| This paper studied the behavior and mechanism of polycarbonate used as food and packaging materials aging in hot water, photo-oxidation and solutions, and discusses the various aging factors on the role of PC properties aging. In addition, the relationship between the bisphenol A(BPA) content and aging degree of PC was established preliminarily.PC aging in hot-water were characterized by stereo-microscope, FTIR, TG, mechanical properties and so on.The results showed that due to the combined effect of water with high temperature, leading to PC material within the system soluble substances dissolve or migrate out of the inside of the specimen to form defects by stereo-microscope, mechanical properties of the PC material decreased after aging. By the means of FTIR and GPC, we found that the hydrolysis of PC occured after absorbing water, its relative molecular weight decreaseed.Modification laws of phenolic hydroxyl absorption intensity in IR spectra and the maximum absorption wavelength red shift of benzene in UV-Vis spectra indicated that the amount of BPA precipitation with the extension of the hot-water aging time increased. Initial weight loss temperature and maximum weight loss rate temperature of PC after hot water aging were reduced by 17-18℃ and 9-10℃ respectively, and the thermal stability reduced, the color of PC did not change significantly. Using the same means of characterization to analysis the influence of PC performance after photo-oxidation aging. It was indicated that the mechanical properties of PC after photo-oxidation aging decreased; UV-Vis spectra showed phenyl salicylate and 2,2-dihydroxy benzophenone generated during photo-oxidation aging, showing that Fries rearrangement occured during aging process. GPC and DSC results showed that PC photo-oxidation degradation reactived; the amount of BPA precipitation decreased after the first increased with photo-oxidation aging time extended;YI, AC significantly increased, T decreased. TG showed that the thermal stability of PC after photo-oxidation aging reduced.The results showed aging in solutions:With the aging time, the number and the sizes of defects in PC material increased at the same aging time, salt solution> acid solution> aqueous.After three solutions aging,the color did not change obviously, however, the mechanical properties of PC significantly deteriorated. The DSC, GPC results showed PC degraded which the molecular weights and Tgs were decreased when PC was aged in solutionssalt solution> acid solution> aqueous solution; the phenolic hydroxyl characteristic absorption peak intensity with reference absorption peak intensity ratio in IR spectra and the maximum absorption wavelength red shift of benzene in UV-Vis spectra after solutions aging indicated PC hydrolysis reaction occurred, the relative content BPA relative content increased. Obviously aging rate in the salt solution than in the acid solution and the aqueous solution, indicating Na+, Cl-presence significantly accelerated aging process. |
PDF Full Text Request