RUBBER TOUGHENED POLYBUTYLENE TEREPHTHALATE - INFLUENCE OF PROCESSING ON MORPHOLOGY AND IMPACT PROPERTIES

The toughening of polybutylene terephthalate (PBT) was achieved by adding to it a functionalized ethylene-propylene (EPR) random copolymer. Maleic anhydride molecules, inserted onto the rubber backbone, provided the functionalized sites with which the terminal PBT hydroxide groups could react. A graft copolymer made from an EPR backbone and by PBT branches acted as an interfacial agent between the matrix and the rubbery dispersed phase. The intensity of mixing, represented by the roller speed of the mixing equiment, was varied from 4 to 64 rpm. The morphological features as well as the mechanical impact performance improved with increasing the roller speed up to a value of 48 rpm. Beyond such a value the situation was reversed due to the mechanical degradation of the molten PBT. This induced a diminished internal interconnection of the matrix and hence a worse impact resistance. Dynamic mechanical analysis proved to be a very sensitive tool to detect the presence of interzones existing between the PBT matrix and the EPR rubbery particles. The extension of such zones represents the adhesion between the two components and was also detected by Charpy impact tests. © 1990.