Influence Of Tertiary Component On Phase Separation In Thermoplastics/Epoxy Blends

The influences of MEK-SiO₂, Powder- Si O2 nanoparticles and PS-b-PCL block copolymer on the reaction induced phase separation（RIPS） of epoxy resin（DGEBA）/polyetherimide（PEI） blends have been studied with time-resolved light scattering（TRLS）, optical microscopy（OM）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）and differential scanning calorimetry（DSC）.We have investigated the effect of different types of nano-silica fillers on the polymerization induced phase separation of thermoplastic modified thermoset at near- and off-critical concentrations. The results of OM, TRLS, SEM showed that the non-filled and filled blends show typical UCST behavior. Introduction of a certain amount of nano-silica nanoparticles induces an obvious decrease of the cloud-point temperatures, which means the temperatures of phase separation of the filled blends are lower than those of the non-filled blend. The influence of MEK-silica nanoparticle on the curing reaction in the tertiary PEI/DGEBA blend has been studied by DSC.The result indicates that the aggregation of the silica particles occurrs at higher loading content and only part of the Si-OH group acts as a catalyst to initiate the curing reaction.PS-b-PCL block copolymer prepared via atom transfer radical polymerization（ATRP） was also used to study its influence on the phase evolution of epoxy resin（DGEBA）/ polyetherimides（PEI） blends. The results of TRLS show a dynamically asymmetric phase separation of epoxy/PEI blend with the presence of block copolymer PS-b-PCL. Such behavior is attributed to the preferential location of the block copolymer PS-b-PCL in the epoxy-rich phase, which reduces the mobility of the epoxy oligomer, therefore slowing its diffusion and leading to an finalinverted structure（continuous PEI-rich matrix） and the secondary phase separation. The above results suggest that the viscoelastic effect will play an important role in reaction-induced phase separation. When the diffusion of the epoxy oligomer is no longer able to follow the size growth of the epoxy-rich domain, secondary phase separation takes place in the dispersion domains.The final structure is fixed earlier while the slow-dynamic phase（PEI-rich phase） is still the continuous morphology.