CHAPTER 5

PREPARATION, MECHANICAL

AND ELECTRICAL STUDY OF

JUTE/GLASS REINFORCED

COMPOSITES AND THEIR

PHYSICO-CHEMICAL STUDY

Preparation…

155

CHAPTER 5

Preparation, mechanical and electrical study of jute/glass reinforced

composites and their physico-chemical study

5.1 General introduction

Composites can be defined as materials that consist of two or more

chemically and physically different phases separated by a distinct interface.

The different systems are combined judiciously to achieve a system with more

useful structural or functional properties non attainable by any of the

constituent alone. Composites, the wonder materials are becoming an

essential part of today’s materials due to the advantages such as low weight,

corrosion resistance, high fatigue strength, and faster assembly. They are

extensively used as materials in making aircraft structures, electronic

packaging to medical equipment, and space vehicle to home building [1]. The

basic difference between blends and composites is that the two main

constituents in the composites remain recognizable while these may not be

recognizable in blends. The predominant useful materials used in our day-to-

day life are wood, concrete, ceramics, and so on. Surprisingly, the most

important polymeric composites are found in nature and these are known as

natural composites.

Composites are combinations of materials differing in composition,

where the individual constituents retain their separate identities. These

separate constituents act together to give the necessary mechanical strength

or stiffness to the composite part. Composite material is a material composed

of two or more distinct phases (matrix phase and dispersed phase) and

having bulk properties significantly different from those of any of the

constituents. Matrix phase is the primary phase having a continuous

character. Matrix is usually more ductile and less hard phase. It holds the

dispersed phase and shares a load with it. Dispersed (reinforcing) phase is

1. A. Shaw, S. Sriramula, P. D. Gosling, and M. K. Chryssanthopoulo, A

critical reliability evaluation of fibre reinforced composite materials based

on probabilistic micro and macro-mechanical analysis, Composites Part

B, 41, 446–453, 2010.

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embedded in the matrix in a discontinuous form. This secondary phase is

called the dispersed phase. Dispersed phase is usually stronger than the

matrix, therefore, it is sometimes called reinforcing phase.

Composite materials can be classified into three categories depending

on the type of matrix materials used such as metal matrix composites,

polymer matrix composites and ceramic matrix composites. Each type of

composite material is suitable for different applications. Among them, polymer

matrix composites are the composites consisting of polymer as matrix

material. These composites are characterized by the various properties such

as high stiffness, high tensile strength, high fracture toughness, good

corrosion and abrasion resistance, low cost, etc. There are two major classes

of polymers used as matrix materials such as thermoplastics and thermosets.

Thermoplastics (nylon, polypropylene, acrylics, etc.), can be repeatedly

softened and re-formed by application of heat. However, thermosets

(phenolic, epoxies, etc.) on the other hand, are materials that undergo a

curing process during part fabrication, after which they are rigid and cannot be

reformed. Among them epoxy is the most widely used matrix due to it

advantages like good adhesion to other materials, good mechanical

properties, good electrical insulating properties, good chemical and

environmental resistance, etc. Generally, the reinforcing material for polymer

matrix composites include synthetic fibers such as glass fiber, kevlar fiber,

carbon fiber, etc. or natural/cellulose fibers such as cotton, jute, kenaf,

bamboo fiber, etc.

Composites in structural applications have the following characteristics:

� They generally consist of two or more physically distinct and

mechanically separable materials.

� They are made by mixing the separate materials in such a way as to

achieve controlled and uniform dispersion of the constituents.

� They have superior mechanical properties and in some cases uniquely

different from the properties of their constituents [2].

2. C. Mayer, X. Wang, and M. Neitzel, Macro- and micro-impregnation

phenomena in continuous manufacturing of fabric reinforced

thermoplastic composites, Composites Part A, 29,783–793, 1998.

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5.2 Natural fiber composites

Natural fibers may be classified by their origin as cellulosic (from

plants), protein (from animals) and mineral. Plant fibers may be further

classified a: seed hairs, such as cotton; bast (stem) fibers, such as linen from

the flax plant; hard (leaf) fibers, such as sisal; husk fibers, such as coconut.

However commercially important natural fibers can be obtained from the seed

hairs, stems, and leaves of plants (Fig. 5.1). The material properties of natural

fibers are comparable with those of synthetic ones, as tabulated in Table 5.1.

Cellulose is the main structural component that provides strength and stability

to the plant cell walls and is one of the most abundant organic compounds on

earth. The amount of cellulose in a fiber influences the properties, economics

of fiber production and the utility of the fiber for various applications [3].

Fig. 5.1: Classification of cellulosic fibers.

3. J. K. Pandey, S. H. Ahn, C. S. Lee, A. K. Mohanty and M. Misra, Recent

advances in the application of natural fiber based composites, Macromol.

Mater. Eng., 295, 975–989, 2010.

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Table 5.1: Physical properties of some natural and synthetic fibers [4].

Fiber

Density

(g/cm3)

Elongation

(%)

Youngs

modulus

(GPa)

Tensile

strength

(MPa)

Specific

tensile

strength

Water

absorption

(%)

E-glass 2.5 2.5 70 2000–

3500

800–

1400

–

Aramide 1.4 3.3–3.7 63–67 3000–

3150

2140–

2250

–

Carbon 1.4 1.4–1.8 230–240 4000 2860 –

Flax 1.5 1.2–3.2 27–80 345-

1500

230–

1000

7

Cotton 1.5–1.6 3.0–10.0 5.5–12.6 287–800 190–530 8–25

Jute 1.3–1.5 1.5–1.8 10–55 393–800 300–610 12

Hemp 1.5 1.6 70 550–900 370–600 8

Sisal 1.3–1.5 2.0–2.5 9.4–28 511–635 390–490 11

Ramie 1.5 2.0–3.8 44–128 400–938 270–620 12–17

Coir 1.2 15–30 4–6 131–220 110–180 10

Glass, carbon, Kevlar, and boron fibers are being used as reinforcing

materials in fiber-reinforced plastics, which have been widely accepted as

materials for structural and nonstructural applications [5]. However, these

materials are resistant to biodegradation and can pose environmental

problems. Natural fibers from plants such as jute, bamboo, coir, sisal, and

pineapple are known to have very high strength and hence can be utilized for

many load-bearing applications. These fibers have special advantage in

comparison to synthetic fibers in that they are abundantly available, from a

renewable resource and are biodegradable. But all natural fibers are

hydrophilic in nature and have high moisture content, which leads to poor

4. E. Zini and M. Scandola, Green Composites: An Overview, Polym.

Compos., 32, 1905–1915, 2011.

5. D. Liu, A. D. McDaid and D. Q. Xie, Position control of an ionic polymer

metal composite actuated rotary joint using iterative feedback tuning,

Mechatronics, 21, 315–328, 2011.

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interface between fiber and hydrophobic matrix. Several treatment methods

are employed to improve the interface in natural fiber composite [6].

Automobile industry in Europe has started using natural fiber composites in a

big way both for exterior and interior of car bodies because of stringent

environmental requirements.

Natural fibers are generally incompatible with the hydrophobic polymer

matrix and have a tendency to form aggregates. Therefore, the surface of

both (matrix and fibers) should be appropriately wetted to improve the

interfacial adhesion and to remove any impurities. The surface of hydrophobic

matrices should be modified by the introduction of polar groups by treating

them with oxidative chemicals such as chromic acid/acetic acid or chromic

acid/sulfuric acid [7]. Cold plasma chemistry opens up new avenues for the

surface modifications of materials for composites and other applications.

Various oxidative and nonoxidative chemical treatments are available for

natural and synthetic fibers to improve the bonding at the interface. Alkali

treatment has been proved to be an effective method for fiber modification

from as early as 1935. It has been reported that on treatment with alkali, some

of the wax components at the fiber surface are saponified and thereby

removed from the fiber surface. Increased fiber/matrix adhesion as a result of

improved surface area and increase in availability of the hydroxyl groups have

also been reported as a result of alkali treatment [8].

6. V. G. Geethamma, T. K. Mathew, R. Lakshminarayanan, and S.

Thomas, Composite of short coir fibres and natural rubber: effect of

chemical modification, loading and orientation of fibre, Polymer, 39,

1483–1491, 1998.

7. S. A. Paul, A. Boudenne, L. Ibos, Y. Candau, K. Joseph, and S. Thomas,

Effect of fiber loading and chemical treatments on thermophysical

properties of banana fiber/polypropylene commingled composite

materials, Composites Part A, 39, 1582–1588, 2008.

8. P. V. Joseph, Computer Sciences Technology, 62, 1357, 2002.

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5.2.1 Applications of natural fiber composites

The natural fiber composites can be very cost effective material for

following applications:

� Building and construction industry: panels for partition and false ceiling,

partition boards, wall, floor, window and door frames, roof tiles, mobile

or pre-fabricated buildings which can be used in times of natural

calamities such as floods, cyclones, earthquakes, etc.

� Storage devices: post-boxes, grain storage silos, bio-gas containers,

etc.

� Furniture: chair, table, shower, bath units, etc.

� Electric devices: electrical appliances, pipes, etc.

� Everyday applications: lampshades, suitcases, helmets, etc.

� Transportation: automobile and railway coach interior, boat, etc.

The reason for the application of natural fibers in the automotive industry

includes:

� Low density: which may lead to a weight reduction of 10 to 30%

� Acceptable mechanical properties, good acoustic properties.

� Favorable processing properties, for instance low wear on tools, etc.

� Options for new production technologies and materials.

� Favorable accident performance, high stability, less splintering.

� Favorable ecobalance for part production.

� Favorable ecobalance during vehicle operation due to weight savings.

� Occupational health benefits compared to glass fibers during

production.

� No off-gassing of toxic compounds (in contrast to phenol resin bonded

wood and recycled cotton fiber parts).

� Price advantages both for the fibers and the applied technologies.

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5.2.2 Advantages of natural fiber composites

The main advantages of natural fiber composites are:

� Low specific weight, resulting in a higher specific strength and stiffness

than glass fiber.

� It is a renewable source, the production requires little energy, and CO2

is used, while oxygen is given back to the environment.

� Producible with low investment at low cost, which makes the material

an interesting product for low wage countries.

� Reduced wear of tooling, healthier working condition, and no skin

irritation.

� Thermal recycling is possible, while glass causes problem in

combustion furnaces.

� Good thermal and acoustic insulating properties.

Jute is an attractive natural fiber for the reinforcement because of its

low cost, renewable nature and much lower energy requirement for

processing. Jute fiber contains high proportion of stiff natural cellulose. Rated

fibers of jute have three principle chemical constituents, namely α- cellulose,

hemicellulose and lignin. In addition, they contain minor constituents such as

fats and waxes, minerals, nitrogenous matter and trace of pigments like β-

carotene and xanthophylls. Several studies of fiber composition and

morphology have found that cellulose content and micro fibril angle tend to

control the mechanical properties of the cellulosic fibers. The specific

mechanical properties of the composites are comparable to those of the glass

fiber reinforced plastics (GRP). Various items such as school buildings, food

grain silos, wood substitutes, low cost housing units, roofing, pipes [9], etc.

have been fabricated from the jute fiber reinforced composites.

9. M. A. Semsarzadesh, Fiber matrix interactions in jute reinforced

polyester resin, Polym. Compos., 7, 23-25, 1986.

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5.3 Glass fiber composites

Two commonly used glass fibers in the industry are E-glass and S-

glass. The primary material in most glass fibers is silica; to effectively produce

theses fibers, the ingredients must be melted in a furnace that at

temperatures of about 1,370 °C. Glass fibers are a popular choice for fiber

reinforcement due to advantageous properties such as high strength (tensile

strength of approximately 3.40 GPa), tolerance to high temperatures and

corrosive environments, and low cost. However, glass fibers have a relatively

low stiffness. Typically values of stiffness for glass fibers range from

approximately 70 to 90 GPa, whereas, the stiffness of carbon fiber can range

from 230 to 830 GPa.

Glass fiber-reinforced composite materials are attractive because their

properties can be tailored to meet the specific needs of a variety of

applications. The mechanical and thermal properties of a composite generally

follow the rule of mixtures. As glass fiber is the major component at 70–75%

by weight (50–60% by volume), selection of the correct glass product is

critical. Glass fiber reinforcement is available in many forms, including

continuous rovings, chopped fibers, fabrics, and nonwoven mats. In addition

to form, selection of a reinforcement product involves choosing a glass type,

chemistry on the glass (sizing) filament diameter, and tex. Glass formulation

or type governs mechanical, thermal, and corrosion properties, whereas

sizing protects the glass during handling and gives compatibility with the resin

system. Filament diameter and strand tex are chosen to balance physical

properties and manufacturing efficiency. A significant amount of tensile

strength, up to 50%, may be lost from a pristine single filament to a multi-

filament roving. To minimize this degradation, the utmost care and

consistency must be exercised in the fiber forming process. This, coupled with

selection of a high-performance glass formulation, enables use of composites

in highly demanding applications, such as pressure vessels and ballistic

armor [10].

10. J. M. Stickel and M. Nagarajan, Glass fiber-reinforced composites: from

formulation to application, Int. J. Appl. Glass Sci., 3, 122–136, 2012.

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5.4 Fabrication of jute/glass fiber composites

For the preparation of jute/glass composites, 70 % of matrix material

was used (Table 5.2). Required quantity of resin was transferred into a 500 ml

beaker containing required methylethyl ketone and stirred well at room

temperature. To this solution 2 % methylethylketone peroxide and 1 % of 6%-

cobalt naphthenate were added as an initiator and an accelerator,

respectively. The solution was stirred well and was applied to jute/glass

fabrics (20cmX20cm) with a smooth brush and solvent was allowed to

evaporate at room temperature. Eight such jute and ten glass impregnated

fabrics were staked one over the other and kept between two teflon sheets.

These teflon sheets were kept between two preheated stainless steel plates

and pressed under 27.58 MPa pressure at 100 °C for 4h and 12 h at room

temperature. Silicone spray was used as a mold releasing agent. Here after

jute composites are designated as J-ETPUPSt, J-ETPAASt, J-ETPMASt and

glass composites as G-ETPUPSt, G-ETPAASt, G-ETPMASt. Samples with

required dimensions were machined for tensile and flexural tests. For

chemical resistance test samples of 3cm x 3cm were machined and edges

were sealed with matrix material.

Table 5.2: Fiber-matrix and compositions for jute and glass fiber composites

Composite Wt of

fabrics (g)

Wt of styrenated

resin (70%) (g)

J-ETPUPSt 122.35 85.64

G-ETPUPSt 105.67 73.96

J-ETPMASt 128.15 89.70

G-ETPMASt 110.35 77.24

J-ETPAASt 132.7 92.89

G-ETPAASt 107.61 75.32

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5.5 Mechanical and electrical properties of the composites

The mechanical properties, among all the properties of plastic

materials, are often the most important properties because virtually all service

conditions and the majority of end-use applications involve some degree of

mechanical loading. Nevertheless, these properties are the least understood

by most design engineers. The material selection for a variety of applications

is quite often based on mechanical properties such as tensile strength,

modulus, elongation, and impact strength. These values are normally derived

from the technical literature provided by material suppliers. More often than

not, too much emphasis is placed on comparing the published values of

different types and grades of plastics and not enough on determining the true

meaning of the mechanical properties and their relation to end-use

requirements.

In practical applications, plastics are seldom, subjected to a single,

steady deformation without the presence of other adverse factors such as

environment and temperature. Since the published values of the mechanical

properties of plastics are generated from tests conducted in a laboratory

under standard test conditions, the danger of selecting and specifying a

material from these values is obvious. A thorough understanding of

mechanical properties, tests employed to determine such properties, and the

effect of adverse conditions on mechanical properties over a long period is

extremely important.

Plastics were considered a relatively weaker material in terms of load-

bearing properties at elevated temperatures. Therefore, the use of plastics in

electrical applications was limited to nonload-bearing, general-purpose

applications. The advent of new high-performance engineering materials has

altered the entire picture. Plastics are now specified in a majority of

applications requiring resistance to extreme temperatures, chemicals,

moisture, and stresses. The primary function of plastics in electrical

applications has been that of an insulator. This insulator or dielectric

separates two field-carrying conductors. Such a function can be served

equally well by air or vacuum. However, neither air nor vacuum can provide

any mechanical support to the conductors. Plastics not only act as effective

insulators but also provide mechanical support for field-carrying conductors.

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For this very reason, the mechanical properties of plastic materials used as

insulators become very important. Typical electrical applications of plastic

material include plastic-coated wires, terminals, connectors, industrial and

household plugs, switches, and printed circuit boards.

5.5.1 Measurements

The tensile strength(ISO/R 527-1996 Type-I), flexural strength (ASTM-

D-790-2003), electric strength (IEC-60243-Pt-1-1998) and volume resistivity

(ASTM-D-257-2007) measurements were made on a Shimadzu Autograph

Universal Tensile Testing Machine, Model No. AG-X Series at a speed of

10mm/min, a high voltage tester (Automatic Electric-Mumbai) in air at 27 oC

by using 25/75mm brass electrodes and a Hewlett Packard high resistance

meter in air at 25 oC after charging for 60 sec at 500 V DC applied voltage,

respectively. Measurements were carried out in triplicate and the mean values

were considered.

5.5.2 Results and discussion

For material scientists mechanical and electrical properties are very

useful for application point of view. Tensile properties of the materials are

most widely useful for the quality characteristics of materials, while flexural

properties are useful in classification of the materials with respect to bending

strength and stiffness. Electrical properties of the materials are useful in

predicting the relative insulation quality characteristic of material selection for

specific properties with respect to combined effect of material composition

and environment. Tensile strength, flexural strength, electrical strength and

volume resistivity of jute and glass composites are presented in Table 5.3,

from which it is observed that jute composites showed moderately good

tensile and flexural properties, while glass composites showed fairly good

tensile property and moderate to fairly good flexural property. Similar behavior

is also observed in case of electrical properties of the composites.

In case of J-ETPUPSt flexural property is increased to a considerable

level, while it decreased drastically for G-ETPUPSt. Both types of composites

showed moderate tensile property and electric strength; and good volume

resistivity. G-ETPUPSt showed approximately ten times volume resistivity.

Moderately good tensile and flexural properties are mainly due to moderate

adhesion between matrix and fiber materials. Similarly low electric strength

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and moderate volume resistivity of J-ETPUPSt is also due to polar free

hydroxyl groups present in jute fibers and matrix material. Moderate tensile

strength, flexural strength, and good volume resistivity of J-ETPUPSt and G-

ETPUPSt signify their importance as low load bearing housing units, in

electrical and electronic applications.

J-ETPMASt and G-ETPMASt showed respectively 1.4 and 1.3 times

more tensile strength as compared to J-ETPAASt and G-ETPAASt. Similarly

they showed respectively 2.1 and 5.7 times low flexural strength. J-ETPMASt

and G-ETPMASt showed 1.2 times electrical strength and 1.6 and 1.2 times

volume resistivity as compared to J-ETPAASt and G-ETPAASt. Thus methyl

substituent in vinyl ester reflected somewhat better mechanical and electrical

properties. This is due to different structure of the two vinyl esters and

difference in property. Mechanical and electrical properties of the composites

depend upon many facts such as nature of fibers and matrix, intrafacial

adhesion, degree of resin cure, test conditions, sample thickness, electrode

area and geometry, voltage application rate, imperfection, impurities, etc.

Moderate tensile strength, flexural strength, and good volume resistivity

signify their importance as low load bearing housing units, in electrical and

electronic applications.

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Table 5.3: Mechanical and electrical properties of jute and glass composites.

Composite Tensile

strength

(MPa)

Flexural

strength

(MPa)

Electrical

strength,

(kVmm-1)

Volume

resistivity

(Ohm cm)

J-ETPUPSt 21.7 31.9 1.8 2.7 x1014

G-ETPUPSt 138.3 29.5 2.2 2.1 x1015

J-ETPAASt 12.8 7.3 1.4 2.2 x1011

G-ETPAASt 131.2 17.4 2.5 9.2 x1011

J-ETPMASt 17.7 15.6 1.7 3.5 x1011

G-ETPMASt 166.7 99.8 3.0 1.1 x1012

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5.6 Chemical resistance study of composites

Chemical resistance of plastics is a complex subject. The test results

are often misinterpreted by engineers and designers. Material selection is

made without a proper understanding of the tests’ limitations and how the

results are derived. Extremely strong and tough plastic like polycarbonate has

limited applications because of its poor chemical resistance. Polypropylene,

on the other hand, has poor physical properties but is impervious to most

chemicals and solvents. The resistance of plastics to chemicals is best

understood through the study of its basic polymer structure. The type of

polymer bonds, the degree of crystallinity, branching, the distance between

the bonds, and the energy required to break the bonds are the most important

factors to consider, while studying the chemical resistance of plastic materials

[11]. For example, highly crystalline structure, lack of branching, and the

presence of very strong covalent bonds between carbon and fluorine atoms in

the main chain makes polytetrafluoroethylene resistant to almost all chemicals

and solvents. Similarly in the case of polyamides (nylons), the regular

symmetrical structure and the molecular flexibility that produces high

crystallinity and the presence of greater intermolecular forces help the

polymer to be rigid, strong, and resistant to chemicals.

Various models have been proposed for water absorption in

composites. It is well established that absorbed water in polymers and

composites plays a significant role in mechanical behavior and long term

durability. Assuming one-dimensional Fickian [12, 13] diffusion in composite,

an attempt has been made to determine diffusivity (Dx) in different

11. T. A. Richardson, Modern Industrial Plastics, Howard W. Sams and Co.,

Indianapolis, IN, p. 112, 1974.

12. Y. J. Weitsman, Fluid effects in polymers and polymeric composites,

Springer, New York, 2012.

13. T. A. Collings, Moisture absorption- Fickian diffusion kinetics and

moisture profiles. In Jones FR (ed) Handbook of polymer-fiber

composites. Horlow: Longman Scientific and Technical. 366, 1994.

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environments. Diffusivity is assumed to depend only on temperature and

independent of the moisture content as well as stress levels in composites.

For one-dimensional water absorption in semi-infinite plate exposed on both

sides to same environment, the amount of water absorbed is given by Eqn.

5.1:

5.1

Where Dx = diffusivity, t = time (second) and h = sample thickness (m)

The water content in the sample at time t can be determined according to

Eqn.5.2:

5.2

Where Mt = % water absorbed at time t, Wm = weight of moist sample and Wd

= weight of dry sample. The solution of diffusion equation in terms of % water

absorption is given by eqn.5.6:

5.3

Where Mm = equilibrium water content. Diffusivity in a given environment can

be determined from the initial slope of the plot of % M against t according to

Eqn. 5.4:

5.4

In present case assuming unidimensional Fickian diffusion, water

absorption in composites was carried in distilled water, 10% of aq HCl and

10% of aq NaCl at 35 oC by a change in mass method. Pre weighed samples

were immersed in distilled water, 10% of aq HCl and 10% of aq NaCl

solutions at 35 oC. Samples were periodically taken out from the solutions,

4 mx

M tM D

h π=

( )2

2

4xm

hD slope

Mπ

=

% 100W Wm dMt Wd

−= ×

( )( )2 2

22 20

2 18 11 exp

2 1x

J

j D tG

hj

ππ

∞

=

+= − −

+ ∑

Preparation…

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wiped with tissue papers, reweighed and reimmersed in the solutions. The

process was carried out till equilibrium was established.

The percentage weight gained by the composites in water, 10 % of aq.

HCl and 10 % of aq. NaCl solutions with the passage of time at 35oC is shown

in Figs. 5.2- 5.7. The % weight gained by each composite increased, reached

maximum and then practically remained constant, when equilibrium was

established in each of the environment. The equilibrium water content and the

equilibrium time for each of the composites in water, 10 % of aq. HCl, 10 %

aq. NaCl environments are recorded in Table 5.4. The observed trend in %

equilibrium water content in studied environments is HCl > H2O > NaCl.

Moreover practically no change in equilibrium water content is found in both

types of the composites with different vinyl esters. It is clearly observed that

water absorption in case of jute fiber reinforced composites is almost three

times than that of glass fiber reinforced composites due to large number of

polar hydrophilic –OH groups in jute fiber and matrix material. The effect of

electrolytes on water absorption is observed to some extent. The presence of

electrolytes in water affects water structure and hence water absorption

behavior as well as diffusivity of water in the composites.

Absorbed water in composites influences mechanical behavior, and

long-term durability of the polymer matrix composites. Water absorption in

composites is proved to be Fickian as well as non-Fickian in character.

Assuming one-dimensional diffusion, water absorption in semi-infinite plate

exposed to same environment was determined. Diffusivity in different

environments was determined by determining initial slope of the plot of Mt Vs

t1/2 and also summarized in Table 5.4. The solvation phenomenon is observed

in the present case, which influenced diffusivity of water in the composites.

Absorption of water in composites causes swelling of fibers till the cell walls

are saturated with water and beyond that water exists as free water in the void

structure leading to composites delamination or void formation. Absorbed

water causes weakening of the interfacial adhesion and hydrolytic

degradation of both matrix and fibers and hence deterioration of tensile

property. Cracking and blistering of fibers cause high water absorption, while

degradation causes leaching of small molecules.

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Table 5.4: Water uptake and diffusivity data of glass and jute composites at 35 oC and in boiling water

Environment Equilibrium

time (h)

%, Equilibrium

water content at

35oC

Diffusivity(Dx),

10-12 (m2s-1)

% Eqm.

water

content in

boiling

water

J-ETPAASt

H2O 192 15.0 11.30 16.04

10 % aq. NaCl 168 11.87 11.70 -

10 % aq. HCl 144 15.99 11.72 -

G-ETPAASt

H2O 168 5.95 0.22 8.15

10 % aq. NaCl 144 4.61 0.27 -

10 % aq. HCl 144 6.97 0.26 -

J-ETPMASt

H2O 192 15.0 9.04 16.1

10 % aq. NaCl 168 10.9 10.56 -

10 % aq. HCl 168 16.6 11.22 -

G-ETPMASt

H2O 144 5.6 1.36 6.7

10 % aq. NaCl 168 4.4 0.95 -

10 % aq. HCl 144 6.5 0.89 -

J-ETPUPSt

H2O 144 19 9.45 19.2

10 % aq. NaCl 168 16.3 10.19 -

10 % aq. HCl 168 21.3 7.49 -

G-ETPUPSt

H2O 96 9.2 4.29 9.7

10 % aq. NaCl 168 7.2 2.90 -

10 % aq. HCl 144 10.4 3.00 -

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Fig. 5.2. The plots of percent weight gain against time for J-ETPAASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.

Fig. 5.3. The plots of percent weight gain against time for G-ETPAASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.

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Fig. 5.4. The plots of percent weight gain against time for J-ETPMASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.

Fig. 5.5. The plots of percent weight gain against time for G-ETPMASt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35oC.

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Fig. 5.6. The plots of percent weight gain against time for J-ETPUPSt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.

Fig. 5.7. The plots of percent weight gain against time for G-ETPUPSt in H2O, 10% of aq. NaCl, 10% of aq. HCl at 35 oC.

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5.7 Water absorption in boiling water

Water absorption in composites mainly depends on temperature

besides presence of hydrophilic groups in composites. The percent weight

gain with the passage of time in boiling water for glass and jute composites

are presented in Figs. 5.8 and 5.9. From Table 5.4, it is clear that equilibrium

time is reduced to 28 times in case of J-ETPMASt, G-ETPMASt and J-

ETPAASt while equilibrium time decreased to 21 times in case of G-ETPAASt

and 29 times in case of J-ETPUPSt, while equilibrium time decreases to 16

times in case of G-ETPUPSt in boiling water as compared to 35 oC. Moreover

all the composites showed excellent hydrolytic stability even in harsh acidic

and saline environments confirming their applications in the field of marine.

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Fig. 5.8. The plots of percent weight gain against time for J-ETPMASt, G-ETPMASt, J-ETPAASt and G-ETPAASt in boiling water.

Fig. 5.9. The plots of percent weight gain against time for J-ETPUPSt and G-ETPUPSt in boiling water.

0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14

% W

t. C

han

ge

Time/ h

J-ETPMASt

G-ETPMASt

G-ETPAASt

J-ETPAASt

0

5

10

15

20

0 5 10 15

% W

t. C

han

ge

Time /h

J-ETPUPSt

G-ETPUPSt