| Polycarbonate has become a very attractive material in the field of high-end transparent parts.Functional coating is an effective approach to improve the surface properties and functionalization of PC without altering its bulk properties. On the other hand, PC is facing new challenges when used in aerospace, defense and other areas, such as high-performance, multi-function, and the service life and security in extreme environments.Therefore, it is of great significant to study the aging and failure behavior of PC transparent parts/functional coating under special environment conditions.This paper focuses on the ultraviolet ageing resistance and environmental stress cracking behavior of PC transparent parts/nano-Ti O2 coating system. Based on the sol-gel preparation of coating and the characterization of the structure and properties of products, the ultraviolet-protection of Ti O2 coating system on PC was analyzed, as well as the failure behavior of PC/inorganic coating products under the combined effect of solvent-stress.The main work was as follows:1. The nano-Ti O2 coating system on PC were prepared by sol-gel, and the structure, optical properties and adhesion properties of the coating were studied. It was found that, the coatings showed an excellent transparency,and an amorphous structure with a nanoscale particle size. The surface of Si O2/Ti O2 composite coating showed a uniform particle size and structure, for the rich microstructure of Si O2 middle layer was beneficial to the growth of Ti O2 particle and the improvement of uniformity;In addition, the UV-modified of PC promoted the chemical combination between the coating and matrix,and improved the adhesion of the coating on PC.2. The ultraviolet aging resistance of PC transparent parts/nano-Ti O2 coating system was investigated. The results showed that, the nano-Ti O2 coating system showed a nice photo-protection for PC, the yellowing index and yellowing rate of the parts had declined, which is due to the shielding effect of Ti O2 coating to UV light. The Si O2/Ti O2 composite coating showed a better photo-protection effect for PC. In addition, an enhanced interfacial bonding and a better coating compactness would appeare after surface modified, which would develop a barrier to oxygen effectively and further reduce the rate of photo-oxidation. There was still a good adhesion between the coating and the matrix after ultraviolet aging, while the hydrophilic of coatings was increased by the light-induced hydrophilic effect of Ti O2 and photodegradation of products.3. The stress relaxation and cracking behavior of PC/nano-Ti O2 coating system in N-butanol solvent environment were investigated. The results show that: inorganic coating played a role of barrier against solvent to a certain degree, which improved the stress relaxation resistance of PC products in the solvent environment. In addition, the density of surface crack on PC coated with inorganic coating was large, the cracks were narrow and short. Particularly, part of the cracks were induced from the intermediate region of the product. The stress relaxation resistance of PC coated with composite coating was properly decreased when the surface of PC was UV-modified previously, and the surface cracking was nearly invariable. |
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