The role of a polyester-based thermoplastic elastomer in the crystallization of an aliphatic polyketone terpolymer

Abstract

The effect of a commercial grade polyester thermoplastic elastomer (HY) on the crystallization behavior of a polyketone terpolymer of ethylene, propylene and carbon monoxide (EPCO) was investigated in terms of shear rate, temperature and blend composition. HY retarded the isothermal crystallization of EPCO in the static state. As the HY content increased, the half-time for the crystallization of the EPCO/HY blends increased, and the cold crystallization temperature (T c ) decreased. In addition, the average value of the Avrami exponent decreased, but the crystallization rate constant increased. The retardation of crystallization could be explained by steric hindrance or a shield effect of the HY phase on the growth of EPCO spherulites at a temperature near the T c . HY also retarded the crystallization of EPCO in the dynamic state. However, the induction time of the blends was slightly decreased by increasing the magnitude of shear rate up to 10 rad s − 1 . X-ray diffraction revealed that the introduction of HY had little influence on the crystal structure of EPCO. INTRODUCTIONThe aliphatic terpolymer of ethylene, propylene and carbon monoxide (EPCO) has attracted much attention from polymer engineers and scientists because of its excellent physicochemical properties. Favorable properties such as high tensile strength, high wear resistance, low gas permeability and high chemical resistance give EPCO great potential as an engineering plastic and a barrier packaging material. 1-9 However, control of the temperature to below 240°C is recommended for the melt fabrication process of EPCO because thermal degradation occurs readily at a higher temperature. 10-14 This is a result of residual palladium, the polymerization catalyst, for EPCO, which frequently causes trouble in the melt processing of EPCO because of a very narrow processing window. 1,7 For example, the exceptionally high rate of crystallization in the injection molding process sometimes causes problems such as blockage of the sprue and warping of the resultant products.It is recognized that most foreign materials lead to a higher crystallization rate of crystalline polymers. However, in addition to improving the notched impact properties, a polyester-based thermoplastic elastomer (HY) retards the crystallization of crystalline EPCO. 15 In this study, we elucidated the retardation mechanism of the crystallization of EPCO by HY by investigating the crystallization behavior of EPCO in the static and dynamic states in terms of the dynamic shearing condition as well as blend composition.

Progress in polyketone materials: blends and composites

“…Block copolymers, consisting of relatively stiff segments and relatively soft segments, are also able to toughen POK. For example, Hytrel is composed of poly(tetramethylene terephthalate) as the hard segments and poly(oxytetramethylene glycol) as the soft segments, as schematically shown in Scheme . When 20 wt% Hytrel was incorporated in POK, an increase of impact strength by 154% was observed but a decline of tensile strength by 184% .…”

“…For example, Hytrel is composed of poly(tetramethylene terephthalate) as the hard segments and poly(oxytetramethylene glycol) as the soft segments, as schematically shown in Scheme 1. [34][35][36] When 20 wt% Hytrel was incorporated in POK, an increase of impact strength by 154% was observed but a decline of tensile strength by 184%. 35 Other block copolymers such as thermoplastic polyurethanes including polyester-based polyurethanes and polyether-based ones, 37,38 polyether esteramide (PEEA) 39 or partially hydrogenated styrene-butadiene-styrene block copolymers modified with maleic anhydride 40 can also toughen POK and result in blends with a balance of toughness and stiffness, as well as solvent resistance and high surface gloss appearance.…”