Thesis-2000-Petiraksakul.pdf (7.57 MB)
Effect of stearate/stearic acid coating on filled high density polyethylene properties
thesis
posted on 2012-12-12, 09:26 authored by Pinsupha PetiraksakulHigh density polyethylene (HDPE) is a widely used plastic but it is also a combustible
material. One way of reducing flammability is to add fillers, such as magnesium
hydroxide (Mg(OH)2). However, this has a deleterious effect on the mechanical
properties of composites. It has been found that one possible method of restoring
mechanical properties is to modifY the filler particles with coating agents, such as
stearic acid. In the present work, this idea was taken a stage further with the use of
various metal stearates (e.g. magnesium stearate, calcium stearate, and zinc stearate)
for modifying filler. The fillers examined were magnesium hydroxide and calcium
carbonate. A filler loading of 40% w/w was used in all samples. Samples were
moulded into a variety of shapes for mechanical testing. Such tests included, tensile,
flexural, and impact testing. To obtain deeper understanding of the effect of the
coating agents on the fillers, a variety of fundamental tests were carried out. These
included Diffuse Reflectance FTIR (DRIFT), Thermal Analysis using a DSC cell, Xray
Diffraction (XRD), contact angle measurement.
Unfilled HDPE, uncoated filled-HDPE, and coated filled-HDPE were compared using
uncoated filled-HDPE as a base line. Uncoated filled-HDPE is more brittle than
unfilled HPDE. Surface modification of filler improves the toughness properties.
Comparing coated filled-compounds, stearic acid and zinc stearate caused a small
improvement, magnesium stearate improved the properties significantly with calcium
carbonate while calcium stearate gave the best results for coating magnesium
hydroxide. One monolayer coating gave the best compound properties compared to
other degrees of coating. Although, tensile/flexural strength was not greatly affected
elongation at yield, extension at maximum load, and impact properties increased
significantly.
DSC was used to observe the disappearance and conversion of coating agents as
coating proceeded. X-ray diffraction showed the effect of injection moulding on the
orientation of the filler and polymer. During coating of the filler particles, XRD and
DSC were used to follow incorporation of stearate particles to produce the monolayer
coverage. Surface free energy results showed that surface modification of filler
resulted in the reduction of hydrophilicity of filler leading to tougher composites
compared with uncoated filled-compounds.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Publisher
© P. PetiraksakulPublication date
2000Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.311020Language
- en