Toughness mechanism in semi-crystalline polymer blends: II. High-density polyethylene toughened with calcium carbonate filler particles

Here we extend the investigation described in the preceding companion commu nication. To rectify its notch brittleness, high-density polyethylene (HDPE ) was modified by rigid particulate fillers consisting of three different s izes of CaCO3 particles of 3.50, 0.70 and 0.44 mu m weight average diameter in various volume fractions. Mechanical properties including notched Izod impact energy of the extrusion-blended/ injection-moulded samples were exam ined as a function of filler particle size and filler volume fraction. In e xactly the same manner as exhibited by the rubber particle-modified composi tions described in the previous communication, the toughness of the CaCO3-f illed materials increased dramatically when the mean interparticle ligament thickness of the matrix polyethylene dropped to values below 0.6 mu m. The stiff fillers used in this study provided the unusual additional benefit o f substantially increasing the Young's modulus of the compounds while also dramatically improving their impact energy. (C) 1999 Elsevier Science Ltd. All rights reserved.