THE FUSION BEHAVIOUR OF UNPLASTICISED POLYVINYL CHLORIDE: EFFECTS OF PROCESSING AND FORMULATION
THE FUSION BEHAVIOUR OF UNPLASTICISED POLYVINYL CHLORIDE: EFFECTS OF PROCESSING AND FORMULATION
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Date
1984-08
Authors
OGABA, PHILIP OBANDE
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Abstract
The fusion behaviour of commercial grade PVC has been studied
by capillary rheometry and thermal analysis for twin-screw extruded rigid
formulations. The role of shear in fusion was also investigated by extrusion
at different rates and by compression moulding.
Aspects discussed include thermodynamic fusion (melting) and
gelation (network formation). The former is measured by thermal analysis
and the latter by rheometry. Fusion is dictated primarily by the level of
heat generated during processing while gelation depends both on the
equipment shear regime and on formulation.
In the molecular weight range studied, M W = 6.0 - 10.0 x
104 g/mol, fusion level is inversely related to M W at a specific processing
temperature, but the maximum fusion level attainable within temperature
limits is largely independent of molecular weight.
At a given processing temperature below 200°C impact strength
(IS) of notched Izod samples is linearly related to the extrusion (shear) rate;
above 200°C, however, little change is observed. The IS of samples
processed at different temperatures, keeping extrusion rate constant, goes
through a maximum, but this depends on the temperature range,the shear
level, and the formulation.
From the results of solvent sorption, density, and wide angle x-ray
diffraction, an overall decrease is observed in the level of order left in the
processed material with increasing processing temperature.
From a mathematical model proposed for the fusion behaviour
percentage fusion is shown to be equivalent to the degree of crystallinity.
The maximum % fusion observed, about 8%, corresponds to the crystalline
level of the unprocessed powder. Based on this model activation energies
of 1.0 kJ/mol and 2.2 kJ/mol are obtained for the fusion of the relevant
morphological units.
Description
A Doctoral Thesis submitted in
partial fulfillment of the requirements
for the award of Doctor of Philosophy
of Loughborough University
of Technology
September, 1984
Supervisors : M. Gilbert, Ph.D., FPRI, MRSC, C Chem.
Institute of Polymer Technology
D.E. Marshall, Ph.D., MIP.
Institute of Polymer Technology
Keywords
FUSION,, UNPLASTICISED,, POLYVINYL,, CHLORIDE:,, FORMULATION