Efeito da adi?§?￡o de PHB na cristaliza?§?￡o a frio do PET

摘要

The present work is concerned with the effect of low concentrations (0.5 e 1.0%) of poly(3-hydroxybutirate) (PHB) on the isothermal cold crystallization of poly(ethylene terephthalate) (PET). Energy curves were obtained by differential scanning calorimetry (DSC) and the kinetics of the crystallization was analyzed using Avrami's method. Two crystallization stages were observed. Results showed that the presence of PHB affects the crystallization rate of PET, as verified by changes in the time needed to reach 1, 10, 30, 50 and 99% of crystallinity. Activation energies for the two crystallization stages were computed using Arrhenius plots; PET/PHB mixtures showed slightly smaller values. The equilibrium melting temperatures were estimated according to the procedure of Hoffman and Weeks; the higher values obtained for the PET/PHB mixtures suggest that PHB affects the crystalline structure of PET.