Neat Unsaturated Polyester Resin Research Articles

Comparison of the mechanical characteristics of biocomposites of unsaturated polyester resin with cellulose extracted from corn silk and treated corn silk

The purpose of this study is to extract cellulose from corn silk (CS) fiber and use it as a reinforcing filler in unsaturated polyester resin (UPR) matrix. In this study, the cellulose is characterized using a Fourier Transform Infrared Spectrometer (FTIR), and the resulting UPR/cellulose biocomposite's mechanical properties (such as flexural and impact testing) are assessed. Scanning electron microscopy (SEM) provided strong support for mechanical rather than a chemical bond between fiber and UPR. Additionally, the sodium hydroxide treated CS in UPR biocomposite and comparing it with neat UPR. The agricultural byproduct rich in cellulose corn silk is a natural polymer known for its structural strength and UPR has garnered attention as a biopolymer with notable flexibility, making it an appealing choice for plastic product manufacturing. However, the drawback of UPR lies in its inherent deficiency in both stiffness and strength. According to the FTIR data, extracted cellulose (CS) had fewer ketone (C = O) and hydroxyl (-OH) groups than virgin cellulose. It was shown that throughout the extraction process, hemicellulose and lignin were more eliminated, producing a more pure form of cellulose. When filled in UPR, cellulose and treated CS both caused the impact strength of UPR biocomposites to drop. For both treated CS and cellulose, it was shown that the flexural modulus and flexural strength increased as the filler amount increased to a definite percentage (12%) after which it decreased. The result revealed the tensile strength and tensile modulus achieved by 0% of fiber with 48 N/mm2 and 51 N/mm2 and highest at 12% of fiber with 54.3 N/mm2 and 68.8 N/mm2 for CS + UPR. And 53.4 N/mm2 and 69.6 N/mm2 for cellulose + UPR composite,, respectively. In comparison, the flexural characteristics of UPR/cellulose were marginally inferior to those of UPR/treated CS. However, the impact resistance showed a significant improvement, particularly with a cellulose loading of 12%. Hence, cellulose presents a greater potential for composite manufacturing due to its ability to maintain the ductile properties of UPR compared to treated CS. Moreover, processed CS and cellulose both can be used as reinforcing agents in polymers to increase their strength and stiffness.

Unsaturated Polyester Resin Filled with Cementitious Materials: A Comprehensive Study of Filler Loading Impact on Mechanical Properties, Microstructure, and Water Absorption.

In recent years, cheaply available cementitious materials (CMs) are increasingly finding useful applications in construction engineering. This manuscript focused on the development and fabrication of unsaturated polyester resin (UPR)/cementitious material composites to be potentially useful in a variety of construction applications. For this purpose, five types of powders from widely available fillers, i.e., black cement (BC), white cement (WC), plaster of Paris (POP), sand (S), and pit sand (PS), were used. Cement polymer composite (CPC) specimens were prepared by a conventional casting process with various filler contents of 10, 20, 30, and 40 wt %. Neat UPR and CPCs were investigated mechanically by testing their tensile, flexural, compressive, and impact properties. Electron microscopy analysis was used to analyze the relation between the microstructure and mechanical properties of CPCs. The assessment of water absorption was conducted. The highest tensile, flexural, compressive upper yield, and impact strength values were recorded for POP/UPR-10, WC/UPR-10, WC/UPR-40, and POP/UPR-20, respectively. The highest percentages of water absorption were found to be 6.202 and 5.07% for UPR/BC-10 and UPR/BC-20, while the lowest percentages were found to be 1.76 and 1.84% for UPR/S-10 and UPR/S-20, respectively. Based on the finding of this study, the properties of CPCs were found to depend on not only the filler content but also the distribution, particle size, and combination between the filler and the polymer.

Strategic design unsaturated polyester resins composites with excellent flame retardancy and high tensile strength

Unsaturated polyester resin (UPR) composites with excellent flame retardancy and high mechanical property is a great challenge to its widely application. In present work, a highly efficient flame retardant (MA-DOPO) containing nitrogen, sulfur and phosphorus elements was designed via a nucleophilic substitution reaction of amino and aldehyde groups. For the UPR/MA-DOPO15 composites, its tensile strength was 28.3 MPa, which was 19.9 % higher than that of neat UPR attributing to the formation of hydrogen bonds with UPR. It should be noted that tensile strength of UPR/MA-DOPO20 composites reached the highest 39.6 MPa, showing a growth trend with the enhancement of incorporation amount of MA-DOPO. Meanwhile, the UPR/MA-DOPO15composites passed the UL-94 V-0 rating with a LOI of 27.0%, and the peak heat release rate (PHRR) and total heat release rate (THR) were reduced by 35.1% and 41.6% in cone calorimeter (CC) test comparing to that of neat UPR respectively. Moreover, the detailed flame-retarding mechanism of MA-DOPO was investigated by the thermogravimetric infrared spectroscopy (TG-IR), Raman spectrum, X-ray photoelectron spectroscopy (XPS) and pyrolysis-gas chromatography/mass spectrometry (PY-GC/MS), in which the releasement of inert gas in gas-phase and the catalytic carbonation in condensed phase jointly taking effect.

The Hyperbranched Polyester Reinforced Unsaturated Polyester Resin.

We report a method of reinforcing and toughening unsaturated polyester resin (UPR) with a kind of hyperbranched polyester (HBP-1). Polyethylene glycol with different molecular weight was used as the core molecule of the preparation reaction, and the reaction product of phthalic anhydride and glycerol was used as the branching unit. The esterification reaction of polycondensation occurred, and then the hydroxyl-terminated hyperbranched polyester was prepared. The reaction product of maleic anhydride and isooctanol was added to the prepared hydroxyl-terminated hyperbranched polyester for esterification reaction. Both ends of the hyperbranched polyester had unsaturated double bond to obtain the hyperbranched polyester (HBP-1). The effects of this treatment on the morphology, mechanical properties and thermal properties of the composites were studied in detail. The HBP-1 was investigated by Fourier Transform Infrared Spectroscopy (FT-IR). The HBP-1/UPR composites were investigated by Thermogravimetric Analysis (TGA), Dynamic Mechanical Analysis (DMA), mechanical properties analysis and Scanning Electron Microscope (SEM). The results showed that HBP-1 enhanced the thermostability and mechanical properties of UPR. However, DMA indicated that the addition of HBP-1 cannot effectively improve the thermodynamic properties of UPR due to the flexible chain in HBP-1 structure. The HBP-1 improves tensile strength, bending strength and impact strength compared to neat UPR.

Effects of nano CaCO3 on the water absorption, tensile and impact properties of unsaturated polyester composites

ABSTRACT In this work, the effects of nano CaCO3 (NCC) on the water absorption, the tensile and impact properties of the unaged and aged unsaturated polyester resin (UPR) have been investigated. The specimens were aged in distilled water at room temperature. It was found that the water uptake and the diffusion rate of the NCC/unsaturated polyester composites tended to increase with the increase of NCC content, by about 15 and 31%, respectively, at the NCC content of 5 wt% compared to neat UPR. For the unaged specimens, the tensile strength was enhanced by adding the NCC of 1 wt% and tended to decrease beyond this content. For the aged specimens, the tensile strength tended to decrease with the increase of NCC content. Nevertheless, the elastic modulus of the unaged and aged specimens tended to increase up to the NCC content of 3 wt% and then decrease at the content of 5 wt%. The elastic modulus of the aged specimens was higher than those of the aged specimens due to water-embrittlement. The impact strength of the unaged and aged specimens tended to increase up to the NCC content of 5 wt%. However, the impact strength of the aged specimens was lower than those of the unaged specimens. The results suggested that the addition of 1 wt% NCC could compromise the tensile and impact properties of UPR both in unaged and aged conditions.

A novel P‐S‐Si‐based cage‐structural monomer for flame‐retardant modification of unsaturated polyester resin

Currently, the issue of improving the flame‐retardant performance of unsaturated polyester resin (UPR) has drawn a lot of attention. In this study, methyl vinyl di (1‐thio‐2,6,7‐trioxal‐1‐phosphabicyclo [2.2] octane‐4‐methoxy) silane (MVDOS) with P‐N‐Si‐based cage unit was synthesized, and it was utilized as a reactive flame‐retardant monomer to modify UPR. The UPR/MVDOS composites were prepared by introducing different ratios of MVDOS into UPR via the reaction of crosslink. The efficiency of the resulted composites was investigated by using the limiting oxygen index (LOI), vertical burning test, and cone calorimeter test. The results showed that the composites reached the V‐0 rate without dripping, and the LOI value was 29.1% when the content of MVDOS was as low as 18 wt%. Cone calorimeter tests revealed the peak of heat release and CO production of UPR/MVDOS‐18 were 238.2 KW/m2 and 0.0167 g/s, which were respectively lower than the ones of neat UPR. The introduction of MVDOS also increased the stability of UPR composites. Furthermore, the scattering electron microscopy, laser Raman spectroscopy, and X‐ray photoelectron spectroscopy studies revealed that the incorporation of MVDOS stimulated the UPR matrix to generate char layer with increased graphitization degree, which provided a good barrier to prevent heat and oxygen from being transferred and then protected the materials inside from further burning. This research provides a new way to obtain flame‐retardant UPR composites with high performance.

Hierarchical Structure: An effective Strategy to Enhance the Mechanical Performance and Fire Safety of Unsaturated Polyester Resin.

It is still a big challenge to prepare polymer/layered double hydroxide (LDH) composites with high performance, due to the strong agglomeration tendency of LDHs in the polymeric matrix. In this study, to avoid the agglomerated situation, the orientated LDH nanosheets were vertically grown on a ramie fabric surface, which was then embedded in unsaturated polyester resin (UPR) through the combination method of hand lay-up and vacuum bag. Due to the increased contact area and the restricted interfacial slip in the in-plane direction, the hierarchically LDH-functionalized ramie fabrics (denoted as Textile@LDH) significantly enhanced the mechanical performance of UPR composites. Then, the phosphorus- and silicon-containing coating (PSi) was used for the further improvement of the interfacial adhesion. The tensile strength of UPR/Textile@LDH@PSi composites increased by 121.67%, compared to that of neat UPR. The reinforcement mechanism was studied through analyzing the surface nano/microstructure and wetting properties of the raw and modified textiles, as well as the interfacial interaction between the ramie fabrics and UPR. Meanwhile, the thermal stability, thermal conductivity, and flame-retardant performance of ramie-reinforced UPR composites were improved. Particularly, as-prepared hierarchical Textile@LDH@PSi inhibited the heat release during the combustion process of fabric-reinforced UPR composites, and the peak heat release rate and total heat release values decreased by 36.56 and 47.57%, respectively, compared with the neat UPR/Textile composites. The suppression mechanism was further explored by analyzing the microstructure and chemical compositions of char residues. This research paved a feasible solution to improve the poor dispersion of LDHs in polymers and prepared the high-performance UPR composites with multifunctional applications.

Freeze dried cellulose nanocrystal reinforced unsaturated polyester composites: challenges and potential

Functionalized cellulose particles were studied as a potential reinforcement for an unsaturated polyester resin (UPR) system, a common material for automotive applications of fiber reinforced plastics. A preliminary process for incorporating freeze-dried cellulose nanocrystal (CNC) powder into UPR was developed. Three surface chemistries were explored including sulfonated, methyl(triphenyl) phosphonium (PhCNC), and maleic acid (MCNC). By optical microscopy the filler was seen to be agglomerated within the matrix. Fractography showed that these agglomerates acted as stress concentration points resulting in decreased tensile and flexural strength. With the addition of 1 wt% CNCs, the flexural and tensile modulus increased by up to 53% and 22%, respectively. Dynamic mechanical analysis indicated that the PhCNC- and MCNC-UPR samples had a 61% and 66% higher glassy modulus than neat UPR, respectively. Despite the lack of nano-scale dispersion of CNC in UPR, these results reflect potential in the use of functionalized CNC agglomerates as an additive in UPR systems to produce composites with high moduli and good thermo-mechanical stability.

Optimising cure cycle of unsaturated polyester nanocomposites using directed grid search method

In this research, a method is proposed for optimising cure cycle of neat unsaturated polyester (UP) resins, and UP resins containing Cloisite 20A (UP/20A), in thin parts. Using the proposed optimisation method, optimised cure cycles for both neat UP resin system and UP/20A were calculated. Results of dynamic mechanical analysis tests show that samples cured by the optimised cure cycles are slightly different from those samples cured using a long-term cure cycle in terms of structural relaxation. This confirms that the proposed optimisation method not only reduces the cure cycle duration efficiently but also preserves the quality of the samples.

Optimizing cure cycle of nanoclay-reinforced unsaturated polyester resins considering various curing kinetic models

In this research, a method has been presented for optimizing cure cycle of neat unsaturated polyester resin and polyester resin containing 3 wt% nanoclay Cloisite® 10 A (UP/10 A) and nanoclay Cloisite® 30B (UP/30B) in thin components. We refer to this optimization method as the directed grid search method. To model cure behaviour of unsaturated polyester resin, four different kinetic models were considered, including advanced iso-conversional method, Kamal method, Kamal method with Chern diffusion factor, and Kamal method with Sbirrazzuoli diffusion factor. The comparison of our proposed optimized cure cycles indicates that addition of nanoclay to the resin causes the cure cycle duration and also the maximum temperature during the cure to decrease. In addition, by adding nanoclay to the resin, the optimal cure cycle is transformed from a five-stage cure cycle to a four-stage one. Our investigations indicate that optimal cure cycles for the UP/10 A and UP/30B systems do not significantly differ. This is because the pre-exponential factor can influence the optimal cure cycle as much as the activation energy. Our results show that the optimal cure cycle obtained from the Kamal model is much shorter than the optimal cure cycle obtained from the advanced iso-conversional method, while the optimal cure cycle obtained from the Kamal model with Chern diffusion factor is very similar to the cure cycle resulting from the advanced iso-conversional method.

Toughened polyester cellulose nanocomposites: Effects of cellulose nanocrystals and liquid epoxidized natural rubber on morphology and mechanical properties

Unsaturated polyester resin (UPR) has been modified with a liquid epoxidized natural rubber (LENR). The addition of LENR improves the toughness, but it is inevitably accompanied by a significant loss in stiffness, yield strength, and thermal resistance. Incorporation of a rigid material into the LENR–UPR blend, such as cellulose nanocrystal (CNC), provided a ternary polyester nanocomposites with desire mechanical properties. In the present work, the effects of different CNC and LENR content on the nanocomposite morphology and mechanical properties were examined. Morphological studies revealed that the size of the rubber particles is independent of the rubber content due to the chemical interaction of rubber and matrix; however, the size of the LENR particles increased with increasing CNC content. Tensile tests indicated that the blend’s tensile strength and elastic modulus could be further improved by incorporation of the CNCs. The high crystallinity and surface area of CNCs were the main factors for improvement of tensile properties of the blend. Moreover, the impact energy of the UPR improved when it was modified with the LENR, and even further improvement was achieved with the CNC addition to form nanocomposites. Dynamic mechanical thermal analysis (DMTA) showed that the storage modulus of nanocomposites with 1.5wt% rubber content was lower than those with 4.5wt% LENR; however, both samples showed a higher storage modulus than the neat UPR and the unfilled blend. The glass transition temperature (Tg) of the UPR decreased with the LENR addition, but improved with the addition of CNCs. The nanocomposites prepared with a higher LENR content displayed better mechanical properties than those with low LENR content.

Cure kinetics of hot cured unsaturated polyester (UP)/nanoclay nanocomposite including dual initiators

In this work, cure behaviour and cure kinetic parameters of unsaturated polyester (UP) resin containing Na-Montmorillonite (Cloisite 30B) is investigated. The state of nanoclay dispersion is analysed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Addition of 1–5 wt-% nanoclay results in decreasing gel time, exothermic peak and increasing cure rate. Cure kinetic parameters are determined employing Borchardt–Daniels method. The modelling results also prove: decreased curing reaction starting temperature, higher reaction rate and higher conversion ratio. Besides decreased activation energy ratio and shorter curing cycle are also observed as the main results of incorporating Cloisite 30B to neat UP resin.

Development of biobased unsaturated polyester resin containing highly functionalized castor oil

A highly functionalized castor oil product mainly composed of castor oil pentaerythritol glyceride maleates (COPERMA) was employed to fabricate a partial biobased unsaturated polyester resin (UPR) through blending it with petroleum-based UPR. The COPERMA product synthesized was characterized by FT-IR, 1H NMR, and ESI-MS to determine its possible structure and its functionality. The 1H NMR results showed that the maleate CC functionality of the COPERMA product was high (2.62). This highly functionalized product was then mixed with 35wt% styrene before blending this mix with petroleum-derived UPR to prepare a new partial biobased UPR. Physical, thermal, and mechanical properties of the UPR/COPERMA resins were carefully studied. Physical properties data indicate that the resultant biobased resins are suitable for liquid molding process and had a less shrinkage than the neat UPR. Compared to the neat UPR, the cured UPR/COPERMA resins demonstrated comparable or even better thermal and mechanical properties when the content of COPERMA resin was up to 10wt%. When the content of COPERMA resin increased to 20wt%, the tensile strength and storage modulus at 35°C decreased gradually, but not as much as reported in other oil/UPR systems, while other properties, such as crosslink density, glass transition temperature, tensile and flexural moduli, and impact strength, were still improved.

Cure kinetic study of organoclay‐unsaturated polyester resin nanocomposites by using advanced isoconversional approach

Curing behavior of an unsaturated polyester (UP) resin containing 3 wt % Cloisite 10A (UP/10A) and 3 wt % Cloisite 30B (UP/30B) catalyzed with methyl ethyl ketone peroxide (MEKP) as initiator and promoted by cobalt naphthenate as accelerator was investigated by dynamic differential scanning calorimetry (DSC) at heating rates of 2, 2.5, 3, and 3.5°C min−1. X‐ray diffraction and transmission electron microscopy were utilized to evaluate the morphology of UP/10A and UP/30B nanocomposites. Kinetic parameters of cure reactions were evaluated using the advanced isoconversional method. The addition of nanoclay resulted in a decrease in the activation energy of the redox reaction compared to that of the neat UP resin. The pre‐exponential factor of the redox reaction for UP/10A and UP/30B was less than that of the neat UP. Results showed an increase in the concentration of styrene between Cloisite 10A platelets leading to a decrease in the intralayer styrene content. The high concentration of styrene between nanoclay layers may lead to the formation of polystyrene chains grafted on the alkyds chains. This homo‐polymerization was also observed in the variation of activation energy of UP/10A specimen versus the degree of conversion for 0.42 ≤ α ≤ 0.6 which is very close to the activation energy of free radical homo‐polymerization of styrene. POLYM. COMPOS., 34:1824–1831, 2013. © 2013 Society of Plastics Engineers

Synthesis and Characterization of Bismaleimide Modified Vinyl Ester Monomer-Unsaturated Polyester Intercrosslinked Hybrid Matrices

Intercrosslinked hybrid matrices were developed from N,N′-bismaleimido-4,4′-diphenyl methane (BMI) modified vinyl ester monomer (VEM), namely cyclohexyl-1,1′-bis[4-(γ-2-methylphenoxy)-α-hydroxypropylacrylate]-unsaturated polyester (UP) resin. BMI-modified VEM-UP hybrid matrices were characterized for their mechanical properties, viz. tensile strength, flexural strength, unnotched izod impact strength and hardness as per ASTM standards. Data obtained from thermal studies indicated that the introduction of vinyl ester monomer into unsaturated polyester resin marginally reduced the values of heat distortion temperature and glass transition temperature compared with those of the neat UP resin. Scanning electron microscopy studies of BMI modified VEM-unsaturated polyester systems exhibited a homogeneous morphology, confirming efficient chemical interaction and the formation of intercrosslinked networks.

The Evaluation of Low Profile Additives on the Shrinkage Control of Unsaturated Polyester Resin Cured at Room Temperature

The unsaturated polyester (UP) resins have the largest consumption of thermoset resins in the composite industry. The copolymerization of alkyd oligomer with styrene monomer at low temperature condition leads to 5-10% volume shrinkage which may cause problems in the surface quality and dimensional control of produced parts. One effective way for the reduction or elimination of the shrinkage is adding a thermoplastic polymer called low profile additive (LPA). The effect of poly(vinyl toluene) (PVT) and poly(ethyl methacrylate) (PEMA), as two new LPAs have been compared to three types of poly(vinyl acetate) (PVAc) and polystyrene (PS) which are used as conventional LPAs. The phase separation results and morphology of samples containing PEMA showed that this LPA enable to reduce the volume shrinkage. It reduced the volume shrinkage of neat UP from 8.3% to 5.4%. The cure kinetics behaviour of the samples containing PVT and PVAc was completely different from that of the neat UP resin.

Kinetic modeling of nanoclay‐reinforced unsaturated polyester resin

AbstractCuring behavior of an unsaturated polyester (UP) resin containing 1 wt% organically modified clay (OMC) catalyzed with methyl ethyl ketone peroxide (MEKP) initiator and promoted by cobalt naphthenate accelerator was investigated by dynamic differential scanning calorimetry (DSC) at five different heating rates of 5, 10, 15, 20, and 25°C/min. X‐ray diffraction and transmission electron microscopy were used to evaluate the morphology of UP/OMC composites. Results showed a mixture of intercalated and exfoliated morphology. The dynamic DSC curing curves showed a bimodal exothermic peak; therefore, two independent reactions, namely, redox and thermal copolymerizations were assumed. Kinetic parameters were calculated by using autocatalytic model and using Down hill simplex method and Runge–Kutta algorithm for each reaction. The addition of nanoclay resulted in decrease of the activation energy of the redox reaction compared to that of the neat UP resin. Also, the pre‐exponential factor of the first reaction for UP/OMC was less than that of the neat UP. Two factors including decreasing the activation energy and decreasing the number ofcollisions of reactionary components finally resulted in increasing the reaction rate of the first reaction out of the whole reaction in the system containing nanoclay compared to the neat UP resin. It is interesting that nanoclay has no effect on the thermal decomposition reaction. POLYM. COMPOS., © 2011 Society of Plastics Engineers.

Kenaf Bast Fiber Bundle–Reinforced Unsaturated Polyester Composites. II: Water Resistance and Composite Mechanical Properties Improvement

Water resistance properties of kenaf bast fiber bundle (KBFB)–reinforced composites with either unsaturated polyester (UPE) or vinyl ester (VE) matrices, developed in previous research, were studied. The effects of styrene content in UPE resin on the neat UPE resin tensile properties and molding pressure on composite flexural properties were evaluated. The effect of laser and plasma radiation on fiber-matrix interfacial shear strengths was studied. The composites exhibited high water uptake during short- and long-term water immersion. Encapsulation by surface coating and edge sealing improved composite water resistance. Statistical analyses indicated that molding pressures of 5 to 7 MPa were preferable to achieve the maximum composite mechanical properties, and 37.6 percent (wt/wt) styrene in the UPE resin gave the highest UPE matrix tensile properties in the studied range. Laser and plasma radiation of the KBFBs significantly improved fiber-matrix interfacial bonding.

Thermal and dynamic mechanical properties of IPNS formed from unsaturated polyester resin and epoxy polyester

The interpenetrating polymer networks (IPNs) were formed by unsaturated polyester resin (UPR) polymerized by free radical initiators: benzoyl peroxide (BPO) or cumene hydroperoxide (CHP) and epoxy polyester (EP), cured with acid anhydrides: tetrahydrophthalic anhydride (THPA) or maleic anhydride (MA). IPNs consisting 10, 30, 50, 70, 90 wt% of EP were prepared. The effect of the EP component in the IPNs and the type of curing agent on the cure behavior, thermal, and viscoelastic properties have been investigated. The results showed that both EP content and used curing system influenced on studied properties. As the EP content increased, the glass transition temperatures (Tg) also increased. Moreover, higher values of tanδmax and lower values of cross-linking density in a rubbery state (νe) of IPNs containing higher EP content, probably due to plasticization effect of EP component were observed. Additionally, more heterogeneous network structure (higher values of the full-width at half-maximum (FWHM) as the EP content decreased was prepared. The thermal and viscoelastic properties of the blends cured with BPO/MA or CHP/MA system were considerably better than those cured with BPO/THPA or CHP/THPA. The higher stiffness, νe, Tg and lower tanδmax values were obtained. It was probably connected with the interactions of carbon–carbon double bonds of MA with vinyl monomer (styrene), UPR and radical initiators causing to obtain more cross-linked polymer network structure. This supposition was confirmed on basis of the cure reaction monitored by DSC. The chemical interactions between two components of the blends and epoxy hardener caused that the BPO/MA or CHP/MA cure systems influenced on the cure behavior of UPR and EP components in the IPNs. The exotherm peak temperature (Tmax1) shifted to lower values compared to these in the neat UPR whilst Tmax2 shifted to higher values than in the neat EP. However, the cure behavior of the UPR was not greatly affected by the presence of EP component when BPO/THPA or CHP/THPA cure systems were used due to the lack of chemical interactions between the components and their curatives.

Kinetic parameters of unsaturated polyester resin modified with poly(ε -caprolactone)

The curing of the neat unsaturated polyester resin (UP) with benzoyl peroxide (initiator) as well as the curing of UP modified with two poly(e-caprolactone) PCL samples (PCL2 and PCL50) of different molecular masses (M n=2⋅103 and M n=5⋅104, respectively), were investigated by non-isothermal differential scanning calorimetry (DSC), at different heating rates. The activation energy was determined from the variation of the peak exotherm temperature, T peak, upon heating rate. Besides, the degree of conversion (α) was obtained from isothermal DSC measurements at 80°C at different curing times for neat UP, UP+ PCL2 and UP+PCL50. Kinetic parameters were deduced assuming the n th order reaction kinetic model for neat UP, UP+PCL2 and UP+PCL50 systems.