【作者】 夏雨；

【导师】 单松高； 薛忠民；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 近年来，随着高性能低成本先进复合材料的发展，低温液体模塑成型工艺(LCM)引起了广泛关注。然而，高温低轮廓添加剂(LPA)的热膨胀机理不适用于低温成型工艺，详尽的低温LPA机理尚待深入研究。论文根据LCM技术发展的需求，对加入LPA的不饱和聚酯(UP)树脂体系中低温固化收缩控制机理进行系统的研究，重点对UP／LPA／苯乙烯体系的相分离和结构形成机理和固化应力进行了研究，进而提出低收缩机理，以突破LCM工艺应用的关键技术和难点。 固化过程中UP／LPA／苯乙烯体系的一个重要特征就是形成两相结构(富LPA相和富UP相)。文中对不同含量LPA的UP树脂中低温固化时的相分离过程进行了研究，依据体系的可混合性和反应动力学，发现样品结构的形成遵循相同的路线，在不同的阶段停止可能形成不同的结构类型。两个重要的因素—富LPA相的体积分数和相分离的周期，即相分离开始和凝胶之间的时间，决定了样品的最终结构以及微观结构形成过程可进行的程度，而LPA含量的变化影响了相分离周期和富LPA相的体积分数。 文中研究了在低轮廓不饱和聚酯树脂体系凝胶后固化时的一维固化应力及低收缩对固化应力的影响，发现LPA对于减小UP树脂体系的固化收缩应力具有明显的效果，LPA的含量、温度及LPA的类型对固化应力的产生和发展均有较大的影响。通过对体积收缩和固化应力的研究，发现收缩与固化应力形成和发展的关系是非线性的。 在上述实验研究基础上，提出了低轮廓不饱和聚酯树脂中低温固化的收缩控制机理。UP／LPA／苯乙烯体系的低轮廓效果有两个主要的步骤决定：相分离和微孔形成。低轮廓不饱和聚酯树脂在低温固化时的反应主要可以分为六大步：引发，旋节分离，(晶粒)粗化长大，连接和成长，凝胶和微孔形成。 掌握LPA的机理不仅使LCM工艺无须依靠试差法，还可为新型LPA的合成与制备提供材料设计指导。论文的研究将为LCM制备技术奠定理论基础，对促进高性能低成本先进复合材料的广泛应用具有重要的意义。更多还原

【Abstract】 In recent years, Liquid Composite Moulding (LCM) process has been focused widely with the development of advanced composites with high quality and low cost. However, the heat-expansion mechanism of low profile additives (LPA) at high temperature is not fit for molding processes at low temperature, which means that the detailed mechanism at low temperature still need to be studied. According to the development of LCM, the shrinkage control mechanism of Unsaturated Polyester (UP) resin system with LPA during curing at low-medium temperature was investigated systemically in this paper. Based on phase separation, structure formation and curing shrinkage stresses in UP/ LPA/styrene system, the low shrinkage mechanism was proposed to break through the key techniques difficulties in LCM application.One of the important features during the cure of UP/ LPA/styrene system is the formation of a two-phase structure (LPA-rich phase and UP-rich phase). In this study, the phase separation process during the cure of UP resins with LPA was investigated. It is found that the structure formation followed the same route in terms of the system miscibility and reaction kinetics, while could end at different stages which resulted in different structures. Two key factors, the volume fraction of the LPA-rich phase and the phase separation period, i.e. the time period between the onset of phase separation and the gelation, determined the final structure and the degree of the microstructure formation, which was effected by the change of LPA concentration.The development of stress under one-dimensional (1-D) shrinkage constraint occurring after the gel point of the low profile UP and the effect of low shrinkage on curing stresses were also investigated. It was found that LPA could obviously reduce the curing stresses hi UP resins. And the concentration and type of LPA together with the temperature had evident effects on the beginning and development of curing stresses. It was also found that the volume shrinkage was non-linear with curing stresses.Based on the above experimental results, a shrinkage control mechanismat low-medium temperature was proposed. The performance of low profile in the UP/LPA/styrene system was governed by two critical steps: phase separation and microvoid formation. The whole reaction process could be divided into six steps: the induction, spinodal decomposition, coarsening, coalescence and growth gelation and microvoid formation.The understanding of the LPA low shrinkage control mechanism not only makes LCM not rely on the trial-and-error method, but also provide guidance of material design for the synthesis and preparation the new type LPA. This study will also establish the theoretic foundation for the LCM technique and has significant influence on prompting the wide applications of composites with high quality and low cost.更多还原