Four types of glassfibre reinforcement are frequently used with Atlac resins.
They are:
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Surfacing veil
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Chopped strand mat
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Woven roving
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Continuous strand roving
Fabrication of a GRP laminate usually begins with the interior layers (the
surface to be in contact with corrosive material). The first laminate layers
are commonly known as the corrosion barrier layer. Its function is to provide
corrosion protection. A surfacing veil saturated with resin forms the base for
successive layers. The corrosion barrier layer generally consists of the
surfacing veil and two layers of chopped strand mat.
Surfacing veils
The purpose of a surfacing veil is to provide
reinforcement for the resin rich inner liner of a corrosion barrier to prevent
cracking and crazing. A second function is to prevent protrusion of the
chopped strand mat fibres to the surface, which could allow wicking of the
corrosive media into the laminate.
The interior surface, which is normally 1 to 2 mm thick, contains about 90% of
resin and 10% of veil material.
The primary type of surfacing veil used in corrosion applications is “C”glass
veil. However, in applications where “C”-glass veil is not suitable, other
veil types made from thermoplastic polyester or carbon fibres may be used.
“C” glass veil is typically recommended for most corrosion environments, but
synthetic veil is preferred in environments such as those containing fluoride
compounds. Synthetic veil is preferred in other environments, (see our
corrosion guide for full details. In severe environments, like alkaline,
multiple plies of veil may be recommended. Carbon veil is often used in
abrasive environments or to provide a conductive liner for static electricity
control. Veils made with other types of glasses, such as “A” and “ECR”, are
used less often in the corrosion industry but may be acceptable in certain
applications.
Chopped strand mat
Chopped strand mat reinforcement consists of
a felted matrix of chopped strand “E” or “ECR” glass fibres, 12.5 – 50 mm long
and loosely held together by a styrene-soluble resin binder. “ECR” mat is made
with more corrosion-resistant “E” type glass fibres. Chopped strand mat is
available in a variety of thicknesses (225 g/m2, 300 g/m2, 450 g/m2 600 g/m2).
Two mats (450 g/m2) are generally used with the surfacing veil to form the
corrosion barrier layer that provides additional corrosion protection. Chopped
strand mats are also used in the structural layer between layers of woven
roving or as the sole reinforcement for the structural wall. The chopped mat
layers in the finished laminate consist of about 70% resin and 30% glass.
Woven roving
Woven roving consists of continuous glass fibre
rovings that are woven together to form a heavy mat, which is available in a
variety of thicknesses and weights. Alternating layers of woven roving and
chopped strand mat are used in the structural portion of hand lay-up
laminates. The resulting laminates are generally about 40-50% glass.
Continuous roving
Continuous strand roving comes in various
densities and sizing finishes for applications in filament winding and
pultrusion. It results in laminates with high glass contents (50 – 70%) for
increased strength. Gun roving is used as a substitute for chopped strand mat
in the corrosion barrier and the structural wall. The resulting laminates are
generally about 30-40% glass.
