Higher-end thermoplastic composites tend to have high matrix viscosity, and the material does not flow as well as it does with some of the lower viscosity resins. That creates challenges with fiber wet-out, which can affect both the performance and appearance of the part.
The upfront costs of thermoplastic composites can be problematic as well. “If manufacturers limit their focus on price per pound, the inherent value of thermoplastics may be missed,” says Lyons. Arkema’s Kepstan, developed to withstand high temperatures, is more expensive than traditional thermoset systems. “We present our value as related to cycle time. If you’re looking at the time and the cost to make a finished product rather than per pound, that’s where it’s competitive,” says Lyons.
Since many manufacturers have already made significant investments in thermoset processing equipment, it may be difficult for them to contemplate spending more for thermoplastic processing equipment. But in the long term, the many benefits of the newer thermoplastic composites are likely to win over more customers.
Reduced Environmental Impact
With more and more companies focusing on improving the sustainability of their operations, the recyclability of thermoplastics is a major benefit. “Having a material that can be recycled makes more sense than using a material made from an irreversible process where at the end of life there’s nothing else that you can do to the part except grind it down and use it as landfill or burn it,” says Bert Keestra, application development engineer at DSM Engineering Plastics.
DSM is recycling some of the prototype tanks it manufactures for experiments with hydrogen and CNG thermoplastic composite pressure vessels. The tanks, made with a polyamide liner and a thermoplastic polyamide base, are ground into 3-millimeter flakes after any metal attachments are removed. The thermoplastic flakes are then used to manufacture new parts.
“We have measured the properties of those recycled granules and compared them to the virgin equivalent; essentially, we find that we are still at 85 percent of the intrinsic original properties,” says Keestra.
DSM is also looking for other ways to make the material more sustainable, replacing oil-derived monomers in some thermoplastics with bio-renewables ingredients. The company’s EcopaXX® is a bio-based, high-performance polyamide that contains 70 percent bio-renewable materials. “It has a zero carbon footprint and has really good properties when you combine it and use it as a matrix for the UD tape to embed your carbon fibers,” says Keestra.