ORIGINAL PAPER

Preparation and Characterization of Polyurethanesfrom Spinifex Resin Based Bio-Polymer

Subrata Mondal • Paul Memmott • Darren Martin

Published online: 29 January 2012

� Springer Science+Business Media, LLC 2012

Abstract In this paper we explore the preparation of

polyurethanes from spinifex resin biopolymer. Polyure-

thanes were prepared by both one-shot and pre-polymer

(two step) processes. Attenuated total reflection—Fourier

transform infrared analysis revealed urethane bond for-

mation in both processes, and the peak intensity for N–H

stretching was more sharp when the network was prepared

by the pre-polymer method. Gel permeation chromatogra-

phy revealed that the molecular weight of synthesized

polyurethane increased with respect to the resin starting

material, and the molecular weight was further increased

when polyurethane was synthesized by the pre-polymer

method. The glass transition temperature was also

increased for the polyurethanes as compared with the

starting resin. Thermo-gravimetric analysis revealed that

the thermal stability of the PU-spinifex resin was reduced

at intermediate temperatures due to the urethane bond

formation. However, thermal degradation properties were

superior at higher temperatures due to the cyclization

degradation reaction of spinifex-polyurethane.

Keywords Bio-polymer � Polyurethane � Spinifex resin �Synthesis � Thermoplastic

Introduction

Demand for polymeric materials in our daily life is

increasing constantly. With our growing population, issues

such as carbon footprint and solid waste disposal are

becoming increasingly critical to the market acceptability of

commercial materials. Consequently, there has been an

increased demand for cost-effective, bio-based products.

With this in mind, scientists are constantly exploring new

bio-based materials which could also potentially decom-

pose to harmless compounds when discarded. This

requirement for polymeric materials which are derived from

renewable resources is expected to increase rapidly [1–3].

Spinifex grasses belongs to the Triodia genus which

comprises over 69 native plant species mainly found in the

semi-arid regions of Australia, and covering at least 27% of

the Australian continent [4–7]. Triodia pungens is one of

27 resinous Triodia grass species that all exude a sticky

resin which is a mixture of volatile and non-volatile bio-

organic compounds. The resin mainly consists of second-

ary metabolites or compounds of terpenoid and/or phenolic

compounds [8]. It is therefore potentially an inexpensive,

abundant renewable polymer feedstock in Australia, and

has been widely manufactured by Australian Indigenous

people for centuries for both functional and ceremonial

purposes. Spinifex resins may be considered as thermo-

plastic bio-organic polymers with quite a low softening

temperature. However, detailed chemical analysis has

shown that additional mineral components and metal ions

(such as Ca2? and Na?) are attached with resin functional

groups [9]. Therefore, it is advantageous to perform acid

treatment to exchange these metal ions and provide more

functionality for reaction with external chemical molecules

to increase the glass transition temperature (Tg) of the

spinifex resin.

S. Mondal � D. Martin (&)

Australian Institute for Bioengineering and Nanotechnology,

The University of Queensland, Cnr College and Cooper Road,

St Lucia, QLD 4072, Australia

e-mail: darren.martin@uq.edu.au

P. Memmott

School of Architecture & Institute for Social Science Research

(ISSR), Aboriginal Environments Research Centre (AERC),

The University of Queensland, St Lucia, QLD 4072, Australia

123

J Polym Environ (2012) 20:326–334

DOI 10.1007/s10924-012-0417-6

Polyurethanes are formed by the reaction of isocyanate

and hydroxyl group containing compounds. Very versatile

chemistry and a wide choice of raw materials available for

the urethane chemist [10, 11] enable the synthesis of a

broad variety of polyurethane products with specific

properties. Polyurethane copolymers have excellent tensile

strength, tear strength and abrasion resistance, and are

widely used in film, foam, fibres, coatings, adhesives and

many other products. The vast majority of polyurethane

polymers are based on polyols derived from petrochemi-

cals. As an alternative for petroleum-based feedstock, some

companies and researchers are exploring and developing

bio-based polyols based on plant oils or similar renewable

compounds [12–24]. Acetone extracted resin from threshed

spinifex resin mixture is quite soft and sticky at ambient

temperatures, but the spinifex resin which is threshed and

thermally treated by Australian Indigenous people for

manufacturing traditional artifacts, contains plant fibres

and possibly other mineral fillers which appear to elevate

the glass transition point so that it sets hard at ambient

temperatures.

The objective of this research is to prepare polyurethane

(PU) from spinifex resin based biopolymer. PU from the

spinifex resin was prepared by both one shot and pre-

polymer (two step) methods. In the one-shot method,

extracted resin material incorporating—OH functional

groups was reacted with 1,6-diisocyanatohexane. In the

two-step (pre-polymer) process, spinifex resin biopolymer

was reacted with excess 1,6-diisocyanatohexane, and the

isocyanate end-capped resin pre-polymer was further

reacted with ethylene glycol. The physical properties of the

resin and the resultant PU were characterized by diamond

‘attenuated total reflection—Fourier transform infrared’

(ATR-FTIR) analysis, ‘inductively coupled plasma—opti-

cal emission spectroscopy’ (ICP-OES), and ‘gel perme-

ation chromatography’ (GPC) techniques. ‘Differential

scanning calorimetry’ (DSC) was employed to characterize

the glass transition behavior of the materials. Further,

thermal degradation properties of resin and their PU

structure were characterized by ‘thermo-gravimetric’ (TG)

analysis.

Experimental Methods

Materials

Acetone was used to extract the spinifex resin biopolymer

from the threshed resin, soil, chaff and mineral mixture.

The detailed extraction procedure is described elsewhere

[9]. Resin was vacuum oven dried at 35 �C for 24 h before

use. Ethylene glycol (EG) was vacuum oven dried at 60 �C

for 3 h prior to use. N,N-dimethylformamide (DMF) was

obtained from auto solvent purifier (MBRAUN MB SPS-

800, Germany) and used as solvent for polyurethane syn-

thesis. Stannous octoate (catalyst) was dried over molec-

ular sieves and 1,6-diisocyanatohexane (HDI) was used as

received. Hydrochloric acid used in this study was labo-

ratory reagent grade.

Polyurethane Synthesis

Extracted spinifex resin bio-polymer was treated with 1

(M) hydrochloric acid for 24 h in order to release some of

the inorganic elements compounded within the resin matrix

so as to obtain more functional groups for reaction with

diisocyanate. Acid treated bio-polymeric resin was vacuum

oven dried to remove any residual moisture and volatile

content before being used for polyurethane synthesis.

Polyurethane polymer preparations were carried out by

one-step and two-step processes. In the synthesis process

the acid-treated spinifex resin was reacted with 1,6-diiso-

cyanatohexane to form either a PU (one-step) or PU pre-

polymer (two-steps), and ethylene glycol was used for

chain extension of the pre-polymer prepared for the two-

step method under continuous stirring by mechanical stir-

rer. The proposed polyurethane formation by the one-shot

and the pre-polymer (two-step) processes is shown sche-

matically in Fig. 1. In a typical one shot process, acid-

treated spinifex resin material was reacted with 1,6-diiso-

cyanatohexane at 80 �C for 6 h in the presence of a stan-

nous octoate catalyst (approximate 0.1% w/w of feed)

under nitrogen atmosphere. In the pre-polymer method,

spinifex resin was reacted with excess 1,6-diisocyanato-

hexane for 3 h at 80 �C in nitrogen atmosphere to obtain an

isocyanate end-capped pre-polymer, and in next step, the

isocyanate end groups were further reacted with hydroxyl

group containing ethylene glycol at the same temperature

for another 3 h to complete the polyurethane formation

process. N,N-dimethyl formamdie used as solvent was

added in the reaction mixture when the viscosity of the

mixture was too high. Solvent (N,N-dimethyl formamdie)

was removed from polyurethane solution at 85 �C for

3 days under nitrogen purge. Sample identification of spi-

nifex resin and their PU network compositions are pre-

sented in Table 1.

Characterizations

Spinifex resin biopolymer and its polyurethane products

were characterized by inductively coupled plasma—optical

emission spectroscopy (ICP-OES), attenuated total reflec-

tion Fourier transform infrared (ATR-FTIR) spectroscopy,

gel permeation chromatography (GPC), differential scan-

ning calorimetry (DSC) and thermogravimetry (TG) anal-

ysis. All the samples were dried at 35 �C under vacuum for

J Polym Environ (2012) 20:326–334 327

123

48 h to remove any residual moisture and solvent before

further characterization.

Elemental analysis of the spinifex resin and the solution

after acid treatment was determined using inductively

coupled plasma-optical emission spectroscopy (ICP-OES)

on a Varian Vista Pro ICPOES instrument. A known

amount of sample was digested using EPA protocol 3052.

The FT-IR spectra of spinifex resins and their polyure-

thane samples were tested and corrected by appropriate

background by using a Nicolet 5700, diamond ATR-FT-IR

in absorbance mode over a wave number range of

400–4,000 cm-1 at a resolution of 4 cm-1 and all spectra

were average of 128 scans. OMNIC Nicolet software was

used for spectral analysis.

Molecular weights (weight average, Mw and number

average, Mn) and their distribution (polydispersity index,

PDI = Mw/Mn) were determined by gel permeation chro-

matography (GPC) techniques using a Waters Alliance

2690 Separations Module attached with an auto-sampler,

column heater, differential refractive index detector, and a

photodiode array (PDA) connected in series. GPC grade

tetrahydrofuran (THF) was used as eluent at a flow rate of

1 mL/min and with a total injection volume of 50 lL. The

column apparatus consisted of three 7.8 9 300 mm Waters

Styragel GPC columns connected in series, comprising

two linear UltraStyragel and one Styragel HR3 column

types. Poly (styrene) standards ranging from 1,000 to

2 9 106 g mol-1 were used for calibration.

Thermal analysis of the resin and resin-based PU sam-

ples was performed by a Mettler Toledo DSC1 Star System

calorimeter with a sub-ambient temperature attachment.

The heating rate was 10 �C/min and all samples were

scanned from -100 �C to 100 �C in a nitrogen atmosphere.

A sample weight in the range of 5–10 mg was taken for all

measurements. Glass transition temperature (Tg) as a

thermal transition temperature of polymeric materials was

identified by the base line shift of the DSC curves.

Fig. 1 Schematic of PU branch formation in one shot and pre-polymer process

Table 1 Chemical composition of polyurethane and resin samples

Samples Weight content (% w/w) Gel permeation

chromatography

Spinifex resin HDI EG Mw Mn PDI

SR 100 – – 1,557 1,231 1.27

SR-A 100 – – 1,519 1,212 1.25

SR-PU1 79 21 – 2,444 1,684 1.45

SR-PU2 62.5 25 12.5 3,068 1,897 1.62

Mw weight average molecular weight, Mn number average molecular

weight, PDI polydispersity index, SR original resin, SR-A acid treated

resin, SR-PU1 PU prepared by one shot method, SR-PU2 PU pre-

pared by two steps process

328 J Polym Environ (2012) 20:326–334

123

Thermal degradation properties of the resin and their

polyurethane samples were measured by a Mettler Toledo

(TGA/DSC 1) stare system thermal analyzer. The thermal

degradation temperatures were reported at which 5 wt%

(Td5%), 10 wt% (Td10%) and 35 wt% (Td35%) of weight loss

of the respective samples would occured. Sample weight

for the TGA experiments was 5–10 mg and all sam-

ples were scanned from 30 to 500 �C at a heating rate of

10 �C/min under nitrogen atmosphere. Maximum degrada-

tion temperatures for all resin samples were identified from

differential thermo-gravimetric analysis (DTA) curves.

Results and Discussion

Physical Properties of Resin and their PU Networks

Gel permeation chromatography data for spinifex resin and

their polyurethane products are presented in Table 1. The

molecular weight of polyurethane network increased when

compared with the as-extracted (SR) and acid treated

(SR-A) spinifex resin biopolymer. With regards to the

polyurethane structure formation resulting from the reac-

tion of acid treated spinifex resin with diisocyanate, it

appears that chain branching (rather than crosslinking)

appears to be occurring (Fig. 1), as the prepared polyure-

thane products are easily soluble in common solvents such

as tetrahydrofuran. The polydispersity index (PDI) data

showed support this observation. Low PDI values for all

PU resin samples are most likely due to the collapsing of

polymer chains in THF as samples contained significant

proportion of inorganic substances and hence the capacity

for additional metal ion complexing. The molecular weight

of polyurethane network prepared by the pre-polymer

method was higher than the polyurethane network prepared

by the one-shot method, hence this finding fits well with

our hypothesis presented in Fig. 1 that urethane linkages

effectively couple to spinifex resin-OH groups. The PDI of

SR-PU2 is higher than the PDI of SR-PU1, hence, more

chain branchings are occurring for the polyurethane pre-

pared by the two-steps prepolymer method.

The major inorganic elemental components of spinifex

resin bio-polymer and the acid-treated resin sample are

presented in Table 2. Inductively coupled plasma (ICP)

analysis results demonstrated that before acid treatment,

the resin (SR) incorporated a high concentration of Mn, Al,

Ca, Fe, Mg, Na, Si, S, P etc. These elements are the

metabolite compounds of the micro-nutrients absorbed by

the spinifex grass during growth as well as from air-borne

mineral elements which are blown on to the resin as dust

before collection [9]. The plant roots uptake the majority of

nutrients and micro-nutrients [25]. Mobile mineral ele-

ments are dispersed in ground water and are taken up by

the plant roots for photosynthesis. Plants first solubilise

these elements, and then transport them to the surface tis-

sues of leaves (and we presume also, into the resin poly-

mer). In this process, plant root tips which have a weak

atomic charge are slightly acidic in nature, can exchange

H? ions for metal cations viz. Ca, Al, Fe, Na, Zn etc.

[9, 25–27]. During the acid treatment of the resin, some of the

functional groups re-form by reverse ion exchange of metal

cation with H? in acidic solution (Fig. 2). In this process we

observe more hydroxyl and carboxylic functional groups in

spinifex resin biopolymer. ICP analysis of solution shows

some metallic ion content after acid treatment as reported in

Table 2; hence a successful acid treatment to release some of

the resin functional groups has occurred.

Chemical groups within a compound could be identified

by attenuated total reflection Fourier transform infrared

(ATR-FTIR) spectroscopy. When infrared radiation is

passed through a polymeric material at a characteristic

frequency, the molecule will absorb the energy and vibrate

at a number of different modes such as stretching and

bending, therefore, a number of peaks appear due to the

presence of particular chemical structures [28]. Various

moieties in the spinifex bio-polymers and their PU are

shown in Fig. 3, and peak assignments with corresponding

wave numbers are presented in Table 3. From Fig. 3a and

Table 3, we can see the appearance of a sharp hydroxyl

Table 2 Major elemental composition of spinifex resin and their

polyurethane products

Unit (mg/kg or L (for solution))

Elements SR SR-A Solutiona

Ca 1,438 617 5.82

Al 3,250 1,652 29

Fe 347 221 0.21

K 268 293 0.52

Mg 221 32 1.17

Mn 15 16 0.02

Na 580 295 6.5

S 885 762 0.3

Si 1,350 797 0.88

a Few milliliter of water solution after resin separation was sent for

ICP analysis

Fig. 2 Formation of hydroxyl groups in acidic condition by release

of Ca and Na ion compounded with spinifex resin functional groups

J Polym Environ (2012) 20:326–334 329

123

group (*3,450 cm-1) signature after acid treatment. This

hydroxyl group stretching peak disappears when the resin

material is reacted with 1,6-diisocyanatohexane, which

demonstrates successful polyurethane formation. Some

new peaks also appear in the PU spectra, such as peaks for

N–H stretching at around 3,340 cm-1 due to the urethane

and amide linkage formation. The isocyanate group of 1,6-

diisocyanatohexane could react with hydroxyl groups in

the resin to form urethane linkages (Fig. 1). Free isocya-

nate groups could also react with carboxylic functional

groups in the resin to form possible amide groups as shown

in Eq. 1. The spectra for the pre-polymer (SR-PU2-Pre)

shows a sharp peak at around 2,270 cm-1 due to the

presence of un-reacted isocyanate end groups. However,

FTIR spectra of SR-PU2 revealed that when this pre-

polymer was further ‘chain extended’ with ethylene glycol,

the peak at around 2,270 cm-1 disappeared, and hence PU

branch formation was achieved .

A close inspection of carbonyl stretching region

(Fig. 3b) revealed that the original resin and the acid-

treated resin both displayed sharp peaks for the free (non-

hydrogen bonded) carbonyl group. In the PU, prepared by

the one-shot process, the hydrogen bonded and non-

hydrogen bonded carbonyl groups were split into two equal

intensity peaks, showing that hydrogen bonded and non-

hydrogen bonded carbonyl groups co-existed in the branch

structure. In other words, when the PU branch structure

was prepared by the pre-polymer method, the hydrogen

bonded carbonyl group peak was sharpened and the non-

hydrogen bonded peak for carbonyl peak disappeared due

to the extensive hydrogen bonding of carbonyl groups with

the (N–H) group of the newly-formed urethane and amide

linkages. In the pre-polymer method, a larger number of

urethane linkages would have formed, as shown schemat-

ically in Fig. 1, and these urethane linkages would have

formed strong hydrogen bonding with the carbonyl groups

as indicated by the disappearance of the non-hydrogen

bonded C=O stretching peak in the FTIR spectra.

Glass Transition Behavior

Glass transition temperature (Tg) is the temperature at

which polymers undergo transformation, when they are

heated, from a glassy to a rubbery state and vice versa.

Polymer molecules which are effectively frozen below

glass transition temperature become free to rotate above Tg,

therefore, it is not surprising that the value of Tg will

depend upon the physico-chemical structure of the polymer

molecules/networks [29]. The Tg onset, midpoint and

endset points for spinifex resin and PUs are reported in

Table 4 and shown in Fig. 4. The onset temperature of Tg

signifies dramatic change in the physical properties of the

polymer such as stiffness, strength and toughness, heat

capacity and thermal expansion co-efficient etc. Figure 4

shows the heating cycle DSC of thermo-gram for spinifex

resin and associated PU network samples. Analysis of these

data revealed a slight decrease in Tg of the resin sample

after acid treatment (SR-A). Interaction of pure resin

functional groups with mineral elements seems to be the

reason for this higher Tg of extracted resin (SR). During the

extraction process, metallic elements could associate with

the resin matrix by covalent and metal complex bonding,

and these mineral elements (such as Na, Al, Fe and Si

which have atomic radii of 0.223, 0.182. 0.172 and

0.146 nm, respectively) may act to increase cohesion in the

resin matrix and subsequently would reduce the segmental

mobility of polymer chains as result of the higher glass

transition temperature of extracted resin sample (SR).

During the acid treatment, some of the functional groups of

resin could re-form by reverse ion exchange of metal cat-

ions with H? in acidic solution, as discussed in detail in the

ICP analysis section [see earlier]. The breaking of the

‘mineral element—resin functional groups’ bonding [9]

and the release of mineral elements from the resin matrix,

would allow more chain movement and result in a lower

Tg. Glass transition temperature typically increases in cases

of PU with increased urethane component due to the strong

urethane bond formation and the corresponding increase in

hydrogen bonding as discussed in FTIR results. The mea-

sured Tg of the PU network formed by the pre-polymer

method is higher than that of the PU formed by the one shot

method. In the pre-polymer method, more urethane groups

(Fig. 1) are formed which could form hydrogen bonding in

the resin matrix. This excess hydrogen bond formation

could act as physical cross-links and form three-dimen-

sional network structures.

1

330 J Polym Environ (2012) 20:326–334

123

Thermal Degradation Properties

Thermal degradation of polymers can occur by either

chain end-degradation or random degradation routes [30].

Chain end-degradation, which is also known as de-poly-

merization, starts from the end of the chain and succes-

sively ‘‘unzips’’ the monomer units; whereas, random

degradation would occur at any point along the polymer

chains. It seems to us, that spinifex resin and its PU

structures would most likely follow the random route of

thermal degradation. The thermal stability of spinifex

resin samples (extracted and acid treated) and their PU

structures were analyzed by TGA under a non-oxidative

environment (nitrogen atmosphere). TGA and DTA

curves showing the percentage of weight loss and rate of

mass loss, respectively, with respect to temperature

change are given in Figs. 5 and 6, and relevant data are

presented in Table 5. From Fig. 5, it can be observed that

under a non-oxidative atmosphere there appears to be

significant differences in the initial and final degradation

behavior of resin and PU. Acid treated resin (SR-A)

displays a slightly lower onset degradation as compared

with the extracted resin (SR), due to the release of

inorganic elements which would act to increase cohesion

(as discussed in detail in Tg behavior). Improvements to

thermal stability of other polymeric materials by rein-

forcement with inorganic nano-filler are currently being

studied by the researchers. Inorganic elements in the bio-

organic polymer render a ‘barrier effect’ which delays

the release of thermal degradation products in comparison

to the pure polymer [31–33]. The TGA data of acid

treated spinifex resin (SR-A) and its PU branch structures

revealed that the thermal stability of the PU was reduced

at intermediate temperatures (inset in Fig. 5) due to the

1000 1500 2000 2500 3000 3500

A

~3450 cm-1~3340 cm-1

2267 cm-1

SR-PU2

SR-PU1SR-PU2-P

SRSR-A

Abs

orba

nce

Wavenumbers (cm-1)

B

Fig. 3 a ATR-FTIR spectra of spinifex resin bio-polymers and their

polyurethanes products; b Carboxylic groups stretching of spinifex

resin and polyurethane products

Table 3 Characteristics of major absorption peaks of spinifex resin and their polyurethane products

Wave numbers (cm-1) Peak assignments SR SR-A SR-PU1 SR-PU2 SR-PU2-P

*3,450 t (OH) for alcohol and/or carboxylic acid H H

3,327–3,338 t (N–H) bonded N–H H H H

2,860–2,926 t (C–H) of sp2 hybridized H H H H H

2,269 t (CNO) H

1,705–1,715 t (C=O), Free H H H H H

1,665 t (C=O), Hydrogen bonded H H H

1,523–1,527 d (N–H) ? t (C–N) H H H

1,456–1,458 r (CH2) H H H H H

1,224–1,250 d (CH3) H H H H H

1,145–1,170 t (C–O–C) H H H H H

1,030–1,095 t (C–O–C) H H H H H

t = stretching; d = bending; r = rocking, H = indicates presence of peaks that were observed in the spectra

J Polym Environ (2012) 20:326–334 331

123

urethane bond formation, as the urethane linkage under-

goes trans-urethanisation above *150 �C. However,

improved thermal stability of PU branch structures at

elevated temperatures may be indicative of cyclization

reactions of secondary stage degradation. The overall

thermal stability of polymeric materials depends on pre-

dominant chain formation and the rearrangement of

functional groups in the polymers backbone structures

[34]. DTA data analysis revealed that a two-stage deg-

radation process occurs for spinifex resin samples; how-

ever, multi-steps degradation occurs for PU branch

structures due to the various bond formations (urethane,

amide etc.) made possible by the reaction of isocyanate

groups with resin functional groups. Maximum degrada-

tion temperature (TMax2) shifted to higher temperature for

PU branch structures as compared with its as-extracted

resin materials. It is evidenced from the TGA and DTA

data that both the maximum rate of degradation and the

final degradation of spinifex resins are affected by PU

branch structure formation.

Table 4 Glass transition behavior of spinifex resin and their poly-

urethane products

Samples Tg-onset

(�C)

Tg-midpoint

(�C)

Tg-endpoint

(�C)

DTg-range

(�C)

SR -1.40 8.64 17.42 18.82

SR-A -3.98 -0.50 7.0 10.98

SR-PU1 12.06 25.78 35.70 23.64

SR-PU2 26.9 32.22 38.07 11.17

-75 -50 -25 0 25 50 75 100

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

-3

-2

-1

0

1

SR

Tg

End

o, H

eat

Flo

w (

mW

)

SR-A

Tg

SR-PU1

Tg

End

o, H

eat

Flo

w (

mW

)

End

o, H

eat

Flo

w (

mW

)E

ndo,

Hea

t F

low

(m

W)

SR-PU2

Tg

Temperature (°)

-75 -50 -25 0 25 50 75 100

Temperature (°)-75 -50 -25 0 25 50 75 100

Temperature (°)

-75 -50 -25 0 25 50 75 100

Temperature (°)

Fig. 4 Heating thermo-gram of spinifex resin and their polyurethane products

Fig. 5 Thermal degradation properties of spinifex resin and their PU

branch structure

332 J Polym Environ (2012) 20:326–334

123

Conclusions

ATR-FTIR analysis revealed urethane bond formation in

prepared polyurethanes and the peak intensity for N–H

stretching was more pronounced for polyurethane prepared

by the two-steps method. GPC revealed that the molecular

weight of synthesized polyurethane increased with respect

to the resin starting material, and the molecular weight of

polyurethane prepared by the two-step method is higher

than the polyurethane prepared by the one-shot process.

The glass transition temperature was also increased for the

polyurethane as compared with the starting resin. Urethane

linkage formation reduces the thermal stability of PU-spi-

nifex at intermediate temperatures due to the trans-ureth-

anisation of urethane above *150 �C.

Acknowledgments This research was funded by ARC Discovery

Grant No DP0877161. Dr. Subrata Mondal would like to acknowl-

edge The University of Queensland’s Postdoctoral Research Fellow-

ship. We acknowledge our Indigenous collaborator, Dugalunji

Aboriginal Corporation in Camooweal for the supply of resin samples

and for the provision of insights into the traditional technology of

spinifex resin manufacture.

References

1. Tsai FJD, Wertheim BC (2001) USA Pat 6(218):009

2. Doke SS, Garag KV (2003) J Text Assoc 64:111–115

3. Karekatti CK, Belkhode P (2003) Synth Fibres 32:14–17

4. Griffin GF (1990) J Veg Sci 1:435–444

5. Valis S (1991) AICCM Bull Aust 17(1&2):61–74

6. Parr JF (2002) Econ Bot 6:260–270

7. Memmott P, Flutter N, Penny M (2009) Cultural crossroads: 26th

international conference of the society of architectural historians,

Australia and New Zealand, 2–5 July

50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500

50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350 400 450 500

SR

dm/d

t

Temperature (°)

Temperature (°) Temperature (°)

Temperature (°)

SR-A

dm/d

t

SR-PU1

dm/d

t

SR-PU2

dm/d

t

Fig. 6 Derivative of thermal degradation of spinifex resin and their PU branch structures

Table 5 Thermal degradation properties of spinifex resin and their

polyurethane products

Samples Td5%

(�C)

Td10%

(�C)

Td35%

(�C)

TMax

(�C)

Char yield (%)

at 500 �C

SR 208.5 237.7 305.9 304.5 5.1

SR-A 195.4 232.7 306.9 311 4.4

SR-PU1 189.4 213.6 323 444 6.6

SR-PU2 198 227.7 336 446 3.2

J Polym Environ (2012) 20:326–334 333

123

8. Langenhleim JH (2003) In: Plant resin: chemistry, evolution,

ecology, and ethnobotany, chap 1, Timber Press, Cambridge

9. Mondal S, Memmott P, Wallis L, Martin D (in press) Mater

Chem Phys

10. Krishnan S (1992) J Coat Fabr 22:71–74

11. Goldsmith J (1998) J Coat Fabr 18:12–25

12. Palaskar DV, Boyer A, Cloulet E, Alfos C, Cramail H (2010)

Biomacromolecules 11:1202–1211

13. Kong X, Yue J, Narine SS (2007) Biomacromolecules 8:

3584–3589

14. Ferrao MF, Godoy SC, Gerbase AE, Mello C, Furtado JC,

Petzhold CL, Poppi RJ (2007) Anal Chim Acta 595:114–119

15. John J, Bhattacharya M, Turner RB (2002) J Appl Polym Sci

86:3097–3107

16. Wang CS, Yang LT, Ni BL, Wang LY (2009) J Appl Polym Sci

112:1122–1127

17. Chian KS, Gan LH (1998) J Appl Polym Sci 68:509–515

18. Hu YS, Tao Y, Hu CP (2001) Biomacromolecules 2:80–84

19. Sharmin E, Ashraf SM, Ahmed S (2007) Int J Biol Macromol

40:407–422

20. Deka H, Karka N (2009) Prog Org Coat 66:192–198

21. Desai SD, Patel JV, Sinha VK (2003) Int J Adhesion Adhesives

23:393–399

22. Lu YS, Larock RC (2008) Biomacromolecules 9:3332–3340

23. Hojabri L, Kong X, Narine SS (2009) Biomacromolecules

10:884–891

24. Liigadas G, Ronda JC, Galia M, Cadiz V (2007) Biomacromol-

ecules 8:1858–1864

25. Reid N, Hill SM, Lewis DM (2008) Appl Geochem 23:76–84

26. Lintern MJ, Butt CRM, Scott KM (1997) J Geochem Explor

58:1–14

27. Hulme KA, Hill SM (2003) Adv Regolith 2003:205–210

28. Lamba NMK, Woodhouse KA, Cooper SL (1998) Polyurethanes

in biomedical applications. CRC Press, Boca Raton, pp 43–89

29. Young RJ, Lovell PA (1991) Introduction to polymers, 2nd edn.

CRC Press, Boca Raton, pp 292–300

30. Singh B, Sharma N (2008) Polym Degrad Stab 93:561–584

31. Cervantes-Uc JM, Espinosa JIM, Cauich-Rodrıguez JV, Avila-

Ortega A, Vazquez-Torres H, Marcos-Fernandez A, Roman JS

(2009) Polym Degrad Stab 94:1666–1677

32. Berta M, Lindsay C, Pans G, Camino G (2006) Polym Degrad

Stab 91:1179–1191

33. Moon SY, Kim JK, Kim JK, Nah C, Lee YS (2004) Eur Polym J

40:1615–1621

34. Ni N, Yang L, Wang CS, Wang LY, Finlow DE (2010) J Therm

Anal Calorim 100:239–246

334 J Polym Environ (2012) 20:326–334

123