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Gel Coat

Gel coat is a cosmetic and/or functional surface applied to a composite component. It is normally brushed or sprayed onto the mould tool before the laminate is made. There is currently considerable interest in in-mould gel-coating (IMGC) to reduce the level of volatile organic compounds (VOC) in the working environment.  ACMC is currently developing a novel (patented) IMGC process with funding from the UK Technology Strategy Board under the Technology Programme for Collaborative R&D call: Meeting the Challenge of the Zero Emission Enterprise (ZEE).  Interplastic Corporation have published a Trouble Shooting Guide for Gel Coat.

See the section on surface finish on the mould tools page.

Spray techniques are described in reference 1.

Hand-lamination is described in reference 1.

Centrifugal casting

Centrifugal casting is a special case of spray manufacture where the spray is directed into the base of a rotating cylindrical mould to manufacture large diameter pipes.  The process can also be used with fabric reinforcement such that the centrifugal force causes resin to permeate the reinforcement fabric or with chopped fibres added to the spray: this creates a smooth finish on the outside of the pipe while excess resin can be added to create a resin-rich corrosion- and abrasion-resistant interior surface.

Reference:

1. D Cripps, T J Searle and J Summerscales,
   Open Mould Techniques for Thermoset Composites,
   In R Talreja and J-A Månson (editors):
   Comprehensive Composite Materials Encyclopædia, volume 2: Polymer Matrix Composites,
   Elsevier Science, Oxford, July 2000, Chapter 21, pp 737-761. ISBN 0-08-043725-7.  UOP Library  Restricted: Download 1.24MB .pdf file
   This text also covers vacuum bagging and infusion techniques.