Structure – property
relationships in polyoxymethylene / thermoplastic polyurethane elastomer blends
Krzysztof Pielichowski* and Agnieszka Leszczyńska
Department of Chemistry
and Technology of Polymers
Cracow University of
Technology
ul. Warszawska 24
31-155 Krakow, Poland
A series of blends of polyoxymethylene (POM) / thermoplastic ester-based polyurethane elastomer (TPU) has been obtained by using a double screw extruder (L/D = 25) in the temperature range of 175-190ºC. Differential scanning calorimetry (DSC) was applied to investigate the influence of TPU on the melting and crystallisation of POM; it was found that there is a decrease of the enthalpy of melting with an increase of TPU amount in the blend (up to 10 wt %); enthalpy of fusion also decreases. X-ray diffraction patterns confirm that the crystalline structure of POM remains unaffected after blending with multiphased TPU. Morphology of the blends, investigated by scanning electron microscopy (SEM), showed that TPU is distributed rather uniformly in POM and forms cylindrical-shaped domains of ca. 10 μm length. Homogeneous distribution may be the consequence of existence of specific interactions in form of hydrogen bonding between ether oxygen (POM) and hydrogen from urethane group (TPU) as evidenced by FTIR measurements. Modified morphology contributes to the better mechanical properties; elongation at break increases with an increase of the TPU content in the blend (for TPU content > 10%).
Keywords: POM, TPU, blends, thermal properties, mechanical properties, morphology