The effect of curing conditions on the physical and mechanical properties of styrenated polyester

The curing behavior of unsaturated polyester resin was investigated. In the present study, styrene, methyl ethyl keton peroxide (MEKP) and cobalt octoate (CO) have been selected as solvent (monomer), catalyst and accelerator, respectively. The effect of the concentration of both MEKP and CO on the curing exotherm, curing time, hardness and compressive strength of the prepared copolymers was investigated.     

Curing behavior of polycardanol by MEKP and cobalt naphthenate using differential scanning calorimetry

In this study, polycardanol, which was synthesized by enzymatic oxidative polymerization of thermally treated cashew nut shell liquid (CNSL) using fungal peroxidase, was partially or fully cured using methyl ethyl ketone peroxide (MEKP) as initiator and cobalt naphthenate (Co-Naph) as accelerator. The curing behavior of polycardanol was extensively investigated in terms of curing temperature, curing time, concentration of initiator and accelerator, and the monomer-to-polymer conversion of polycardanol by means of differential scanning calorimetry (DSC). The curing behavior significantly depends on the thermal condition given and it was monitored with the change of the exotherms as a function of temperature. The optimal conditions for fully curing polycardanol are 1 wt% MEKP, 0.2 wt% Co-Naph, curing time 120 min, and curing temperature 200 °C. This study suggests that a polycardanol with high monomer-to-polymer conversion would be useful for processing a polycardanol matrix composite under the optimal conditions of curing.     

Determination of airborne methyl ethyl ketone peroxide

Summary A new method for the determination of airborne methyl ethyl ketone peroxide (MEKP) is based on the reaction of peroxides with 4-tert-butyl catechol, in which the peroxide radicals oxidize the catechol to the corresponding benzoquinone. The yellow colour generated is measured at 395 nm. Sampling from factory air can be performed by aluminium oxide sampling tubes. Glacial acetic acid is used as a solvent and for the desorption of the peroxide from the aluminium oxide. The detection limit (0.05 mg/m³ for 4 h samples) for the MEKP in air is well below the current hygienic reference value (1.5 mg/m³). The method was used for MEKP determinations during lamination applications in the production of reinforced unsaturated polyester plastics, where the airborne concentrations of the peroxide were well below the current hygienic reference values.     

不饱和聚酯/有机蒙脱土复合材料的固化动力学

用动态扭振法研究不饱和聚酯／有机蒙脱土复合材料的固化动力学行为。结果表明该实验体系能够很好地应用Flory理论和Avami方程进行拟合。用非平衡态热力学涨落理论对纳米复合材料的固化作了理论顸估,顸估结果与实验固化曲线有很好的相符性。有机蒙脱土的加入降低了不饱和聚酯的固化反应速率,对固化反应表现活化能和复合材料的形成过程没有很大的影响。根据实验结果分析不饱和聚酯在有机蒙脱土存在下的固化分为定型和熟化两个阶段,在一定的固化温度和填充含量下。从动态扭振曲线上可以明显地观察到这种“二次固化”现象。     

Simultaneous study of cure kinetics and rheology of montmorillonite/vinyl ester resin nanocomposites

In this work, the effect of quaternary ammonium salt containing nanoclay content (1–5 wt%) on phase morphology, rheology, cure kinetics, and mechanical properties of the vinyl ester resin (VER)‐based nanocomposites was studied. The morphological characterization including d‐spacing measurement, microscopy observation and phase‐height image processing were performed on the prepared nanocomposites using small angel X‐ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). According to the results obtained from these techniques, it was concluded that an intercalated morphology existed for all the nanocomposites. The kinetic analyses of the isothermal curing followed by storage modulus obtained from the rheometry experiments are shown to be an affective rheological characteristic to investigate the cure behavior of VER/clay nanocomposites. In addition, the most important finding regarding the effect of nanoclay on the cross‐linking behavior of VER systems lays on the chemisorption and physisorption of the reacting monomers and initiator molecules on the nanoclay platelets surface which is found to be responsible for the retardation of the cure reaction caused by organoclay. Eventually, the mechanical characterizations were performed through the tensile, flexural and impact analysis tests. In this case, a considerable improvement of the bulk mechanical responses such as tensile and flexural strengths and also the corresponding moduli were observed for the nanocomposites. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal and dynamic mechanical properties of epoxy resin/poly(urethane‐imide)/polyhedral oligomeric silsesquioxane nanocomposites

Linear isocyanate‐terminated poly(urethane‐imide) (PUI) with combination of the advantages of polyurethane and polyimide was directly synthesized by the reaction between polyurethane prepolymer and pyromellitic dianhydride (PMDA). Then octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS) and PUI were incorporated into the epoxy resin (EP) to prepare a series of EP/PUI/POSS organic–inorganic nanocomposites for the purpose of simultaneously improving the heat resistance and toughness of the epoxy resin. Their thermal degradation behavior, dynamic mechanical properties, and morphology were studied with thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and transmission electron microscope (TEM). The results showed that the thermal stability and mechanical modulus was greatly improved with the addition of PUI and POSS. Moreover, the EP/PUI/POSS nanocomposites had lower glass transition temperatures. The TEM results revealed that POSS molecules could self assemble into strip domain which could switch to uniform dispersion with increasing the content of POSS. All the results could be ascribed to synergistic effect of PUI and POSS on the epoxy resin matrix. Copyright © 2010 John Wiley & Sons, Ltd.     

Interpenetrating Polymer Networks of Uralkyd Resin Based on Hydrogenated Castor Oil and Poly(Butyl Acrylate)

Abstract

Semi‐ and full‐interpenetrating polymer networks (IPNs) of uralkyd (UA) resin based on hydrogenated castor oil and poly(butyl acrylate) (PBA) were prepared by the sequential mode of synthesis. These IPNs were characterized for their resistance to thermal behavior, swelling (%), and mechanical properties. The morphology of the IPNs was studied by scanning electron microscopy (SEM). The effect of the variations of the blend ratios on the above‐mentioned properties was examined. The mechanical properties significantly enhanced by increasing UA component in the blend. Full‐IPNs exhibited higher apparent densities, mechanical properties, and thermal stability than the corresponding semi‐IPNs.     

Modified montmorillonite combined with intumescent flame retardants on the flame retardancy and thermal stability properties of unsaturated polyester resins

Modified montmorillonite‐containing phytic acid (PA‐MMT) has been prepared by acid treatment and then introduced into unsaturated polyester resin (UPR) with an intumescent flame retardant (IFRs). The flame retardancy and thermal degradation of UPR/IFRs/PA‐MMT were evaluated by a limiting oxygen index (LOI) test, a vertical burning test (UL‐94), a thermogravimetric analysis (TGA), and a cone calorimeter test (CCT). Besides, the mechanical properties were studied by a universal testing machine. The LOI value of UPR/IFRs/PA‐MMT composites was increased to 29.2%. The CCT results indicated that the incorporation of PA‐MMT and IFRs significantly improved the combustion behavior of UPR. The results of the mechanical properties indicated that 1.5 wt% loading of PA‐MMT in UPR/IFRs showed the highest improvement in flexural strength and tensile strength. The flame‐retardant mechanism of PA‐MMT/IFRs was examined and discussed based on the results of combustion behavior and char analysis.     

含介晶结构单元的反应性增韧剂改性环氧树脂研究──Ⅱ.材料断裂面形态结构的研究

该文合成了一种既含聚醚柔性链又含介晶结构单元的环氧树脂改性剂LCEU（PEG），用其改性环氧树脂／双氰双胺（E－51／dicy）固化体系，对改性体系的动态力学行为和冲击性能作了研究，用扫描电子显微镜（SEM）对试样断裂面的形态结构进行了观察，并探讨了体系的形态结构与动态力学行为、冲击性能之间的关系。结果表明改性体系断裂时产生大量应力条纹，断裂面呈微观两相网络结构，为韧性断裂。     

功能基化介晶高聚物增韧环氧树脂性能研究——材料断裂面形态结构与力学性能的关系

在系统研究含介晶基团的高聚物ＬＣＥＵＰＰＧ增韧环氧树脂Ｅ ５１／双氰双胺（ｄｉｃｙ）固化体系固化反应活性、反应机制、动态力学行为及冲击性能的基础上,以扫描电镜（ＳＥＭ）为手段,对材料断裂面的形态结构进行了研究,并对体系的形态结构与动态力学行为、冲击性能之间的关系进行了探讨．结果表明,改性后材料断裂面的形态均呈微观两相网络结构,明显不同于未改性体系,正是由于两相网络结构的存在,导致了改性体系的冲击强度大幅度提高．     

Synthesis and properties of phosphorus-containing bio-based epoxy resin from itaconic acid

A phosphorus-containing bio-based epoxy resin (EADI) was synthesized from itaconic acid (IA) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO). As a matrix, its cured epoxy network with methyl hexahydrophthalic anhydride (MHHPA) as the curing agent showed comparable glass-transition temperature and mechanical properties to diglycidyl ether in a bisphenol A (DGEBA) system as well as good flame retardancy with UL94 V-0 grade during a vertical burning test. As a reactive flame retardant, its flame-resistant effect on DGEBA/MHHPA system as well as its influence on the curing behavior and the thermal and mechanical properties of the modified epoxy resin were investigated. Results showed that after the introduction of EADI, not only were the flame retardancy determined by vertical burning test, LOI measurement, and thermogravimetric analysis significantly improved, but also the curing reactivity, glass transition temperature (T _g), initial degradation temperature for 5% weight loss (T _d(5%)), and flexural modulus of the cured system improved as well. EADI has great potential to be used as a green flame retardant in epoxy resin systems.     

High efficiency synthesis of octavinylsilsesquioxanes and its high performance hybrids based on bismaleimide‐triazine resin

An improved method is developed to synthesize octavinylsilsesquioxanes (VPOSS) with shorter time and higher yield, and then VPOSS is used to prepare new hybrids based on bismaleimide‐triazine (BD/CE) resin, coded as VPOSS/BD/CE. The effect of the content of VPOSS on the key properties including curing behavior, thermal, mechanical, and dielectric properties as well as water resistance of VPOSS/BD/CE hybrids were systematically discussed. Compared with BD/CE resin, hybrids show similar curing behavior but different chemical structures and thus macro‐performance. These key properties of hybrids are dependent on the content of VPOSS, all hybrids show significantly improved dielectric properties, water resistance, and dimensional stability; moreover, the hybrids with suitable content of VPOSS have bigger impact strengths. Specifically, with the addition of 7 wt% VPOSS to BD/CE resin, the dielectric constant decreases from 3.7 to 3.2, the dielectric loss decreases 55%, and the coefficient of thermal expansion reduces 23%; moreover, the glass transition temperature and initial decomposition temperature increase about 15°C. The attractive integrated properties suggest that VPOSS/BD/CE hybrids have great potential to be used as structural and functional materials for many cutting‐edge fields. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis, morphology and properties of polydimethylsiloxane-modified allylated novolac/4,4′-bismaleimidodiphenylmethane

Polydimethylsiloxane was incorporated into the backbone of allylated novolac (AN) to improve the toughness of allylated novolac/4,4′-bismaleimidodiphenylmethane(AN/BDM). Polydimethylsiloxane-modified allylated novolac (PDMS-AN) was synthesized via the hydrosilylation reaction between the terminal Si-H groups of α,ω-hydrogen functional dimethylsiloxane oligomer (PDMS) and the allyl groups of allylated novolac resin (AN). The blend of PDMS-AN and 4,4′-bismaleimidodiphenylmethane (BDM) could undergo co-cure reaction at elevated temperatures, and the co-cure system was denoted PDMS-AN/BDM. PDMS-AN was characterized by Fourier transfer infrared (FTIR) spectroscopy, ¹H and ²⁹Si nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The curing behavior of PDMS-AN/BDM was evaluated by differential scanning calorimetry (DSC). The morphology of the cured resins was examined by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The effects of the content and number-average molecular weight of the incorporated PDMS on the mechanical and thermal properties of PDMS-AN/BDM were investigated. The results indicated that the incorporation of PDMS could improve the impact toughness of AN/BDM.     

含聚醚间隔链的扩链脲改性环氧树脂/双氰双胺固化体系性能研究

合成了一系列含不同分子量聚环氧丙烷 (PPG)柔性间隔链的扩链脲 ,系统考察了扩链脲改性环氧树脂E 5 1/双氰双胺 (dicy)固化体系的固化反应活性、动态力学行为、冲击性能和断裂面形态结构 ,并对体系的冲击性能、形态结构与动态力学行为之间的关系进行了探讨 .结果表明 ,改性体系固化反应活性明显提高 ,固化反应表观活化能降低 ,固化反应峰顶温度从 190℃降低至 14 0℃ ,固化反应的表观活化能由 14 5 5kJ/mol降至 70～ 80kJ mol;改性体系冲击强度明显提高 ,其中所含PPG柔性链分子量为 10 0 0的扩链脲改性的E 5 1/dicy体系冲击强度较未改性的E 5 1/dicy体系提高了 8倍 ,其冲击试样断裂面的形态具有明显的韧性断裂特征 ,微观两相网络结构的存在导致了改性体系冲击强度显著提高     

Thermal conductivity epoxy resin composites filled with boron nitride

Boron nitride (BN) micro particles modified by silane coupling agent, γ‐aminopropyl triethoxy silane (KH550), are employed to prepare BN/epoxy resin (EP) thermal conductivity composites. The thermal conductivity coefficient of the composites with 60% mass fraction of modified BN is 1.052 W/mK, five times higher than that of native EP (0.202 W/mK). The mechanical properties of the composites are optimal with 10 wt% BN. The thermal decomposition temperature, dielectric constant, and dielectric loss increase with the addition of BN. For a given BN loading, the surface modification of BN by KH550 exhibits a positive effect on the thermal conductivity and mechanical properties of the BN/EP composites. Copyright © 2011 John Wiley & Sons, Ltd.     

Mechanical behavior of polyester polymer concrete under low strain rate loading conditions

Polymer concrete (PC) has superior mechanical properties in comparison with cement concrete. In this research, the mechanical behavior of polyester polymer concrete (PPC) and its polyester resin were studied at different loading rates. Special specimens for testing the PPC and the polyester resin under low strain rate loading conditions were fabricated. Experiments were performed under different strain rates, from 0.00033 to 0.15 s⁻¹, and results for the PPC and the polyester resin were compared. Furthermore, the influence of strain rate on the mechanical response of the neat polyester and the PPC was investigated. The results show a maximum 40% increase in tensile strength of the neat polyester, while the elastic modulus does not change significantly. The compressive strength of the PPC increases by 25%. These results show that the mechanical behavior of the polyester resin and its PC is extremely sensitive to the strain rate.     

Novel bio‐based IPNs obtained by simultaneous thermal polymerization of flexible methacrylate network based on a vegetable oil and a rigid epoxy

A series of novel vegetable oil‐based interpenetrating polymer networks (IPNs) have been successfully prepared: on one hand, methacrylated camelina oil (MCO) and a polyethyleneglycol dimethacrylate (PEG, MW 750 g/mol) and on the other hand, diglycidylether of bisphenol A (DER), in various blend ratios (75/25, 50/50, and 25/75 wt). Hence the appealing innovative direction of the current work was to build oil‐based poly(methacrylate) network using PEG macromonomer which is able to modulate adequately the crosslinking degree of the oil‐based network. These innovative combinations of cross‐linkable resins in terms of flexible methacrylate network based on camelina oil (CO) and PEG and a rigid epoxy (DER) were simultaneously polymerized using two independent non‐interfering curing reactions: free‐radical process for MCO and anionic polymerization of epoxy resin in the presence of a tertiary amine. The effect of the IPNs composition compositional characteristics on the reactivity of methacrylate or epoxy groups was studied using differential scanning calorimetry. The influence of the MCO‐PEG bio‐based polymer on the system properties was evaluated after curing by dynamic mechanical and thermogravimetric analyses. In addition mechanical and morphological studies were also carried out. The results suggested that blending of MCO and DER gave synergistic effects on the overall properties of the developed oil‐based IPNs and a dependence on the methacrylate/epoxy ratio was clearly noticed. Copyright © 2014 John Wiley & Sons, Ltd.     

Toughening of a trifunctional epoxy system: IV. Dynamic mechanical relaxational study of the thermoplastic-modified cure process

Dynamic mechanical spectroscopy has been used to investigate the cure of a thermoplastically modified trifunctional epoxy resin. The complex dissolution, curing behavior, and variations in the glass transition of the thermoplastic (PSF) phase were described, as was the T_g behavior of the epoxy phase. Prereaction of the PSF material with the epoxy resin was found to greatly increase the solubility of the PSF in the epoxy phase with little effect on the concentration of the epoxy monomer dissolving in the PSF phase. The curing behavior of the epoxy component in the thermoplastic phase was also investigated, in addition to changes in the mobility of the network at both gelation and vitrification. © 1997 John Wiley & Sons, Inc.     

含介晶结构单元化合物改性环氧树脂E—51／DDM固化体系的动态力学行为

合成和表征了含有介晶结构单元的单环氧官能团化合物4-(4'-甲基基苯甲酰氧基)苯基缩水甘油醚(MPEP),以一定比例的MPEP加入到环氧树脂E-51/4,4'-二氨基二苯基甲烷(DDM)固化体系,获得了一系列在高分子链上悬挂介晶结构单元的固化网络结构,并对其动态力学行为进行了表征,侧链上介晶结构单元的引入使固化体系的交联密度降低,链段柔顺性增加,表现为与未加MPEP的体系相比,含有介晶结构单元的体系的玻璃化温度和动态模量下降,而且MPEP的加量越大,玻璃化温度和动态模量下降幅度越大.     

含柔性间隔基的扩链脲潜伏性固化、增韧环氧树脂性能研究

合成了含聚乙二醇柔性问隔基的扩链脲(U_i),并对其与环氧树/二苄胺混合体系的反应活性、贮存性能、动态力学性能及抗冲击性能进行了研究.结果表明:环氧树脂/扩链脲/二苄胺混合体系在323K下贮存期可达40h,其固化物抗冲击强度最高可达55.8kJ/m²,较环氧树脂/小分子取代脲(U₀)/二苄胺混合体系提高近5倍.