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Water assist Injection Technology (WIT) has been
discussed, analysed and evaluated by research scientists and engineers
at various conferences for the last 4-5 years. However, this technology
has not yet been used commercially.
Water, due to its superior incompressability is considered better
to create cores in moulded parts. Water, compared to gas offers
some advantages such as faster cooling due to higher thermal conductivity
against Nitrogen gas. Water, however, due to efficient cooling can
create problems for semi crystalline polymers like PP. With water,
semi crystalline polymers form a skin layer. This skin formation
would create higher shrinkage or voids in thicker sections. WIT
therefore has been found more suitable for amorphous polymers such
as Nylons.
Gas assisted injection moulding has seen wide usage, but water
assisted injection moulding is slowly catching the 'niche' market.
Infact, the first commercial application of automobile ducts for
engine cooling system from Nylons are likely to commercialize in
2002.
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