Miscibility, melting and crystallization behavior of two bacterial polyester/poly(epichlorohydrin-co-ethylene oxide)blend systems

摘要

The miscibility, melting and crystallization behavior of two bacterial polyester/poly(epichlorohydrin-co-ethylene oxide)(PECH-EO)blend systems was studied. PECH-EO containing 48 mol% of epichlorohydrin is miscible with poly(3-hydroxybutyrate)(PHB) and with existence of a single glass transition temperature (T_g) and a depression of the equilibrium melting temperature of PHB or PHBV in each blend. The T_g-composition dependence of the blends can be described by the Kwei equation.The interaction parameters obtanined frommelting point depression analysis are -0.089 and -0.075 for PHB/PECH-EO and PHBV/PECH-EO blends, respectively. The melting and cold crystallization behavior of PHB and PHBV during DSC heating trns is markedly affected by the addition of PECH-EO.During the nonisothermal crystallization process, the cold crystallization temperature (T_(cc)) of PHB first shows a slight decrease with increasing PECH-EO content from 0to 50wt.%, and then a significant increase with further increase fo PECH-EO content to 90 wt.% in PHB/PECH-EO blends.For PHBV/PECH-EO blends, the T_(cc) of PHBV in creases with increasing PECH-EO content in the whole composition range studied duringthorp ecess. For samples after cold crystallization, the phase crystallinity of PHB remains constant, while that of PHBV decreases significantly with increasing PECH-EO content. Under isothermal condition, the radial growth rates of bacterial polyester spherulites in the blends are lower than that of pure bacterial polyester samples at higher crystallization temperatures. Spherulitic growth kinetics is analyzed using the Lauritzen-Hoffman model, and the kinetic parameters are determined.Nucleation constant decreases with increasing PECH-EO content in both PHB/PECH-EO and PHBV/PECH-EO blends.