Test MethodCharacteristics of the brittle/tough transition of poly(butylene terephthalate)/maleinized poly(ethylene-octene) blends determined by the essential work of fracture procedure

Blends of poly(butylene terephthalate) (PBT) with varying contents of a maleic anhydride modified poly(ethylene-octene) were obtained by melt processing. The comparison of the standard Izod impact test with the essential work of fracture (EWF) procedure against either the blend composition or the inter-particle distance (τ) revealed that the EWF steadily increased with the rubber content, and the blend composition causing the brittle/tough transition obtained by the standard Izod technique was similar to that obtained using the non-essential work of fracture (β wp).The slight increase in toughness in the brittle zone of the impact strength curve when compared with either the rubber content or τ does not appear in the curve for the β wp. In the tough zone of the EWF curve, unlike that of the impact test, toughness increases of up to 30% and some change of morphology of the fracture surfaces were seen.