Chapter: 3 Application of 1,3-propanediol

Transcription

1 Chapter: 3 Application of 1,3-propanediol

2 CHAPTER: 3 APPLICATION OF 1,3-PROPANEDIOL This chapter deals with the utilization of 1,3-PDO obtained during bioconversion of glycerol. The synthesized 1,3-PDO was utilized for manufacturing of unsaturated polyester resin. Various parameters like temperature, reaction time, mole ratio and effects of various catalyst were optimized. The synthesized polyester resin was characterized by FTIR, DSC. 3.0 INTRODUCTION 1,3-PDO is an emerging commodity chemical and renewed interest in its biotechnological production has recently arisen. 1,3-PDO is demanded for the development of a various polymers such as saturated and unsaturated polyester, polyester polyol, polyether polyol and polyurethane [1]. Polymers square measure the substances whose molecules accommodates an oversized range of units of a number of types i.e. the units themselves, consisting of variety of atoms. The square measure typically noted because the structure of every molecule contains units of each monomers. Such a chemical compound is termed polymer and therefore the method of its synthesis is termed copolymerization. They are wide used commercially as fibers, plastics, composites and for coatings applications too [2,3]. They are hetero chain macromolecules that possess process organic compound teams as associate integral element of their chemical compound backbones. Polyesters area unit one amongst the foremost versatile artificial polymers. Polyesters area unit created in high volume that exceeds thirty billion pounds a year worldwide [4,5]. Polyester resins have been known and applied as polymeric binders since many years. Saturated polyester was obtained by reacting multifunctional acids or anhydrides such as phthalic anhydride, adipic acid, isophthalic acid with multi-functional alcohols such as 1,3-PO, 1,2-PDO, neopentyl glycol, di-ethylene glycol. The polymeric backbone containing reacted polyols and polyacids linked to each other by ester groups [6]. 133

3 The polyester resins can be molecularly engineered to offer a wide range of chemical and physical properties. Due to this, saturated polyesters was designed to provide similar or even better mechanical properties and outdoor durability than other resins. Therefore, saturated polyester resins were widely used in fiber, coatings and adhesive industry for outdoor application [7]. Hydroxyl polyester resin was used to combine with amino crosslinking resin to form a paint system, or with the polyisocyanate to form a two-component polyurethane system which is room-temperature-curing. Carboxyl polyester resin was used for compounding with epoxy resin in powder coatings applications [8]. Saturated polyester resins were widely supplied as solutions in organic solvents such as aliphatic hydrocarbons, aromatic hydrocarbons, alcohols and glycols. The conventional resins were still being widely used. The resins were still being developed with a wide range of reactivity, flexibility, hardness and durability suitable for a variety of industrial applications. A wide range of relatively cost effective raw materials were available to formulate tailor made polyesters for a variety of industrial applications [9]. The unsaturated polyester resin are a thermoset material and capable of cured from a liquid or solid state under proper condition. In the 1900 s, plastics such as vinyl, polystyrene, phenolic and polyester were developed [10]. Unsaturated polyester resins were first patented in As unsaturated polyester resin having good curing properties, it became the dominant choice for resins in manufacturing today. Carlton Ellis reported that unsaturated polyester pre-polymer might be mixed with phenyl ethylene, vinyl resin, polyvinyl resin and copolymerized into a rigid polymer [11]. These resins became commercially necessary consecutive for a decade as they were strengthened with glass fibers giving structural merchandise with high mechanical strength. Nowadays unsaturated polyesters are the foremost necessary matrix resins for composite materials [12]. Unsaturated polyesters are a large family of polymers with a wide range of applications stemming from their ability to undergo various polymerization reactions. Unsaturated polyester was utilized in high-gloss coatings, as insulating materials, in drug delivery systems and biomedical applications such as tissue engineering [13]. 134

4 The polymer industry currently relies heavily on petroleum-based feedstocks but with fossil fuel resources due to be soon depleted, biomass sources were of increasing interest in this research area. Bio-derived diacids were noticeable choices due to their potential for incorporation into polyesters preparation. Additionally, some bio-derived unsaturated polyester resin contain inherent bio-degradability and biocompatibility [14,15]. The synthesis of bio-derived UPEs was already well documented. Monomers based on itaconic acid (IA) were frequently utilized due to the double bond functionality of this bio-derived di-acid. Because of its conjugation with the adjacent carbonyl, the vinyl group acts as a Michael acceptor and allows for post-polymerization functionalization and hence property tuning of the itaconate polyesters [16]. A variety of compounds have been incorporated into the oligomers alongside the itaconate moiety such as; alcohols i.e. 1,4-butanediol, ethylene glycol, trimethylolpropane, sorbitol, isoamyl alcohol; epoxides i.e. propylene oxide, glycidyl ether, epichlorohydrin; and other di-acids i.e succinic acid, maleic acid or fumaric acid; and this helps introduce extra functionality [17]. Another method of functionalization was via a cross-linking agent and again a wide variety have been used, from straightforward dimethyl itaconate to highly functionalized N-alkylated dinitrones. The synthesis of larger oligomers by polycondensation has been laden by the tendency of the itaconate double bond to itself act as a cross-linker and often, radical inhibitors were needed to enable efficient formation of even the smallest oligomers [18]. The difference between saturated and unsaturated polyester resins comes from the incorporation of unsaturated dicarboxylic acid compounds in unsaturated polyesters. The more important unsaturated compounds used in the preparation of unsaturated polyesters include maleic acid, maleic anhydride and fumaric acid. Inclusion of such compounds in unsaturated polyesters provides them with the ability to copolymerize with unsaturated compounds such as styrene [19]. Thermosetting saturated polyester resins were either formulated with excess hydroxyl or acid groups which can then be crosslinked with suitable curing agents. The curing agents that were mostly used for hydroxyl terminated polyester resins were aminoplasts. Melamine formaldehyde resins were among the more important aminoplasts [20]. Saturated polyester resins in 135

5 combination with melamine formaldehyde resins were specifically designed for stoving finishes applied on industrial articles. Unsaturated polyester resin was cure between temperature range from C to C [21]. The unsaturated resin was easily handled in processes such as filament winding, hand layup, resin transfer moulding in liquid form. The unsaturated resin possess good mechanical and service properties; have excellent thermal stability and weather resistant. The unsaturated polyester resin were used in number of application i.e. in moulding compounds, insulation and coil coatings, fiber reinforced plastic products, sandwich panels and also in industries such as automotive and architectural [22]. In the present work 1,3-PDO (obtained from bioconversion of crude glycerol) was utilized for the preparation of saturated and unsaturated polyester resin. Reaction parameters were optimized to get best result. SATURATED POLYESTER RESIN 3.1 MATERIALS AND METHODS 3.2 MATERIALS Phthalic anhydride, zinc acetate, p-toluene sulfonic acid (PTSA), zinc chloride and potassium hydroxide (KOH) were purchased from Sigma- Aldrich. Xylene, toluene, benzene and methanol were purchased from National chemicals, Baroda. Solvents and other laboratory chemicals were used after routine purification and they were of analytical reagent (AR) grade. 3.3 METHODS Preparation of saturated polyester resin Phthalic anhydride (13.28gm), 1,3-PDO (11.73ml) obtained from bioconversion of crude glycerol, catalyst (0.2gm) as catalyst and xylene (10ml) as solvent were added in four neck flask. The reaction temperature 136

6 was slowly raised to C till the mass becomes clear. Then raise the temperature gradually up to C under nitrogen atmosphere. The reaction was continued till acid value was reached to below 15. Water was formed during esterification process was continuously removed using azeotropic distillation where xylene was used as solvent. Xylene was recovered at the end of reaction by distillation Acid value determination At regular interval resin sample from the esterification process was taken and titrated against a standard alcoholic KOH solution. The burette readings were noted and the acid value was calculated by the following equation. Acid value = B. R. x N x 56.1 Weight of the sample Where, N = Normality of the alcoholic KOH solution FTIR spectroscopy FTIR spectrometer is used to collects high spectral resolution data over a wide spectral range. This deliberates a significant advantage over a dispersive spectrometer which measures intensity over a narrow range of wavelengths at a time. FTIR is a technique which is used to obtain an infrared spectrum of absorption, emission, photoconductivity or Raman scattering of a solid, liquid or gas. In the IR spectroscopy, IR radiation is passed through a sample where some of the infrared radiation is absorbed by the sample and some are transmitted. The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample. Similar a fingerprint no two unique molecular structures produce the same infrared spectrum. This makes infrared spectroscopy useful over several types of analysis. The resulting product were characterized by FTIR spectroscopy using Perkin Elmer spectrum GX instrument, by the KBr pellets method Differential scanning calorimeter Differential scanning calorimetry (DSC) is a thermo-analytical technique in which the difference in the amount of heat required to 137

7 increase the temperature of a sample and reference is measured. The sample and reference, both are maintained at nearly the same temperature throughout the experiment. The temperature for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. The reference sample have a well-defined heat capacity over the range of temperatures to be scanned. When the sample undergoes a physical transformation more or less heat will need to flow to it than the reference to maintain both at the same temperature. Less or more heat must flow to the sample depends on whether the process is exothermic or endothermic. If a solid sample melts to a liquid, it will require more heat flowing to the sample to increase its temperature at the same rate as the reference. This is happened due to the absorption of heat by the sample as it undergoes the endothermic phase transition from solid to liquid. Similarly, as the sample undergoes exothermic processes less heat is required to raise the sample temperature. Differential scanning calorimeters are measured the amount of heat absorbed or released during such transitions by observing the difference in heat flow between the sample and reference. DSC is used to observe physical changes, such as glass transitions. It is widely used in industrial settings as a quality control instrument due to its applicability in studying polymer curing. DSC of prepared saturated polyester resin was carried out by heating sample from temperature of C to C at a heating rate of 10 0 C/min using Perkin Elmer Pyris 1 DSC instruments. 3.4 RESULT AND DISCUSSION OPTIMIZATION STUDY OF PARAMETERS Saturated polyester resin was prepared using 1,3-PDO and phthalic anhydride. Various optimization studies parameters such as effect of temperature, reaction time, solvent and catalyst on reaction were carried out. Looking to the optimized data it was confirmed that prepared saturated polyester resin was better in process condition i.e. temperature, reaction time and raw material. The compared data of commercial product made in SIRALES is shown below, 138

8 PE ,3-PDO based saturated polyester :16mg/KOH acid value : 10.24mg/KOH acid value Effect of temperature Effect of temperature on the synthesis of polyester was optimized. The results were tabulated in table: 1. Temperature ( 0 C) Catalyst Time (hours) Solvent Acid value PTSA 7 Xylene Table: 1 Effect of temperature During the esterification process, temperature plays a very important role. At C temperature, desired acid value may obtained but it takes longer reaction time than the reaction carried out at C. If the temperature was kept around C to C for 7 hours reaction time, than product may thermally decompose. More specifically at the higher temperature sublimation of phthalic anhydride may occur. Ultimately there was shortage of one of the important constituent was taking place. Due to this reason, the desired acid values may not possible and reactions stop early. Moreover, the high temperature leads to the loss of solvent and there so, the reaction may not forward and high acid value product was obtained. However, the temperature was maintained around C properly than reaction proceed in smooth way. Therefore, the optimum acid value was obtained using C temperature Effect of solvent Solvent Catalyst Time Temperature Acid value (hours) ( 0 C) Benzene Xylene PTSA Toluene Table: 2 Effect of solvent 139

9 Effect of solvent on the synthesis of polyester was optimized. The results were tabulated in table: 2. In this study, xylene, toluene and benzene were used as solvents but among them xylene was set perfectly in the reaction for esterification process because of the boiling point of xylene was higher than the boiling point of benzene and toluene. In addition, to inhibit the loss of solvent in the reaction system, xylene was utilized instead of benzene and toluene. Xylene proceeds the reaction in forward direction but excess of it may inhibits the reaction and it results into the higher acid value product while small amount of xylene inhibits the water removal. Thus, the optimum acid value was obtained using 10 ml of xylene proceed Effect of reaction time Effect of reaction time on the synthesis of polyester was optimized. The results were tabulated in table: 3. In the 3hours reaction time generally higher acid value resin was obtained. Low acid value was obtained using zinc acetate, zinc chloride and PTSA as catalyst if the reaction time was increased. Lower acid values were obtained during 7hours reaction time than 5hours reaction time. There so, 7hours reaction time was optimum. Time (hours) Catalyst Solvent Temperature ( 0 C) Acid value PTSA Xylene Table: 3 Effect of reaction time Effect of catalyst Catalyst Time Solvent Temperature Acid value (hours) ( 0 C) Zinc acetate PTSA 7 Xylene Zinc chloride Table: 4 Effect of catalyst 140

10 Effect of catalyst on the synthesis of polyester was optimized. The results were tabulated in table: 4. Zinc acetate, PTSA and zinc chloride were used as a catalyst for the saturated esterification process. But, small difference in acid values was observed. Overall PTSA gives lowest acid value among other catalyst used Optimum Parameters The following are the optimum parameters for the reaction 1. Temperature: C 2. Solvent: Xylene 3. Reaction time: 7hours 4. Catalyst: PTSA FTIR spectroscopy The FTIR spectrum of saturated polyester resin is shown in figure: 1. The core structure of polyester resin sample had ester, aromatic ring, alcohol and anhydride because they may remain unreacted in sample. Due to meta substituted benzene deformation vibration observed at cm -1. The strong absorption band at cm -1 confirms formation of aryl ester group. The O H stretching vibration at cm -1 confirms the presence of alcohol. Moreover, the strong absorption band was observed at cm -1 confirms the incorporation of 1,3-PDO to the polyester. 141

11 Figure: 1 FTIR spectra of saturated polyester resin Differential scanning calorimeter The DSC of saturated polyester is shown in figure: 2. DSC was carried out to find out the glass transition and other changes in heat energy of synthesized saturated polyester resin. DSC defines the glass transition as a change in the heat capacity as the polymer matrix goes from the glass state to the rubber state. This is requires heat to go through the transition so in the DSC the transition appears as a step transition and not a peak such as might be seen with a melting transition. Glass transition temperature of saturated polyester resin obtained using 1,3-PDO was found at C and no major change in the graph was observed thereafter. Figure: 2 DSC of saturated polyester resin 3.5 CONCLUSION 1,3-PDO was utilized for the manufacturing of saturated polyester resin where different parameters like the temperature, reaction time, solvents and catalyst were optimized. Consequently from the result, best parameters for manufacturing saturated polyester was 0.5:1 molar ratio of phthalic anhydride and 1,3-PDO respectively in the presence of catalyst PTSA for 7hours at C with acid value was obtained. Product 142

12 data was compared with SIRALES. It shows better property than commercial product. UNSATURATED POLYESTER RESIN 3.1 MATERIALS AND METHODS 3.2 MATERIALS Phthalic anhydride, maleic anhydride, zinc acetate, p-toluene sulfonic acid (PTSA), zinc chloride, potassium hydroxide (KOH), hydroquinone were purchased from Sigma- Aldrich. Xylene, benzene, toluene, methanol and styrene were purchased from National chemicals, Baroda. Solvents and other laboratory chemicals were used after routine purification and they were of analytical reagent (AR) grade. 3.3 METHODS Preparation of unsaturated polyester resin Phthalic anhydride (7.40gm), 1,3-propanediol (8.97ml), catalyst (0.2gm) and xylene (40ml) as solvent were added in four neck flask. The temperature of reaction mass was raised to C till the reaction mass becomes clear. At this stage maleic anhydride (4.90gm) was added and the temperature was raised to C under nitrogen atmosphere. The reaction carried out until acid value was reached to below 15. Water formed was continuously removed using azeotropic distillation using xylene as solvent. Xylene was recovered at the end of reaction by distillation. The product was allowed to up to cool C, and then hydroquinone (15mg) was added as inhibitor. The further cooling was carried out up to C, 30% styrene was added as diluent Acid value determination At regular interval resin sample from the esterification process was taken and titrated against a standard alcoholic KOH solution. The burette readings were noted and the acid value was calculated by the following equation. 143

13 Acid value = B. R. x N x 56.1 Weight of the sample Where, N = Normality of the alcoholic KOH solution FTIR spectroscopy The resulting product were characterized by FTIR spectroscopy using Perkin Elmer spectrum GX instrument, by the KBr pellets method Differential scanning calorimeter DSC of prepared unsaturated polyester resin was carried out by heating sample from temperature of C to C at a heating rate of 10 0 C/min using Perkin Elmer Pyris 1 DSC instruments. 3.4 RESULT AND DISCUSSION OPTIMIZATION STUDY OF PARAMETERS Unsaturated polyester resin was prepared using 1,3-PDO, phthalic anhydride and maleic anhydride. Various optimization studies parameters such as effect of temperature, reaction time, solvent and catalyst on reaction were carried out. Unsaturated polyester resin was prepared using 1,3-PDO and phthalic anhydride. Various optimization studies parameters such as effect of temperature, reaction time, solvent and catalyst on reaction were carried out. The compared data of commercial product made in Paint and Coating Industry (PCI) is shown below, PCI made :10mg/KOH acid value 1,3-PDO based unsaturated polyester : 08.21mg/KOH acid value 144

14 Effect of solvent Solvent Catalyst Time (hours) Temperature ( 0 C) Acid value Benzene Zinc Xylene acetate Toluene Table: 5 Effect of solvent Effect of solvent on the synthesis of unsaturated polyester was optimized. The results were tabulated in table: 5. In this study, xylene, toluene and benzene were used as solvents but among them xylene was set perfectly in the reaction for esterification process because of the boiling point of xylene was higher than the boiling point of benzene and toluene. In addition, to inhibit the loss of solvent in the reaction system, xylene was utilized instead of benzene and toluene. Xylene proceeds the reaction in forward direction but excess of it may inhibits the reaction and it results into the higher acid value product while small amount of xylene inhibits the water removal. Thus, the optimum acid value was obtained using xylene Effect of reaction time Time (hours) Catalyst Solvent Temperature ( 0 C) Acid value Zinc Xylene acetate Table: 6 Effect of reaction time Effect of reaction time on the synthesis of unsaturated polyester was optimized. The results were tabulated in table: 6. High acid value was obtained during 8hrs reaction time. If the reaction time was increased low acid value was obtained using zinc acetate, zinc chloride and PTSA as catalyst. Almost same acid values were obtained during 12hours and 16hrs reaction time so 12hours reaction was economical. In the case of zinc acetate catalyst low acid value was obtained compare to other catalyst. 145

15 Effect of catalyst Catalyst Time (hours) Solvent Temperature ( 0 C) Acid value PTSA Zinc acetate 12 Xylene Zinc chloride Table: 7 Effect of catalyst Effect of catalyst on the synthesis of unsaturated polyester was optimized and the results were tabulated in table: 7. Catalyst plays a very important role for any reaction. Zinc acetate, PTSA and zinc chloride were used as a catalyst for the unsaturated esterification process. Where the zinc acetate proves the great thermal stability at higher temperature. Low acid value (8.21) was obtained using zinc acetate as catalyst during 12hours reaction time. While in case of other catalyst comparatively higher acid value were obtained. So zinc acetate proves best as a catalyst for manufacturing unsaturated polyester resin Optimum Parameters The following are the optimum parameters for the reaction 1. Solvent: Xylene 2. Reaction time: 12hours 3. Catalyst: Zinc acetate FTIR spectroscopy The FTIR spectrum of polyester resin is shown in figure 3. The main structure of the polyester resin sample had ester, aromatic ring, alcohol and anhydride because they may remain unreacted in the sample. The strong vibration observed at cm -1 which confirms the present of benzene group. The C=O streching observed at cm -1 which confirms the carbonyl group. The bending observed at cm -1 which confirms the C=C group. Due to meta substituted benzene deformation, vibration observed at & cm -1. While incorporation of 1,3-PDO into polyester confirms by strong absorption band at cm

16 Figure: 3 FTIR spectra of unsaturated polyester resin Differential scanning calorimeter Figure: 4 DSC of unsaturated polyester resin The DSC of unsaturated polyester is shown in figure: 4. As the unsaturated polyester resin synthesized was from the maleic anhydride there is always some possibility of crystallization of meting of one of these fraction and which could be obtained in DSC. DSC was carried out to find out the changes in heat energy of synthesized unsaturated polyester resin. 147

17 Glass transition of unsaturated polyester resin obtained from maleic anhydride and 1,3-PDO as monomer was at C and thereafter no changes was observed. 3.5 CONCLUSION This 1,3-PDO was utilized in the unsaturated polyester resin manufacturing. In this method there are so many parameters that have to keep in mind like the reaction temperature and time, catalyst and solvent etc., to be best unsaturated polyester resin manufacturing. So from the result, best parameters for manufacturing unsaturated polyester were, 0.5:1.25:0.5 molar ratios of phthalic anhydride, 1,3-PDO and Maleic anhydride in the presence of zinc acetate catalyst for 12 hours at C where the 8.21 acid value was obtained. The product data was compared with PCI. The synthesized product shows better property than commercial product. 3.6 REFERENCES 1. Chanda, S.; Ramakrishnan, S. Poly(alkylene itaconate)s-an interesting class of polyesters with periodically located exo-chain double bonds susceptible to Michael addition. Polym. Chem. 2015;6: Paul, S.; Zhu, Y.; Romain, C.; Brooks, R.; Saini, P.K.; Williams, C.K. Ring-opening copolymerization (ROCOP): Synthesis and properties of polyesters and polycarbonates. Chem. Commun. 2015;51: Goerz, O.; Ritter, H. N-Alkylated dinitrones from isosorbide as crosslinkers for unsaturated bio-basedpolyesters. Beilstein J. Org. Chem. 2014;10: Lehtonen, J.; Salmi, T.; Immonen, K.; Paatero, E.; Nyholm, P. Kinetic model for the homogeneously catalyzed polyesterification of dicarboxylic acids with diols. Ind. Eng. Chem. Res. 1996;35: Yang, Y.S.; Pascault, J.P. Modeling of unsaturated polyester prepolymer structures. II. Hydroxyl and carboxyl functionalities. J. Appl. Polym. Sci. 1996; 2:

18 6. Goodman; J. A. Rhys; Polyesters; Saturated Polymers; Iliffe Books; London. 1965; P. W. Morgan; Condensation Polymers; By Interfacial and Solution Methods; Inerscience Publishers; New York; Bikiaris DN, Papageorgiou GZ, Giliopoulos DJ, Stergiou CA. Correlation between chemical and solid-state structures and enzymatic hydrolysis in novel biodegradable polyesters. The case of poly(propylene alkanedicarboxylate)s. Macromol Biosci. 2008;8: Thomas J. Farmer, Rachael L. Castle, James H. Clark and Duncan J. Macquarrie. Synthesis of Unsaturated Polyester Resins from Various Bio-Derived Platform Molecules. Int. J. Mol. Sci. 2015;16: Goodman; Encyclopedia of Polymer Science and Engineering; 2nd ed.; 12; Wiley; New York; O. C. Zaske and S. H. Goodman; Unsaturated Polyester and Vinyl Ester Resins, in: S. H. Goodman; (Ed.); Handbook of Thermoset Plastics; 2nd Ed.; Noyes Publication, Westwood. 1998; Tang. T.; Moyori, T.; Takasu. A. Isomerization-free polycondensations of cyclic anhydrides with diols and preparation of polyester gels containing cis or trans carbon double bonds via photo-cross-linking and isomerization in the gels. Macromol 2013;46: Gandini, A.; Lacerda, T.M. From monomers to polymers from renewable resources: Recent advances. Prog. Polym. Sci. 2015;48: Farmer, T.; Mascal, M.; Clark, J.; Deswarte, F. Introduction to Chemicals from Biomass, 2nd ed;john Wiley and Sons: Chichester, UK, 2015; Tokiwa, Y.; Calabia, B.P. Biodegradability and biodegradation of polyesters. J. Polym. Environ. 2007;15: Gowsika, J.; Nanthini, R. Synthesis, characterization and in vitro anticancer evaluation of itaconic acid based randon copolyester. J Chem. 2014; 2014:

19 17. Barrett, D.G.; Merkel, T.J.; Luft, J.C.; Yousaf, M.N. One-step syntheses of photocurable polyesters based on a renewable resource. Macromol 2010;43: Dai, J.; Ma, S.; Liu, X.; Han, L.; Wu, Y.; Dai, X.; Zhu, J. Synthesis of bio-based unsaturated polyester resins and their application in waterborne UV-curable coatings. Prog. Org. Coatings 2015;78: Kharas, G.B.; Kamenetsky, M.; Simantirakis, J.; Beinlich, K.C.; Rizzo, A.T.; Caywood, G.A.; Watson, K. Synthesis and characterization of fumarate-based polyesters for use in bioresorbable bone cement composites. J. Appl. Polym. Sci. 1997;66: Koro de la Caba, Pedro Guerrero, Inaki Mondragon & Jose M. Kenny. Comparative Study by and DSC FTIR Techniques of an Unsaturated Polyester Resin Cured at Different Temperatures. Poly Int. 1998;45: R. B. Patel, K. S. Patel, R. N. Patel and K. D. Patel. Thermal and mechanical properties of modified polyester resin and jute composite. Der Chemica Sinica. 2014;5: E.M.S. Sanchez, C.A.C. Zavaglia, M.I. Felisberti. Unsaturated polyester resins: influence of the styrene concentration on the miscibility and mechanical properties. Polymer. 2000;41: