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... cont'd.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.