Plastics
Plastic is made from polymer resin and derives its name from its plastic, or moldable, quality. Plastics can be formed into any desired shape when heat and pressure are applied, and continue to retain this shape when cooled. The resins used to make plastic can be natural, although the majority of plastics are made from synthetic materials. Plastics are beneficial for their flexibility in color, shape, and hardness, as well as for their ability to withstand extreme temperatures.
Generally plastics fall into two different categories: thermoplastics and thermosets. Thermoplastics become pliable when they are heated and rigid when cooled. Common thermoplastics include acrylics, polypropylene, and butyl. Thermoplastic polymers differ from thermosetting polymers, which can never be melted or remolded after being cured. Other common plastics include nylon, celluloid, rayon, polyvinyl chloride (PVC), polystyrene (PS), polyethylene, and many more.
Increasing environmental concern has led to a higher prevalence of recycled plastics. Within the U.S., plastic recycling programs are becoming more and more common. In order to aid in the recycling effort, the Plastic Bottle Institute of the Society of the Plastics Industry devised a now-familiar method of marking plastic bottles by plastic type. There has also been research performed on biodegradable plastics, but so far these plastics have proven too costly and limited for most uses.
As the diverse environments in which plastic materials are used require different kinds of plastics, it is important to understand the specific properties of each variety of plastic. Plastics are used everywhere in today's world. They are used in almost every environment, including medical, commercial, domestic, and industrial settings.