Gelcoat Troubleshooters Guide

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We trust you will find this gelcoat troubleshooting information useful.
Gelcoat Troubleshooters Guide
Image
Problem
Air Bubble
Cause
Air pockets
Raw catalyst
Alligatoring
(Tripe)
Blisters
(Osmosis)
Chalking
(Gelcoats will chalk over an
extended period of time, degree
of chalking is related directly to
the environment).
Cracks
Reverse Impact
Cracks
Frontal Impact
Image
Problem
Cause
Cracks
Stress
Check rollout procedures.
Solutions & Checks
Stress due to flexing
Excessive gelcoat thickness. Laminate too thin.
Part pulled too green, laminate undercured.
Demoulding or handling procedure. Sticking to the
mould.
Mould mark
Defect in the mould.
Contamination
Check for water, solvent or improperly mixed
catalyst. Overspray. Seedy resin. Excess binder on
the glass mat.
Check for leaks or overspray.
Solvent
Do not reduce product with solvents.
Thin gelcoat
Use > 0.40mm, wet film.
Insufficiently cured gelcoat before laminating
Catalyst too high/low. Temperature too low. Gel
time too long. Insufficient time between coats.
Other
Thin laminate or gelcoat. Very dry laminate. Pin air
entrapped. Postcuring of the laminate.
Insufficient cure
Striping gelcoat sags over cured gelcoat
Check sag resistance of striping gelcoat. Spray
stripe coat as soon as possible. Stripe thin film of
stripe colour over the wet base coat.
Catalyst too high/low. Wait longer before pulling part
from mould. Check for low temperature.
Transfer from mould
Refinish mould.
Glass Cloth
Cloth too close to gelcoat. Should have 900g/m2 of
chopped glass between gelcoat and cloth.
Woven Roving
Roving too close to gelcoat. Should have 1350g/m2
of chopped glass between gelcoat and roving.
Gelcoat too thin
Apply > 0.40mm, wet film.
High exotherm of laminate
Cure laminate more slowly. Laminate in stages.
Use lower exotherm laminating resin.
Water, oil or silicone contamination
Drain air lines. Check mould release wax.
Dust or dirt on mould
Check lubricating used within equipment.
Gelcoat film too thin
Apply 0.50mm in three separate passes.
Low viscosity material
Old material, rotate stocks.
Contamination
Clean pump and lines.
Strain and keep material covered. Keep overspray minimised. Be sure moulds are clean. Spray
perpendicular to mould surface.
Bleeding
Blisters
(Catalyst Drop)
Solutions & Checks
Dimples
Monomer in laminating resin
Check for excess monomer in laminating resin.
Gelcoat backside cure
Change gelcoat.
Unreacted catalyst or undercure
Distortion &
Fibre Print
Check catalyst percentage additions, catalyst
overspray, mixing procedure and leaks.
Solvent, water or oil
Check air lines, material and rollers.
Air pockets
Check rollout procedure.
Water blisters
Various causes and solutions. CCP recommends
referring to the latest edition of CCP’s Composites
Applications Guide.
Cure
Check catalyst , film thickness, water and solvent.
Insufficient buffing
Wipe buffed area with solvent rag. If gloss remains,
area is OK. If gloss dulls, part needs further buffing.
Fisheyes
Pigment Darting
Poor mould condition
Reduce sanding and buffing requirements by
keeping moulds in good condition.
Foreign particles
Check handling and demoulding procedures.
Caution staff about hammering on parts.
Entrapped air
Wrong air pressure. High pressure is fine porosity.
Impact from laminate side
Catalyst
Ensure catalyst grade is recommended for gelcoat.
Gelcoat thickness
Apply 0.50mm in three separate passes.
Contamination
Ensure there is no water or solvent contamination.
Excessive mixing
Mix for 10 minutes before shift, at low turbulence.
During cure - Showing as dull gloss and obvious
surface distortion.
Ensure catalyst levels and grade are appropriate.
Check gelcoat thickness. Gelcoat curing too long.
Do not alter gelcoat without manufacturer approval.
After cure - Showing as a visible sharp line, with
increased fibre print on the prereleased side.
Laminate too high in exotherm. Uneven laminate
thickness. Resin drain-out or puddling.
Polystyrene/wax build up
Perform a regular mould cleaning program. Do not
clean moulds with used rags or reclaimed cleaners.
Excessive gelcoat thickness
Use a gelcoat gauge. Do not apply > 0.60mm
Mould mark
Defect in the mould.
Impact from front side
Be careful.
Porosity
(Magnified 10x)
Prerelease
Yellowing
(Inset shows 1.5mm
thick gelcoat. Gelcoat yellows Inadequate gelcoat cure
rapidly when exposed to sunlight
and/or heat and moisture).
Prerelease
Ensure catalyst levels and grade are appropriate.
Ensure temperature levels are appropriate.
See causes and solutions for prerelease.
CCP Composites Australia advocates CCP Composites Application Guide - or The Cook Book as the benchmark
industry reference. Much information presented here is taken from the latest edition of The Cook Book.
www.ccpcomposites.com.au
April 2012