Processing Thermosets

Pultrusion 

Overview
The Pultrusion process starts by pulling/drawing continuous reinforcements (in rovings or mat / roving forms) through a resin impregnation system. Each fibre is coated with a specially formulated resin; the process is controlled to ensure full “wetting out” of the fibre reinforcement. Excess resin is then removed to expel any trapped air and to compact the fibres.

The coated fibres are passed through preforming guides to align reinforcement and preform the part to the desired shape before entering the heated die. The shape and dimensions of the end product are ultimately determined by the die cross section. The temperature of the die is carefully controlled to ensure that the composite is fully cured, the rate of reaction is controlled by heating and cooling zones in the die.

Resin Transfer Moulding

Overview
RTM is a low pressure moulding process, where a mixed resin and catalyst are injected into a closed mould containing a fibre pack or preform. When the resin has cured the mould can be opened and the finished component removed.
A wide range of resin systems can be used including polyester, vinylester, epoxy, phenolic and methyl methacylates etc, combined with pigments and fillers including aluminium trihydrates and calcium carbonates if required.

The fibre pack can be either, glass, carbon, arimid, or a combination of these. There are a large variety of weights and styles commonly available.

SMC / DMC Moulding

Overview
How The Materials Are Made DMC & BMC
Manufactures of DMC/BMC compounds is a batch process. The ingredients, chopped glass fibres, resin, mineral fillers, catalysts and a mould release DMC Conduit Box agent are loaded into a special mixer. Output from the mixer is in a flock form which is subsequently extruded in a rope type extrusion.

SMC
Manufacture of SMC is a continuous in-line process. The material is sheathed both top and bottom with a plastic film. A Paste is prepared comprising resin, styrene, heat activating catalysts, inert fillers, release agents and thickeners. The paste is spread uniformly onto an SMC Junction Box the bottom film. Chopped glass fibres are randomly deposited onto the paste. The top film is introduced and the sandwich is rolled into a pre-determined thickness. The sheet is allowed to mature for 48 hours.