Enhancement of the dielectrical strength of low density polyethylene(LDPE) by means of blending of some new elastic polymers was studied. The di- and tri-block styrene-isoprene copolymers were found to be most effective for improving the impulse breakdown strength of LDPE. The most optimum blending ratio for individual copolymers, for example, di-block copolymer with styrene content of 20 wt% gave the most significant improvement of Imp. BDS of LDPE with 35 to 40 wt% blending ratio. In this copolymer, styrene block offers a hard segment, and the isoprene unit behaves as a soft segment. This structure can be considered to give direct influence on the final morphology of the elastomer/LDPE blends. TEM observation on several blended polymers which gave excellent Imp. BDS revealed that the dispersion and morphological nature of these samples were closely related to the processing temperature. Certain relation of improvement in Imp. BDS of blended LDPE and its morphological nature are discussed.
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