INTRODUCTION
TO GLASS FIBRE REINFORCED PLASTICS
The technique of moulding glass fibre reinforced plastic is to achieve a composite
material, comprising layers of minute glass fibres enclosed in a rigid plastic
layer. These glass fibres act as reinforcement within the plastic (polyester
resin), very much as steel bars act in reinforced concrete. The process involves
thoroughly impregnating with liquid resin, layers of glass fibre, into pre-conceived
shapes. A chemical change then takes place due to the inclusion of a hardening
agent (catalyst) in the resin, and the material sets into a rigid laminate.
All glass fibre moulding work is a variation on this simple, theme.
WORKING CONDITIONS
Ideally, the working conditions should be warm and
dry, but it is essential that there is adequate ventilation. Damp and cold
conditions will inhibit the cure of the resin.
MOULDS AND PATTERNS
The items normally associated with glass fibre mouldings
such as boats, car bodies, motor cycle fairings, have all been produced from
a mould. This can be made of many materials, hardboard, timber, aluminimum: or a combination of these. Where a production
run is envisaged, the mould is quite commonly made of glass fibre itself,
this mould having previously been cast over a pattern representing the shape
of the finished moulding.
Having constructed the mould, the surface must be sealed where necessary with
varnish or similar material and then flatted down and polished to the required
standard.
Of course the handyman's first introduction to glass fibre is likely to be
to carry out repair work to an existing moulding, and often a mould will not
be required.
PARTING OR RELEASE AGENTS
It should be mentioned at this stage that the mould will have to be protected
with a Parting Agent to present the moulding adhering to the mould surface.
LAMINATING OR LAYING UP
On most applications the smooth moulded exterior
surface of the laminate consists of an initial layer of specially formulated
resin containing no glass fibre reinforcement, this lover is called the gel-coat.
The built-in colour associated with glass fibre mouldings is incorporated
in this layer. The object is to back up the, gel-coat with layers of glass
fibre reinforcement which are thoroughly impregnated with catalysed laminating
resin, all the entrapped air bubbles haying been squeezed out, by use of a
laminating roller.
All tools must be washed in cleaning solvent as soon as gel-coating or laminating
is finished, before the resin sets on the tools, making them useless.
RELEASING
The cure induced by the addition of catalyst to the
resin is a gradual process taking several hours. Do not be over anxious to
release the moulding-it is preferable to leave overnight to ensure a full
cure.
FINISHING
Glass reinforced plastic can be readily cut and sanded by a variety of mechanical
and hand tools.
PAINTING
The glass fibre moulding can be painted if the surface
is thoroughly prepared to remove any parting agent, and to give a key for
the paint. Must paint suppliers normally give recommendations for painting
glass fibre, which are similar to painting metal and other non-porous surfaces.
PRECAUTIONS
WHEN USING AND STORING POLYESTER BASED MATERIALS
Resin materials have been specially prepared to enable inexperienced personnel
to fabricate a sound laminate or repair a damaged glass fibre moulding with
ease.
The materials used in the glass reinforced plastics industry do however present
their own problems which must be borne in mind when using them.
SAFETY
PLEASE READ THIS SECTION
CAREFULLY
Resins, cleaning solvent, parting agents, pigments and especially catalysts,
are all inflammable and care must be taken to ensure that they are stored
in their own containers in a cool place out of the sunlight and away from
any naked flame. Glass fibre reinforcements should be kept thoroughly dry
as any trace of dampness in these materials will impair the quality of the
finished job.
Resins are chemicals which by their very nature are undergoing a slow, constant
and irreversible change from a liquid to a solid. Ryplas
resins therefore have a limited shelf life even in their original sealed containers
of between three to nine months dependant upon temperature. When handling
resins avoid contact with the skin and particularly the eyes. Resin may be
removed from the skin with Ryplas cleaning solvent
used sparingly. Liquid catalyst must be handled with extreme care as it is
an organic peroxide and may cause severe skin irritation.
• Eye contact:
Rinse with water and continue this treatment for at least 15 minutes. If possible,
alternate rinsing with a 5% aqueous sodium ascorbate solution* or a 2% aqueous
sodium. bicarbonate solution*. Do not apply an oil
or fat containing ointment. Afterwards a doctor, preferably an eye specialist,
must be consulted without delay.
• Skin contact:
Rinse with water and wash thoroughly with soap: next apply an ointment such
as lanoline.
• Ingestion:
Drink large quantities of water or take the 5°/, aqueous sodium ascorbate
solution and try to vomit instantly. Consult a doctor without delay to give
an additional stomach wash.
When handling any of the above materials it is wise to use barrier cream and
rubber gloves wherever possible.
Glass reinforcement can cause irritation of the skin. Although it is unlikely
to have any lasting effect it can be temporarily unpleasant and it is therefore
advisable to handle with care and try to avoid the glass fibre from penetrating
clothing. If continuous use of the material is anticipated it will be as well
to keep a set of loose fitting clothing apart for this purpose. Always work
in a well ventilated area. When trimming and particularly when sanding finished
mouldings it is advisable to wear a respiratory mask to reduce inhalation
of trimming dust.
* Both solutions deteriorate on storage: they must
be freshly made every month.