Composites are a broad and intricate topic, with thousands of real-world applications. We briefly sat down with our Material Application Engineer, Sam Ellis, to discuss composites and their many applications.
Q: Let’s start with the basics. What are composites?
Sam: In general, composites are a mixture of any two or more materials. There is typically always a matrix (what holds it together) and a reinforcement (pieces that add important properties). Typically, the point is to combine the properties of several materials to form a new unique material. Concrete is a composite (gravel, lime, water), Coreboard is a composite (hurd, binder). Wood itself is a composite, composed of cellulose fibers (as the reinforcement) coated in lignin to hold it together. Anything made up of two or more materials is a composite.
Q: Well then, how can Sunstrand’s material be used in a composite?
Sam: Most modern composites are typically fiber-reinforced plastic. These composites are used in boat hulls, bathtubs, skateboards, automobile parts, rockets, and many other engineered materials. Manufacturers are typically looking to add strength. The most common fiber types are glass fibers and carbon fibers. When combining with the matrix, fibers can be randomly placed or preformed into a woven or nonwoven mat. Our natural fibers have high strength and very low density and can serve as a great replacement to these synthetic fibers in many applications.
On the other hand, a popular use of core, or hurd, material is to blend it with thermoplastics through a process called compounding, creating a composite of plastic and biomass. The plastic/biomass blend works with most common part forming techniques and can lower density and plastic consumption for everyday plastic goods.
Q: Okay, so what is compounding, why is it different than a composite?
Sam: Compounding is a method of mixing plastic with other materials. Companies can precisely meter additives to modify and improve a plastic. Usually mixing is done with augers and the final product is extruded to form pellets or rolls of filament that can be used in injection molding, 3D printing, and more. A large run is called a masterbatch. Many companies sell proprietary blends of premade pellets that can be used for all types of plastic parts. Generally, our material feeds well into the machines and is compatible with many common plastics, from PP, PE, and PVC to PLA and ABS. So, in most cases when people say hemp plastic, they are referring to a blend of biomass and plastic. The core can be more visible by using larger particles or more blended by using smaller ones. Regardless, it has a cool aesthetic and a great environmental story.
Q: Alright, let’s switch gears a little. What is a polymer blend? Can sustainable materials be used in polymer blends?
Sam: A polymer blend is a mixture of two or more polymers. Polymers are chemical compounds with molecules bonded together in long, repeating chains. So, if you mix ABS (Acrylonitrile Butadiene Styrene) and PLA (Polylactic Acid), you get a polymer blend. Our sustainable materials are not polymers. Polymers are plastic. Sustainable materials are basically cellulose, like wood. Polymers can be made from sugars in bio-based materials, but our sustainable materials don’t have sugar. This isn’t to say that we will never use sustainable materials to make polymers, just that there are easier methods. If for example you were making a polymer blend and wanted to add a filler, we would be the filler.
Q: You mentioned fillers a little earlier – what do you mean by filler? And what are sustainable materials’ role here?
Sam: I guess there are two types that fall into this category. There are true fillers and there are additives; the difference lies mostly in intention. Fillers don’t add any value to the product but tend to reduce a negative impact, while keeping the products’ integrity intact. Usually, companies use sustainable fillers because they want to reduce the cost of their product to their pockets or to the environment. Additives are materials that add benefits to the product, as the name would imply. Companies love to use sustainable materials for their absorbent products, due to the natural absorbent properties of hemp, kenaf, and flax. Examples of these absorbent products include wipes, paper towels, and hygiene. Other reasons for using sustainable materials as additives include comfort, strength, and durability.
Q: Hemp plastic… I get a lot of questions about what it is and if we can make it. What can you tell those people?
Sam: Well, technically yes, but not likely. Our material is a lignocellulosic biomass, meaning it’s made up of mostly different forms of cellulose and lignin, like the composition of wood. In this case, we are better suited to pulp our material and make paper than we are to make plastic. Although cellulose-based polymers currently exist, it’s difficult for them to compete. Who knows, maybe a steady supply of hemp, kenaf, and flax is what the industry has been waiting for. Other bio-based plastics already exist, such as PLA, which is derived from corn starch.
For more information on composites or any other questions, contact us.