Plastics 101

Hello to all of you plastic pellet and plastic bead enthusiasts and small processors! We get many many questions about what type of plastic polymer is best for different applications. The answers, of course, are dependent on the specific application and the desired performance of the end product. Some of the requirements or properties of the end product can be fairly complex. This is not the place for complex technical discussions, however, we can discuss some of the basic plastic terminology and chemistry to give some guidance to our novice customers. So...hang on...here we go.

There are two basic classes of plastics or polymers, depending on how they are formed and flow. "Thermoplastic" polymers are those plastic materials which will "flow" when heated. The ability to flow when forces are applied to the heated polymer allow the plastic or polymer to be "formed" into parts, film, sheeting, or objects. The reason that the polymers flow is that the heat excites the molecules and gives them the energy to break down the forces holding the molecules together. They are then able to flow past one another when forces are applied.

"Thermosetting" plastics are those plastics or polymers which are bonded together or "crosslinked" so tightly that the energy needed to break these bonds is so high that the polymer will typically oxidize or burn before these bonds are broken. These polymer molecules will NOT flow at all. The molecules are linked together permanently through chemical bonding agents, heat, or other energy sources like UV energy or electron beams.  

Almost all of the products that we sell are thermoplastic in nature. This is due to the markets we serve and the cost/value relationships. This is not to say that thermosetting polymers will not work in applications such as weighted blankets, cornhole bags, reborn dolls, stuffed animals, cat genies, filter media, rock tumbling media, or other applications we serve. It simply means that most of the thermoplastic polymers are less expensive and the properties are excellent for our applications. We also sell a good bit of product to small extruders or injection molders and other processors who need the product to flow through molds and dies to form their products.   

Now for a little chemistry lesson. Plastics or polymers are named based on their chemical structure. Many of the plastics use the prefix "poly", meaning "many" in the nomenclature. For example, one of the most common plastic materials we use is polyethylene. This plastic is made of many many "ethylene" molecules bound together through a chemical reaction into "polyethylene" molecules. Polypropylene, then, is made up of many many "propylene" molecules in a long chain to form "polypropylene". Polystyrene, then, is a bunch of styrene molecules! Isn't that easy?

Most of the applications listed in our website are very well served by polyethylene or polypropylene plastic pellets or beads. The pellet or bead geometry can be quite different depending on how the plastic flows through the dies and how it is cooled. This is discussed in another blog post. Due to the way the molecules align themselves and form a semi crystalline structure, they have the heat resistance to withstand commercial washers and dryers. They also have good chemical and solvent resistance due to their chemical structure and morphology.   

Now....we could go on and on and on, but you are probably already bored to tears. We will be very happy to discuss other specific properties or requirements if you have more sophisticated applications. Best to call us at 336-442-4209 for these technical discussions. Good luck with your projects and HAVE FUN!!!