Viscoelastic properties correlations to morphological and mechanical response of HDPE/UHMWPE blends

Melt-mixed and injection molded binary blends of high density polyethylene (HDPE)/ultra high molecular weight polyethylene (UHMWPE) were evaluated for their structural, thermal, rheological, morphological and mechanical attributes. X-ray diffraction (XRD) study has revealed the absence of any significant changes in the crystalline alignment/morphology of the two polyethylene components. Differential scanning calorimetry (DSC) studies revealed the increase in melting temperature, whereas the properties such as crystallization temperature and percentage crystallinity remained broadly unaffected. Dynamic rheological behavior revealed a transition from liquid like behavior (G'aEuro parts per thousand < GaEuro(3)) to solid like behavior (G'aEuro parts per thousand > GaEuro(3)) in the composition range of 20-30 wt% of UHMWPE. Scanning electron microscopy (SEM) of the cryo-fractured surface depicts two phase morphology along with very strong interface. The blending of UHMWPE with HDPE matrix has caused improvement in tensile, impact and flexural properties, whereas strain at break suffered a decrease. The analysis of tensile fractured surface morphology by SEM has proved to be useful in qualitatively understanding the underlying failure mechanisms. Eventually, a viscous-to-elastic transition in the rheological behavior has been observed and found to have a correspondence with structural, mechanical and morphological response in the similar composition window.