The apparent shear viscosity （ηα） of a blend composed of 97 wt % high-density polyethylene （HDPE） and 3 wt % polyamide （PA-66） was measured by capillary rheometry at different shear rates, below, near and abov...
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The apparent shear viscosity （ηα） of a blend composed of 97 wt % high-density polyethylene （HDPE） and 3 wt % polyamide （PA-66） was measured by capillary rheometry at different shear rates, below, near and above the melting point of PA-66, i.e. 240℃, 260℃ and 280℃, respectively. At 260℃ and a high shear rate, ηα of the blend reduced abnormally; and at 260℃, was lower than that at 280℃. The images of etched surface of extrudate observed by the SEM showed different dispersed phase morphology, induced by flow at different temperatures. It is suggested that the formation of fibrillar morphology of dispersed phase is a key factor for the abnormal reduction of ηα for the HDPE/PA blend.
An iPP-g-St graft copolymer synthesized by free-radical initiated solid-state grafting polymerization of styrene in nascent spherical iPP granules was effectively fractionated by temperature gradient extraction fracti...
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An iPP-g-St graft copolymer synthesized by free-radical initiated solid-state grafting polymerization of styrene in nascent spherical iPP granules was effectively fractionated by temperature gradient extraction fractionation (TGEF) into fractions of different styrene content. The fractions were characterized by FTIR, 1H-NMR, DSC, PLM and WAXD. The fraction extracted at room temperature (25°C) is homopolymer of styrene, and the fractions collected at 70, 90, and 105°C are iPP-g-St graft copolymer with decreasing degree of grafting. All the fractions of the grafting product contain a certain amount of styrene, meaning that almost all the iPP chains in the granules are accessible to the grafting monomer. The internal morphology of the iPP granules is highly porous, which enables the grafting monomer and the radicals to reach at each iPP chain during the polymerization. As styrene content of the iPP-g-St fraction increases, its crystallinity decreases, the size of iPP lamella decreases, and the crystalline morphology becomes more irregular.
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