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  • Writer's pictureNed Patton

More About Natural Fibers, Resins, and Biocomposites

In this post I’m going to delve a little deeper into natural fibers and plant-based resins and their applications. There is a very large motivation in the composites industry to move away from petroleum based resins and synthetic fibers, for several reasons. First, of course, is because these plant-based or natural raw materials do so little damage to our environment, even when they are processed into composites. They can also be less expensive to produce with the skyrocketing price of oil, and they are more sustainable since all you have to do is grow plants and you can make composite structures from what mother nature gives you.

The plant-based resins that make up natural composites are called biopolymers – polymers that you can find in nature. This class of polymers is vast and varied, and it includes things like proteins, nucleic acids (RNA, DNA), starches, and sugars. The collagen that makes up most of our cell walls is a biopolymer, as is corn starch, and even lignocellulose and lignin that make up the glue that holds plant fibers together. And the main structural component of brown algae, alginate, is also a very useful and abundant biopolymer.

There are many uses of these polymers in medicine, food packaging, and even water purification using chitosan which is the glue in oyster and clam shells. The attraction of the food industry to biopolymers is its compatibility with food, it is non-toxic, and are very easily biodegradable. By far the biggest attraction to biopolymers is their sustainability and low cost.

There are a few drawbacks to some biopolymers that make them less suitable as composite resins. For one they tend to take up water, so things have to be done to the chemistry of the biopolymers to make them resistant to water uptake. One such biopolymer is PLA (polylactic acid – yes that’s right an organic acid made up from lactose). PLA can be used and is used in the place of polystyrene or polyethylene, and is also one of the resins of choice for plant-based composites.

In composites, to make them completely sustainable, these biopolymers are combined with natural fibers – what I talked about last week – to make true biocomposites. A good example are bowls that are made of formed bamboo. Bamboo is a wonderful starting material for composites because not only does it grow very quickly and can be easily farmed, the wood of the bamboo itself has all of the raw materials needed to make a composite. There is a great deal of the lignin/pitch glue along with very strong and long fibers that are naturally part of the bamboo stalk.

Flax is another very good starting plant material for composites. It is an oily plant which makes it ideal for taking the oil, polymerizing it, and making a glue. The stalks of the flax plants also have very strong fibers that make a wonderful string for a composite. The chair in the pic at the top of this post is entirely made from flax.

Finally, the biocomposite market is expected to grow from about $24 billion in 2021 to over $51 billion in 2026, that’s more than double what the market is today. This is being driven by several industries, automotive for one. The auto manufacturers want to lessen their carbon footprint in a big way as they transition to electric vehicles from gasoline powered cars. One way to do that is to replace non-structural parts like door liners, body parts, trunk liners, etc. with biocomposites. And they are doing the research and development of processing technology to enable them to move away from petroleum based resins and synthetic fibers for all of their composites needs. And of course, this is happening more in the E.U. than it is in the U.S. It appears that the Europeans are a bit ahead of us when it comes to sustainable products and reduction of their carbon footprint.

Which leads me to what I’m going to talk about in several other posts – composites and climate change. Yes, composite manufacturers are paying attention, so the carbon footprint of the composites industry is getting smaller.

There is a lot to talk about. You can read those posts in my "Sustainability" category here on the website.


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