Plastic Materials
Plastic is made from polymer resin and derives its name from its plastic, or moldable, quality. Plastic materials 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. This material is used in almost every environment, including medical, commercial, domestic and industrial settings. Plastic materials are formed into many different shapes, including sheets, pipes, profiles, fittings, film and rods and are used to produce an extremely wide range of products that span every industry--anything from computer housings to children's toys are made from plastic materials.
Generally, plastic materials 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 US, 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.