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The flammability levels, flame retardancy ratings, and reaction-to-fire (fire response) properties (under five radiant heat fluxes, i.e., 15, 25, 35, 50, and 75 kW m−2) for same real E-glass fiber-reinforced unsaturated polyester resin (UPR) composite wind turbine blade (WTB) samples were determined by experimental techniques like limiting oxygen index (LOI), vertical flame test (VFT), and cone calorimeter test (CCT). Based on typical CCT results (main test parameters), thermal and non-thermal hazard assessment index systems were selected, calculated, and compared to deduce corresponding hazard characteristics of the blade samples. The WTB shows a LOI value of 25.10% (combustible) and a non-rated (NR) UL (Underwriters Laboratories) 94 classification according to the after-flame time criterion. CCT analyses indicate that higher external heat fluxes correspond to increased peak heat release rate (PkHRR), total heat release (THR), and mass loss rate (MLR) values, and reduced ignition time (tig), flame duration (tfl), and overall flame (combustion) duration (FD) values. Meanwhile, CCT analyses indicate that higher external heat fluxes result in elevated specific extinction area (SEA), rate of smoke released (RSR), total smoke released (TSR), CO yield (COY), and CO production rate (COP) values, and relatively lower CO2 yield (CO2Y) and CO2 production rate (CO2P) values. These results reflect real WTB fires will pose severe situations with noticeable thermal and non-thermal hazards. Multiple physical and chemical evolution processes undergo in burning processes of such fires with higher PkHRR values through heat releases, transfers, exchanges, and feedback. Composite blade materials may be largely deformed and disintegrated in faster rates. Burning blade blocks may form spotting fires and cause secondary ground fires. Local air quality, visibility levels, working, and health conditions of related persons may be worsened. It is really urgent to develop mature, effective, novel, and even revolutionary fire protection and suppression technologies for such fires. [ABSTRACT FROM AUTHOR]

The increased interest in the use of polymer composites with natural, biodegradable and renewable fillers is the result of increased awareness of the environment. Therefore, the search for new materials that meet the above expectations is becoming a current issue. The article presents the results of research on composites containing pistachio shells (Pistacia vera L.), which are common agricultural waste, with unsaturated polyester resin based on post-consumer recycled poly(ethylene terephthalate) and vinyl ester resin based on bisphenol-A. The environmentally friendly polymeric cobalt solution was used as the accelerator. In order to study the degradation of the composites, accelerated ageing, immersion in various solvents, and high temperature were used. From the obtained results, it can be observed that accelerated aging resulted in the additional cross-linking of the resin, while the filler absorbed the UV light. During immersion, the polymer matrix was degraded in acetone, whereas the incorporation of pistachio increases its water sorption and the plasticisation effect was also observed. The alkali environment initiated the hydrolysis of ester linkages. The vinyl ester resin-based materials were more chemically and thermally resistant than those from the unsaturated polyester. [ABSTRACT FROM AUTHOR]

Facile preparation of chopped carbon fiber-reinforced low-density unsaturated polyester resin (CCFR-LDUPR) composite samples were realized under the synergistic action of initiator and accelerator at a low temperature of 58.0 ℃ and with NH4HCO3 as the foaming agent. CCFR-LDUPR composite sample presented excellent properties of ρ being 0.58 ± 0.02 g cm−3 and Ps being 53.56 ± 0.83 MPa g−1 cm3. Curing thermodynamics analysis revealed that the crosslinking spontaneity and curing tendency of unsaturated polyester resin did not be influenced by the synergistic effects of initiator and accelerator. The crosslinking of unsaturated polyester resin was retarded by the decomposition of NH4HCO3 and the steric retardant of chopped carbon fibers. Curing kinetics results illustrated that under the synergistic action of initiator and accelerator, the steric retardant of chopped carbon fibers to unsaturated polyester resin cross-linking was weakened, values of E and ΔG were both reduced, and the crosslinking of unsaturated polyester resin was accelerated, which was different from that with the only presence of initiator. Under such specific curing thermodynamics, the specific curing kinetics, and proper content of chopped carbon fibers, unique "plate microstructure" emerged layer by layer in resin matrix and regular "dimples" distributed in fine lines adhered to chopped carbon fibers. CCFR-LDUPR composite samples exhibited excellent compressive strength and specific compressive strength under the rapid curing process of unsaturated polyester resin; however, the curing reaction enthalpy (ΔH) was almost the same as that of slow curing process of unsaturated polyester resin. [ABSTRACT FROM AUTHOR]

The thermal degradation behaviors of commercial flame-retardant unsaturated polyester glass fiber-reinforced plastic (polyester GFRP) containing aluminum trihydrate (ATH) were studied using thermogravimetric analysis and a combination of TG-Fourier transform infrared-gas chromatography/mass spectrometry (TG-FTIR-GC/MS). From the variation of derivative thermogravimetry curves, it is found that the degradation of polyester GFRP can be divided into two stages with the critical conversion rate of 0.35. Activation energies were calculated by Starink method, and then the kinetic triplet was further determined by Coats-Redfern method. The results show that the dehydration of ATH and breakage of ester linkages lead to the first major mass loss, and volatile products including H2O, dicyclopentadiene, benzaldehyde and dimethyl phthalate are generated. Consecutive reaction occurs in the second stage. The statistical rupture of polyester and polystyrene chains leads to the formation of toxic volatiles, especially styrene, α-methylstyrene, toluene, ethylbenzene, benzaldehyde, phenol and phthalic anhydride. Possible reaction mechanisms are discussed in order to explain the observed results. The experimental results could give guidance to the fire safety design of high-speed train and provide basic data for numerical simulation of fire accidents. [ABSTRACT FROM AUTHOR]

A mussel-inspired intumescent flame-retardant (MIFR) was introduced into unsaturated polyester resin (UPR) to modify its flame retardancy. Its flame retardant and smoke suppression properties were studied by cone calorimetry test (CCT) and limiting oxygen index (LOI), UL-94, and the flame-retardant mechanism was studied by scanning electron microscopy and thermogravimetric analysis (TG). The LOI data showed that MIFR could greatly enhance the flame retardancy of UPR. The UPR composites with 10 mass% of MIFR have a LOI 27.8% and passes the UL-94 V-0 test without melt-dripping, while that for UPR-MAPP is only 25.5% with V-2 test at the same content. The mechanical properties of UPR-MIFR composites are higher than those of UPR-MAPP composites. The CCT revealed that MIFR can significantly decrease the heat release and the amount of smoke production. The TG test showed that MIFR could catalyze degradation of UPR composites and promote the char formation in the combustion process of UPR. In summary, the microencapsulation coating of the TA–Fe3+ modified the surface of MAPP enhanced the mechanical properties, flame retardancy and smoke suppression. [ABSTRACT FROM AUTHOR]

The curing kinetic analysis of unsaturated polyester (UP) with tert-butyl peroxybenzoate (TBPB) and cobalt octoate (CoOct) was investigated by differential scanning calorimeter. It was found that apart from enhancing the curing reaction, the less time and lower temperature to cure will be both achieved by the addition of promoter (CoOct). To further study the UP/TBPB/CoOct system, the automatic Kamal model was applied to the experiment. According to the thermokinetic parameters that were evaluated by the automatic Kamal model, the results show that the experimental data fit well with the Kamal model fitting except in the last stage. Considering about the different effects of diffusion control and curing control on the experimental system, a diffusion factor was introduced into the Kamal model; consequently, the fitting results were much better than with Kamal model. Modified Kamal model with diffusion factor was proven to be more suitable for UP resins cured with TBPB and CoOct, since the isothermal runs of differential scanning calorimeter can predict time profiles successfully during the molding process. [ABSTRACT FROM AUTHOR]

The synergistic flame retardant effects of AlPi and ATH in UPR were investigated. The flammability and thermal stability of UPR composites were evaluated with LOI, UL-94 vertical burning, MCC and TG. The structure and morphology of filler and char residues were examined with SEM and FTIR. The interaction between AlPi and ATH was observed when the mass ratio of AlPi and ATH was 3:2 and LOI value of flame-retarded UPR increased to 30 and UL-94 rating passed V-0; however, the SEM showed that AlPi and ATH have a good dispersion in UPR. The pHRR of UPR-15AlPi/10ATH was 241.6 Wg, decreasing by 30.4 % compared with pure UPR. The experimental TG curve of AlPi/ATH in N was lower than calculated one at the second stage and had lower char residue at 700 °C, demonstrating interaction of AlPi and ATH during thermal degradation. The char residue of UPR-15AlPi/10ATH at 700° suggested that the interaction between AlPi and ATH strengthened the char -formation ability and thermal stability of UPR, so the SEM showed a strong and dense char surface. The FTIR of char residues at different temperatures showed that AlPi and ATH interactions changed the type of aluminum phosphates, making char residue of UPR/AlPi/ATH system increased eventually. [ABSTRACT FROM AUTHOR]

The saturated aliphatic binary carboxylic acid, including succinic acid, adipic acid and sebacic acid, were used to improve the curing process of unsaturated polyester resin (UPR), and the effect of chain length of acid on the curing thermodynamics and kinetics of UPR was investigated. The analysis of Fourier transform infrared (FTIR) and gel permeation chromatography (GPC) showed that the pre-esterification between the various binary carboxylic acids and dihydric alcohol in UPR proceeded with the same activity and that the molecular chain of saturated polyester generated in the process became longer as the chain length of the binary carboxylic acid increased. The curing thermodynamics of UPR was detected by isothermal DSC, and the curing dynamics was analyzed by non-isothermal DSC. The saturated aliphatic binary carboxylic acid showed different mechanism from the previous inhibitor and retarder making the free radical inactive, and the generated polyester performed steric effect on the curing process of UPR. The Gibbs free energy change (Δ G) of UPR curing increased from −297.4 to −263.4 kJ mol, indicating the reduction in curing tendency of UPR. The activation energy ( E) of the UPR in curing process increased from 80.85 to 90.29 kJ mol with the increase in the chain length of saturated aliphatic binary carboxylic acid. The acceleration of energy barrier made the UPR curing retard, the curing time was prolonged from 21.52 to 32.36 min, and the curing degree decreased from 0.92 to 0.70. Saturated aliphatic binary carboxylic acid made improvements in the curing thermodynamics and kinetics of the UPR, and a dual chemical effect of hindering and retarding mechanism was proposed, different from the previous single effect of inhibitor or retarder. [ABSTRACT FROM AUTHOR]

The effect of glass-fibre content on the thermal and mechanical properties of cross-linked composites based on unsaturated polyester resins have been investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and by measuring the heat distortion temperature (HDT). Two different matrix resins and two different glass mats were used, and the glass-fibre contents varied. Altogether 12 composite systems were tested. The glass- transition temperature of each composite was characteristic to the matrix resin and did not depend on the glass-fibre content, as it was expected. The effect of glass-fibre content on the storage modulus and on HDT has been elucidated. It has been found that up to 12 mass% (6 vol%) glass-fibre content the HDT did not change, above this value it increased with increasing glass-fibre content for each composite, but not at the same extent. This means that matrix-fibre interaction has an important role in the performance of the composites at elevated temperatures. Storage moduli increased with increasing glass-fibre content. The temperatures detected by dynamic mechanical thermal analysis corresponding to the storage modulus of 750 MPa-calculated by Takemori-are above the glass-transition and also increased with higher glass-fibre content in accordance with the real heat-distortion temperature measurements. It may be concluded that the effect of reinforcement on the performance of the composite could be detected more reliably by HDT measurements, since it gives information on the deformation of the composites. Matrix-fibre interaction has an essential role on the performance and on the HDT of the composite materials. [ABSTRACT FROM AUTHOR]

The influence of the structure of succinic or glutaric anhydride modified linear unsaturated (epoxy) polyesters on the course of the cure reaction with styrene initiated by benzoyl peroxide (BPO) or the mixture of benzoyl peroxide/tetrahydrophthalic anhydride (BPO/THPA) or benzoyl peroxide/maleic anhydride, as well as viscoelastic properties and thermal behavior of their styrene copolymers have been studied by DSC, DMA, and TGA analyses. Additionally, mechanical properties: flexural properties using three-point bending test and Brinell’s hardness for studied copolymers were evaluated. It was confirmed that the structure of used polyesters had a considerable influence on the course of the cure reaction with styrene, viscoelastic, thermal, and mechanical properties of prepared styrene copolymers. Generally, one or two asymmetrical peaks for the cure reaction of succinic or glutaric anhydride modified linear unsaturated epoxy polyesters with styrene were observed. They were connected with various cure reaction, e.g., copolymerization of carbon–carbon double bonds of polyester with styrene, thermal curing of epoxy groups, polyaddition reaction of epoxy to anhydride groups in dependence of used curing system. In addition, only one asymmetrical, exothermic peak attributed to the copolymerization process of succinic or glutaric anhydride modified linear unsaturated polyesters with styrene was visible. Moreover, the obtained styrene copolymers based on succinic or glutaric anhydride modified linear unsaturated epoxy polyesters were characterized by higher values of $$ E_{{20\,^{\circ}{\text{C}}}}^{\prime} $$, T, E″, ν, E, F, hardness, IDT, FDT but lower ε − F compared to those values observed for styrene copolymers prepared in the presence of succinic or glutaric anhydride modified linear unsaturated polyesters. This supported to the production of stiffer and more thermally stable polymeric structure of copolymers based on unsaturated epoxy polyesters. Moreover, the copolymers prepared in the use of glutaric anhydride modified linear unsaturated (epoxy) polyesters were described by lower values of $$E_{{20\,^{\circ}{\text{C}}}}^{\prime} $$, T, E″, ν, E, F, hardness, IDT, FDT but higher ε − F than those based on succinic anhydride modified linear unsaturated (epoxy) polyesters. The presence of longer aliphatic chain length in polyester’s structure leads to produce more flexible network structure of styrene copolymers based on glutaric anhydride modified linear unsaturated (epoxy) polyesters than those based on succinic anhydride modified linear unsaturated (epoxy) polyesters. [ABSTRACT FROM AUTHOR]

The cure reaction of NADIC/PA modified unsaturated (epoxy) polyesters with styrene initiated by benzoyl peroxide (BPO) or the mixture of benzoyl peroxide/tetrahydrophthalic anhydride (BPO/THPA) and the thermal properties of obtained styrene copolymers have been studied. Based on non-isothermal DSC analysis, it was proved that the course of the cure reaction clearly depended on the structure of polyesters as well as used curing agent. Generally, one or two asymmetrical peaks for the cure reaction of NADIC/PA modified unsaturated epoxy polyesters with styrene were observed. They were attributed to the copolymerization process of carbon–carbon double bonds of polyester and styrene and/or to the thermal curing of epoxy groups or polyaddition reaction of epoxy groups to anhydride groups, in dependence of used hardener. In addition, only one asymmetrical peak connected with the copolymerization process for the cure reaction of NADIC/PA modified unsaturated polyesters and styrene was observed. Moreover, the cure process of NADIC/PA modified unsaturated epoxy polyesters with styrene initiated with BPO/THPA was more exothermic (higher values of ΔH) compared to the cure process initiated only with BPO. The obtained styrene copolymers based on NADIC/PA modified unsaturated epoxy polyesters were characterized by better thermal properties compared to copolymers based on NADIC/PA modified unsaturated polyesters. It has manifested by higher E′20 °C, E″max, tgδmax, Tg as well as higher IDT, T10%, T20%, T50% and Tk temperatures. Moreover, the introduction of non-polymerizable cycloaliphatic anhydride (NADIC anhydride) into unsaturated (epoxy) polyester structure caused improvement of the thermal properties of cured copolymers compared to copolymers based on non-polymerizable, aromatic (PA) modified unsaturated (epoxy) polyesters. [ABSTRACT FROM AUTHOR]

The influence of chemical modification of unsaturated polyesters on viscoelastic properties and thermal behavior of styrene copolymers has been investigated by DMA and TG analyses. Chemical modification of unsaturated polyesters obtained in polycondensation of cyclohex-4-ene-1,2-dicarboxylic anhydride (THPA), maleic anhydride (MA) and suitable glycol: diethylene glycol (DEG) or triethylene glycol (TEG) was performed using 38–40% peracetic acid. It allowed to selective and successful oxidation of carbon-carbon double bonds in unsaturated polyesters giving modified unsaturated polyesters/unsaturated epoxypolyesters/containing both carbon-carbon double bonds in polyester chain and new functional groups-epoxy groups in cycloaliphatic rings. Both unsaturated polyesters and unsaturated epoxypolyesters were used as a component of styrene copolymers cured with different hardeners. It has been demonstrated that the use of modified unsaturated polyesters as a component of styrene copolymers allowed obtaining more stiffness and more cross-linked network structure compared to styrene copolymers based on unmodified polyesters. The higher values of storage modulus, glass transition temperatures and better thermal stability for styrene copolymers based on unsaturated epoxypolyesters were obtained. [ABSTRACT FROM AUTHOR]