Consulting and marketing company Flexi-StiX, LLC secured a patent for its process of incorporating pultrusion into a thermoplastic tube. The immediate result of its invention is a lightweight exercise tool, but the technology could soon permeate elsewhere.
President Gordon Brown previously co-invented bombproof wallpaper, which Berry Plastics is targeting for military and construction use. During the wallpaper-making process, he used an extruded thermoplastic urethane for the matrix rather than a typical epoxy resin. “It was sort of a novel approach, as we now have a way to put reinforcements into polyurethanes,” he says. “The industry needs to deliver cost-effective solutions to our customers through a combination of fibers and resins, and we believe our way was unique in accomplishing that.”
Using that same thought process, Brown focused on another way to give extruded thermoplastics additional strength and stiffness for better performance properties. He combined an extruded thermoplastic tube such as polyvinyl chloride (PVC) with a rectangular pultruded composite (materials such as fiberglass, reinforced vinyl ester, epoxy, carbon, or aramid). The pultruded composite is slipped inside the tube, after which closures are placed on the end to stop the fiberglass from falling out, effectively creating a flexible pole.
“Straight extruded PVC is flexible, but too much so for most applications,” says Brown. “All pultruded round tubes are too stiff, and aluminum steel and metal are very rigid poles. This process offers a way to take low-cost extruded thermoplastics and make them stronger.”
The genesis for the product’s creation came while Brown worked for Strongwell. In the mid-1980s, the company was approached by Universal Gym Equipment to develop a product to use composites for bending resistance. “We came up with a product that was developed and marketed, but we took a pultruded shape, and ran it through an extruder and put a tight covering of thermoset rubber over it. That gave it a round shape, but there were concerns the fiberglass would splinter in people’s hands,” says Brown. Universal wanted something over the outside of the fiberglass to prevent that, but the product and process ended up being too expensive at the time, so that project was abandoned.
However, that concept never fully left Brown’s mind, and over 15 years later he saw a hollow piece of PVC tube in a hardware store. “I simply wondered what would happen if I put a pultruded piece of fiberglass down the center of that tube. In all of our thinking, no one ever thought to take an extruded thermoplastic tube and put fiberglass inside it,” he notes. That was the breakthrough he needed, and he immediately worked on patenting the product as a lower-cost, more effective exercise tool.