Study Of Enhanced Viscoelastic Effect Of Mesoscopic Fillers In The Phase Separation Of Thermalplastic/Epoxy Blends

The influence of mesoscopic fillers on polymerization-reaction-induced phase separation and mechanical properties in PES/DGEBA, PS/DGEBA and PEI/TGDDM blends have been studied with Optical Microscopy(OM), Time-Resolved Light Scattering(TRLS), Scanning Electron Microscopy(SEM), Transmission Electron Microscopy(TEM) and Differential Scanning Calorimetry(DSC).Enhanced viscoelastic effect of mesoscopic fillers in phase separation of dynamic asymmetric system has been found by study in filler/thermoplastic/thermo-setting blends. OM, TRLS and SEM results show that incorporation of a small amount of mesoscopic fillers into the blends can decrease the decomposition rate of the network formed by slow phase leading to decreased characteristic length scale and refined phase structures. DSC results show that the addition of mesoscopic fillers does not change the polymerization conversion of epoxy at fog point, which means that the dramatic change of phase separation process comes from kinetic rather than thermodynamic changes. TEM results show that mesoscopic fillers are preferentially immersed into the slow dynamic phase and phase interface, and influence the phase separation by entangling with polymer chains of the slow phase. It is also found that the influence of fillers on phase structure is relative to the size and dispersion condition of the fillers. Enhanced viscoelastic effect will diminish or disappear in the systems with low viscoleastic effect or dynamic symmetry when the curing temperature is very high or the curing rate is very slow.In PEI/TGDDM blends, phase structure and mechanical properties are also influenced by the added sepiolites. When PEI content is at 5wt%, phase separation of the blends follows nucleation and growth mechanism. Due to the entanglememt, PEI is mainly distributed in the surface of mesoscopic particles, leading to the disappearance of spherical PEI rich phase. Tensile strength and elongation at break of the material are increased while Young's modulus varies little. When PEI content is at 13wt%, bicontinuous structures are formed in phase separation which follows spinodal decomposition mechanism. Due to the enhanced viscoelastic effect, much more refined phase structures are obtained. Tensile strength, elongation at break and Young's modulus of the material are all increased.