The effect of crystallization on hydrolytic stability of polycarbonate

Bisphenol A polycarbonate (PC) was chosen as the representation of polyester resins for investigating the effect of aggregative state on hydrolytic stability of this kind of materials. Surface-crystallized PC was prepared by solvent-induced crystallization method. Moreover, a comparative study on hydrolytic stability of amorphous PC and surface-crystallized PC had been carried out by means of mechanical performance testing, static water contact angle, IR, GPC and DSC measurements. The results indicated that the surface-crystallized PC had better hydrolytic stability than amorphous PC, manifesting as: (1) the hydrophobicity of PC was enhanced obviously when the surface of material crystallizes via solvent-induced method; (2) the reduced rate of the elongation at break of surface-crystallized PC was much smaller than that of amorphous PC during hydrolysis; (3) the impact strength of amorphous PC reduced rapidly in the early stage of hydrolysis, while that of surface-crystallized PC firstly increased, following by a slightly decrease; (4) the reduced rate of weight-average molecular weight of surface-crystallized PC was smaller than that of amorphous PC; and (5) the stability of the chemical structures of surface-crystallized PC was much higher than that of amorphous PC during hydrolysis, resulting in fewer changes in the glass transition temperature (T-g), as well as less cleavage of polycarbonate linkage after hydrolysis in 65 degrees C water for 36 days. This investigation clearly shows that solvent-induced crystallization on surface can be an efficient way to enhance the hydrolytic stability of polycarbonate. (C) 2013 Elsevier Ltd. All rights reserved.