Thermoplastic

Thermoplastics are polymers that soften when heated and harden when cooled, enabling repeated heating and reshaping. Unlike thermosetting polymers, they do not form permanent crosslinks during curing, so they can be reheated without significant chemical change. They include a broad range of materials from inexpensive packaging to engineered plastics.

They can be amorphous or semi-crystalline, and they soften at a defined temperature. Amorphous plastics are characterized by a glass transition temperature (Tg), while crystalline or semi-crystalline types have a melting temperature (Tm). Processing and performance depend on chemical structure, molecular weight, crystallinity, and additives. Common examples include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polycarbonate (PC), polymethyl methacrylate (PMMA), ABS, nylon, and polyetheretherketone (PEEK). Mechanical properties range from rigid and strong to flexible and impact-resistant, with behavior influenced by crystallinity and additives.

Processing methods include extrusion, injection molding, blow molding, thermoforming, and 3D printing. They are generally recyclable by remelting, but recycling effectiveness depends on purity and the compatibility of blends and additives. Environmental considerations include energy use during heating and potential emissions during processing.

Applications span packaging, electronics housings, automotive components, medical devices, and consumer goods, reflecting the broad tunability and versatility of thermoplastics.