Processing

Spray up

Spray up is a partly mechanized version of the hand lay up process. The resin is applied by means of a spray gun to the mould surface simultaneously with the chopped glass fiber roving.

In the spray gun, the resin is premixed with the organic peroxide. At the same time the glass fibers are pulled from a roving spool and by means of air pressure fed into rolling knives (cutters). They are cut into lengths, varying from 20 to 60 mm. The glass fibers are blown into the resin spray and are together with the resin deposited on the mould surface.

Similar to the hand lay up process, it is also necessary to impregnate the glass fibers with the resin. The glass fibers must be wetted out completely by the resin and air bubbles must be removed with special serrated rollers.

In the conventional spray up process, a certain amount of styrene is evaporating. New spray equipment nowadays works with sophisticated ways to spray the resin without forming a mist of small particles. Specially shaped nozzles or fluid impingement techniques are used to reduce the evaporating surface area of the resin droplets. A considerable reduction in the styrene emission is the result.

This modern equipment in combination with the use of resins with a lower styrene content and skin forming additives have reduced the exposure of workers to styrene considerably. The spray up technique is particularly suitable for the production of parts with complicated shapes.

The glass fiber for spray up is used in the form of continuous roving. This is the cheapest available form of glass fibre. The production capacity of the spray up process is higher than the hand lay up process.

With spray up, the quality of the final products depends also, similar to the hand lay up technique, on the skills of the operator. A constant laminate thickness is more difficult to achieve, compared to hand lay up.