Diatomaceous earth filled HDPE
The objective of this research programme was to study the influence of filler incorporation on the rheological, mechanical and morphological properties of high density polyethylene. Several compositions of general moulding grade of HDPE filled with increasing concentrations of diatomaceous earth, an amorphous silica-based particulate mineral of high porosity and friable nature, were compounded in a single-screw extruder. Good filler dispersion into the polymer matrix was achieved with complete polymer permeation through the porous structure of the diatomite particles, and with no apparent filler aggregates or voids being observed on fracture surfaces from SEM photomicrographs of the composites. The specific volume of the filled polymer was a simple linear additive function of the specific volumes of the individual components. DSC measurements carried out on the polyethylene in the composite, indicated very minor influence of the filler incorporation on the crystallinity content of polyethylene and, therefore, the diatomite filler was considered as non-active filler for the polyethylene matrix used.