POLYACETAL AND THERMOPLASTIC POLYURETHANE ELASTOMER TOUGHENED POLYACETAL - CRYSTALLINITY AND FRACTURE-MECHANICS

The effect of thermoplastic polyurethane (TPU) elastomer on the meltin g point and the percentage crystallinity of polyacetal (POM) is studie d by differential scanning calorimetry (DSC). Wide angle X-ray diffrac tion (WAXD) scans of POM, TPU and their blends have been taken and the results indicate that the crystalline structure of POM remains unaffe cted even after the addition of amorphous TPU. The influence of defect s like holes and notches on the ultimate tensile strength has been exa mined. The resistance to crack initiation (J(c)), the resistance to st eady state crack propagation (R(p)) and the resistance to crack growth at maximum load (R(max)) are estimated. The POM/TPU blends display hi gher crack resistance values than pure POM. The hysteresis energy of b lends is determined and is found to increase with TPU content.