CSP ultimately created nearly 50 different ply shapes, which are cut and laid up by hand in seven layers in the compression mold. The continuous fiber prepreg material features Reichhold’s new line of ADVALITE™ resins, a monomer-free vinyl hybrid resin. This was critical to CSP’s production. “It takes a considerable amount of time to lay up one of these enclosures by hand, and it may be several days by the time we mold it,” says Johnston. “With a traditional styrene-based vinyl ester resin, all the styrene would be lost before we were done and it would not be moldable. This formulation gives us the working time we need.”
Probir Guha, vice president of research and development at CSP, says combining the SMC material with the prepreg allowed the company to mold a complex geometry that couldn’t be achieved with prepreg alone. “I think this will be an important trend going forward – learning how to combine the strength and performance characteristics you get with continuous fiber format materials with the processability of chopped fiber format materials,” says Guha. “Compression molding provides the ideal process for volume production of that type of technology.”
Industry professionals cite other trends in the high-performance market:
Monomer-free resin formulations – Customers are seeking chemistries without styrene, says Jim Bono, senior technical manager for Reichhold. That’s why the supplier, like many of its competitors, has created a line of monomer-free resins. “You can take the styrene out and replace it with something else, but we took a step back. We wanted to get rid of the monomer altogether,” says Bono. “We came up with a thermoset that still meets stringent requirements for high-performance composites, but does not contain any small monomer or VOC-associated material.” One highly sought after benefit of monomer-free resins is they give off no or low smell, which make them ideal for indoor applications, says Landis.
Improved E-glass – “New sizing formulations can load higher amounts of fiberglass and get higher performance than ever before,” says Landis. The fiber density remains the same and the glass fabric can still be wetted out, he adds. Improved E-glass yields better flexural and tensile properties.
Better translation from raw material to end use – The tensile strength of raw fibers under ideal lab conditions is greater than in end-use applications, after they have been mixed with resins and processed. “The amount of translation of stresses and strains is very important,” says Carling. “Our customers are looking to heighten the translation in their end application by having the optimal fiber performance, with surface treatment and sizing chemistry for the specific resin they are using. This is tricky.”