Blend of high-density polyethylene and a linear low-density polyethylene with compositional-invariant mechanical properties

This article presents the tensile properties and morphological characteristics of binary blends of the high-density polyethylene (HDPE) and a linear low-density polyethylene (LLDPE). Two constituents were melt blended in a single-screw extruder. Injection-molded specimens were evaluated for their mechanical properties by employing a Universal tensile tester and the morphological characteristics evaluated by using a differential scanning calorimeter and X-ray diffractometer. It is interesting to observe that the mechanical properties remained invariant in the 10-90% LLDPE content. More specifically, the yield and breaking stresses of these blends are around 80% of the corresponding values of HDPE. The yield elongation and elongation-at-break are around 65% to corresponding values of HDPE and the modulus is 50% away. Furthermore, the melting endotherms and the crystallization exotherms of these blends are singlet in nature. They cluster around the corresponding thermal traces of HDPE. This singlet characteristic in thermal traces entails cocrystallization between these two constituting components. The clustering of thermal traces of blends near HDPE meant HDPE-type of crystallites were formed. Being nearly similar crystallites of blends to that of HDPE indicates nearness in mechanical properties are observed. The X-ray diffraction data also corroborate these observations. (C) 2002 John Wiley Sons, Inc.