Effects of mixing on morphology, rheology, and mechanical properties of blends of ultra‐high molecular weight polyethylene with linear low‐density polyethylene

Abstract

Various blends of ultra‐high molecular weight polyethylene (UHMWPE) with linear low‐density polyethylene (LLDPE) were prepared in an internal (Banbury type) mixer, a static mixer, and by solvent blending. Two mixing techniques, namely simultaneous and sequential loading methods, were employed with the internal mixer. In the former case, the two polymer components were simultaneously loaded at 180°C and mixed. The latter method allowed the UHMWPE component to diffuse at 250°C and cooled it down to 180°C, then the LLDPE component was added subsequently and mixed. Rheological and mechanical properties of these blends are profoundly affected by the mixing techniques used. Rheological results shows yield characteristics of UHMWPE/LLDPE blends, in particular in blends of high UHMWPE contents. Tensile properties of sequentially loaded blends vary more or less linearly with blend compositions. However, negative or positive deviations are seen in the simultaneously prepared blends. Differential scanning calorimetry (DSC) studies indicate that co‐crystallization takes place between UHMWPE and LLDPE components in sequentially mixed blends. DSC and small‐angle light scattering (SALS) studies show that separate crystallization takes place in simultaneously blended compounds as a result of poor mixing. It seems that the sequential loading method provides more homogeneous compounds than those of simultaneous blending.