condensation polymers from natural oils
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Progress in Polymer Science 33 (2008) 1199–1215
Contents lists available at ScienceDirect
Progress in Polymer Science
journa l homepage: www.e lsev ier .com/ locate /ppolysc i
ondensation polymers from natural oils
inay Sharma, P.P. Kundu ∗
epartment of Chemical Technology, Sant Longowal Institute of Engineering and Technology, Sangrur, Punjab 148106, India
r t i c l e i n f o
rticle history:eceived 23 August 2007eceived in revised form 1 June 2008ccepted 1 July 2008vailable online 23 August 2008
eywords:oybean oilastor oilahar seed oilolyolsondensation polymersolyurethanesolyesters
a b s t r a c t
Innovative technologies and competitive industrial products are reducing the dependenceon petrochemicals for the production of polymers. Increasing concerns about the deteri-orating environment caused by conventional polymers have directed worldwide researchtoward renewable resources. Vegetable oils are one of the most readily available alterna-tive renewable resources. The functional groups present in natural oils can be activatedfor condensation polymerization. Accordingly, various types of useful condensation poly-mers, such as polyurethanes, polyesters and polyethers, are being produced by this route.The incorporation of natural oils into the polymer chain allows tailoring the properties ofpolyurethane products, for their widespread applications.
© 2008 Published by Elsevier Ltd.
ontents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11991.1. Polyols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12001.2. Polyurethanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1200
2. Polymers based on soybean oil polyols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12003. Polymers and IPNs based on castor oil polyols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205
3.1. Polymers based on castor oil polyols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205
3.2. Interpenetrating and semi-interpenetrating networks based on castor oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1209. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1212. . . . .. . . . .. . . . .
4. Polymers based on nahar seed oil polyol . . . . . . . . . . . . . . . . . . . . .5. Other polymers based on oil polyols . . . . . . . . . . . . . . . . . . . . . . . . . .6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction
Since the synthesis of polyurethanes by Bayer in937 [1], their utilization has become ubiquitous. Theseolymers are synthesized by reacting three basic compo-ents: polyisocyanate, polyhydroxyl containing polymer
∗ Corresponding author.E-mail address: [email protected] (P.P. Kundu).
079-6700/$ – see front matter © 2008 Published by Elsevier Ltd.doi:10.1016/j.progpolymsci.2008.07.004
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1213
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1214
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1214
(i.e., polyester or polyether polyol) and a chain extender(usually a low molecular weight diol or diamine). Cur-rently, the majority of polyols (polyether and polyesterpolyols) is derived from petrochemicals, a resource sub-ject to depletion. Hence, bio-based materials are receivingwide attention as the oil crisis and threat of global warming
deepen. The synthesis of bio-based materials from naturaloils affords an alternative route [2–4] to natural oil-basedaddition polymers, which we discussed in an earlier review[5].
in Polym
1200 V. Sharma, P.P. Kundu / ProgressVegetable oils are becoming extremely important asrenewable resources for the preparation of polyols requiredfor the polyurethane industry. Polyols from natural oils,such as soybean, castor, and palm oils are increasingly beingviewed by industry as a viable alternative to hydrocarbon-based feedstocks. These oils are annually renewable, andare cost-competitive as well as environment friendly.According to a market summary published by the UnitedSoybean Board in February 2000, vegetable oil-basedpolyurethanes are best suited to three markets namely:polyurethane foams, polyurethane binders and agriculturalfilms (the last may not be polyurethanes). Currently, thetotal U.S. annual market size is approximately 3000 millionpounds for polyurethane foams and 400 million poundsfor polyurethane binders and fillers. The introduction ofnatural oils as polyols into the polyurethane supply chaincan provide an opportunity for polyurethane suppliers andcustomers to reduce their dependence on natural gas andcrude oil, whose highly volatile and increasing costs con-tinue to make it difficult for them to compete.
Vegetable oils are excellent renewable source of rawmaterials for the manufacture of polyurethane componentssuch as polyols. The transformations of the double bondsof triglycerides of oils to hydroxyls and their application inpolyurethanes have been the subject of many studies [6].The main technological advantages of these polyurethanesfrom vegetable oils are high strength as well as stiffness,environmental resistance and long life.
1.1. Polyols
Oil-based polyols are often oligomers with a wide dis-tribution of molecular weights and a considerable degreeof branching, which affect the viscosity and processingproperties of polyurethane foams produced from them.Precise characterization of the polyol composition and itsproperties are very important for understanding syntheticprocesses as well as for quality control. Polyols are a compo-nent in the production of polyurethanes used in appliances,automotive parts, adhesives, building insulation, furniture,bedding, footwear and packaging. Although, polyols arecurrently produced from petroleum, vegetable oils are alsoused extensively for their production. The vegetable oilmolecules must be chemically transformed in order toobtain hydroxyl moieties. For example, soybean oil doesnot contain hydroxyl groups, but it has an average of 4.6double bonds per molecule. The unsaturated portion of theoil can be converted to hydroxyl groups.
1.2. Polyurethanes
Polyurethanes (PU) are polymers containing urethanelinkages (–NHCOO–) in the main polymer chain. They canbe classified in the following major groups: (a) flexiblefoams, (b) rigid foams, (c) elastomers, (d) fibers, (e) moldingcompositions, (f) surface coatings and (g) adhesives.
Depending upon the degree of cross-linking,polyurethane foams may be flexible or rigid. Polyesterpolyols used in the foams are based on industrial wastestreams of polyester and depolymerized PET from scrapbottles. Flexible foam is based on a flexible aliphatic
er Science 33 (2008) 1199–1215
polyester polyol (such as adipic polyester resin) and rigidfoam is prepared from aromatic polyester polyol, e.g.depolymerized PET.
The biggest challenge for the production of PU usingpolyols from natural oils is the variation of the unsatura-tion content among natural oils. If the double bond contentin natural oils is not properly controlled, the nature of thepolyol will be changed, affecting the performance of thefinal polyurethane product. Polyurethane foam finds appli-cation as one of the most effective insulating materials.Blowing agents are generally used to create a fine cellu-lar foam structure. Upon dissociation the blowing agentgenerates gases, which are trapped within the small cells(or closed cell) of the foam. This enhances the insulatingproperties of the PU foam.
2. Polymers based on soybean oil polyols
Petrovic and co-workers [7] studied polyurethanefoams-based on soybean oil. They prepared bothhydrochlorofluorocarbon (HCFC) and pentane blownrigid polyurethane (PU) foams from polyols derived fromsoybean oil. The effect of process variables on foam prop-erties was studied by varying the amounts and types ofcatalyst, crosslinker, blowing agent, surfactant and water.The foams prepared from these polyols were found to havemechanical and insulating properties such as compressivestrength and thermal strength comparable to those ofcommercially available polypropylene oxide (PPO)-basedfoams. The commercial PU foams derived from PPO-basedtriols have the disadvantages of thermal degradationand thermal oxidation. It was observed that the soybeanpolyol derived PU foams were more stable. Comparativethermo-gravimetric analysis (TGA) of PU foams-based onPPO triols and soybean polyols in air and in nitrogen N2 isshown in Fig. 1. In air (Fig. 1b), both the PU samples fromPPO and soy polyol show higher weight loss, comparedwith the thermo-gravimetric loss in nitrogen (Fig. 1a).The weight loss of up to 5% is important as PUs are neverused beyond this weight loss level because of substantialdeterioration in mechanical and other properties. The PUsfrom soy polyol were observed to be more stable thanthose from PPO-based polyol at around 200 ◦C, where theweight loss was less than 5%.
Petrovic and co-workers [8] studied the thermal sta-bilities of PU-based on various vegetable oils. They usedTGA and Fourier-transform infra-red (FTIR) spectroscopyfor thermal analysis of the polymers. In TGA, PPO-basedPU showed single-stage degradation, while the vegetableoil-based PUs degraded in two stages. The isothermal (at250 ◦C) thermo-gravimetric loss of PPO-PU, SOY-PU andcastor-PU versus time is shown in Fig. 2. The PU from PPO(arcol, as shown in Fig. 2) was more stable at 250 ◦C thanthe PUs from soy and castor polyol. The degradation pat-tern with temperature of these three PUs derived from PPO,castor and soybean oils are shown in Fig. 3. This figure
shows four derivative peaks for oil-based and two peaksfor PPO-based PUs. The temperature for initial degradationup to 10% by weight was almost the same for all PUs. Theresidue at 500 ◦C appeared to correlate with the amount ofisocyanate in the polymer, except for PPO-based PU. From
V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215 1201
Fig. 1. Thermal behavior of soybean oil polyol based foam versus PPO-based fopermission of John Wiley and Sons, Inc.
Fig. 2. Isothermal TGA curve at 250 ◦C of three polyurethanes in nitrogen.Reproduced from Javni et al. [8] with permission of John Wiley and Sons,Inc.
Fig. 3. Derivative TGA curves of PPO-based PU, castor-based PU andsoybean-based PU in air. Reproduced from Javni et al. [8] with permissionof John Wiley and Sons, Inc.
am: (a) TGA in N2. (b) TGA in air. Reproduced from Guo et al. [7] with
Fig. 3, the PPO-based PU showed the fastest rate of weightloss and the smallest residue at 300 ◦C. On the other hand,at the same temperature the oil-based PUs were thermallymore stable than PPO-based PU. From these studies, Petro-vic et al. proposed three mechanisms of decomposition ofurethane bonds, as shown in Scheme 1. All three reactionsmay proceed simultaneously.
The Petrovic group [9] also studied the structure andproperties of PUs prepared from halogenated as well asnon-halogenated soybean polyols. They determined thestructure and properties of these polymers by spectro-scopic, chemical and physical methods. In this study, theymodified epoxidized soybean oil (ESBO) with hydrochloricacid, hydrobromic acid, methanol and hydrogen. The effectsof these modifications on PUs were studied by infra-red(IR) spectroscopy, nuclear magnetic resonance (NMR), gelpermeation chromatography (GPC) and rheological meth-ods. The properties of polyols obtained from ESBO aregiven in Table 1. From these polyols, four types of polyolpolyurethanes were prepared [10]. The properties of thesepolyurethanes followed the same pattern as those of thepolyols. For example, the brominated PU had higher den-
sity, followed by chlorinated, then by methoxylated and,finally, hydrogenated PUs. For the preparation of PUs, twotypes of isocyanates PAPI-2143L (a crude MDI) and Isonate2143L (a liquid MDI prepolymer containing carbodiimideScheme 1. Mechanisms of decomposition of urethane bonds. Reproducedfrom Javni et al. [8] with permission of John Wiley and Sons, Inc.
1202 V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215
Table 1Properties of polyols derived from epoxidized soybean oila
Polyol Reagent Yield (%) Hydroxyl no.(mg KOH/g)
Equivalent weight(g/equivalent)
Functionality Polyol, Mn Physical state atroom temperature
Soy-H2 H2 89 212 265 3.5 938 GreaseSoy-Met CH3OH 93 199 282 3.7 1053 LiquidSoy-HClb HCl 94 197 285 3.8 1071 GreaseSoy-HBrb HBr 100 182 308 4.1 1274 Grease
and Sonents an
a Reproduced from Guo and Petrovic [9] with permission of John Wileyb All values were calculated on the basis of the analyzed Cl and Br cont
group.
bonds) were used. The PUs from both of these isocyanatesshowed comparable thermal stability, mechanical strengthand dielectric properties.
The PU networks from soybean oil had numerous valu-able properties. These properties solely depended upon thechemical composition and cross-link density. The NCO/OHmole ratios (isocyanate index) in the polyol directly affectedthe physical and mechanical properties of the resultingPU networks [11]. NCO/OH molar ratios were varied from1.05 to 0.4 with the resulting properties shown in Table 2.With a decrease in the NCO/OH mole ratio, the glass tran-sition temperature Tg decreased linearly from 64 to −3 ◦C.The tensile strength of the networks decreased from 47.3to 0.3 MPa with a decreasing NCO/OH mole ratio. Thepolyurethane networks, prepared with lowering of themolar ratio of NCO and OH groups, had an increasingamount of imperfections in the form of dangling chainends. Therefore, the properties of the networks deterio-rated with a decrease in the NCO/OH molar ratio. Petrovicet al. [12] also studied the properties of vegetable oil-basedPUs through hydroformylation. Hydroformylation is analdehyde synthesis process that falls under the general clas-sification of a Fischer–Tropsch reaction. Hydroformylation,also known as the oxo synthesis, is an important industrialprocess for the production of aldehydes from alkenes. Thischemical reaction entails the addition of a formyl (CHO)group and a hydrogen atom to a carbon–carbon doublebond.
The double bonds of the soybean oil were first converted
to aldehydes using either rhodium or cobalt as catalyst.The aldehydes were hydrogenated to alcohols forming atriglyceride polyol. Polyols from a rhodium-catalyzed reac-tion (95% conversion) resulted in a rigid polyurethane,Table 2Molecular weights Mc between crosslinks and concentration �e of ENAC for poly(between 1.05 and 0.4)a
NCO/OH mole ratio Density (g/cm3) Degree of swelling (W1/W0) Sol fra
1.05 1.104 1.5199 0.821 1.104 1.5528 1.020.95 1.104 1.5911 1.290.9 1.101 1.6334 1.550.8 1.095 1.7299 2.780.7 1.088 1.8480 5.200.6 1.083 2.0165 8.680.5 1.074 2.350 11.670.4 1.064 3.060 24.78
a Reproduced from Petrovic et al. [11] with permission of Plenum Publishing Co
s, Inc.d under the assumption that each halogen is accompanied by a hydroxyl
while polyols from a cobalt-catalyzed reaction (67%conversion) resulted in hard PU rubbers with lowermechanical strength. The soybean-based polyurethaneswere prepared from aliphatic, cycloaliphatic and aromaticisocyanates [13]. The isocyanates used in this study were4,4′-diphenylmethane diisocyanate (MDI), 2,4:2,6-toluenediisocyanate (TDI), hydrogenated MDI (RMDI), isophoronediisocyanate (IPDI), hexamethylene diisocyanate (HDI),Desmodur N-100 and Desmodur N-3300 (triisocyanatesderived from 1,6-hexamethylene diisocyanate), DesmodurRF-E (a tris (p-isocyanato-phenyl)-thiophosphate) andDesmodur CB 75N a (trimethylol propane TDI-based pre-polymer). A higher cross-link density of the PU networksresulted for triisocyanates than for diisocyanates.
The density, glass transition temperature [measured bydifferential scanning calorimetry (DSC), thermal mechan-ical analysis (TMA) and dynamic mechanical analysis(DMA)] and the degree of swelling in toluene arereported in Table 3. In comparison with diisocyanates,the triisocyanates resulted in better overall propertiessuch as density, Tg, swelling and mechanical properties.The triisocyanates RF-E [a tris (p-isocyanato-phenyl)-thiophosphate-based prepolymer] and CB 75N (a trimethy-lol propane TDI-based prepolymer) showed flexural moduliof the order of 2480 and 2040 MPa and tensile strengths of48 and 65 MPa, respectively.
Petrovic et al. [14,15] also studied the properties ofpolyisocyanurate cast resins and foams from soybeanoil-based polyols. Polyisocyanurate cast resins are heat
resistant materials obtained by polycyclotrimerizationof diisocyanates or isocyanate-terminated prepolymers(Scheme 2). The formation of polyisocyanurate fromthe prepolymer took place at higher temperatures com-urethanes (based on soybean polyol and MDI) withNCO/OH mole ratios
ction (%) Affine model Phantom model
�e (mol/cm3) Mc (g/mol) �e (mol/cm3) Mc (g/mol)
2.73 × 10−3 404 4.30 × 10−3 2572.45 × 10−3 451 3.91 × 10−3 2822.17 × 10−3 509 3.52 × 10−3 3131.92 × 10−3 574 3.17 × 10−3 3481.48 × 10−3 741 2.52 × 10−3 4351.12 × 10−3 981 1.96 × 10−3 5567.65 × 10−4 1415 1.41 × 10−3 7694.13 × 10−4 2601 8.09 × 10−4 13721.49 × 10−4 7118 3.19 × 10−4 3333
rp.
V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215 1203
Table 3Density, Tg (measured by DSC, TMA, and DMA), and degree of swelling in toluene of soybean oil-based polyurethanesa
Isocyanate Density (kg/m3) Tg by DSC (◦C) Tg by TMA (◦C) Tg by DMA (◦C) Swelling degree (%)
MDI 1104 59 55 74 55TDI 1104 47 53 62 64RMDI 1062 50 47 69 75IPDI 1061 48 48 68 79HDI 1066 10 15 22 79N100 1082 26 25 41 52N 25R 64C 85
a and Son
pppswespisrfThwhohtl1ai
−adc3sb
SR
I, because polyol II contains a primary hydroxyl groupas well as one additional carbon atom in the crosslink-ing chain after hydroformylation, while polyol I containsa secondary hydroxyl group and methoxy groups as sidechains.
3300 1096 25FE 1272 NAB 75N 1186 93
Reproduced from Javni and Petrovic [13] with permission of John Wiley
ared to the reaction temperature for the formation ofolyurethane [14]. As a result, the isocyanate terminatedrepolymers (PU) also reacted with themselves, producingtrong isocyanurate chains (Scheme 2). These cross-linksere stronger than normal bonds in polyurethane. For
xample, polyisocyanurate foam from soy polyol (59 MPa)howed nearly double the stress at break than PPO-basedolyisocyanurate foam (31 MPa). Thus, the resulting poly-
socyanurate foam was chemically and thermally moretable (disintegration started above 400 ◦C). Polyisocyanu-ates are used in applications where the material is exposedor an extended period of time at an elevated temperature.wo polyols (PPO 168 and Soypolyol 173) having the sameydroxyl number, functionality and molecular weight, butith significant structural differences, were used. PPO 168ad terminal OH groups, which on reaction with isocyanatef polyisocyanurate formed polyurethane. Soypolyol 173ad internal hydroxyl groups positioned in the middle ofhe fatty chain. Thus, Soypolyol 173 exhibited higher cross-ink density of the polyisocyanurate network than PPO68. The soybean polyol-based polyisocyanurate showedhigher Tg (about 30 ◦C higher) than PPO 168-based poly-
socyanurates.All the PU foam samples showed a �-transition at about
30 to −20 ◦C [15]. The PPO 168-based PUs decomposedt a higher rate at 235 ◦C, while the maximum rate ofecomposition for soy polyol-based PUs was 370 ◦C. The
ompression strength (measured at a stress of 10, 20 and0% strains with applied force parallel to the foam rise ofoy polyol-based PU foams was much higher than for PPO-ased PU foams, as shown in Fig. 4. The PPO-based foamscheme 2. Schematic representation of polyisocyanurate structure.eproduced from [14] with permission of John Wiley and Sons, Inc.
37 5984 2292 12
s, Inc.
were semi-rigid at an isocyanate index of 110, but the soypolyol foams had a higher density at an index of 110 andshowed higher compressive stress.
The thermal and mechanical properties of glass rein-forced soybean oil-based polyurethane composites werealso studied by Petrovic [16]. PUs in this study werederived from a soybean oil-based polyol (Soypolyol 204)and petrochemical polyol (Jeffol G30-650). Although the Tg
of jeffol composites was slightly higher than that of soypolyol composites, the oxidative, thermal and hydrolyticstability of the latter was superior to propylene glycol-based polyurethanes [17–19], suggesting that it couldfind increasing applications in the composites area. Thestructure–property relationships were further studied byPetrovic et al. [20]. They prepared two types of soybeanpolyols, one from epoxidation of soybean oil, followedby methanolysis and the other from hydroformylation ofsoybean oil, followed by hydrogenation [18,19]. The mech-anistic paths of these processes are shown in Scheme 3.The polyol II in Scheme 3 was more reactive than polyol
Fig. 4. Compression stress of soybean-based foams and PPO-based foams.Reproduced from Javni et al. [15] with permission of Plenum PublishingCorporation.
1204 V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215
ion of s
Scheme 3. Schematic representation of methanolysis and hydroformylatScience and Business Media, LLC.Dunjic and co-workers [21] prepared a series of ure-thane acrylates derived from soybean fatty acid modifiedhyperbranched aliphatic polyesters through a two stepprocess. The material obtained was used as oligomer inradiation curable compositions. The UV cured acrylatesexhibited good mechanical and thermal properties. Thetensile strengths of these samples ranged from 15.73 to72.53 MPa and they showed 5% weight loss at around 300 ◦Cduring thermal degradation. Fan et al. [22] reported soy-based polyamide resins via condensation polymerizationfrom different dimer acids and diamines. The polyamide
prepared from 1,4-phenylenediamine showed a rapidincrease in molecular weight above 260 ◦C. Polyamide from1,4-phenylenediamine showed higher Tg, melting temper-ature (Tm), decomposition temperature and mechanicalstrength than aliphatic polyamides. The flexibility of dimeroybean oil. Reproduced from Guo et al. [20] with permission of Springer
acid and its macrostructure, such as the contents ofmonomer and trimer acids, directly affected the resultingpolymer properties.
Deng et al. [23] reported the synthesis of soy-based copolyamides with different �-amino acids. Thecontents of amino acids were varied, keeping the con-tents of dimer acid and phenylenediamine constant. Thecopolyamides thus prepared showed a drastic decreasein mechanical strength. For instance, Young’s modu-lus for homopolymer was 2116.0 MPa; and that forcopolymers containing tyrosine, glutamic acid and pheny-
lalanine were 330.8, 242.9 and 183.2 MPa, respectively.John et al. [24] studied PU foams derived from soybeanoil. The reaction was monitored by FTIR spectroscopy.The introduction of soybean oil caused an increase inhydroxyl values and acid values as well as molecular
V. Sharma, P.P. Kundu / Progress in Polym
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ig. 5. SEM micrographs of (a) soybean polyol foam at 3-php water andb) voranol polyol foam at 3-php water. Reproduced from Singh and Bhat-acharya [25] with permission of John Wiley and Sons, Inc.
eight, whereas iodine values and fatty acid contentecreased.
Singh and Bhattacharya [25] also studied PU foamsrom soybean oil. They studied the viscoelastic changesnd cell opening by using vane geometry in a strain-ontrolled rheometer. They identified four stages ofodulus development during the foaming reaction namely,
i) bubble nucleation and growth, (ii) packing of bubble net-ork/liquid foam, (iii) urea microphase separation and cell
pening, and (iv) final curing. In their study, they furthernvestigated the effects of temperature, voranol (a syntheticolyol), water and straining frequency on the properties ofU foam. A SEM micrograph for soybean oil polyol foamnd voranol polyol foam at 3-php (parts per hundred parts)ater is shown in Fig. 5. The size and shape of the cells was
ess uniform for soybean polyol foams compared to syn-hetic voranol foams (Fig. 5). Soybean polyol-based foamsad more pinhole openings and more partially open celltructures rather than completely open cells.
Rosch and Mulhaupt [26] synthesized polyester resinsnd blends from anhydride-cured epoxidized soybean oil.he mechanical and thermal properties of the casting resinsere dependent upon the type of anhydride used. At low
poxy conversions, i.e., using low accelerator content oress reactive anhydrides such as cycloaliphatic anhydrides,he crosslinked polyesters were highly flexible. For exam-le, norbornene dicarboxylic acid anhydride resulted in
er Science 33 (2008) 1199–1215 1205
polyester with a Tg of −5 ◦C, which indicated the rubberynature of the polyester. With maleic and phthalic anhy-drides, stiffer polyesters with flexural moduli in the range of500–1000 MPa and Tg between 43 and 75 ◦C were obtained.Eren et al. [27] polymerized maleinized soybean oil withdifferent alcohols such as low molecular weight polyolsand long chain diols [glycerol, pentaerythritol, polyethy-lene glycol (PEG) 160, PEG 400, PEG 600, etc.]. The materialobtained was highly crosslinked and become jellylike incommon solvents like acetone and chloroform.
Mohanty and co-workers [28] evaluated the thermo-mechanical properties of PU-based on soybean phosphateester polyols and polymeric dipenylmethane diisocyanate(pMDI). The glass transition temperature of the PUs var-ied from 69 to 82 ◦C and the values of storage moduli werebetween 4 × 108 and 1.3 × 109 Pa. The PU samples werepostcured at 100 and 150 ◦C. The crosslink density �e ofthe samples postcured at 100 ◦C was lower than for thosepostcured at 150 ◦C, despite a longer postcure time. Mon-teavaro et al. [29] investigated the thermal properties ofsoybean oil-based PUs by thermogravimetric analysis. TheTGA was carried out under nitrogen at a heating rate of10 ◦C min−1 for dynamic TG, and isothermal measurementswere carried out at 230, 240 and 250 ◦C. Fig. 6a presentsthe rate of weight loss in isothermal measurements at 230,240 and 250 ◦C for the PU samples. The curves show anincrease in the rate of weight loss with an increase in tem-perature. The rate of weight loss was highest in the initialperiod (up to approximately 100 min). From Fig. 6a, one canmeasure the time for weight loss of 4, 5 and 7% at 230, 240and 250 ◦C. Fig. 6b shows the log–log plot of time versustemperature for 4, 5 and 7% weight loss of PU. The verti-cal lines in Fig. 6b correspond to iso-conversional (for sameweight loss) plots and the plots along the temperature axiscorrespond to isothermal lines. If the PU had followed thesame decomposition pattern at different temperatures, theisothermal lines would be expected to be parallel. Instead,they are not parallel, indicating different decompositionprocesses at different temperatures.
Pechar et al. [30] synthesized PU networks from soybeanoil polyol, petroleum-based polyols and their blends. Thesoybean polyols were prepared by air oxidation of raw soy-bean oil and hydroxylation of epoxidized soybean oil. TheTg of the PU samples ranged from −21 to +83 ◦C and waslinearly related with the hydroxyl numbers (55–237 mgKOH/g) of the soybean oil polyols. Quintero et al. [31]developed the vegetable oil macro-monomer (VOMM)technology for application to aqueous coatings. This wouldhelp to reduce the volatile organic content in waterbornecoatings. They used soybean acrylated macro-monomer(SAM) as a copolymerizable hydrophobe for miniemulsionpolymerization. This system allowed an improvement inflow and smoothing of the coated film before crosslinkingand cessation of flow.
3. Polymers and IPNs based on castor oil polyols
3.1. Polymers based on castor oil polyols
The use of castor oil in the polyurethane industry addsvalue to the crop. Bao et al. [32] studied the effect of the
1206 V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215
Scheme 4. Preparation of modified castor oil polyurethane dispersions. Reproduced from Bao et al. [32] with permission of Iran Polymer and PetrochemicalInstitute.
V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215 1207
Fig. 6. (a) Isothermal TG curves for PU04 (from toluenediisocyanate andsoy polyol with NCO/OH ratio 0.80) at 230, 240 and 250 ◦C in nitro-gen (b) Variation of degradation time (isothermal) with temperature(tfP
NoPwttdpas
iccanaToa
for thermal stability and chemical resistance.
dynamic TGA) in nitrogen to achieve the same conversion level at threeemperatures (isothermal and isoconversion lines) for PU04. Reproducedrom Monteavaro et al. [29] with permission of Associacao Brasileira deolimeros.
CO/OH mole ratio on the structure and properties of aque-us PU from modified castor oil (MCO). The synthesis of theU from modified castor oil (MCPU) is shown in Scheme 4here acid-ended modified castor oil used for the produc-
ion of PU-polyamide forms salts with a triamine, leadingo the formation of a water-soluble polymer. A three stepegradation was observed for all the PU-polyamide sam-les. In the first stage, a weight loss of less than 5% occurredt about 210–240 ◦C. In the second stage, a rapid weight losstarted at 250 ◦C and continued up to 360 ◦C.
Barrett et al. [33] studied the crystallization kinet-cs of poly ethylene terephthalate (PET) from a mixtureontaining naturally functionalized triglyceride oil. Therystallization of PET was dependent on several factors suchs plasticization due to the presence of the triglyceride oil,ucleation from added agents, bond interchange reactions
nd the formation of a crosslinked triglyceride oil network.he identification of such factors allowed some controlver microstructure of these products and similar blendsnd semi-IPNs. The Avrami analysis supported the effec-Fig. 7. Avrami plots for castor oil, sodium benzoate and related PETcompositions during isothermal crystallization from the melt at 220 ◦C.Reproduced from Barrett et al. [33] with the permission of John Wiley andSons, Inc.
tiveness of castor oil. Avrami plots for castor oil, sodiumbenzoate and related PET compositions during isothermalcrystallization from the melt at 220 ◦C are shown in Fig. 7.In the presence of castor oil, a high curvature appeared inthe Avrami plot for the crystallization of PET. This showeda smooth transition from the primary to secondary crys-tallization. The sodium benzoate blends displayed a rapidtransition from primary to secondary crystallization. Themixture of castor oil and sodium benzoate showed a grad-ual transition.
Kansara et al. [34] statistically studied the reactionkinetics of castor oil (CO)-based polyol and TDI. They useda second-order rate expression for the equimolar reactionbetween polyol and TDI. For a specific case, a moles of bothof the reactants are present at the start of the reaction andat a specific instant t, x moles of the reactants are reacted.Then, one can find from the bimolecular rate expressionthat the quantity x/a(a − x) is directly proportional to thetime t. Thus, plots of x/a(a − x) versus time were linear.They studied the reactivity of ortho and para—NCO groupsin TDI with varying temperature, catalyst ratio and polyolchain length of. The prepolymers R60 and R92 were polyols-based on castor oil. The hydroxyl value, equivalent weightand Brookfield viscosity (cP) of R60 and R92 were reportedto be 5, 220, 620 and 6, 190, 700, respectively. R60 and R92showed higher conversion compared with the parent castoroil at all temperatures and catalyst concentrations.
Kansara and co-workers [35] also studied castor oil-based polyurethane adhesives. They used two teak woodpieces and applied the adhesive solution to a thickness of0.1 mm and joined the pieces together under a load of 2.5 kgfor 12 h. These samples were found to have 10 times morelap shear strength as compared with commercially avail-able wood adhesives. The adhesive films were also tested
Yeganeh and Mehdizadeh [36] investigated millablePU elastomers from castor oil-based polyols. Millable PUelastomers (MPE) are a special type of synthetic rub-ber. MPEs can serve the rubber industry as they can be
in Polymer Science 33 (2008) 1199–1215
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mixed, extruded, calendared, and compression or injec-tion molded in conventional rubber processing equipments[37]. The MPEs were prepared by the reaction of difunc-tional castor oil and TDI dimer in an inert atmosphere. Thesynthesis of difunctional castor as reported by Yeganeh andMehdizadeh [36] is as follows. In a three-necked, round-bottomed flask equipped with a stirrer, dropping funneland thermometer, dried castor oil (100 g) was added. Thetemperature was brought to 100 ◦C, followed by dropwiseaddition of phenyl isocyanate (8.33 g) under stirring. Thereaction was continued for 2 h, before cooling.
These MPEs showed two-step degradations, one at270 ◦C and the second one at 380 ◦C. The mechanical prop-erties of these MPE were dependant on the contents ofcastor oil and the chain extenders. On comparison witha commercially available elastomer (Urepan 600), theseMPEs exhibited comparable tensile strength, compressionset, resilience and slightly inferior abrasion resistance andelongation at break.
Novel PU insulating coatings from glycolyzed PET(GPET) and castor oil were also investigated by Yeganehand Shamekhi [38]. First, they synthesized polyhydroxycompounds from different compositions of CO and GPET.Several types of reactions can occur during the prepara-tion of polyhydroxy compounds (PHC). So, proper analysissuch as measurement of hydroxyl values and acid val-ues was carried out to ascertain the transesterificationas the major reaction. The thermal and electrical prop-erties of the PUs obtained from the PHCs are shown inTable 4. The Tg of the samples ranged from 47 to 61 ◦C. Thetensile strength was between 19 and 47 MPa and the elon-gation was 8–24%. It was observed that with a decreasein the hydroxyl value of PHC, the crosslink density alsodecreased. Yeganeh and Hojati-Talemi [39] also studiedbiodegradable PU networks obtained from the PHCs ofcastor oil and PEG. The PU networks obtained were char-acterized by their physical, mechanical and viscoelasticproperties. The stress–strain curves for the castor oil PUs(CPU) are shown in Fig. 8. Fig. 8 shows a smooth transition instress–strain behavior for CPU1 and CPU2 samples similarto that in lightly crosslinked amorphous rubber. However,the stress–strain behavior of CPU3 and CPU4 was different:these showed a yield point due to presence of a crystallinephase.
Because of the higher crystallinity of CPU4, it showedhigher initial modulus and tensile strength and lowerelongation at break. The tensile strength of theseCPUs ranged from 0.66 to 2.51 MPa. The Tg of thesamples was below room temperature (between −2.0and 5.1 ◦C).
Preparation of PU nanoparticles by miniemulsionpolymerization from castor oil polyol was reported byZanetti-Ramos et al. [40]. The PU particle size measuredby dynamic light scattering ranged from 200 to 300 nm.Ogunniyi et al. [41] reported the preparation and proper-ties of PU foams from the reaction of TDI with a mixture
of castor oil polyol and polyether polyol. The introduc-tion of castor oil polyol in the formulation of PU foamsincreased the tensile strength from 3.33 to 138.89 kN/m2and compression set from 5.2 to 49.25% with increasing oilcontent. Ta
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Fig. 8. Stress–strain curves for CPU 1–4. CPU1 containing100% epoxy mod-ified PU prepolymer-based on castor oil (EPU1) and 0% epoxy modifiedP1i[
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U-based on polyethylene glycol (EPU2), CPU2 containing 90% EPU1 and0% EPU2, CPU3 containing 70% EPU1 and 30% EPU2 and CPU4 contain-ng 50% EPU1 and 50% EPU2. Reproduced from Yeganeh and Hojati-Talemi39] with permission of Elsevier Ltd.
.2. Interpenetrating and semi-interpenetratingetworks based on castor oil
Polymer systems comprising of two or more networks,hich are at least partially interlaced on a molecu-
ar scale, but not covalently bonded to each other, arealled interpenetrating polymer networks (IPN). Theseolymer networks cannot be separated unless chemicalonds are broken. Polymer systems comprising one poly-er network and another of linear or branched polymer,
haracterized by the penetration on a molecular scalef the linear or branched macromolecules in the poly-er networks, are called semi-interpenetrating networks.
emi-interpenetrating polymer networks are distinguishedrom interpenetrating polymer networks because the con-tituent linear or branched polymers could, in principle, beeparated from the constituent polymer network(s) with-ut breaking chemical bonds. When they can be separated,hey are called polymer blends.
Attempts have been made to synthesize interpenetrat-ng polymer networks (IPN) and a series of cross-linkedopolymers and IPNs from epoxidized vegetable oils andaleinized tung oil [42]. Cross-linked copolymers were
ynthesized by mixing epoxidized vegetable oils anddduct of tung oil with maleic anhydride in differentroportions. The IPNs were tested by dynamic mechan-
cal spectroscopy (DMS) to investigate compatibility andamping properties. The IPNs formed by triglycerides wereound to increase the toughness and fracture resistancen conventional thermoset polymers. There are reports ofevelopment of IPNs consisting of cross-linked polystyrene
nd epoxidized linseed oil elastomers [43]. IPNs from cross-inked polystyrene and castor oil elastomers have alsoeen reported [44–46]. Suthar and co-workers [47–50]repared IPNs from polyurethanes-based on castor oilith other vinyl monomers. They found that the IPNser Science 33 (2008) 1199–1215 1209
formed were tougher than the corresponding homopoly-mers.
Patel and Suthar [51] synthesized liquid pre-polyurethanes from castor oil and TDI under differentconditions and with varying NCO/OH ratios. Then, thepre-polyurethane was reacted with poly (ethyl acrylate) toobtain IPNs. These IPNs were characterized by chemical,mechanical and thermal methods. The glass transitiontemperature of these IPNs ranged from 38 to 41 ◦C. Thechemical resistance of the IPNs was studied in differentreagents: 25% H2SO4, 15% HCl, 5% HNO3, 5% NaOH, 25%acetic acid, 5% H2O2, 40% NaCl, methylethyl ketone, dis-tilled water, carbon tetrachloride and toluene for seven7 days. The IPNs were stable in all the media exceptmethylethyl ketone, carbon tetrachloride and toluene.The IPNs were stable up to 300 ◦C with 7–9% weight loss;54–57% weight loss was observed around 400 ◦C anddecomposition was complete beyond 550 ◦C. Mechanicalproperties of these IPNs are given in Table 5.
Suthar and Patel [52] studied IPNs from castor oil-based PU and poly (methyl acrylate). The castor oil wasreacted with 4,4′-diphenylmethanediisocyante to obtainpre-polyurethane, which was further reacted with methylacrylate monomer and ethylene glycol dimethacrylate asa crosslinker. These IPNs showed low chemical resis-tance towards CCl4, methylethyl ketone and toluene. Theyshowed high light transmittance (49–81%). These poly-mers were stable up to 300 ◦C, lost 45% weight rapidly ataround 450 ◦C and decomposed completely beyond 600 ◦C.The tensile strength of these polymers was between 0.43and 1.87 mN/m2 and they had elongations in the range of84–102%.
Suthar et al. [53] also studied the IPNs from castoroil-based polyesters and poly (methyl methacrylate). Thepolyesters were synthesized from castor oil and dibasicacids such as malonic, succinic, glutaric, adipic, suberic andsebacic acids. These IPNs showed two glass transitions cor-responding to their individual component networks. Thefirst Tg was in the range of −76 to −70 ◦C and the second wasbetween 25 and 34 ◦C. The tensile strength was between140 and 280 kPa and Young’s modulus was 730–1200 kPa.These polymers were stable upto 300 ◦C showing only2–4% weight loss, whereas they showed 50% weight lossat around 400 ◦C. The samples decomposed completelybeyond 500 ◦C.
Suthar et al. [54] synthesized three series of IPNs-based on PU from castor oil and TDI with polystyrene,poly (methyl methacrylate) and poly (n-butyl methacry-late). They studied the effects of structural variables suchas composition, type of vinyl monomer and the effect ofinteraction of phases on the dielectric properties. TheseIPNs were characterized in terms of the variation of dielec-tric permittivity E′, dissipation factor E′′ and tan ı versustemperature. The dielectric relaxation studies showed thatthese IPNs behaved like homogeneous materials. Sperlingand co-workers [55,56] reported the preparation of inter-
penetrating networks from castor oil-based polyurethanesand styrene monomer. The resulting IPNs were char-acterized by electron microscopy, modulus-temperaturemeasurements and stress–strain analysis. The interpen-etrating networks (IPN) showed stress–strain behavior
1210 V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215
Table 5Mechanical properties of IPNsa
Sampleb,c Tensile strength (mN/m2) Young’s modulus (mN/m2) Elongation @ break (%) Hardness shore A
IPN-1 (PPU-25 + EA-75) 3.41 1.64 194 79IPN-2 (PPU-35 + EA-65) 3.66 2.17 182 83IPN-3 (PPU-45 + EA-55) 2.85 1.90 188 95IPN-4 (PPU-25 + EA-75) 3.37 3.67 148 81IPN-5 (PPU-35 + EA-65) 7.10 3.01 225 73IPN-6 (PPU-45 + EA-55) 6.38 2.99 200 80IPN-7 (PPU-25 + EA-75) 9.38 4.67 183 86IPN-8 (PPU-35 + EA-65) 10.60 4.13 186 87IPN-9 (PPU-45 + EA-55) 8.67 3.84 178 79PEAd 62.30 2500 16 92
a and Soin parenNs 7–9 i
Reproduced from Patel and Suthar [51] with permission of John Wileyb Contents of pre-polyurethane (PPU) and ethyl acrylate (EA) are givenc NCO/OH molar ration for IPNs 1–3 is 1.6, for IPNs 4–6 is 1.8 and for IPd PEA is the homopolymer of ethyl acrylate.
similar to reinforced elastomers. The properties of the IPNshowed a dependence on the NCO/OH ratio in the castor oil-based PU and the content of polystyrene. At a fixed NCO/OHratio of 0.75, with a decrease in the polystyrene contentin the IPN from 53 to 50%, the IPNs exhibited an increasein elongation from 130 to 140% and in tensile stress from1000 to 2500 psi. For a fixed 50% content of polystyrene,a decrease in elongation (from 140 to 130%) and in tensilestress (from 2500 to 1200 psi) was observed for an increasein the NCO/OH ratio from 0.75 to 0.85. The decrease inpolystyrene content and NCO/OH ratio caused a decreasein the amount of stiff material in the IPN, leading to anincrease in elongation. The decrease in stiff material wasexpected to cause a decrease in tensile stress; but con-trary to expectation, the tensile stress increased with adecrease in stiffer material. This phenomenon has not beenexplained [56], but may possibly be due to synchronizationof the phases.
Prashantha et al. [57] studied IPNs-based onpolyol modified castor oil polyurethane and poly (2-hydroxyethylmethacrylate). They investigated mechanicaland thermal properties of the IPNs such as tensile strength,elongation, hardness, Tg and degradation. The tensilestrength ranged from 27 to 38 MPa and elongation at breakwas between 58 and 120%. All the IPNs showed about 2–4%decomposition at 200 ◦C, about 10% at 300 ◦C and about40% at 400 ◦C. There was a rapid weight loss from 40 to90% in temperature ranges of 400–500 ◦C.
Sanmathi et al. [58] synthesized and characterized IPNsfrom modified castor oil-based polyurethane and poly (2-ethoxyethyl methacrylate). The preparation of these IPNsis shown in Scheme 5. The triglyceride of castor oil wasexchanged with glycerol, followed by reaction with a diiso-cyanate to form castor-based PU (GC-PU). 2-Ethoxyethylmethacrylate was subsequently polymerized in the pres-ence of GC-PU to prepare the IPNs. The presence ofH-bonding between poly (2-ethoxyethyl methacrylate) andcastor PU (GC-PU) is also shown in Scheme 5. The incor-poration of poly (2-ethoxyethyl methacrylate) in GC-PU
during the formation of IPN caused an increase in tensilestrength and decrease in elongation, when compared withthe individual components of GC-PU and (2-ethoxyethylmethacrylate). These IPNs exhibited Young’s modulus ofthe order of 2.9–84 mN/m2.ns, Inc.thesis.
s 2.0.
Kansara et al. [59,60] also studied the sorption anddiffusion behavior of IPNs-based on PU and unsaturatedpolyester (UPE). The PU was prepared from castor oil polyol.The sorption behavior of these IPNs was studied withchanges in crosslink density, NCO/OH mole ratio, composi-tion of the constituents and hydroxyl value. Chlorobenzenewas used to study the swelling behavior of the IPNs. Sorp-tion was inversely related to the NCO/OH mole ratio. Thecrosslink density ranged from 5 to 27 × 104 mol/g for dif-ferent IPNs, as calculated by the Flory–Rehner equation[61]. An increase in diffusion coefficient was observed withan increase in the NCO/OH molar ratio and the content ofunsaturated polyester.
Xie and co-workers [62] studied the damping behav-ior of grafted interpenetrating networks. They preparedIPNs from castor oil, toluene diisocyanate, monohydroxyterminated acrylic prepolymer and acrylic monomer in thepresence of dibutyltin dilaurate and redox initiators. Thedynamic mechanical properties of the IPNs were observedto exhibit high damping properties over a wide range oftemperature.
Xie and Guo [63] studied adhesives made from IPNs forbonding with rusted iron without pretreatment. They pre-pared two types of room-temperature curable IPNs: onefrom castor oil-based PU and vinyl or acrylic polymer andthe other from castor oil PU, unsaturated polyester and vinylor acrylic polymer. The lap shear strength of joints betweenrusted iron plates and IPNs (adhesives) ranged from 1.51 to8 MPa.
Nayak and co-workers [64–68] also synthesized andcharacterized castor oil-based interpenetrating networks.First, they prepared polyurethanes from castor oil and hex-amethylene diisocyanate by varying the NCO/OH ratio andthen prepared IPNs by reacting polyurethanes with variousacrylates such as hydroxyethyl methacrylate and cardanylmethacrylate by using benzoylperoxide as initiator andethylene glycol dimethacrylate as crosslinker. Infra-red IRspectroscopy, NMR spectroscopy, TGA, etc. were employedto study the properties of resulting IPNs.
Cunha et al. [69] employed a statistical method toaccurately evaluate the properties of castor oil-based semi-interpenetrating polymer networks (sIPN). They used a23 factorial experimental design for optimization of theproperties. The semi-interpenetrating polymer networks
V. Sharma, P.P. Kundu / Progress in Polymer Science 33 (2008) 1199–1215 1211
ed from
(csm
Scheme 5. Preparation of GC-PU/poly (2-EOEMA) IPNs. Reproduc
sIPNs) were prepared from castor oil polyol, toluene diiso-yanate and methyl methacrylate. The properties of theseIPNs depended upon the ratio of the contents and theole ratio NCO/OH. Various techniques were employed
Sanmathi et al. [58] with permission of John Wiley and Sons, Inc.
to study the properties of the sIPNs. They showed differ-ent swelling properties for different samples. The samplecontaining maximum methyl methacrylate exhibited lowswelling. Mechanical properties were also largely influ-
in Polym
1212 V. Sharma, P.P. Kundu / Progressenced by the methyl methacrylate content. For instance,the sIPN containing 20% MMA showed 22.6% swelling and1.48 MPa elastic modulus, whereas the sIPN containing 60%MMA showed 17.4% swelling and 6.49 MPa elastic modulus.
4. Polymers based on nahar seed oil polyol
Nahar (Mesua ferrea L.) seed oil contains mainly triglyc-erides of linoleic, oleic, palmitic and stearic acids [70]. Karakand co-workers [71–74] studied polyester, polyesteramide,polyurethane and polyurethane amide resins from naharseed oil [71–74]. They prepared polyester resins fromnahar seed oil monoglycerides and phthalic and or maleicanhydrides [71]. Nahar seed oil was first converted intomonoglycerides by alcoholysis and then the resins wereprepared by reacting monoglycerides with phthalic andor maleic anhydrides. The alcoholysis and polycondensa-tion reaction of the oil with acid anhydride is shown inScheme 6. An increase in the maleic anhydride content inthe resin decreased the curing time. Resin with 50% maleicanhydride took 7 h for complete curing, whereas resin with
75% maleic anhydride took 6 h. The polyester films werehighly resistant to dilute HCl (10%), aqueous NaCl salt solu-tion (10%) and distilled water.Polyesteramide resins from nahar oil were also studiedby Karak and Mahapatra [72]. The oil was first converted
Scheme 6. Alcoholysis and poly-condensation reaction of oil with acid anhydride
er Science 33 (2008) 1199–1215
into methyl ester, and then reacted with diethanol amideto form diethanol amide of fatty acids. The fatty acids amidewas then reacted with dibasic acid or their derivatives. Thehardness of the resins was tested as pencil hardness.
The pencil hardness test is used to test coatings for theirhardness and resistance to scratches and wear. The princi-ple of operation uses a pressure applied to allow the pencillead to just crush and therefore, repeatable results for thehardness of the coating can be obtained. These pencils,when pressed for a specified number of times on the coat-ing, will also allow a wear factor to be determined. Thiswear factor is related to the hardness of the pencil used.Pencils of different grades are used in the test, ranging from9H to 9B. [H signifies hardness and as one goes to a lowerH number, the lead becomes softer, and grades HB to 9Bdesignate increasing softness (B = blackness).]
The pencil hardness of the cured resins as reported byKarak and Mahapatra [72] ranged from HB to 2H. The curedresin had a gloss between 81 and 85 at 60◦ and had 100%adhesion. Karak and Dutta [73] studied the effect of theNCO/OH ratio on the properties of nahar seed oil modified
PU resins. The resins were prepared by varying NCO/OHmolar ratio from 0.8 to 2.0. The coating properties suchas pencil hardness, gloss, adhesion was studied. The hard-ness of the resins ranged from HB to 3H, the gloss at a 60◦angle was from 109 to 117% and the adhesive strength was
. Reproduced from Dutta et al. [71] with permission of Elsevier B.V.
in Polymer Science 33 (2008) 1199–1215 1213
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V. Sharma, P.P. Kundu / Progress
25–336 kN/m. These properties were found to increaseith increasing NCO/OH ratio from 0.8 to 2.0. The PU resinith equal proportions of NCO and OH showed three degra-ation stages at temperatures of 295, 375 and 490 ◦C. Theegradation temperatures were observed to decrease with
ncreasing NCO/OH ratio. Resin with a NCO/OH ratio of 1.5howed two-stage degradation at 290 and 390 ◦C and theesin with a NCO/OH ratio of 2 showed a single-stage degra-ation at 320 ◦C.
Karak and Dutta [74] synthesized poly (urethane amide)esins from nahar seed oil and TDI in the presence of dibutylin dilaurate (DBTDL) as catalyst. The coating performancef these resins was tested by measuring gloss, pencil hard-ess, adhesion and chemical resistance. The gloss at a 45◦
ngle ranged from 66 to 70 and the pencil hardness rangedrom HB to 2H. Chemical resistance was studied for 10 daysnsolutions of NaOH, HCl, NaCl, ethyl alcohol and in dis-illed water. The cured PU amide resin showed average toxcellent chemical resistance.
. Other polymers based on oil polyols
There are many vegetable oils other than soybean, cas-or and nahar that can be used in the synthesis of polyolsor PUs, such as rapeseed oil, palm oil, canola oil, linseedil, olive oil, sunflower oil, safflower oil, etc. Rapeseedil methyl esters have been synthesized by the reactionf rapeseed oil and methanol at a temperature range of0–70 ◦C with sodium hydroxide as a catalyst. They haveeen produced on an industrial scale for use as biodieseluel [75].
Hu et al. [76] prepared rigid polyurethane foam fromapeseed oil polyol. They first converted the oil into polyoly hydroxylation, followed by alcoholysis. The alcoholysisf the hydroxylated rapeseed oil was required because ofts low hydroxyl value (ca. 100 mg KOH/g), which is notuitable for the preparation of rigid polyurethanes. Theolyol thus prepared was compared with a commerciallyvailable polyester polyol, Daltolac P744. The experimentalata indicate that the compression strength of the PU foamade from rapeseed oil polyol is lower than that of Dalto-
ac P744-based foam. The other properties of the rapeseedil polyol foam are similar to those of commercial foam,altolac P744.
Chian and Gan [77] reported the development ofigid PU foams from palm oil. Their PU foams exhib-ted high compression strength (1–35 MPa) and densities200–300 kg/m3). Desai and co-workers [78] reported PUdhesive from argemone oil and castor oil for wood bond-ng applications. The best performing adhesive (argemineil-based) was compared with various commercially avail-ble adhesives such as Dunlop adhesive, Fevicol andraldite. The average lap shear strength of PU adhe-ive was 63.1 × 105 N/m2, while the highest strength forhe commercially available adhesives was observed to be8.3 × 105 N/m2 for araldite.
Ahmad et al. [79] synthesized polyesteramide fromongamia glabra oil for biologically safe anticorrosive coat-ngs. The oil was first converted to N,N-bis(2-hydroxyethyl). glabra fatty amine (HEPGA) and then HEPGA was con-erted into polyesteramide (PGPEA) by reaction with
network/PET semi-IPN compositions. First heat data, the materials as syn-thesized (A) and second heat data, recorded after cooling rapidly from300 ◦C. Reproduced from Barrett et al. [81] with permission of John Wileyand Sons, Inc.
phthalic acid. The PGPEA coatings showed 10% weight lossup to 275 ◦C, 50% weight loss up to 370 ◦C and 78% weightloss up to 400 ◦C. Almost all of the physico-mechanicalproperties such as scratch hardness (3.5 kg), gloss (up to90% at a 60◦ angle) and adhesion strength (100%) weresuperior to those of polyesteramides obtained from otherseed oils. Ahmad et al. [80] also studied ambient curedPU modified epoxy coatings from linseed oil. The linseedoil was first hydroxylated and then linseed oil PU wasprepared. The linseed oil PU obtained by 10% loading ofTDI showed the best physico-mechanical and anticorrosiveproperties.
Barrett et al. [81] synthesized semi-IPNs from vernoniaoil–sebacic acid polyester network (VOSA) and PET. Thesemi-IPN containing 50% PET and 50% VOSA was observedto be over 15 times tougher than PET and over 50 timestougher than the neat vernonia oil elastomer. The semi-
IPN with 50% PET showed better properties than the othersemi-IPNs, e.g. the tensile strength for the semi-IPN with50% PET was 6030 MPa and the modulus was 25.8 MPa. Thederivative plots for the first and the second heating scansin DSC heat flow around the Tg region are shown in Fig. 9.
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1214 V. Sharma, P.P. Kundu / Progress
All the semi-IPNs showed two glass transitions in the firstscan, which transformed into a single transition in the sec-ond scan after rapid cooling from 300 ◦C. Thus the materialswere multiphase as prepared, but after heating to above themelting point of the PET and cooling, they became nearlysingle phase or microheterogeneous.
6. Conclusions
Waste plastic materials are the major concerns of envi-ronmentalists. Thus, renewable resources are now greatlyfavored for the production of polymers. The wide rangeof mechanical properties and the ability for easy machin-ing and forming cause the plastic foams and elastomers tofind wide industrial and consumer applications. In partic-ular, urethane foams and elastomers have been found tobe well suited for many applications. The vegetable oilsprovide a large variety of options for the preparation ofpolyurethanes. All the vegetable oils are triglycerides offatty acids and most contain unsaturated groups. Only a fewoils contain other groups such as hydroxyl in castor oil, saf-flower oil and lesquerella oil, and oxirane group in vernoniaoil. Soybean and linseed oils are also used in the prepa-ration of polyurethanes by converting them into epoxiesor by hydroformylation. The incorporation of oils in thepolyurethanes provides a great opportunity to tailor theproperties of polyurethane products.
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