模塑成型工艺中低收缩、低轮廓添加剂的作用机理和选择

本文阐述了模塑成型工艺中低收缩、低轮廓添加剂的作用机理和选择方法,并介绍了需要使用低收缩,低轮廓添加剂的ＦＲＰ制品及应用领域。     

改性不饱和聚酯树脂的研究进展

综述了目前不饱和聚酯（UPR）改性研究的最新进展。介绍了UPR增韧改性的方法,包括分子结构改性、互穿网络结构增韧改性UPR、基于第二相材料共混改性;讨论了含磷阻燃剂和无卤阻燃剂对UPR的影响;综述了低收缩研究发展的4个阶段。并指出了UPR改性中存在的问题和发展方向：     

一维固化收缩应力的研究

本文利用自制的测试固化应力的仪器测试研究了树脂固化时一维固化收缩应力的产生情况,然后通过低温固化低轮廓添加剂控制收缩,进一步测试研究其产生情况,观察了低收缩对固化应力的影响.     

中国不饱和树脂工业进展

综述了近几年中国不饱和树脂(UPR)及其下游产品的技术进展,其中包括:低收缩性UPR、阻燃乙烯基树脂、胶衣树脂、树脂制造工艺的改进、UPR工业废水处理,生物基UPR及复合材料,功能化UPR的研究应用。     

高性能铜箔的研发以及有机添加剂的应用

本文简要介绍了契合当今微电子行业发展要求的低轮廓铜箔和无轮廓铜箔的发展现状,列举了一些国际知名铜箔制造厂生产的该类铜箔的性能指标,同时也提供了国外科研机构在铜箔生产中使用钯系催化剂的研究成果.     

低苯乙烯不饱和聚酯树脂开发

综述了不饱和聚酯树脂中的各种交联剂，降低苯乙烯散发的途径及国外UPR制造商成功开发的几种低苯乙烯树脂，指出环保型低苯惭烯不饱和聚酯树脂的研制开发将是我国今后的发展方向与重要的研究领域。     

不饱和聚酯树脂国外近十年研究进展

综述了不饱和聚酯树脂工业技术国外近十年来的研究进展,其中包括:低收缩性树脂、耐腐蚀树脂、强韧性树脂、低吸水型不饱和聚酯树脂、透明性不饱和聚酯树脂、低游离苯乙烯残量的不饱和聚酯树脂、PET型不饱和聚酯树脂、低挥发性树脂、胶衣树脂、发泡不饱和聚酯树脂、玻璃钢渔船专用树脂、耐热性UPR树脂和光固化UPR树脂。对不饱和聚酯树脂的改性及其阻燃技术国外研究进展也作了专门的论述。     

不饱和聚酯树脂改性研究进展

综述了不饱和聚酯树脂(UPR)改性的研究进展。介绍了收缩率控制机理,低收缩研究发展的4个阶段,低收缩剂LSA的典型代表——聚苯乙烯(PS),聚甲基丙烯酸甲酯(PMMA),聚醋酸乙烯(PVAc),PVAc-PS共聚物。讨论了UPR增韧改性方法,提高分子主链对称性,在分子结构中引入长链醇与长链酸,长链醇包括一缩二乙二醇、二缩三乙二醇及聚乙二醇;长链二元酸如己二酸等。此外还可加入热塑性弹性体,如液体橡胶、液体聚氨酯等以形成互穿网络结构增韧UPR。论述了提高UPR阻燃性的2种途径,即选用本质阻燃性树脂和向UPR中添加阻燃剂。介绍了含卤有机阻燃剂、无机阻燃剂、主链或主链与侧链均含磷的阻燃剂和赋予阻燃性的影响因素。介绍了部分采用可降解的植物纤维——竹纤维制备的UP复合材料和木粉改善UPR的性能。这些方法使不饱和聚酯树脂在低收缩性能、力学性能、阻燃性能等方面得到了改善,扩展了其应用范围。     

S-602树脂收缩特性的研究

通过添加不同含量的低轮廓添加剂，运和比重法测定了Ｓ－６０２树脂的固化收缩率，分析了ＬＰＡ对Ｓ－６０２树脂工艺性能和力学性能的影响。     

玻璃钢废料改性不饱和聚酯树脂的研究

将玻璃钢边角废料加工成60μm以下的粉末(FRP)，作为低收缩添加剂加到不饱和聚酯(UPR)中，对FRP粉末填充的UPR的体积收缩率和其浇铸体的轴向拉伸性能进行了实验研究。结果表明．加入FRP粉末后UPR的体积收缩率降低；其浇铸体的拉伸弹性模量升高．拉伸强度变化不大。可将玻璃钢边角费料制成粉末加到UPR中，以回收利用。     

Graphite Nanosheet as Low Shrinkage Additive,Curing Accelerator,and Conducting Filler for Unsaturated Polyester Resin

The effect of graphite nanosheets on electrical properties, curing behavior, and polymerization shrinkage of unsaturated polyester resin has been investigated. A solution of polystyrene was used as low profile additive to reduce shrinkage. The results showed that graphite nanosheets have been well dispersed/distributed in the unsaturated polyester matrix where they have high aspect ratio and high surface area. Graphite nanosheet exhibited an accelerating effect on the curing of unsaturated polyester and reduced the polymerization shrinkage as low as 3.6%. Despite large reduction of flexural properties by low profile additive, graphite nanosheet considerably increased the flexural strength and modulus of unsaturated polyester/low profile additive by 47 and 103%, respectively. Therefore, graphite nanosheet can be used as a new low profile additive for unsaturated polyester resins where it is also able to improve mechanical properties and curing rate.     

Dilatometric study of low profile unsaturated polyester resins

An in-house-built and designed dilatometer was applied to the study of low profile unsaturated polyester resins. This article first describes the dilatometer used including its calibration then its application to low profile unsaturated polyester resins. Several series of dilatometry experiments were performed, to study the effect of low profile additive concentration and cure temperature on shrinkage control. Scanning electron micro-graphs of the samples were also prepared to show the correlation between shrinkage control and polymer morphology.     

H870-901用于淤泥填充微收缩不饱和聚酯材料的研究

采用高分辨魔角旋转核磁共振(HR/MAS-NMR)、DSC结合SEM分析研究了极性低收缩剂H870-901对淤泥填充不饱和聚酯树脂体系收缩性的影响及其作用机理。结果表明,当H870-901的质量分数为12%(以树脂计)时,体系的收缩率满足低收缩热固性不饱和聚酯材料收缩率0.25%的要求;质量分数达到18%时,体系的收缩率满足微波纹材料收缩率0.1%的要求。体系中形成的微孔和H870-901包覆的未完全固化交联的小胶粒结构是抑制体系收缩的2个主要原因。     

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。     

不饱和聚酯树脂的合成研究进展

综述了不饱和聚酯树脂(UPR)的合成研究进展,特别针对功能化不饱和聚酯树脂如气干性、阻燃性、强韧性、光敏性和低收缩性不饱和聚酯树脂的合成方法和特性进行了介绍,对了未来不饱和聚酯树脂的发展方向和广泛的应用前景的展望。     

Mechanism of low profile behavior in unsaturated polyester systems

The mechanism by which low profile character is achieved in unsaturated polyester systems has been investigated. Using techniques of microscopy, data are developed that support a model in which micro stress cracking is induced to relieve stress promoted by polymerization shrinkage. Thus the strain is accommodated internally in a molded part, rather than through macroscopic shrinkage of the article.     

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.     

Modeling PVTX diagrams: Application to various blends based on unsaturated polyester—Influence of thermoplastic additive,fillers, and reinforcements

The model previously proposed to predict the volume change of filled blends was extended to unsaturated polyester/styrene blends without or with thermoplastic additive and to blends with fillers and/or fibers. This model was based on experimental results from Pressure Volume Temperature X (PVTX) setup where temperature, conversion degree, and volume at a controlled pressure were monitored simultaneously. Predictions obtained from the model were compared to experimental results and were in good agreement. This model took into account thermal expansion, polymerization shrinkage, and shrinkage compensation via porosity formation. These phenomena were deconvoluted from the experimental curve and separately quantified. It was shown that shrinkage and its compensation induced a volume variation exhibiting a linear dependence with conversion degree. The influences of low‐profile additive content, pressure, fillers, and fiber presence on shrinkage control were highlighted. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2976–2988, 2004     

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.     

Effects of molecular weight and molecular structure of low profile additives on the properties of bulk molding compound (BMC)

The effects of molecular weight and molecular structure of styrene(St)‐based and vinyl acetate(VAc)‐based low‐profile additive (LPA) on the curing kinetics and compatibility of unsaturated polyester (UP)/LPA system and linear shrinkage, water absorption rate, surface gloss and pigmentability of bulk molding compound (BMC) were investigated. Results show that the curing reaction rate decreases with an increase of the molecular weight of LPA due to the chain entanglement effect. The plasticizing effect of LPA on the (UP) network was reduced with an increase of the molecular weight of LPA. Water absorption of BMC increases as the molecular weight of LPA increases, implying that more microvoids were formed inside the BMC, resulting a lower linear shrinkage rate, and worse pigmentability. However, good shrinkage control LPA does not necessarily lead to a smoother surface and better surface gloss. Furthermore, modified LPAs possess better compatibility with UP, the final curing conversion of UP is elevated, and both better shrinkage control and surface properties are also observed.