Gas-assisted compression moulding of glass reinforced polypropylene
Brzeski, Ian (2009) Gas-assisted compression moulding of glass reinforced polypropylene. PhD thesis, University of Warwick.
WRAP_THESIS_Brzeski_2009.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Official URL: http://webcat.warwick.ac.uk/record=b2338296~S15
A new process of combining gas injection with compression moulding was developed
and studied in this research work. The process is called Gas Assisted Compression
Moulding (or GasComp). The principle is based on the injection of nitrogen gas
during a conventional compression moulding cycle. The flow of the material due to
the compressive force of the press is assisted by the injection of gas into the centre
of the molten material. The gas assists in the flow by coring out the material,
reducing the weight by up to 45 percent and increasing the dimensional stability of
Novel glass matt thermoplastic mould tools were designed and developed during the
course of the research program for use with the process. These designs were of a
flash compression mould tool design with a horizontal clamping face, rather than the
conventional positive plug compression mould tool with a vertical shear edge. This
created a fixed volume mould tool, which when used in conjunction with a short shot
of material, would allow the gas to flow the material to fill the remaining volume.
Several materials were investigated for their suitability with the process. Their
characterisation showed that they contained different glass fibre contents and
architectures. A material with a short, dispersed glass fibre content of 11 percent
proved to consistently contain a significant gas cavity. The glass architecture proved
to be the most significant contributing factor in the creation of a successful gas cavity.
The most significant processing parameter in the creation of a large volume cavity
proved to be the gas injection delay time. The gas pressure and gas ramp time
affected the cavity shape, length and extent of gas fingering.
The shrinkage was reduced in the presence of a gas cavity, along with the visible
reduction of sink marks. The presence of other moulding features, such as hesitation
marks, gas packing and the change in fibre orientation were also discussed.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||T Technology > TP Chemical technology|
|Library of Congress Subject Headings (LCSH):||Molding (Chemical technology), Injection molding of plastics, Glass-reinforced plastics, Nitrogen, Polypropylene|
|Official Date:||July 2009|
|Institution:||University of Warwick|
|Theses Department:||School of Engineering|
|Extent:||xxi, 196 leaves : ill., charts.|
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