【作者】 余英丰；

【导师】 李善君；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2004， 博士

【摘要】 本文研究了不同热塑性树脂改性环氧体系的复杂相分离现象，主要讨论了两种不同的相分离机理-粘弹相分离和二次相分离机理的区别和联系。研究了聚酯酰亚胺(PEtI)、聚醚酰亚胺(PEI)、聚醚砜(PES)及其共混改性环氧体系时，采用不同固化剂时的复杂相分离现象。通过光学显微镜(OM)，扫描电子显微镜(SEM)，透射电子显微镜(TEM)，时间分辨激光光散射(TRLS)，流变仪和DSC等仪器跟踪研究相分离过程，固化反应活化能、转化率以及共混物流变行为等。 通过比较链增长和逐步聚合体系的相分离差别，发现由于扩散流动的主体不同，即前者为环氧单体(Monomer)而后者为环氧增长链(Growing epoxy)，造成二者在相分离时热塑性富集相不同特征流变时间和特征形变时间比，即动力学不对称性的差异。链增长聚合体系由于两相动力学不对称而发生粘弹相分离；逐步聚合体系在热塑性树脂用量较少时，由于相分离初期界面流动引起环氧富集相相间尺寸快速增长，同时热塑性树脂的粘弹性效应阻碍环氧组分的扩散，造成区域浓度偏离平衡状态，进而发生了二次相分离。 由光学显微镜跟踪发现，因固化聚合机理不同，双连续相结构的形成遵循不同的演化机理：粘弹相分离和二次相分离机理。对于粘弹相分离过程，从相分离开始阶段，体系即形成相反转结构，随着固化反应的进行，热塑性富集相由弹性变形发展到粘性流动，环氧单体／增长链从热塑性树脂富集相中扩散出来，形成大的不规则分散相，然后粗化长大，合并，成为连续相。而对于发生二次相分离的体系，相分离初期形成微观双连续结构，再演化到双连续相结构，然后在双连续相中自发发生二次相分离，形成微细尺寸的二次结构。扫描电镜和透射电镜的结果证明了两种复杂相分离机理的存在。 对发生旋节线(Spinodal)相分离的体系进行时间分辨激光光散射研究，结果发现：对于粘弹相分离过程，不论链增长或逐步聚合机理，光散射矢量qm随中文摘要笼军k李俘d匕学位论文固化时间指数衰减，可以由Maxwen粘弹性方程q，(t)二q。十AO exP卜t/约描述，对于部分热塑性树脂改性体系，光强的增长趋势同样符合松弛关系。流变分析发现体系的粘度即热塑性富集相的粘度随相分离时间指数增长，证明光散射所观测的相分离松弛行为与体系粘度存在相互联系。 改变固化温度，从而得到各体系不同温度下的对应于快动力学相从慢动力学富集相扩散的松弛时间丁。用WLF方程拟合光散射实验得到的松弛时间及移动因子，发现对于最终相结构相近的各个不同热塑性树脂改性体系，同一温度下松弛时间及移动因子不因热塑性树脂而有大的变化，但热固性树脂的链增长聚合和逐步聚合固化机理对其影响很大，即光散射反映的松弛时间在链增长聚合体系主要对应于环氧单体，而逐步聚合体系对应于环氧增长链的扩散流动行为。 对照两相组成与转化率的相图发现，环氧体系的转化率在相分离过程中变化很小，而且一般早于环氧的化学凝胶点。在相分离中后期，不论相反转或双连续体系，体系中热塑性树脂的含量都远低于静态对称线，膜状(membrane一1 ike)热塑性连续相的形成由于其弹性形变引起。发生二次相分离体系，由于分相初期流动快于扩散而导致两相浓度变化滞后于粘弹分相体系。 流变分析发现:相分离发生时由于相反转结构的形成导致体系粘度突然快速增加;最后由于热塑性树脂富集相的玻璃化而导致体系发生物理凝胶。双连续相结构体系的流变行为与相结构演化相符，由相反转向双连续转变时体系粘度和弹性模量亦随之下降。 采用咪哇引发的快速链增长固化体系，发现可以通过调节咪哇种类即环氧体系的凝胶化不同而使体系冻结在未分相或相分离的不同阶段。TEM跟踪相分离过程，证明了粘弹相分离初期就形成相反转结构。更多还原

【Abstract】 Viscoelastic phase separation and double phase separation process were choosed to study the complex phase separation processes in thermoplastics modified epoxy systems. With different hardeners, polyesterimide, polyetherimide, polyethersulfone and their blend modified epoxy systems were used to study the relationship between thermoplastics and their complex phase separation behaviors. The development of morphologies, activate energy of curing reaction and the relationship between rheological behavior and phase separation were followed by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Time-Resolved Light Scattering (TRLS) and rheolometry.The differences in dynamic asymmetry, or compactions between the characteristic rheological time and characteristic deformation time in the phase separation process of polyethersulfone modified systems, were caused by the diffusion/flow ability of epoxy monomer and growing-epoxy due to the cure mechanism: chainwise and step wise polymerization. Dynamic asymmetry in chainwise system caused viscoelastic phase separation while dynamic equiluim in stepwise system with low thermoplastic concentration caused double phase separation at the early stage of phase separation.A structure evolution process from phase inversion to bicontinuous structure was observed in the viscoelastic phase separation by opitical microscopy. While in double phase separation, the high hydrodynamic flow due to interface motion causes the geometrical coarsening too fast for diffusion to follow, thus it will bring the system out of equilibrium and leads to secondary phase separation.Light scattering results with final phase inversion morphology show a typical exponential decay procedure of scattering vector qm and light intensity Im. The temperature-dependent relaxation time r was thus obtained.The values of relaxation time r had been fitted with Williams-Landel-Ferry equation separately. It was found that the reference temperature Ts obtained from the fitting, about 50K higher above Tg of epoxy-anhydride blend, consisted with each other. It demonstrates experimentally that the coarsening processes of epoxy droplets and the final morphologies obtained in these thermoplastic-epoxy systems are affected by viscoelastic behavior and the viscoelastic behavior could be attributed to the escape movement of epoxy monomer or growing epoxy chain from the PEI-rich phase.The rheological behavior during phase separation corresponded well with the morphology evolution. The viscosity increase at the beginning of phase separation was caused by the formation of thermoplastic-rich continuous phase structure. And the physical gelation, which corresponds to the crosspoint of modulus G’ and G", was resulted from the vitrification of thermoplastic-rich phase.Viscoelastic phase separation process was demonstrated by the transformation of phase inversion to bicontinuous structure due to the earlier chemical gelation of epoxy resin cured with imidazole. And systems cured with imidazole could obtain homogenous structure due to the fast gelation before phase separation.更多还原