A team at Baylor University has made trunk liners, floorboards and car-door interior covers using fibers from the outer husks of coconuts, replacing the synthetic polyester fibers typically used in composite materials.
The approach has potential because coconuts are an abundant, renewable resource in all countries near the equator, including the Philippines, Indonesia and India. The husks are burned or thrown away, generating garbage. This is the first time that coconut fibers have been used to make these automotive products, said Walter Bradley, an engineering professor who is leading the project.
In Ghana, as one of Bradley’s students told him, the discarded husks pile up in mounds, creating a health hazard because they collect water where malaria-causing mosquitoes can breed.
“We are trying to turn trash into cash to help poor coconut farmers,” Bradley said, adding that the long-term goal is to increase demand for coconuts to millions of pounds, and thereby raise their market price.
Currently, there are about 11 million coconut farmers in the world making an average annual income of $500, he said.
The production process starts with the coconut husk.
“The coconut that you see in the grocery store has a real hard shell that comes in a larger volume that’s twice as big — the husk, that is very fibrous,” Bradley told LiveScience.
Coconuts now are used primarily to produce coconut milk or coconut oil (which is the milk minus the water in it).
The husk is made mainly of fiber and coconut dust, or piph. The piph is spongy at first, but dries and contracts into dirt-like particles that Bradley’s team confirmed to have the capacity to absorb 10 times its weight in water.
“The fiber has very good strength, stiffness and ductility, and potentially can be used for all kinds of things,” Bradley said, including a more environmentally friendly particle board (used in construction) that requires no binders.
A lightweight composite
The husk fibers are blended with polypropylene fibers before being hot-pressed (compression-molded) into required shapes. The coconut fiber provides a rigid architecture for the lightweight, yet stiff, composite.
Preliminary testing shows that the coconut composites can meet the specifications for industrial tests, Bradley said. In fact, the mechanical properties of coconut fibers are just as good, if not better, than synthetic and polyester fibers when used in automotive parts, he said. Also, coconuts also do not burn very well or give off toxic fumes, which is key in passing tests required for their use in commercial automotive parts.
Bradley’s team is now working with a Texas-based fiber processing company that supplies unwoven fiber mats to four major automotive companies. The team is creating a 600-pound roll of the composite material and assisting with the safety performance tests for certification.
Husks, not shells