Polyacetal and thermoplastic polyurethane elastomer toughened polyacetal: crystallinity and fracture mechanics

The effect of thermoplastic polyurethane (TPU) elastomer on the melting point and the percentage crystallinity of polyacetal (POM) is studied by differential scanning calorimetry (DSC). Wide angle X-ray diffraction (WAXD) scans of POM, TPU and their blends have been taken and the results indicate that the crystalline structure of POM remains unaffected even after the addition of amorphous TPU. The influence of defects like holes and notches on the ultimate tensile strength has been examined. The resistance to crack initiation (Jc), the resistance to steady state crack propagation (Rp) and the resistance to crack growth at maximum load (Rmax) are estimated. The POM/TPU blends display higher crack resistance values than pure POM. The hysteresis energy of blends is determined and is found to increase with TPU content. © 1995 Chapman & Hall.