In the preparation and application of PC/PBT (75:25) alloy, compatibility and thermal processing yellowing are two closely interrelated core technical issues that must be addressed. The root cause lies in the fact that although both are polyester materials with similar chemical structures, "transesterification reactions" may occur between the ester groups of PC and PBT during melt blending. Moderate transesterification can achieve a certain compatibilization effect; however, excessive reaction will damage the original molecular chain structure and crystallization properties of the polymers, leading to a significant decline in key material properties such as mechanical strength and toughness of the alloy, and directly manifesting as severe yellowing of the material macroscopically.
Therefore, the core of the technical route lies in the precise regulation of transesterification reactions, supplemented by effective compatibilization schemes. Firstly, to prevent excessive transesterification, it is recommended to add transesterification inhibitors such as PGPB ZPV, with a suggested addition amount of 0.2%-0.3%. This effectively inhibits the abnormal breakage and recombination of molecular chains under high-temperature shear, stabilizes the melt structure and properties, and fundamentally stabilizes material performance while reducing yellowing. Secondly, to solve the compatibility problem at the two-phase interface, specific compatibilizers need to be introduced. A highly effective choice is reactive compatibilizers containing Glycidyl Methacrylate (GMA) groups, such as PTW, 8900, and U993. Products like 8900 can react with the end groups of polymers during melting, forming chemical bridging at the two-phase interface, which significantly improves compatibility and toughness. However, they may have a certain impact on the surface gloss of products (resulting in a matte effect). If it is necessary to improve compatibility while maximizing the retention of surface appearance, a more balanced compatibilizer such as U993 can be considered, with a suggested addition amount of 0.3%-0.4%.
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