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On the automotive side, Henkel AG & Co. KGaA (Düsseldorf, Germany) emphasized on its JEC stand a glass fiber-reinforced composite leaf spring, based on Henkel’s polyurethane matrix resin Loctite MAX 2, used in the chassis of the new Volvo (Gothenberg, Sweden) XC90, a premium crossover SUV; the platform of this vehicle is expected to be applied to other Volvo cars in the coming years. Frank Kerstan, global program manager, automotive composites, says BENTELER-SGL (Ried im Innkreis Austria) is making the leaf springs via resin transfer molding (RTM) in 30-second cycle times. Able to produce eight to 10 leaf springs in each mold, BENTELER-SGL plans to manufacture up to 500,000 leaf springs per year by 2018. On the developmental side, Kerstan says Henkel is working on several intriguing technologies, including a urethane-based adhesive for multi-material automotive bonding applications that have a CTE mismatch. Also in the works is an RTM-based molding system using urethane resin that allows for the fast production of Class A surface body panels. This is done, says Kerstan, by use of a double-injection process in which the second injection creates the high-quality part surface that Class A requires.

Meanwhile, at its JEC World stand, Huntsman Advanced Materials (The Woodlands, TX, US) announced that it has developed a new epoxy resin system and a novel, cost-efficient compression molding process, to facilitate the simple production of structural composite parts, and enable cycle times as low as 1 minute without any further post-curing for high-volume applications such as automo- tive. Currently, a trademarked ARALDITE is used to manufacture BMW’s (Munich, Germany) i-Series cars. With a cure time of 2 minutes at 130°C, this system gives a total cycle time of around 2,5 minutes. However, the latest rapid-cure ARALDITE epoxy system reportedly provides a cure time of only 30 seconds and displays a higher T_g, thus enabling robust processing up to 150°C and a press cycle time of only 1 minute, without further post-curing of the part. Following cure, the epoxy system displays a tensile elongation in excess of 5% with a Tg of 120°C.

To complement this new epoxy system, an innovative and simple Dynamic Fluid Compression Molding (DFCM) process also has been developed by Huntsman, which eliminates high-pressure injection and, in many cases, even the need for a preform. Resin impregnation occurs through the thickness, greatly reducing the potential for fiber displacement, a common problem with resin transfer molding (RTM). Company tests show reduced void content of laminates in comparison to conventional wet-compression molding (WCM) processing, and porosity of less than 1%, making it comparable to high-pressure RTM (HP-RTM) or autoclave, even in deep-draw parts. Fiber volume content of 66% can be easily achieved with no special processing conditions. The new DFCM process means lower mold pressures and a lighter press, plus no need for a high-pressure injection machine. Plus, DFCM eliminates resin waste because no surplus of resin or fiber is required to remove air from the part. The new process enables fast processing of thermoset parts, without the expense of prepreg and higher-priced thermoplastics.