Huntsman announces 60-second cycle times with compression process

Huntsman's new high-Tg epoxy, used in its dynamic fluid compression molding process, allows a 30-second cure and a 60-second cycle time.

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Huntsman Advanced Materials (Basel, Switzerland) reports that it has developed a new epoxy resin system and a novel and cost-efficient compression molding concept.

By combining a new fast-cure ARALDITE epoxy chemistry with a new compression molding process, Huntsman says it is enabling cycle times as low as 1 minute without any post-cure. For high-volume applications such as automotive, this process makes cost-efficient manufacture of high-performance structural parts using thermoset technology a reality.

Huntsman says that the current, commercial epoxy solution for high-volume manufacture of composite parts is the ARALDITE system that’s used to manufacture the BMW i-Series of cars. With a cure time of 2 minutes at 130°C, this system gives a total cycle time of around 2 minutes 30 seconds. However, the latest rapid-cure ARALDITE epoxy system is not only quicker, but it also displays a higher Tg, thus enabling robust processing up to 150°C.

Bringing these factors together provides a cure time of just 30 seconds at 140°C, meaning that a press cycle time of only 1 minute is possible. Following curing, the epoxy system displays a tensile elongation in excess of 5% with a Tg of 120°C.

To complement this new, rapid-cure epoxy system, the dynamic fluid compression molding (DFCM) process has been developed by Huntsman. The simplicity of the new process removes the need for high-pressure injection and in many cases, even the need for a bonded fiber preform, thus eliminating a complex and costly step in production. Furthermore, resin impregnation of the fibers through-thickness is said to virtually eliminate fiber wash, a common problem with high-volume resin transfer molding (RTM) production parts.

In tests carried out by Huntsman, it was established that one of the main advantages of the new process is that it reduces void content of laminates in comparison to conventional wet-compression molding (WCM) process. It allows typical porosity content of less than 1%, making it comparable to high-Pressure RTM (HP-RTM) or autoclave cure.

Significantly, says Huntsman, fiber wet-out is so effective that fiber volume contents of 66% can be achieved with no special processing conditions. Heavy-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.