The effect of glass fibers and some fire retardant additives on the kinetics and mechanism of crystallization of poly(butylene terephthalate) (PBT) has been investigated. Shorter half times of crystallization and higher optimum crystallization temperatures of the filled samples are attributed to the nucleating ability of the additives. Based on the percent crystallinity determined, the efficiency of the different quenching media studied can be arranged in the order: ice water > 25°C water ⩾ dry ice/ethanol > liquid nitrogen. The inefficient quenching of dry ice/ethanol arid liquid nitrogen media is attributed to their poor heat transfer. The Tg of these quenched samples is, however, independent of the percent crystallinity.

SynopsisThe two-phase nature of a graft copolymer of ethylenepropylene-1:4 hexadiene (EPDM) and poly(viny1 chloride) (PVC) has been established by dynamic mechanical measurements. The interaction of different additives with the isolated graft copolymer has also been inferred from their dynamic mechanical and thermal properties. Carbon black and titanium dioxide act as inert filler, while the effect of including straight-chain hydrocarbons (e.g., n-hexadecane and n-hexatriacontane) is strongly dependent upon the melting point of the hydrocarbons. Sunflex 110 plasticizes the rubber phase of the graft copolymer while dioctyl (di-2-ethyl hexyl) phthalate (DOP) plasticizes the PVC phase and reduces Tg. At lower temperatures, however, the elastic modulus is increased by an "antiplasticization" effect. The local environment of PVC chains in the graft copolymer is modified by the presence of the rubber and PVC chains are less mobile.

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