NCC Associate Member, Huntsman, develops new compression molding process

Huntsman Advanced Materials has developed a new epoxy resin system and a new efficient process which could give an entirely new compression moulding concept.

According to the company, the new compression moulding process, which uses a fast-cure Araldite epoxy, makes it possible to make structural composite parts with cycle times as low as one minute without any further post-curing. It is also suitable for making structural parts using thermoset technology for high-volume applications such as automotive. 

The company’s current system for high-volume manufacture of composite parts is the Araldite system used to make the BMW i-Series of cars. With a cure time of two minutes at 130°C, this system gives a total cycle time of around two minutes, 30 seconds. The latest rapid-cure Araldite epoxy system is quicker and also displays a higher Tg, enabling processing up to 150°C, and a cure time of just 30 seconds at 140°C. This means that at a press cycle time of only one minute is possible, without any further post-curing of the part.  Following curing, the epoxy system displays a tensile elongation in excess of 5% with a Tg of 120°C.

Resin impregnation

Huntsman has also developed a dynamic fluid compression moulding (DFCM) process to go with the new epoxy system. According to the company, the new process removes the need for high-pressure injection and in some cases, the need for a bonded fibre preform. The resin impregnation of the fibres through-thickness almost eradicates fibre-wash, a common problem with high-volume resin transfer moulding (RTM) production parts, Huntsman says.

In tests carried out by the company, the new process reduced the void content of laminates in comparison to conventional wet-compression moulding (WCM) process. It also allowed typical porosity content of less than 1%, making it comparable to high pressure RTM (HP RTM) or autoclave prepregs. Fibre volume contents of 66% can be achieved with no special processing conditions, while feavy-tow industrial fabrics proved similarly easy to impregnate, with virtually void-free parts, even when parts were made with a 960 gsm plain weave fabric.