Thermoforming
Thermoforming process is becoming
very popular in India with newer
applications and modern processing
techniques.
Introduction
Among the various plastic processing
techniques, thermoforming is one
of the not so widely known technique
as compared to injection moulding,
blow moulding, extrusion and compression
moulding.
It is, however, one of the fastest
growing techniques in India.
Thermoforming is a term used for
producing plastic articles from a flat
sheet. Heat softened thermoplastic
sheet is draped on the mould and
shaped by applying vacuum between
the sheet and the mould
(mostly used for thick sheets) or by
air pressure above the sheet (mostly
used for thin sheets). More complex
systems have pneumatic prestretching
of the sheet, mechanical
plug assist, automatic sheet placement
etc.
Materials
Only thermoplastics can be used for
thermoforming because only these
materials are softened by heat and return
to their original rigidity when
cooled. Commonly available thermoplastics
include:
* Polystyrene (PS and HIPS)
* Polyvinyl chloride (PVC)
* Polypropylene (PP)
* Polymethacrylates (PMMA)
* Acrylonitrile-butadiene-styrene
(ABS)
* Polyethylene (LDPE and HDPE)
* Polycarbonates (PC)
* Polyethylene terephthalate (PET)
Applications
The thermoforming industry can be
broadly divided in two types, which
the thick sheet thermoforming (generally
more than 1.5 mm thick) employing
mostly vacuum and thin
sheet thermoforming (generally less
than 1.5 mm thick) using rolls employing
compressed air as well as
vacuum.
Thick sheet forming in India has
the following major applications:
Automotive Industry
* Door inner liners
* Engine and chassis encapsulation
* Instrument Panel Skins
....contd.
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