A Study On The Phase Separation Behavior Of Poly (Methyl Methacrylate)/Poly (Styrene-Co-Acrylonitrile) Blends In The Presence Of Silica Nanoparticles

In this paper, wo studied the phase separation behavior of poly(methyl methacrylate)/ poly(styrene-co-acrylonitrile) (PMMA/SAN) and the silica nanoparticle filled ternary system PMMA/SAN/SiO₂ with the rheology technique. Based on our experiment data, it was found that the traditional rheology methonds had a big error on the determination of two systems'phase separation temperature. So we proposed the more reasonable and accurate methods to obtain the binodal temperature and spinodal temperature of the two blends. The main perpose of accquirring the phase separation temperature is that, it is the fundation for the reasearch of paitially miscible blends'phase behavior and the polymer prcessing to control the properties of material. The results are as follows:1) We proved the variation of the time-temperature-superposition (TTS) principle, vGP plot, Han plot, Cole-Cole plot methods to judge the phase separation in PMMA/SAN blends and PMMA/SAN/SiO₂ blends, and got the range of the binodal temperatures. In our paper, we found the traditional method had a large error that we take the transition point in the slope of G ' ^T curve as the binodal temperature in PMMA/SAN blends and PMMA/SAN/SiO₂ blends.2) The binodal temperatures of PMMA/SAN blends'near-critical compositions were obtained by the gel-like behavior during spinodal decomposition, which is a character of polymer blends with co-continuous morphology. The Cole-Cole plot method was introduced to determine the binodal temperatures of off-critical compositions based on the appearance of shoulder-like transition in the terminal regime of blends with droplet morphology. Such method is found also applicable in nanoparticle filled polymer blends.3) Moreover, a new method to determine the PMMA/SAN blends'spinodal temperature from Fredrickson-Larson mean field theory and Doi-Edwards model was suggested, where the concentration fluctuation's contribution to the storage modulus is used instead of the whole dynamic moduli. This method was also successfully extended to nanoparticle filled polymer blend,if we consider the fact that SiO₂ had the selective location in PMMA component. 4) The influences of the concentration and the average diameter of silica particles on the phase separation temperature were studied. It was found that the small amount of the silica nanoparticles in PMMA/SAN blends will significantly change the phase diagram, which is related to the selective location of silica in PMMA. The comparisons with the Ginzburg's thermodynamic theory of particle filled polymer blends are also discussed.