Effect of nanoclay on shrinkage control of low profile unsaturated polyester (UP) resin cured at room temperature

The addition of a small amount of nanoclay (1-3 wt%) can provide excellent volume shrinkage control of unsaturated polyester (UP)/styrene (St)/poly(vinyl acetate) (PVAc) systems cured at room temperature. PVAc serves as the low profile additive (LPA). In this study, both temperature-induced phase separation of the uncured resin mixture and transmission electron microscopy (TEM) of the cured sample revealed that nanoclay resided in the LPA-rich phase, leading to a higher reaction rate and earlier onset of micro-cracking in the LPA-rich phase or at the interface of the LPA-rich and UP-rich phases. Consequently, an earlier volume expansion during curing was observed in reactive dilatometry, resulting in better shrinkage control. On-line measurement of the composite thickness change during vacuum-infusion liquid composite molding [e.g. the Seemann Composite Resin Infusion Molding Process (SCRIMP)] further proved excellent volume shrinkage control of nanoclay filled systems, leading to a smoother composite surface.     

Control of shrinkage and residual styrene of unsaturated polyester resins cured at low temperatures: I. Effect of curing agents

In low temperature molding processes, control of resin shrinkage and residual monomer is an important concern. The presence of low profile additives (LPAs) can reduce the shrinkage of unsaturated polyester (UP)/styrene (St) resins under proper processing conditions but may increase the residual styrene content. A systematic study was carried out to investigate the effect of the initiator system and reaction temperature on sample morphology, final resin conversion, and resin shrinkage of UP resins with LPA. It was found that the final conversion of the resin system could be improved by using dual initiators. The effect is more obvious at low temperatures. Volume shrinkage measurements of the resin system initiated with dual initiators revealed that good LPA performance was achieved at low (e.g. 35 °C) and high (e.g. 100 °C) temperatures but not at intermediate ones. This can be explained by how temperature affects phase separation, reaction kinetics in the LPA-rich and UP-rich phases, micro-void formation, and thermal expansion.     

Comparison of unsaturated polyester and vinylester resins in low temperature polymerization

Many composite products are produced at low temperatures in processes such as resin transfer molding (RTM), vacuum infusion molding (e.g., Seemann Composite Resin Infusion Molding Process—SCRIMP), and hand lay‐up. These processes are widely used for marine, civil infrastructure, transportation and defense applications. Unsaturated polyester and vinylester resins are two major resins used in these processes due to their low cost, good performance, and processibility. In this study, the reaction kinetics and rheological changes of these two resins cured at low temperatures were studied. Effects of resin type, initiator, promoter, inhibitor and retarder on the reaction kinetics and rheological behaviors were examined using a Differential Scanning Calorimeter (DSC) and a Rheometrics Dynamic Analyzer (RDA). A model was developed to quantify the effects of resin type, temperature, and different curing agents on the gel time for both polyester and vinylester resins cured at low temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1230–1242, 2001     

不饱和聚酯树脂的粗化工艺

介绍了不饱和聚酯树脂的粗化工艺流程及各工艺规范通过正交试验确定了最佳粗化工艺条件：粗化液的体积分数为400ml／L温度为80～85℃,粗化时间为20min。讨论了粗化液用量、粗化温度和时间对粗化效果和镀层质量的影响经检测表明,该金属镀层与基体结合力良好目前该工艺已应用于生产中。     

Control of volume shrinkage and residual styrene of unsaturated polyester resins cured at low temperatures. II. Effect of comonomer

The effect of a comonomer, methyl methacrylate (MMA), on volume shrinkage and residual styrene content of an unsaturated polyester (UP) resin with low profile additives (LPAs) cured at low temperature was investigated by an integrated reaction kinetics-morphology-property analysis. MMA affects the volume shrinkage and residual styrene content differently depending on MMA to styrene (St) CC bond molar ratio. At low MMA/St ratio, residual styrene decreases and the volume shrinkage of the resin system remains unchanged. At high MMA/St ratio, residual styrene can be substantially reduced, but the resin system suffers poor volume shrinkage control. Reactivity of the comonomer MMA and its compatibility to other components in the resin system can explain the observed results. A series of Seemann composites resin infusion molding process (SCRIMP) were conducted to study the relationship among materials, processing, and properties of molded composites in low temperature curing processes.     

Dynamic mechanical analysis of segmental relaxation in unsaturated polyester resin networks: Effect of styrene content

The effect of styrene content on non-exponential and non-Arrhenius behavior of the α-relaxation of cured unsaturated polyester resins (UPR) was investigated by dynamic mechanical analysis (DMA). To compare the temperature dependence of the relaxation times, the Angell fragility concept was applied to samples with different crosslink densities. Furthermore, the number of structural units per cooperatively rearranging region (CRR) was estimated using random walk model and the modified Adam-Gibbs theory. The results showed that rising styrene content enhanced the crosslink density of the networks, which altered the intensity and broadness of the α-relaxation. The fragility index, a measure of temperature dependence of relaxation time, and the average size of CRR at glass transition region was also increased by styrene content. Therefore, the segmental relaxation in networks with higher crosslink density could be associated with stronger intermolecular coupling. In addition, it was observed that the mean required energy for internal rearrangement of structural units within the CRR decreased as the fragility index increased, while the mean barrier height for repositioning of a CRR in cooperation to its local environment was nearly constant.     

高黏度不饱和聚酯树脂的合成研究

以邻苯二甲酸酐、顺丁烯二酸酐和丙二醇为原料合成了一类可用于SMC(片状模塑料)和BMC(团状模塑料)的高黏度不饱和聚酯树脂。并对其原料配比、阻聚剂用量、温度﹑搅拌速度和惰性气体流量等对合成工艺的影响进行了研究。     

不饱和聚酯树脂固化动力学研究进展

介绍了不饱和聚酯树脂(UPR)固化反应动力学的n级反应模型和自催化模型,指前因子(A)和表观活化能(E)的求解方法:Kissinger法,Ozawa法和Friedman法以及由Crane方程或形状指数Si求解反应级数(n)的方法,综述了目前国内外DSC法研究UPR固化动力学的进展。     

成分比例不同的MEKP固化不饱和聚酯树脂研究

通过45,50,55和60℃等温DSC固化研究了成分(过氧化氢、MEKP单体和二聚体)比例不同的过氧化甲乙酮(MEKP)对不饱和聚酯树脂(UP)固化诱导期、峰值时间和固化率的影响,并讨论了固化引发机理。结果发现,过氧化氢质量分数较少、单体和二聚体质量比为1.5∶1的MEKP对UP固化有利。     

不饱和聚酯树脂稳定化研究进展

介绍了不饱和聚酯树脂稳定化方面的新近研究进展,包括不饱和聚酯制品如玻璃钢表面新型涂层及新型稳定剂(紫外线吸收剂、受阻胺光稳定剂和抗氧剂)等。研究表明,只使用单一的稳定剂效果不佳,必须将主抗氧剂、副抗氧剂和其他添加剂(例如某些环氧化合物)并用,才能取得较好的稳定效果。     

不饱和聚酯树脂微乳液的研究(Ⅲ) 磺酸盐不饱和聚酯树脂微乳化的表征

研究了4种正构醇(正丙醇、正丁醇、正戊醇和正己醇)对磺酸盐不饱和聚酯树脂的粘度和电导率的影响,聚酯树脂中醇含量增加,溶液的电导率增大,粘度下降;聚酯树脂中的醇含量相同时,醇的碳链越短,溶液的粘度越低,电导率越大。在一定的温度和搅拌速度下,将含有一定量醇的磺酸盐不饱和聚酯树脂加水微乳化,用微乳化过程中体系粘度和阻抗的变化表征了微乳化相反转过程,发现粘度比电导表征相转变更好。用差示扫描量热法的吸收热焓和吸收峰的温度判断了不同含水量时体系的相态。     

Curing reaction of unsaturated polyester resin modified by dicyclopentadiene

The objective of this research is to prepare modified unsaturated polyester resin(UPR) with good processibility, dimension stability and mechanical properties. In this study, dicyclopentadiene (DCPD) is selected as a modifier and the effect of DCPD content on the curing behavior of the modified UPR is examined via Differential Scanning Calorimetry (DSC) and Rheometrics Dynamic Analysis (RDA) experiments. The results of ¹H NMR identification for the chemical structure of modified UPR show that the trans-structure of UPR decreases as the DCPD content increases. The curing time necessary to reach peak maximum in DSC during the curing reaction lengthens as the stereo obstacles formed by the binary rings increase.     

不饱和聚酯/复合引发体系非等温固化动力学研究

采用非等温DSC法研究了不饱和聚酯/复合引发体系在不同升温速率下的固化行为,通过T-Φ外推法确定了该体系的凝胶温度、固化温度和后固化温度分别为102.7℃,124.0℃和196.5℃。通过Kissinger和Crane方程对DSC数据进行处理,获得了固化反应的表观活化能E=116.88 kJ/mol,碰撞因子A=7.35×1014,反应级数n=0.945,并由此得到了该体系的固化动力学方程。     

Influence of TDI concentration on the properties of unsaturated polyester resins

Three different unsaturated polyester resins were modified by toluene diisocyanate (TDI). All the resins studied were commercially available. One, 2, and 3% additions of TDI caused important changes of the resins properties. With an increase of TDI concentration gelation times increased. Suppression of the exotherm peaks—desired effect from practical point of view—was observed. Unfortunately, increase of TDI concentration caused enormous increase of the resins viscosity. Additionally the resins with 3% of TDI exhibit thixotropic properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1201–1206, 2001     

国外不饱和聚酯树脂工业新进展

综述了国外不饱和聚酯树脂的市场动态及技术进展。     

191不饱和聚酯胶粘剂的改性研究

不饱和聚酯在固化过程中，由于初级自由基与空气中的氧反应产生的新游离基不能引发聚合，故其表面发粘，为解决此问题，本文选用了烯丙基醚，液体石蜡和碱金属氧化物进行试验，结果表明，烯丙基醚可有效吸收氧气，从而消除氧的阻聚作用，加入了烯丙基醚的191不饱和聚酯，30min可完全固化，表面不发粘。     

近年来阻燃不饱和聚酯树脂的研究进展

综述了近年来在不饱和聚酯树脂中添加含铝、镁、磷及膨胀型阻燃剂阻燃不饱和聚酯树脂以及以含磷元素的阻燃剂或含阻燃元素的单体为反应物制备阻燃型不饱和聚酯树脂的研究进展。     

不饱和聚酯增韧技术进展及机理探讨

简单介绍不饱和聚酯树脂增韧的研究进展及基本理论,并分别探讨不饱和聚酯树脂的液体橡胶增韧、互穿网络增韧和刚性粒子增韧的增韧机理。     

Study of the porous network developed during curing of thermoset blends containing low molar weight saturated polyester

Polymerisation of unsaturated polyester/styrene blend added with a thermoplastic additive leads to the formation of a porous biphasic polymer network. In this paper, the porous medium was specifically studied by TEM associated with images analysis by chord length distribution and small angle X-ray scattering (SAXS). When the molar weight and/or the amount of low profile additive (LPA) are sufficient to ensure porosity higher than 2%, chord length distribution can be performed and is characteristic of a Debye random medium and Porod's law was observed in SAXS. The lengths deduced from Porod's law are similar to those observed for Debye random regime and are lower than 50 nm. These characteristics are closely related to the processes happening during curing and especially to the phase separation. For less porous samples, deviation from Porod's law was observed and could be attributed to additional scattering intensity coming from concentration fluctuations within polymer matrix. For nonporous samples, scattering intensity was only due to concentration fluctuations.     

低收缩型不饱和聚酯树脂的研究进展

综述了目前不饱和聚酯树脂低收缩性的研究进展,探讨了包括聚醋酸乙烯酯、聚苯乙烯、聚氨酯和嵌段共聚等在内的添加低收缩添加剂和改变原料或工艺对收缩率的影响。论述了新型低收缩不饱和聚酯的合成和工艺方法等。参考文献13篇。