Blends of high-density polyethylene with solid silicone additive

Silicone masterbatch (SMB) is a pelletized formulation containing 50% of an ultrahigh molecular-weight polydimethylsiloxane dispersed in polyethylene. This SMB is designed to be used as an additive in polyethylene-compatible systems to impart benefits such as processing improvement and modification of surface characteristics. In this work, binary blends of high-density polyethylene (HDPE) and SMB were prepared by melt-mixing technique to study the influence of this masterbatch on the processing and mechanical properties of HDPE. Ternary blends were also prepared by the addition of silane-grafted polyethylene (HDPE-VTES) as compatibilizer. The blends were analyzed by melting flow rate (MFR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and tensile tests. Data of final torque and MFR showed that SMB improved the processability of pure HDPE. DSC results showed differences in crystalline behavior between binary and ternary blends. In the former, the degree of crystallinity increased up to 10 wt % of SMB content; beyond this concentration, it decreased. In ternary blends, a reverse behavior was observed. The morphologic study showed silicone particles uniformly distributed in HDPE matrix. With high SMB concentration, the addition of HDPE-VTES significantly reduced the size of silicone particles. In the range of SMB composition studied, the mechanical properties of blends lower slightly compared to pure HDPE. (C) 2002 John Wiley Sons, Inc.