The Synergistic Effect Of Ultraviolet Photo-oxidation And Environmental Stress Cracking In Injection Molding Of Amorphous Polymers

The photo-oxidation cause physical and chemical changes of polymer material and also affects the properties of polymer products. Environmental Stress Cracking (ESC) is a complicated failure behavior of polymer materials. Thereore, it has important academic and engineering meanings to study on the synergistic effect of photo-oxidation and environmental stress cracking in injection molding of polymers and investigate the failure behavior and mechanism of polymers in a multi-environment. It can provide experimental evidence and theoretical guidance for predicting and improving the service performance of polymer injection molding products.This Paper aims at PC and ABS injection-molded tensile specimens and plates. The mechanical and cracking behavior of the polymer products which are before and after UV aging under different conditions was investigated. And the effect of different solvents on the environmental stress cracking behavior was compared. The main tasks are as follows:1. The effect of the ESC behavior of the PC injection-molded parts after photo-oxidation was studied. The mechanics and cracking behavior of PC with or without ethanol solvent was investigated, The results show that Photo-oxidation effects can improve the tensile properties of PC material samples. Ethanol can accelerate the PC material failure. Compared with the single factor, the synergy between the photo-oxidation effect and ethanol make more obvious environmental stress cracking effects of the PC products. PC products after photo-oxidation have higher stress relaxation rate and more obvious surface cracking in ethanol solvent. Maybe the photo-oxidation products are more interactive with the ethanol solvent to exacerbate the effects of stress cracking. The stress relaxation test can be found more suitable to reflect the synergy of the photo-oxidation and environment stress cracking effects to the PC samples.2. The ESC behavior of PC injection-molded plates in carbon tetrachloride was analyzed. It is found that the cracking behavior and variation trend of PC injection plates in carbon tetrachloride are different with the ethanol environment, The ESC resistance after photo-oxidation in carbon tetrachloride gets better. The injection molding process parameters affect the ESC behavior evidently. When the holding pressure and holding time increased, the specimens are more susceptible to environmental stress cracking. While as the melt temperature and injection rate increasing, the ESC resistance of the products is lower.3. The mechanical property and ESC of ABS and PC injection-molded parts immersed in air-condition oil were studied. The results showed that the mechanical property changed much after the ultraviolet irradiation. The ultraviolet break the double bones of the ABS resin which caused the ABS material getting brittle, reduce the toughness and presents apparent ESC phenomena. Compared with the stress cracking behaviorl in the air-condition oil, the cracking behavior in the ethanol is more obvious. The reason is that the interaction between different solvents with materials have different sensitivity.