. Starch can be

made into thermoplastic material through destructurization in presence of

specific amounts of plasticizer (water and/or poly-alcohols) in specific

extrusion conditions (Bastioli 1988), however, its sensitivity to humidity,

makes it unsuitable for many applications. The thermoplastic starch alone is

mainly used in soluble compostable foams, such as loose fillers, expanded

trays, shape moulded parts and expanded layers as a replacement for

polystyrene.

Soy protein plastics of different compositions have been prepared

from soy beans, which essentially contain about 20% oil and 40% protein.

Soy plastics have been used for manufacturing automobile parts by Ford

Company (Ly et al 1998). Soy proteins possesses unusual adhesive

4

properties, with proper moisture barrier, soy protein are a potential starting

material for engineering plastics. Blending the biodegradable soy protein

plastic with poly phosphate filler greatly reduces its water sensitivity allowing

new uses in moist and load-bearing environments where the unfilled plastic

was not usable (Otaigbe et al 1999).

Bio polymers derived from bacterial sources such as poly

(β-hydroxy alkonates) (PHA’S) and Poly (β-hydroxy butyrates) have attracted

much attention as a biodegradable thermoplastic polyester. However, it

suffers from some disadvantage compared with conventional plastics like

brittleness (Barham et al 1986). In order to improve the properties, various

copolymers such as poly (3-hydroxy butyrate-co-3-hydroxy valerate)

(PHBV), are produced by Monsanto and sold under the trade name Biopol u®.

Potential uses of PHB and PHBV are motor oil containers, film formation,

paper-coating materials, plastic containers and bottles.

Bio polymers derived from petro - bio mixed resources is used as

high performance polymers with a wide range of applications. Epoxidized

soybean oil allylsoyate and petro-based epoxy namely diglycidyl ether of

bisphenol - A mixture cured with different curing agents were used for

manufacturing aerodynamic materials in vibration – sound attenuation

applications (Shabeer et al 2005). Soy polyols derived from hydroxylation of

epoxidized soybean oil are used in the production of polyurethanes (Zlatanic

et al 2004).

1.3 SOY BEAN OIL

Bio based polymer derived from epoxidized soy bean oil is the

subject matter of discussion in the present thesis. Soy bean oil possesses the

following composition of fatty acids.

5

O

O

O

C

O C

O

C

O

Triglyceride molecule a major component of soy bean oil

Fatty acid Carbon chain length:

double bond Soybean oil

Myristic 14:0 0.1

Palmitic 16:0 11

Palmitoleic 16:1 0.1

Stearic 18:0 4.0

Oleic 18:1 23.4

Linoleic 18:2 53.2

Linolenic 18:3 7.8

Arachidic 20:0 0.3

Behenic 22:0 0.1

Average Double Bond

/ triglyceride - 4.6

These triglycerides contain active sites amenable to chemical

reaction: the double bond, the allylic carbon and the ester group. These active

sites can be used to introduce polymerizable groups on the triglyceride using

the same techniques applied in the synthesis of petrochemical-based

polymers. The key step is to reach a higher level of Mw and cross-linking

density, as well as to incorporate the chemical functionalities known to impart

stiffness in a polymer network. From the natural triglyceride, it is possible to

introduce acrylates, maleates and vinyl functionalities and also to convert the

unsaturation into epoxy functionalities (Athawale et al 2003 and Petrovic et al

2002). It is also possible to obtain hydroxyl functional triglycerides

(soy polyols) by the hydroxylation of epoxidized soy bean oil and is used in

the production of polyurethanes (Zlatanic et al 2004, Sanmathi et al 2004,

Guo et al 2002).

6

1.4 EPOXIDIZATION OF SOY BEAN OIL

Epoxidization of soy bean oil is carried out in a 500 ml three-

necked round bottom flask equipped with a thermometer sensor, a mechanical

stirrer, and a septum pierced with an injection needle to equalize the pressure.

The apparatus was kept in water bath to maintain temperature 80 oC. 100 gm

of soy bean oil, 50 ml of toluene, 25 gm of amberlite and either 15 gm of

glacial acetic acid or 11.8 gm of formic acid was added in to the RB flask.

With agitation 83.7 g of 30 % H2O2 were added slowly through a separating

funnel over a period of 30 minutes. The precaution was taken to prevent over

heating of the system due to exothermic nature of epoxidation reaction

(Petrovic et al 2002).

O

O

O

C

O C

O

C

O

O

O

O

C

O C

O

C

O

O

O O

O O O

CH3COOH / H20280oC

Scheme 1.1 Epoxidization of soy bean oil

The epoxidation reaction takes place by electrophilic attack of

peroxy acids on the double bond as given below:

H3CCOOH H2O2 H2O CH3COOOH

C

C

H

O

OC

O

R

C

C

OC

O R

OH

7

The sample thus obtained was purified by dissolving in ethyl acetate

and washed with warm water until the pH of the solution maintained neutral.

The oil phase was further dried above anhydrous sodium sulfate and then

filtered. The solvent was removed using a rotary evaporator.

1.5 PETRO BASED EPOXY RESIN

Epoxy resin is defined as any molecule containing more than one

epoxy group capable of being converted to a useful thermoset form. Epoxy

resins are characterized by the epoxide or oxirane functionality. With the

application of heat and curatives they cure chemically to a cross-linked,

insoluble and infusible matrix resin. The epoxy compounds are classified into

different types namely glycidyl ethers, epoxy novalac resin, cycloaliphatic

resins, glycidyl esters and glycidyl amine. These resins are cured by hardener

(curing agent) to form a three dimensional network.

1.5.1 Diglycidyl ether of bisphenol-A resin (DGEBA)

The epoxy resins first developed commercially are the glycidyl

ethers based on diphenylolpropane (DPP), also known as bisphenol-A and

epichlorohydrin. The basic process of detailed synthesis is well-documented

(Bruins 1968 and Potter 1970).

Where, n = 0 - 10.

+ HO C

CH3

CH3

OH

O

CH2 CH CH2 C

CH3

CH3

OO CH2 CH CH2 O

OH

C

CH3

CH3

O

CH2 CHCH2O

n

O

CH2 CH CH2Cl

NaOH -NaCl

8

The important criteria to be observed during epoxidization are:

i) Excess of epichlorohydrin, a molar ratio of at least 10:1 of

epichlorohydrin and hydroxyl compound, has to be used to

minimise oligomers or the higher homologues

ii) Using lower reaction temperatures during the initial stage of

reaction and increasing the temperature at the end can

minimize formation of side products such as 1,3-chlorohydrin.

Diglycidylether of bisphenol-A (DGEBA) resins are used in

filament winding, pultrusion, vacuum impregnating, contact moulding and for

manufacture of prepregs from glass and carbon fibres. They can be cured with

a wide range of curing agents both at ambient and elevated temperatures. The

glycidyl ethers of novolac, resorcinol and aliphatic polyols such as glycerol,

pentaerythritol have been synthesised for variety of applications (Anderson

1968). They provide high temperature stability and have good chemical

resistance.

1.6 CURING AGENTS, CURING REACTIONS AND

MECHANISM

In epoxy resin technology the term ‘curing’ is used to describe the

process by which epoxy resins are transformed from low molecular weight

molecules into a highly cross-linked network and is achieved by the addition

of a curing agent. The network may be composed of segments involving only

the epoxies (catalytic homopolymerization) or both epoxy resin and the curing

agent (hardener).

9

The types of curing agents play an important role in determining

the structure, mechanical properties and morphology of epoxy resin (Mika

1973). The most commonly used curing agents are aliphatic amines, aromatic

amines, polyamido amines and acid anhydrides (Potter 1970, Ashcroft 1993).

The reactivity of the epoxide groups towards any of these reagents will be

different, depending on the electronic environment of the group and sterric

factors (Mika 1973). For example glycidyl amines are less reactive towards

amine curing agents than glycidyl ethers but more reactive towards

anhydrides.

1.6.1 Aliphatic amine

Both primary and secondary amines are used for curing the epoxy

resins at room temperature, the former being more reactive than the latter

(Glover et al 1988). In the curing reactions, hydrogen in the primary and

secondary amino groups is reactive and they are bi- and mono-functional

respectively. Various amines used are diethylenetriamine (DETA,

functionality = 5), triethylenetetramine (TETA, functionality = 6),

hexamethylenediamine (HMD, functionality = 4), etc. (Parthun and Johari

1992, 1992a and Greenlee 1948). They are highly reactive due to their

unhindered polyfunctional nature and give cross-linked networks due to the

short chain distances between active sites. The cured resins have excellent

solvent resistance and mechanical strength but have poor flexibility. TETA is

a mobile pale yellow liquid used to cure DGEBA resin at room temperature. It

is used for casting, tooling and wet lay-up, laminating applications. Heat

distortion temperature (HDT) of the cured system can be post-curing at

elevated temperatures (Weatherhead 1980). Hexamethylenediamine has low

viscosity and has better chain flexibility due to long repeat distances between

cross-link sites. The long hydrocarbon chain makes them hydrophobic.

10

H2N-CH2-CH2-NH-CH2-CH2-NH2 - Diethylenetriamine

H2N-CH2-CH2-NH-CH2-CH2-NH-CH2-CH2-NH2 - Triethylenetetramine

H2N-CH2-CH2-CH2-CH2-CH2-CH2-NH2 - Hexamethylenediamine

1.6.2 Aromatic amine

Aromatic amines, which require heat curing and are widely used for

lamination applications to provide excellent mechanical, electrical and

chemical resistance. Commonly used aromatic amines are

4,4’-diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA) and

diaminodiphenylsulphone (DDS). DDM is an off-white solid at room

temperature and is melted at 90o C and added to the resin. DDM is used for

wet lay-up lamination, casting or prepreg preparations. Major advantage of

DDM over other curing agents is the ability to cure liquid DGEBA resins

down to 0 °C in solution in presence of an accelerator such as phenol or

salicylic acid (Ellis 1993).

4,4′-diaminodiphenylmethane (DDM)

1.6.3 Polyamidoamine

Polyamidoamines are also called aminopolyamides or

amidopolyamines (Ashcroft 1993). They are dimerized or polymerised fatty

acids that have been co-reacted with various aliphatic amines such as

ethylenediamine, diethylenetriamine (DETA), triethylenetetramine (TETA),

tetraethylenepentamine (TEPA). The resultant products are very large and

H2N NH2CH2

11

contain varying levels of primary and secondary amino-hydrogen’s, reactive

amides, and carboxyl groups, all of which contribute to epoxy curing.

They are user-friendly systems since tolerance on mix ratio is very

broad (Goodman 1986 and Ellis 1993). They are slow curing and the cured

products are tough and hard. The fatty acid backbone provides excellent

corrosion resistance by its water repelling nature. Their low viscosity and

corrosion resistance makes them suitable for electrical potting and filament

winding applications.

1.6.4 Effect of epoxide structure on reactivity

Cure of epoxy resins normally occurs without the formation of any

by-products. The curing reactions are exothermic. Klute and Viehmann

(1961) measured the heats of polymerization of liquid epoxy resins with

amine curing agents. Several reviews on curing of epoxy resins with different

curing agents are reported. The effect of epoxide structure on reactivity, the

mechanism of curing reactions and the statistical treatment to cross-linking in

the curing process are dealt with, in detail (Tanaka et al 1973, St. John and

George 1994, Enns and Gillham 1983).

During the process of an amine cured thermoset, the reaction of

primary amine (R-NH2) with an epoxide group first forms a secondary amine

(RNH-), which in turn reacts with another epoxy group to form a tertiary

amine (RN<). For a given amine, these two reactions occur concomitantly,

with two distinct values of reaction rate constants leading to the formation of

fully connected network at the gel point (Enns and Gillham 1983, Barton and

Wright 1985). After gelation, the reactions become diffusion controlled and

eventually lead to vitrification. The extent of reactions at the time of

vitrification depends on the temperature of cure and is found to lie

12

O H

C H 2 C H

R O H

N C H C H 2 +

O H

R N H C H 2 C H C H

O

H 2 C

O H

R N H C H 2 C H R N H 2 + C H

O

H 2 C

approximately between 80% and 100%. A typical curing reaction (Penn and

Chiao 1990) is shown below.

1.7 BISMALEIMIDE (BMI) RESIN SYSTEMS

Bismaleimides represent a class of thermosetting resins which can

be used at elevated temperature (200-230°C). These resins have better thermal

stability, flame resistance and retention of mechanical properties at high

tempratures than the epoxy resin.

Monomers are usually synthesized from maleic anhydride and an

aromatic or cycloaliphatic diamine, the bismalemic acid formed is

cyclodehydrated to a bismaleimide resin. The double bond of the maleimide is

very reactive and can undergo chain extension reactions. Epoxy blends of

BMI can be used at temperatures upto 245°C. Bismaleimides are low

molecular substances (dry powders) containing imide structures with

monomer form. These monomers can be polymerized through polyaddition

reaction with themselves as well as with other co-monomers.

Bismaleimide resins (BMIs) are considered as thermosetting

polyimides and can polymerize via multiple carbon-carbon bond formation

without generating volatiles. The thermal curing characteristics of BMIs are

similar to that of epoxy resins and have superior thermal and flame retardant

properties over epoxy resins. The rapid development on the area of BMIs in

recent years demonstrates the attractive properties and application potentials

13

of BMIs. The polyaddition reaction leads to form three-dimensionally cross-

linked, thermoset structures with high thermal resistance. Moreover, the

polyaddition reactions of BMIs do not produce any volatile side products.

Bismaleimides are used as matrix resins for high performance

fibre-reinforced composite materials in the aviation and space industries. Very

often, these matrix resins require high curing temperatures (more than 200°C)

and long curing times.

Bismaleimide is used as a plastic modifier for ABS, PVC, PVA and

other engineering plastics to improve heat-resistant and anti-oxidant

properties. It is also used as an intermediate for the synthesis of cross-linking

agents, pharmaceuticals, pesticides, antiseptics and crystalline adducting

agents.

1.8 BIO NANOCOMPOSITES

1.8.1 Soy based epoxy layered silicate nanocomposites

Bio-based nanocomposites have attracted significant interest

because these materials have social and environmental advantages. Most

research has concentrated on epoxidized plant oils. Initial studies showed the

formation of intercalated or exfoliated structures and reinforcement effect

through clay addition. The additions of clay to triglyceride-based polymers to

form nanocomposites and can broaden the application of these new bio-based

materials by improving their mechanical properties. The extremely large

surface area and high aspect ratio (between 30 and 2000) of the clay make it

possible for property improvements leading to the formation of a

nanocomposites.

14

Organo modified or

unmodified clay

The most commonly used layered silicate in nanocomposites is the

natural clay from the smectide family: montmorillonite (MMT). The layer

structure of montmorillonite was deduced by Hofmann et al. On the basis of

its similarity to that of pyrophyllite. Their crystal lattice consists of two silica

tetrahedral sheets fused to an edge-shared octahedral sheet of either

aluminium or magnesium hydroxide. Isomorphous substitution of Al3+

for

other cations (e.g., Mg2+

, Fe2+

, Fe3+

) in octahedral sites and less frequently, of

Si4+

for Al3+

in the tetrahedral lattice causes an excess of negative charges

with in the MMT layers, which are counter balanced by hydrated alkali or

alkaline earth cations situated between the layers. Normally, the silicate

surface is hydrophilic, which hinter the homogeneous dispersion in organic

matrix. Ion exchange reactions with cations render silicate surfaces

organophilic, which makes them organophilic and compatible with the

polymer matrix.

Figure 1.1 Structure of polymer-layered silicate composites

Conventional

composite

Intercalated

nanocomposite Exfoliated

nanocomposite

15

Depending on the nature of the components used and the

preparation method, three main types of composites can be formed, as shown

in the Figure 1.1. When the polymer is unable to intercalate between the

silicate sheets, a phase separation occurs that results in traditional micro

composites. The formation of conventional composites improves rigidity, but

they often sacrifice strength, elongation, and toughness. Beyond the

conventional composites, two types of nanocomposites are possible: an

intercalated structure in which a single or more extended polymer chain is

intercalated between the silicate layers, resulting in a well-ordered multilayer

with alternating polymeric and inorganic layers, and an exfoliated or

delaminated structure, in which the silicate layers are completely and

uniformly dispersed in a continuous polymer matrix. The formation of nano

composites optimizes the number of available reinforcing elements for

carrying an applied load and deflecting cracks, which results in improving

stiffness, strength, and toughness. Additionally, they are lighter when

compared to the conventional composites because they use far less inorganic

material. They also exhibit outstanding diffusion barrier properties, which

enhances chemical resistance and flame retardancy and reduces solvent

uptake.

Essentially, three different approaches are used to synthesize

polymer-clay nano composites: melt intercalation, solution, and insitu

polymerization. The synthesis of nanocomposites using triglyceride-based

resin is the subject matter of discussion in the present thesis. The

nanocomposites prepared by first swelling the organo-modified clay with the

monomers, followed by the cross-linking reactions. Most of the epoxy-based

nanocomposites show an exfoliated structure. In addition, the self-

polymerization of epoxy resin in organophilic clays due to the presence of

alkyl ammonium ions facilitated the formation of exfoliated structure.

Triglyceride-based monomers optionally have polar groups such as hydroxyl

16

and carboxyl groups, these molecules are favored in the formation of a

possible exfoliated structure (Kornmann et al 2000). The present work

discussed in this thesis is a triglyceride type of soy based epoxide resin and

nanocomposites.

1.8.2 Synthesis of polymer layered silicate nanocomposites

1.8.2.1 In-situ polymerisation

In-situ polymerisation was the first method used to synthesize

polymer layered silicate nanocomposites. In this process, the organoclay is

swollen in the monomer. This step requires a certain amount of time, which

depends on the polarity of the monomer molecules, the surface treatment of

the organoclay, and the swelling temperature. Polymer-clay nanocomposites

based on epoxy, unsaturated polyester, polyurethanes and polyethylene

terepthalate can be synthesized by this method.

1.8.2.2 Solution method

Polar solvents can be used to synthesize intercalated polymer-clay

nanocomposites. The organoclay is first swollen in the solvent. Then the

polymer, dissolved in the solvent, is added to the solution and intercalates

between the clay layers. The last step consists of removing the solvent by

evaporation usually under vacuum. Nanocomposites based on high density

polyethylene, polyimide and nematic liquid crystal polymers have been

synthesized by this method.

1.8.2.3 Melt intercalation

The strategy consists of blending a molten thermoplastic with an

organoclay in order to optimise the polymer-clay interactions. The mixture is

17

then annealed at a temperature above the glass transition temperature of

polymer and forms a nano composite.

1.9 LITERATURE REVIEW

Crivello (1976) studied the condensation of maleimide compounds

with hydrogen sulfide and bisthiols in several model systems and found that

bismaleimide compounds undergo rapid, exothermic polymerization with

thiol-containing compounds in dipolar and basic solvents to give cross-linked

polyimide-thioethers. Effective suppression of the cross-linked reaction was

achieved by carrying out the polymerization in the presence of a proton donor

to inhibit anionic polymerization.

White (1986) prepared high-molecular-weight poly(imido sulfides)

and poly (aspartimides) by reacting dithiols and diamines with bismaleimides

via Michael addition process and discussed the structural effects on the

thermal, morphological and mechanical characteristics of the materials

developed.

Rao et al (1989) synthesized bismaleimides containing ester, amide,

urethane and imides groups in the backbone from maleimidobenzoic acid via

its acid chloride or isocyanate with 4,4'-dihydroxydiphenyl-2,2-propane,

3,3'-diaminodiphenylsulphone and 3,3', 4,4'-benzophenone tetracarboxylic

acid anhydride by simple condensation or addition reaction. The

bismaleimides were characterized by IR, 1H NMR and elemental analysis.

DSC studies of these bismaleimides indicated a curing exotherm in the

temperature range 150-270oC with heat of polymerization 30-50 J/g. Thermo

gravimetric analysis of the uncured resins showed high thermal stability and

char yield for imides containing bismaleimide.

18

Nagai et al (1990) studied the thermal behaviour of the mixtures of

two different cured bismaleimides namely 2,2-bis[4-(4-maleimidophenoxy)

phenyl]propane (BBMI) and bis (4-maleimidophenyl) methane (BMI) using

DSC. The study revealed that the cured product of BBMI has thermal stability

similar to that of BMI. Moreover, the cured product of BBMI has a high

flexural strength and a high flexural elongation owing to the presence of

flexible ether bonds and long phenoxy groups within the monomer structure.

Rao et al (1992) carried out kinetic studies on epoxy resin cured

with a novel polyamine. Differential scanning calorimeter (DSC) was used to

study the curing kinetics of the epoxy resin with two hardeners

(diaminodiphenylmethane and a poly(keto-amine)). The results showed that

the curing of the epoxy resins by poly(keto-amine) occurs at higher

temperature and the activation energy required for poly(keto-amine) was

higher when compared with that of diaminodiphenylmethane curing process,

showing the lower reactive nature of poly(keto-amine).

Patel and Patel (1992) studied the differential scanning calorimetric

curing kinetics and thermal stability of the epoxy systems composed of

conventional, tetrafunctional and phosphorylated epoxy resins using different

anhydrides as curing agents and triethylamine as curing catalyst. The study

revealed that the curing reactions of epoxy-anhydride systems followed

Arrhenius-type kinetics. The kinetics of thermal degradation that the stability

of the cured epoxy resins depends upon the structure of resin and the curing

agents and the incorporation of the phosphorylated epoxy resin into the

system increases its flame retardancy.

Park and Jang (1992) prepared novel bismaleimides from

monomaleimides and DGEBA and the prepared bismaleimides possess good

processibility and good thermal stability with improved water resistance.

19

Morgan et al (1993) reported the processing, toughening procedures

and performance of bismaleimide (BMI)-carbon fibre composites. The BMI

matrix was 4,4'-bismaleimidodiphenylmethane/O,O'-diallylbisphenol-A. The

effect of toughening procedures on composite performance in terms of GIC

toughness and impact penetration was discussed and it was observed that the

increase in fibre volume fractions were found to have decreased GIC

toughness and increased impact penetration.

Patel and Shah (1993) carried out Michael addition reaction of

N,N'-1,4-phenylene bismaleimide with DDM at 1:1, 1:1.5 and 1:2 molar

ratios and these oligomers were used to cure epoxy resin. The polyimide

oligomers were characterized by elemental analysis and IR spectral studies.

Liao and Hsieh (1994) developed novel bismaleimides (BMI) from

maleic anhydride and polyurethane prepolymers based on

4,4'-diphenylmethane diisocyanate (MDI) and polyether/polyester polyols

with various chain lengths. DSC studies revealed that the thermal

polymerization of BMIs can be carried out in the temperature range of 102oC-

245oC and the curing behaviour was significantly affected by the molecular

weight of the BMIs. The cross-linked BMI elastomers showed good

mechanical properties and better thermal stability than that of traditional

polyurethane elastomers. The glass transition temperature, mechanical and

dynamic mechanical properties were dependent on the types of polyols used

and the resultant cross-link densities due to varying chain lengths of the

BMIs.

Patel and Shah (1995) developed glass-reinforced composites based

on a novel oligoimide-epoxy resin system. They synthesized benzidine

bismaleimide-diaminodiphenyl methane and ethylene bismaleimide-

diamonodiphenyl methane oligomers having more reactive -NH2 groups

20

through Michael addition reaction. These oligoimides were used for curing

epoxy resin in the range between 120oC and 140

oC to fabricate glass fibre

reinforced oligoimide-epoxy composites.

Mishra et al (1996) synthesized a number of semi IPNs by reacting

polyurethanes (prepared from castor oil) and various diisocyanates and a

phenolic resin. The physico-chemical properties of the semi IPNs have been

investigated. The thermogravimetric analysis of polymers was followed using

a computer analysis method for assigning the kinetic mechanisms. Various

kinetic equations have been used to evaluate the kinetic parameters. The

suggested mechanism for the degradation of the semi IPNs is based on the

kinetic parameters.

Crivello et al (1997) synthesized novel fiber glass-reinforced

composites from epoxidized vegetable oils by ultraviolet and visible

irradiation in the presence of onium salt cationic photo initiators. A variety of

lay up techniques and experimental conditions were explored to optimize the

composite fabrication. A series of composite samples were prepared using

mixtures of epoxidized vegetable oils and synthetic epoxy resins. Based on

these measurements, it was concluded that photochemical routes to the

fabrication of composites derived from epoxidized vegetable oils provide a

simple, direct, and inexpensive route to the fabrication of composites with

many potential low-performance applications.

Ping Huang et al (1997) studied the miscibility and mechanical

properties of epoxy polysulfone blends cured with DDM. Bisphenol-A based

pholysufone was found to be miscible with uncured bisphenol – A type epoxy

resin [diglycidyl ether of bisphenol - A (DGEBA)], as shown by the existence

of a single glass transition temperature (Tg) with in the whole composition

range. Scanning Electron Microscopy (SEM) observations showed that the

21

DDM – cured epoxy/PSF blends was homogeneous. Both tensile and flexural

properties of the blends were slightly improved compared to the pure DDM

cured epoxy resin. The fracture toughness and fracture energy were increased

upto 20% with the addition of PSF to the system.

Gupta and Varma (1998) studied the effect of structure of epoxy

network on the interfacial shear strength of glass epoxy composites.

Diglycidyl ether of bisphenol-A (DGEBA) was cured by using stoichiometric

amount of aromatic diamines i.e., 1,3-bis(4-amino phenoxy)benzene,

1,4-bis(4-aminophenoxy)benzene, 2,2'-bis[4-(4-aminophenoxy)phenyl]

propane, 4,4'bis(aminophenoxy)benzophenone, bis[4-(4-aminophenoxy)

phenyl]sulfone and 4,4'diaminodiphenylmethane. The results showed that the

interfacial shear strength (determined by using the fragmentation technique)

was found to depend on the polarity of the epoxy network and was highest

when DGEBA cured with bis[4-(4-amino phenoxy)phenyl] sulfone.

Raymond and Bui (1998) developed full interpenetrating polymeric

networks from epoxy and castor oil based polyurethane. TDI was used as a

curing agent for castor oil and DGEBA was cured and cross-linked using

2,4,6-tris(dimethylaminomethyl)phenol(TDMP). The SEM observations

showed homogeneous morphology of IPN samples of PU compositions up to

40 wt%. It was observed that the grafting structure appears not to enhance

their impact resistance.

Guo et al (1999) prepared both HCFC and pentane blown rigid

polyurethane foams from polyol derived from soybean oil. These foams were

found to have comparable mechanical and thermo insulating properties of

foams of petrochemical origin. A comparison in the thermal and

thermooxidative behaviours of soy polyol and poly propylene oxide (PPO)

based foams revealed that the former is more stable toward both thermal

22

degradation and thermal oxidation. The lack of ether linkages in the soy-based

rather than PPO based polyol is thought to be the origin of improved thermal

and thermo-oxidative stabilities of soy based foams.

Ng et al (1999) synthesized nano TiO2 epoxy composites. The

ultrasonic method was used to disperse the nanoparticles in epoxy, thus

eliminating the need for solvent without sacrificing the ease of processing.

The composites were characterized by SEM, tensile tests and scratch tests.

Gultekin et al (2000) described a novel macromer technique for the

styrenation of castor oil. The macromer was prepared through the

interesterification of castor oil with linseed oil followed by esterification with

acrylic acid. Various castor oil/linseed oil ratio’s were applied to obtain a

macromer which gave a copolymer with good film properties after

copolymerization with styrene. It was observed that the styrenation leads to

improved film properties.

Boquillon and Fringant (2000) synthesized polymer network

derived from epoxidized linseed oil cured with anhydrides. The reaction was

catalysed with different types of tertiary amine and imidazol. It was observed

that the thermosets obtained with phthalic anhydride and methyl-

endomethylenetetrahydrophthalic anhydride hardeners have a lower cross

linking density than those obtained with cis-1, 2, 3, 6-tetra hydrophthalic

anhydride.

Wold and Soucek (2000) studied the cross-linking density and glass

transition temperature of various ceramic coatings. The metal oxide creamer

coatings were developed using linseed oil as the organic phase with titanium

isopropoxide and zirconium propoxide as the inorganic sol-gel precursors.

The phase morphology, and thermal decomposition of these creamer coatings

23

were evaluated using small–angle X-ray scattering and TGA. The

morphology of these creamer coatings was found primarily depend on sol-gel

precursor concentrations. TGA revealed that the thermal history of the

ceramic coatings also depended on sol-gel precursor concentration.

Li et al (2000) synthesized thermosetting polymers from fish oil the

cationic copolymerization of native or conjugated fish oil with divinyl

benzene norbornadiene or cyclopentadiene comonomers initiated by boron

trifluoride. DMA analysis shows that the produced thermosetting polymers

possesses densely cross-linked structures. TGA indicates that the three

distinct decomposition temperature which corresponds to evaporation of

unreacted free oil, carbonization of the cross-linked polymer network and

oxidation of carbon.

Hu et al (2000) synthesized a series of polyurethaneurea-vinyl

polymer hybrid aqueous dispersions from castor oil, butyl acrylate and

styrene. The effect of hybrid between polyurethaneurea and vinyl polymer on

the morphologies and the mechanical properties are studied. The

polyurethaneurea - vinyl polymer specimens with high content of castor oil

exhibit excellent comprehensive mechanical properties, resulting from the

reinforcement of cross-linked polyurethaneurea phase existing in the systems.

Guo et al (2000) synthesized four polyols intended for application

in PU by oxirane ring opening epoxidized soybean oil with hydrochloric acid,

hydrobromic acid and methanol. The structures of polyol were characterized

by spectroscopic, chemical and physical methods. The brominated polyol had

higher functionality of 4.1 than other polyols.

Ke et al (2000) studied the effect of a catalyst and coupling agent as

well as a curing process on exfoliation behaviour of CH3(CH2)15NH3+

24

montmorillonite clay in an anhydride cured epoxy clay system. The results

obtained from XRD, DSC and TEM shown that the organoclay is easily

intercalated by the epoxy precursor during the mixing process and the clay

galleries continue to expand during the curing process. The results also

indicated that in the cured system without any promoter although partial

exfoliated clay layers have already formed, an amount of the intercalation

structure still remains.

Khot et al (2001) studied the development and application of

triglyceride based polymers and composites. Triglyceride oils derived from

plant oils have been used to synthesize several different monomers for use in

structural applications. These monomers have been found to form polymers

with a wide range of physical properties. They exhibit a tensile moduli in the

1-2 GPa range and glass transition temperature in the range 70-120oC. At low

glass fiber content (35 wt%), the composites produced from acrylated

epoxidized soybean oil displayed a tensile modulus of 5.2 GPa, a flexural

modului 9 GPa, a tensile strength of 129 MPa, and a flexural strength of 206

MPa.

Tsujimoto et al (2001) studied the enzymatic synthesis of

crosslinkable polyesters. Polymerization of divinyl sebacate and glycol using

candida antartica lipase as catalyst in the presence of unsaturated higher fatty

acids produced the polyesters having an unsaturated group in the side chain.

The polyester was subjected to hardening by cobalt naphthenate catalyst or

thermal treatment, yielding cross-linked transparent film.

Hilker et al (2001) studied the kinetics of chemo-enzymatic

epoxidation of linseed oil. The multiphase process consists basically of a

consecutive reaction - a lipase catalyzed peracid formation followed by a

Prilezhaev epoxidation. Kinetic measurements were carried out in an enzyme-

25

recycle reactor. The kinetics of the process are incorporated in a semi-batch

model and the rate constants of the involved reactions are determined by

means of non-linear regression. Simulations with this mathematical model

agree well with the experimental data obtained for the reaction system.

Kornmann et al (2001) synthesized epoxy –clay nanocomposites

using montmorillonite clay with different cation-exchange capacities (CEC).

The results showed that the CEC plays an important role in the synthesis of

nanocomposites because it determines the amount of alkylammonium ions,

which can be intercalated between the layers. A montmorillonite with low

CEC is exfoliated already during swelling in the epoxy resin prior to curing.

A mechanism responsible for influence of CEC on nanocomposite

interlamellar spacing is discussed.

Salahuddin et al (2002) developed a new technique to prepare a

highly filled epoxy- montmorillonite (MMT) nanocomposite using an

organically modified MMT. Composites with clay content up to 70 wt%

exhibit unusual transparency, which is related to spatial distribution of the

mineral nanodomains. Dispersion of the layered silicate within the cross-

linked epoxy matrix was verified using X-ray diffraction pattern, with a layer

spacing of 30 and 70Ao.

Ashok Kumar et al (2002) synthesized the siliconized

epoxy-bismaleimide intercross-linked matrix materials. Data obtained from

mechanical studies and thermal characterization indicated that the

introduction of siloxane into epoxy resin improved the toughness and thermal

stability with reduction in strength and modulus values. Similarly the

incorporation of bismaleimide into epoxy improved both tensile strength and

thermal behaviour. However, the introduction of both siloxane and

26

bismaleimide into epoxy resin enhanced both mechanical and thermal

properties according to their percentage content.

Dinakaran et al (2002) synthesized the bismaleimide

(N, N′-bismaleimido-4,4′-diphenyl methane) unsaturated polyester modified

epoxy inter-crosslinked matrices and studied the thermo-mechanical

properties. The mechanical properties of the epoxy system increased with

increasing unsaturated polyester content in the epoxy matrix system is found

to increase the stress-strain properties, glass transition temperature and

thermal degradation temperature at higher concentration of unsaturated

polyester whereas the plain strain fractures toughness decreased with

increasing bismaleimide concentration.

Musto et al (2002) studied the molecular interactions in the

diffusion of water through epoxy and epoxy-bismaleimide networks. The

molecular interactions between absorbed water molecules and a

tetrafunctional epoxy resin were characterized by FT-IR. Molecular

spectroscopy analysis confirmed the existence of mobile water localized into

network defects (microvoids) that did not interact with the networks and

water molecules bound to the networks through hydrogen-bonding

interactions. In the BMI-containing system, the fraction of bound water

decreased significantly with respect to the unmodified epoxy resin. This was a

relevant result because the bound water was primarily responsible for the

plasticization of the network and for the consequent reduction of mechanical

performance. Water diffusion was investigated with gravimetric sorption

measurements and time-resolved Fourier transforms IR spectroscopy

measurements. The studies indicated that the presence of BMI decreased the

water uptake at equilibrium, enhanced the diffusivity and reduced the

activation energy for diffusion. A dual-mode model for diffusion was found to

be suitable for accurately describing the mass-transport process in both the

27

investigated systems. The results of the model simulations allowed estimating

the ratio of free and bound water, which was in good agreement with that

obtained from the spectroscopic analysis.

Chen et al (2002) synthesized norbornyl epoxidized linseed oil at

high pressure and high temperature followed by epoxidization. Photo induced

curing kinetics of norbornyl epoxidized linseed oil coatings was investigated

using real-time FT-IR spectroscopy with a fiber optic UV-curing system.

The norbornyl epoxidized linseed oil was formulated with three different

divinyl ether reactive diluents. Among the three divinyl ethers used, coating

triethylene glycol divinyl ether showed the highest curing rate and coating

with cyclohexane dimethanol divinyl ether showed the lowest curing rate.

Petrovic et al (2002) synthesized polyurethane networks from

soybean oil. In this work the NCO/OH ratio was varied from 1.05 to 0.40.

Polymers prepared from with NCO/OH ratios from 1.05-0.8 were glassy

while the others were rubbery. The synthesized polyurethane polymers

showed a decrease in the values of glass transition temperature, tensile

strength and increased values of elongation at break.

Guo et al (2002) studied the structure-property relationship in

polyurethanes derived via the hydroformylation of soybean oil. The double

bonds of soybean oil are first converted to aldehydes through

hydroformylation using either rhodium or cobalt as a catalyst. The aldehydes

are hydrogenated by Raney nickel to alcohols, forming a triglyceride polyol.

The later is reacted with polymeric MDI to yield the polyurethanes.

Depending on the degree of conversion, the material can behave as hard

rubbers or rigid plastics. The rhodium catalyzed reaction afforded a polyol

with a 95% conversion, giving rise to rigid polyurethane, while the cobalt-

catalyzed reaction gives a polyol with a 67% conversion, leading to a hard

28

rubber having lower mechanical strength. Addition of glycerin as a cross-

linker systematically improves the properties of polyurethane.

Devaux et al (2002) improved the flame retardancy to the

polyurethane coated textile fabrics by incorporating nano additives such as

montmorillonite clay and polyhedral oligomeric silsesquioxanes (POSS). The

flame retardancy properties were studied using cone calorimetry and thermo

gravimetric analysis. The efficiency of the additive chosen is clearly

demonstrated and the potential use of POSS for fire retardant application is

highlighted.

Petrovic et al (2002) studied the kinetics of epoxidation of soybean

oil. Epoxidization was carried out in toluene with peroxoacetic acid and

peroxoformic acid in the presence of ion exchange resin as a catalyst. The

reaction was found to be first order with respect to double bond concentration.

At higher temperatures and at higher conversion a deviation from the first

order kinetics was observed.

Bharadwaj et al (2002) synthesized polyurethane elastomers from

castor oil based polyol, polyethylene glycol of various molecular weight and

toluene diisocyanate. The sorption, mechanical and thermal properties have

been studied. The diffusion coefficient and sorption coefficient were found to

decrease with an increase in chain length of polyethylene glycol. The thermal

degradation of all elastomers starts at 250oC regardless of PEG chain length.

Villas et al (2003) synthesized semi and full IPNs of uralkyd resins

(UA) based on hydrogenated castor oil and poly(butyl acrylate) (PBA) were

prepared by the sequential mode of synthesis. These IPNs were characterized

for their resistance to thermal behaviour, swelling and mechanical properties.

29

The morphology of the IPNs was studied by SEM. The mechanical properties

significantly enhanced by increasing UA component in the blend.

Latere Dwan’Isa et al (2003) synthesized bio based polyurethane

from soybean oil derived polyol and polymeric diphenylmethane

diisocyanate. The cross-linked bio based polyurethane being prepared from

soy phosphate ester polyols with hydroxyl content ranging from 122 to

145 mg KOH/g and pMDI at 150oC show cross linking densities ranging from

1.8 × 103 to 3.0 × 10

3 M/m

3, whereas the glass transition temperature vary

from approximately 69 to 82 oC. The cross-linking densities improved

significantly for hydroxyl content of 139 and 145 mg KOH/g at curing time of

24 hours. Similarly, the glass transition temperature and storage moduli are

increased.

Latere Dwan’Isa et al (2003a) synthesized bio based polyurethanes

from soybean oil derived polyol and polymeric diphenylmethane diisocyanate

(pMDI). The cross-linked bio based polyurethanes being prepared from soy

phosphate polyol and MDI within 5 min of reaction time at 150oC in absence

of any catalyst show cross-linking densities ranging from 1.8 × 10 3

to

3.0 × 103

M/m3. The glass transition temperature varies from approximately

69 to 82 oC. The loss factor (tan δ) curves show single peaks for all these bio

based polyurethanes, thus indicating a single-phase system. The storage

moduli (G’) at 30 o

C range from 4 × 108 to 1.3 × 10

9 Pa. Cross-linking

densities are improved significantly for hydroxyl content of 139 and 145 mg

KOH/g at curing time of 24 hours. Similarly, the glass transition temperature

and storage moduli are also increased.

Athawale and Pillay (2003) developed semi and full

Interpenetrating networks (IPN) of uralkyd (UA) resin based on hydrogenated

30

castor oil and poly(butyl acrylate). The IPN’S were characterized for their

mechanical properties. The mechanical properties significantly increased by

increasing UA component in the blend. Full IPN’S exhibited higher apparent

densities, mechanical properties and thermal stability than the corresponding

semi - IPN.

Copinet et al (2003) studied the behaviour of agricultural mulch

co-extruded poly (lactic acid) (PLA)/starch films. The prepared bio-polymer

blends were studied for ultraviolet treatment (UV) at 315nm and

biodegradation. On exposure to the ultraviolet radiations the glass transition

temperature and weight loss was observed.

Uyama et al (2003) synthesized a novel green nano composite from

epoxidized soy bean oil using a thermally latent cationic catalyst benzyl

sulfonium hexafluoroantimonate in presence of octadecyl modified

montmorillonite at 150oC. The XRD study shows that the clay layer is

exfoliated. Similarly a clay nano composite prepared from epoxidized linseed

oil shows higher cross-linking density due to the increase in content of

reactive epoxy group.

Lu et al (2003) functionalized the triglycerides into acrylated

epoxidized soybean oil, maleinized acrylated epoxidized soy bean oil and

soybean oil pentaerythritol maleates, combined with styrene and used as

polymer matrix. The clay nano composite is prepared using functionalized

triglyceride monomer at 66.7 wt% and 33.3 wt% of styrene. The formation of

nanocomposite was confirmed by both X-ray data and transmission electron

microscopy. The morphology showed a mix of intercalated and partially

exfoliated sheets. The flexural modulus increased to 30 % with the

incorporation of 4 wt% of clay content.

31

Tsujimoto et al (2003) developed a green nano composite by an acid-

catalysed reaction of epoxidized plant oil and glycidoxypropyltrimethoxysilane

(GPTMS), in which both oxirane groups of epoxidized plant oil and GPTMS

were copolymerized to produce an organic polymer matrix and

simultaneously forming a silica network. The hardness and mechanical

properties improved by incorporating the silica network in to the polymer

matrix. It was observed that the linkage between organic and inorganic

polymers would control the nanocomposite structure in nanoscale, leading to

improvement of coating properties.

Zlatanic et al (2003) synthesized polyurethane networks from six

different polyols derived from sunflower, canola, soybean, corn and linseed

oils with 4,4′-diphenylmethane diisocyanate. The differences in the network

structure reflected the number of functional groups in vegetable oils and

resulting polyols. It was observed that the canola, corn, soybean, and

sunflower oils gave polyurethane resins of similar cross-linking density and

linseed oil based polyurethane had higher cross-linking density and higher

mechanical properties.

Suprakas Sinha et al (2003) studied the melt rheological behaviour

of PLA/MMT nanocomposites. Based on the data’s obtained rheological

behaviour, the foam processing of pure PLA and one representative

nanocomposite by a newly developed pressure cell technique using

supercritical carbon dioxide as a physical blowing agent.

Tsujimoto et al (2003) developed green nanocomposite coatings

based on renewable plant oils. An acid-catalyzed curing of epoxidized plant

oils with 3-glycidoxypropyltrimethoxysilane produced transparent

nanocomposites. The hardness and mechanical strength improved by

incorporating the silica network into the organic polymer matrix, good

32

flexibility was observed in the nanocomposite. The nanocomposites showed

high biodegradability.

Hongwen Zhandg et al (2003) synthesized nanocomposites using

interpenetrating polymer networks of polyurethane and epoxy resin with

varying concentrations of nanosized silicon dioxide particles. The prepared

nanocomposites were studied by dynamic mechanical analysis, scanning

electronic microscopy, wide-angle X-ray diffraction and small angle X-ray

scattering. The result showed that adding nanosized silicon dioxide can

improve the properties of compatibility, damping and phase structure of IPN

matrices.

Zlatanic et al (2003) synthesized six polyurethane networks from

4,4′-diphenylmethane diisocyanate and polyols of midoleic sunflower,

canola, soybean, sunflower, corn and linseed oils. The functionality of the

polyols varied between 3.5 and 5.2. It was concluded that the linseed oil-

based polyurethane had higher cross linking density and higher mechanical

properties, whereas midoleic sunflower oil gave softer polyurethane and

possesses lower Tg and lower strength.

Jiang et al (2003) synthesized epoxy nano TiO2 modified

composites using high speed shearing emulsification technique. A jet type

vacuum ultraviolet (VUV) source was used to simulate the VUV spectrum in

space and acquire various dosages of VUV radiation. The results showed that

the incorporation of nano-TiO2 particles into epoxy matrix not only improved

the mechanical properties but also exhibit resistance to VUV radiation. The

damage to the epoxy matrix on exposure to VUV radiation was observed by

means of SEM.

33

McGlashan et al (2003) synthesized biodegradable starch-polyester

nanocomposite materials using film blowing tower. The physical properties

of different films have been examined by thermal and mechanical analysis

and X-ray diffraction. The results showed that the addition of an organoclay

significantly improved both the processing and tensile properties over the

original starch blends.

Dinakaran et al (2003) prepared the bismaleimide modified

bisphenol dicyanate epoxy matrices. The mechanical properties of the epoxy

system increased with increasing the percentage incorporation of cyanate

ester. The introduction of bismaleimide into the cyanate ester modified epoxy

system was found to increase the stress-strain properties, glass transition

temperature and thermal degradation temperature. The mechanical properties

of the epoxy system increased with increasing cyanate ester content. The

introduction of bismaleimide into the cyanate ester modified epoxy system

was found to increase the stress-strain properties, glass transition temperature

and thermal degradation temperature.

Dinakaran et al (2003) developed the epoxy-cyanate ester

interpenetrating network matrices/organoclay nanocomposites. Data obtained

from mechanical studies and thermal characterization indicates that the

introduction of cyanate ester into epoxy resin improved the toughness and the

thermal stability with reduction in strength and modulus values. The

organophilic montmorillonite clay-epoxy and cyanate ester-epoxy

nanocomposites were evaluated by X-ray diffraction (XRD), dynamic

mechanical analysis (DMA) and SEM.

Jeng et al (2003) studied the thermal properties and flame

retardancy of a phosphorus-containing bismaleimide and epoxy resins. The

results showed that the epoxy resins were found to exhibit glass transition

34

temperatures as high as 212°C, thermal stability at temperatures over 350°C,

and excellent flame retardancy with limited oxygen index (LOI) values

around 40. The incorporation of BMPPPO into epoxy resins simultaneously

enhanced the thermal properties and flame retardancy.

Shu et al (2004) prepared the phosphonate-containing bismaleimide

and blended with epoxy. Data obtained for mechanical and thermal studies

indicated that the introduction of bismaleimide increased the storage modulus

and glass-transition temperature with reduction in the mechanical strength of

the epoxy blends. The initial pyrolysis temperatures of all the blending

systems gradually decreased as the phosphorous content increased, the flame

retardancy of all the phosphonate-containing epoxy systems was promoted

significantly by increasing contents of BMI.

Park et al (2004) synthesized and characterized epoxidized soybean

oil (ESO) and epoxidized castor oil (ECO). The cationic polymerization of

ESO and ECO with a thermal catalyst N-benzyl hexafluoroantimonate (BPH)

was initiated at 80 oC and 50

oC respectively. The cured ECO samples show a

higher Tg and lower coefficient of thermal expansion than those of ESO, due

to the higher intermolecular interaction in the ECO/BPH system.

Park et al (2004) fabricated the green nanocomposites from

cellulose acetate powder, eco-friendly triethylcitrate plasticizer and

organically modified clay. The effect of the amount of plasticizer varying

from 15 to 40 wt % on the performance of the nanocomposite has been

evaluated. The morphologies of these nanocomposites were evaluated by

X-ray diffraction, atomic force microscopy and transmission electron

microscopy studies. The tensile strength, modulus and thermal stability of

cellusosic plastic reinforced with organo clay showed a decreasing trend with

the increase in the plasticizer content from 20 to 40 wt %.

35

Sanmathi et al (2004) synthesized IPNs of glycerol modified castor

oil PU and poly (2-ethoxy ethyl methacrylate) was synthesized using benzoyl

peroxide as initiator and ethylene glycol dimethacrylate as crosslinker. The

IPNs are characterized in terms of their resistance to chemical reagents,

thermal behaviour and mechanical behaviour including tensile strength,

Young’s modulus, hardness and elongation.

Uyama et al (2004) prepared organic-inorganic hybrid from ESO

and ELO by acid catalyzed curing in the presence of MMT clay. The

reinforcement effect due to the addition of clay was confirmed by dynamic

viscoelasticity analysis. The hybrids showed high thermal stability. The

barrier properties of the hybrid showed towards water vapour was superior to

that of the oil polymer.

Lu et al (2004) synthesized a new class of clay nanocomposites

from acrylated epoxidized soybean oil, mealeinized acrylated epoxidized

soybean oil and soybean oil pentaerythritol maleates combined with styrene

polymer matrices. The formation of nanocomposite was confirmed by TEM

and XRD. The morphology showed a mix of intercalated and partially

exfoliated sheets.

Pandey et al (2005) prepared nanocomposites of starch via different

addition sequences of plasticizer and clay by solution method. The extent of

dispersion of filler was evaluated by wide angle X-ray diffractometry in the

resulting composites. Thermal stability, mechanical properties and water

absorption studies were conducted to measure the material properties whereas

FT-IR spectroscopy was used to study the microdomain structure of the

composites. The sequence of addition of components (starch/plasticizer

(glycerol)/clay) had a significant effect on the nature of composites formed

and accordingly properties were altered. The filler dispersion becomes highly

36

heterogeneous and the product becomes more brittle when starch was

plasticized before with clay due to the formation of bulky structure resulting

from electrostatic attractions between starch and plasticizer. It was concluded

that the best mechanical properties can be obtained if the plasticizer is added

after mixing of clay in the starch matrix.

Dutta et al (2005) synthesized a series of polyurethane resins with

varying NCO/OH ratios from monoglyceride of Meusa Ferrea L. seed oil,

polyethylene glycol and 2,4 toluene diisocyanate in the presence of dibutyl tin

dilaurate as a catalyst. The effect of NCO/OH ratios of the synthesized resins

on the physical properties, such as hydroxyl values, acid values,

saponification values, iodine values, specific gravities and isocyanate values

have been studied. The formation of polyurethane resins was confirmed by

FT-IR and 1H NMR spectroscopic studies. The thermo gravimetric analysis

(TGA) shows that the thermal stabilities of the cured resins increased with the

increase in NCO/OH ratios.

Miyagawa et al (2005) processed bio based epoxy containing

epoxidized linseed oil (ELO), diglycidylether of bisphenol F and its clay

nanocomposites using anhydride curing agent. The new bio-based epoxy clay

nanocomposites showed high elastic modulus, high glass transition

temperature, and high fracture toughness with larger amount of ELO.

Miyagawa et al (2005a) processed bio based neat epoxy materials

containing ELO and ESO using anhydride curing agent. A percentage of

diglycidyl ether of bisphenol F(DGEBF) was replaced by ELO and ESO.

Izod impact strength and fracture toughness were significantly improved

dependent on epoxy content of oil. The phase separated morphology was

studied using SEM.

37

Miyagawa et al (2005b) investigated polymer nano composites

made with matrix of anhydride cured diglycidyl ether of bisphenol-A

(DGEBA) and reinforced with organo-MMT clay. The thermal properties of

nano composites were measured with DMA. TEM analysis showed well

dispersed platlets in the nano composites. The clay nano platelets were

observed to be well intercalated/expanded in the anhydride cured epoxy resin

system.

Shabeer et al (2005) prepared epoxidized allyl soyate (EAS) by the

process of trans esterification of food grade soybean oil. The effect of

concentration of EAS and the two different types of cross-linking reagents on

the dynamic mechanical behaviour of soy based system have been

investigated. The room temperature storage moduli and the Tg increased for

the anhydride cured and they were decreased for the amine cured resins.

Huang et al (2006) prepared epoxy/TiO2 composites by solution

mixture method. According to the experimental results it is observed that

hydrogen bonds may be formed by mixing TiO2 particles and epoxy resin.

The SEM analysis suggests that TiO2 particles are uniformly distributed

within the material, while some silver streaks occur at the surface of

materials. Besides the thermo-resistance and mechanical property of

materials are found to improve with the addition of TiO2, but degrades if the

nano-TiO2 is excess of 3 wt%.

Lligadas et al (2006) studied the preparation and properties of a new

class of bio nanocomposite from ELO and 3-glycidylpropylheptaisobutyl-T8-

polyhedral oligomeric silsesquioxane (G-POSS). FT-IR, DMTA, TGA and

SEM were employed to characterize the POSS reinforced oil based polymer

networks. The enhanced Tg and storage moduli of the networks in the glassy

state and rubber plateau were observed to be higher than those of POSS - free

oil based polymer network.

38

1.10 SCOPE OF THE PRESENT INVESTIGATION

Use of renewable resources in the areas of energy and materials has

been one of the major scientific and technological issues for the past few

decades. Renewable resource based bio polymers including cellulose plastics

(plastics made from wood), polylactic acid (corn-derived plastic),

polyhydroxy alkonate (bacterial polyester), thermo plastic starch, vegetable

oils are of significant importance from both industrial and economic view

points. Vegetable oils are made of triglycerides possess double bonds, which

are used as reactive sites in coating. They can also be functionalized by

epoxidization. These triglycerides possess aliphatic chains, and consequently

the triglyceride-based materials are incapable of possessing necessary rigidity

and strength required for high performance applications

Several attempts have been taken to improve the thermal and

mechanical properties of vegetable oil based polymers by reinforcing natural

fibers and metal oxides. A new class of green organic-inorganic hybrid

materials was also produced by incorporating nano clay and silica in

vegetable oil based polymer.

The green composites, though they are biodegradable and cost

competitive, they exhibit some inferior thermo mechanical behaviour

unsuitable for high performance applications. Hence, an attempt has been

made to develop bio-based polymers from petro-bio mixed resources

involving both naturally occurring resins (functionalized oils) and petroleum

based epoxy resins in order to make composites suitable for high performance

applications.

Though the incorporation of soy epoxy resin into the petroleum

based epoxy resins improves its impact strength and tensile properties, it

39

reduces thermal stability and glass transition temperature. In order to prevent

the loss of thermal properties and to further improve the mechanical

properties making them suitable for high performance applications,

modification of soy based epoxy system with rigid materials like

bismaleimides is essential owing to their superior thermo-mechanical

properties viz. high cross linking ability, high glass transition temperature,

high thermal stability, high char yield, excellent fire resistance and low water

absorption.

In the present investigation an attempt is made:

• to develop soy based epoxy matrices by blending epoxidized

soy bean oil and DGEBA at varying concentrations

• to study the effect of incorporation of epoxidized soy bean oil

at different concentrations in the base DGEBA epoxy resin on

the mechanical, thermal properties and cure reaction

behaviour.

• to synthesize three different types of bismaleimides namely

N,N′-(bismaleimido)-4,4′-diphenylmethane,1,3-(bismaleimido)

benzene and 3,3′-bis(maleimidophenyl) phenylphosphine

oxide.

• to study the effect of introduction of various bismaleimides

into soy based epoxy systems at appropriate concentrations on

thermal, mechanical, thermomechanical, flame retardancy,

water absorption and morphological properties.

• to develope organophilic clay reinforced soy based epoxy

nanocomposites and to study the effect of incorporation of

nano clay in soy based epoxy matrix system on thermal,

40

mechanical, thermomechanical, water absorption and

morphological behaviour.

• to study the effect of incorporation of nano metal oxide such

as TiO2 nanoparticles in the soy based epoxide matrix on

mechanical, thermal, thermomechanical, water absorption and

morphological properties.

All this forms the subject matter of the present investigation and the

thesis is divided into eight chapters, the first chapter details the role and

importance of bio-based polymers from various renewable resources, epoxy

resin, curing agents, chemical modifiers like bismaleimides, bio

nanocomposites and literature review including the scope of the present

investigation.

Chapter two describes the synthesis of various bismaleimides,

preparation of soy based epoxy matrices and different bismaleimides

modified soy based epoxy matrices and preparation of various bio-based

nanocomposites. It also includes the experimental procedures for the studies

of physico-chemical, mechanical, thermal, thermomechanical, flame

retardancy and morphological properties of matrix systems and

nanocomposites.

Chapter three presents the discussion of physico-chemical

properties of matrices viz., FT-IR, NMR characterization of epoxidized soy

bean oil, synthesised bismaleimides and the formation of network structure

between soy based epoxy, DGEBA and bismaleimides modified matrices.

The disappearance of peaks at 3097cm-1

, 3105 cm-1

and 3102 cm-1

in the IR

spectra of bismaleimide modified soy based epoxy matrices confirms the

homopolymerization of bismaleimides occurred at lower temperatures

(160 oC-180

oC) in the presence of epoxy resin.

41

Chapter four studies the mechanical properties such as tensile

strength, tensile modulus, flexural strength, flexural modulus, impact strength

of neat DGEBA, soy based epoxy, bismaleimides modified soy based epoxy

matrix materials and various bio based nanocomposites were studied as per

ASTM standards.

Chapter five discusses the thermal properties like cure reaction

behaviour, glass transition temperature (Tg), thermal degradation temperature,

percentage weight loss, flame retardancy, dynamical mechanical analysis and

heat distortion temperature of soy based epoxy and bismaleimide modified

epoxy matrices. This chapter further confirms the homopolymerization of

BMIs rather than Michael addition reaction with the amine, by the increae in

the glass transition temperature (Tg) of the bismaleimide modified soy based

epoxy systems.

Chapter six presents the morphology and water absorption

behaviour of neat DGEBA, soy based epoxy matrices and various

bismaleimide modified soy based epoxy matrices.

Chapter seven discusses the confirmation of nanocomposites

structure by XRD analysis. It also includes the mechanical, thermal, thermo

mechanical, morphology and water absorption characterization of the

prepared organo clay, TiO2 and ZrO2 filled bio-based nanocomposites.

Chapter eight presents the summary and conclusion, which include

the utility of these hybrid matrices and nanocomposites for high performance

engineering and industrial applications. It also describes the potential

substitution of these bio based hybrid matrices instead of petro-based epoxy

matrices.