Toughening and Modification of PBT

Polymer materials has the characteristics of high strength, low cos and high heat resistance, in recent years is increasingly used in the automotive field (such as automotive interior, shell and so on) . Polybutylene terephthalate (PBT) has become the most widely used polymer material for vehicle because of its excellent comprehensive properties. However, pure PBT has poor impact toughness, poor flammability and high notch sensitivity, which limits its application in automobile field. Toughening and modification of PBT can solve this problem.

The key factors affecting the properties of toughened modified materials include the shear modulus, matrix properties, dispersed phase morphology, particle size, interfacial compatibility and content of the blends. When stress is applied to the blend granules, stress concentration can be produced. Therefore, it is necessary to select blends with lower shear modulus (e. G. Elastomer) to improve the toughening effect. On the other hand, the blends should have good structural retention in the manufacturing process, which requires a moderate degree of crosslinking between the blend and PBT. If excessive crosslinking, the heat resistance of PBT will be reduced.

The toughening methods of PBT are divided into chemical method and physical method.

Chemical method: The polymerization structure of PBT was changed by chemical method, and a new structural segment was introduced to improve the properties of PBT.

Physical method: By blending and compounding the modifier with PBT, the modified PBT material has the advantages of both mechanical properties and rheological properties.

Because of the simplicity and good controllability of physical modification , it is the main method to toughen and modify PBT. At present, the most widely used modifiers for PBT toughening are PET, olefins polymer, PC, styrene series polymer, polyurethane, PA, elastomer, glass fiber and so on.

In order to improve the compatibility of EVA with PBT, a small amount of styrene-maleic anhydride copolymers are added to the blends to improve the strength of the blends. Styrene-maleic anhydride copolymer contains maleic anhydride group, which is a reactive functional group with high activity. It can react with PBT to form block copolymers, reduce the interfacial tension and enhance the interfacial strength.