COMPATIBILIZATION OF HIGH-DENSITY POLYETHYLENE POLYISOPRENE BLENDS WITH POLYETHYLENE/POLYISOPRENE THREAD-THROUGH COPOLYMERS/

The compatibilization of high density polyethylene (HDPE)/polyisoprene (PI) blends with polyethylene/polyisoprene (PE/PI) ''thread-through'' copolymers was investigated. The proliferating structure of PE/PI wit h segments chemically identical to HDPE and PI, respectively, is diffe rent from that of graft copolymers. Studies showed that the dispersed domain size in the blends was significantly reduced and interfacial ad hesion was improved by the compatibilization action of the copolymer. In the differential scanning calorimetry (DSC) analysis, the crystalli zation peak of HDPE in the blends became broad with adding the copolym er and fractionated crystallization appeared in the HDPE/PI blend comp atibilized with the copolymer at a weight ratio of 30/70 while it appe ared in the blend without copolymer at a weight ratio of 20/80. DMA re sults showed that by adding the copolymer, both the glass transition t emperature (T-g) of the PI component and the alpha-relaxation of HDPE shifted to lower temperature, demonstrating the enhanced penetration o f the two components. Mechanical properties of the blends were improve d, especially the elongation at break, by the presence of the copolyme rs. The characteristic yielding at the fractured surface of the blends compatibilized with the copolymer indicates the fractural behavior of the material changed from brittle to tough.