Non-isothermal crystallization behavior of Styrene butadiene rubber/high density polyethylene binary blends

Abstract

The thermal and crystallization behavior of the blends are studied by differential scanning calorimetry and XRD. The presence of the amorphous component in the blend is found to influence the non-isothermal crystallization of HDPE. The addition of small quantities of SBR resulted in an increase in the rate of crystallization whereas nucleation is delayed. As compared to HDPE, larger crystallite size, a narrower size distribution, were observed in low SBR (~up to 30 wt%) content blends. The half time of crystallization also found to reduce as the SBR content in the blend increased. However, a lower degree of crystallinity was observed in these blends. The results thus show that incorporation of SBR in HDPE, while accelerating the rate of crystallization, lower the degree of crystallization. The reduction in the overall crystallization rate at high-SBR content is attributed to a decrease in the growth rate in the later stages of crystallization. It is observed that in dynamically cross-linked blends, the presence of crosslinked SBR that can acts as heterogeneous nuclei facilitated the nucleation of HDPE. However, the crystal growth may be impeded. As a result the overall crystallinity of the crosslinked blends found to decrease. From XRD profiles it had seen that addition of SBR and dynamic crosslinking does not exert an effect on the crystalline structure of HDPE. The dynamic vulcanization of SBR/HDPE blends enhanced the process of crystallization of HDPE phase. These conclusions are supported by the thermal characterization (DSC) results also.