thermoplastic - Temperature dependence, List of thermoplastics

A class of resin which softens and hardens reversibly on heating and cooling any number of times.

For other uses, see Plastic (disambiguation).

A thermoplastic is a material that is plastic or deformable, melts to a liquid when heated and freezes to a brittle, glassy state when cooled sufficiently. Most thermoplastics are high molecular weight polymers whose chains associate through weak van der Waals forces (polyethylene);

Temperature dependence

Thermoplastics are elastic and flexible above a glass transition temperature Tg, specific for each one — the midpoint of a temperature range in contrast to the sharp freezing point of a pure crystalline substance like water. Below a second, higher melting temperature, Tm, also the midpoint of a range, most thermoplastics have crystalline regions alternating with amorphous regions in which the chains approximate random coils. e.g., nylon rope and fishing line.) Above Tm all crystalline structure disappears and the chains become randomly interdispersed.

Thermoplastics can go through melting/freezing cycles repeatedly and the fact that they can be reshaped upon reheating gives them their name.

Some thermoplastics normally do not crystallize: they are termed "amorphous" plastics and are useful at temperatures below the Tg. Some typical examples of amorphous thermoplastics are PMMA, PS and PC. Generally, amorphous thermoplastics are less chemically resistant and can be subject to stress cracking.

Most other thermoplastics will crystallize to a certain extent and are called "semi-crystalline" for this reason. Typical semi-crystalline thermoplastics are PE, PP, PBT and PET. The speed and extent to which crystallization can occur depends in part on the flexibility of the polymer chain. Semi-crystalline thermoplastics are more resistant to solvents and other chemicals.

Semi-crystalline thermoplastics become less brittle above Tg.

Although modestly vulcanized natural and synthetic rubbers are stretchy, they are elastomeric thermosets, not thermoplastics. Each has its own Tg, and will crack and shatter when cold enough so that the crosslinked polymer chains can no longer move relative to one another.

List of thermoplastics

Acrylonitrile butadiene styrene (ABS) Acrylic Celluloid Cellulose acetate Ethylene-Vinyl Acetate (EVA) Ethylene vinyl alcohol (EVAL) Fluoroplastics (PTFEs, including FEP, PFA, CTFE, ECTFE, ETFE) Ionomers Kydex, a trademarked acrylic/PVC alloy Liquid Crystal Polymer (LCP) Polyacetal (POM or Acetal) Polyacrylates (Acrylic) Polyacrylonitrile (PAN or Acrylonitrile) Polyamide (PA or Nylon) Polyamide-imide (PAI) Polyaryletherketone (PAEK or Ketone) Polybutadiene (PBD) Polybutylene (PB) Polybutylene terephthalate (PBT) Polyethylene terephthalate (PET) Polycyclohexylene dimethylene terephthalate (PCT) Polycarbonate (PC) Polyhydroxyalkanoates (PHAs) Polyketone (PK) Polyester Polyethylene (PE) Polyetheretherketone (PEEK) Polyetherimide (PEI) Polyethersulfone (PES)- see Polysulfone Polyethylenechlorinates (PEC) Polyimide (PI) Polylactic acid (PLA) Polymethylpentene (PMP) Polyphenylene oxide (PPO) Polyphenylene sulfide (PPS) Polyphthalamide (PPA) Polypropylene (PP) Polystyrene (PS) Polysulfone (PSU) Polyvinyl chloride (PVC) Spectralon

Polymerisation can only take place at double double carbon bonds