| A novel technique - Pan-Milling Mixing was developed to prepare high performance polymer blends and composites and to control the microstructure by applying the excellent pulverizing, mixing and in-situ compatibilizing functions of our self-designed pan type milling equipment. The pulverizing process and its mechanism of polymers in pan-mill were systematically investigated. Through this method, a polypropylene/polyamide 6 (PP/PA6) blend was obtained. The two constituents were compatibilized in-situ by mechanochemical reactions induced by pan-milling and the microstructure of the blend can be controlled conveniently by adjusting processing conditions. Polyamide 6/ground limestone powder (PA6/CaCO3) and Polyamide 6/silicon dioxide (PA6/SiO2) composites were also prepared through this method. Those PA6 blends and composites exhibit improved microstructure and superior mechanical properties to the systems mixed by conventional mixing methods.The pulverizing process and the mechanism of polymer materials during pan-milling were studied by analyzing the variation of particle shape, particle size and particle size distribution. During the initial pan-milling period (1-5milling cycles), a sudden particle size reduction was observed, which can be described by "avalanche" pulverizing mechanism, i.e., large amount of energy caused by pan-milling press force accumulated in deformable polymers to a critical point and then the deformed polymer flakes suddenly collapsed to small particles by shear force. In the following milling stage, the particle size gradually reduced and the particle size distribution became wider, which is in accordance with R-R-B (Rosin-Rammler-Bennet) equation and can be described by "surface" pulverizing mechanism. The two pulverizing mechanism during pan-milling was caused by its unique stress field exerting on materials, which is mainly composed by press force and shear force. In comparison with impact force dominated conventional pulverizing equipment, pan-mill is especially effective for the pulverization of polymer materials. Experimental results show that not only commodity polymers such as polystyrene and polypropylene but also coriaceous engineering plastics such as PA6 can be effectively pulverized by pan-mill. After 20 milling cycles, the particle size of PA6 can be reduced from original 3-4mm to around 1μm. Some particles even reached nano scale (40-80nm) after 30 milling cycles.Pan-milling has great influence on polymer structure. DSC and X-ray diffraction results show that after pan-milling, the crystallinity and the size of micro crystals of PA6 decrease. Melting point increases and crystallization temperature decreases. Spherulites dimension also decreases due to the chemical changes occurred during pan-milling. Viscosity test shows that chain scission occurred during pan-milling, which caused slight reduction of mechanical properties.Polypropylene/polyamide 6 (PP/PA6) ultra-fine powder was prepared through pan-milling at ambient temperature. The particle size can be controlled by adjusting processing conditions such as milling time, rotating speed of milling pan, static pressure between milling pans and milling temperature, etc.Average article size of the powder reduced to micrometer scale in relatively short time and a fraction of which even reached nano scale. The particle size distribution exhibits two peaks due to the different pulverizing efficiency on the two polymers. Besides, pan-milling mixing can compatibilize the two polymers in-situ through mechanochemical reactions. Viscosity analysis, thermal analysis and FT-IR experiments show that the Tg of PP in PP/PA6 co-powder formed by pan-milling mixing and its thermally molded article increased a lot compared to that of PP in PP/PA6 simple blend. After adequate extraction of PA6, the sample still exhibits characteristic absorbance of amide group, which is caused by the formation of PP-PA6 copolymer induced by the macro-radicals formed by chain scission. The copolymer can enhance the interfacial...
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