Theory
Above its glass transition temperature, Tg, and below its melting point, Tm, the physical properties of a thermoplastic change drastically without an associated phase change. Within this temperature range, most thermoplastics are rubbery due to alternating rigid crystalline and elastic amorphous regions, approximating random coils.
Some thermoplastics do not fully crystallize below Tg, retaining some, or all of their amorphous characteristics. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, as a light wave cannot pass through larger crystallites than its wavelength. Amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure.
Brittleness can be lowered with the addition of plasticizers, which interfere with crystallization to effectively lower Tg. Modification of the polymer through copolymerization or through the addition of non-reactive side chains to monomers before polymerization can also lower Tg. Before these techniques were employed, plastic automobile parts would often crack when exposed to cold temperatures. Recently, thermoplastic elastomers have become available.
| Polymer | Tg | Tm |
|---|---|---|
| Acrylonitrile butadiene styrene (ABS) | 105 °C | |
| Acrylic (PMMA) | 160 °C | |
| Celluloid | ||
| Cellulose acetate | ||
| Cyclic Olefin Copolymer (COC) | ||
| Ethylene-Vinyl Acetate (EVA) | ||
| Ethylene vinyl alcohol (EVOH) | ||
| Fluoroplastics (PTFE, alongside with FEP, PFA, CTFE, ECTFE, ETFE) | 175-130°C | |
| Ionomers | ||
| Kydex, a trademarked acrylic/PVC alloy | ||
| Liquid Crystal Polymer (LCP) | ||
| Polyoxymethylene (POM or Acetal) | 175 °C | |
| Polyacrylates (Acrylic) | ||
| Polyacrylonitrile (PAN or Acrylonitrile) | ||
| Polyamide (PA or Nylon) | ||
| Polyamide-imide (PAI) | ||
| Polyaryletherketone (PAEK or Ketone) | ||
| Polybutadiene (PBD) | ||
| Polybutylene (PB) | ||
| Polybutylene terephthalate (PBT) | 40 °C | 225 °C |
| Polycaprolactone (PCL) | 62 °C | |
| Polychlorotrifluoroethylene (PCTFE) | ||
| Polyethylene terephthalate (PET) | 75 °C | 255 °C |
| Polycyclohexylene dimethylene terephthalate (PCT) | ||
| Polycarbonate (PC) | 267 °C | |
| Polyhydroxyalkanoates (PHAs) | 145 °C | |
| Polyketone (PK) | ||
| Polyester | 75 °C | 260 °C |
| Polyethylene (PE) | -127 °C | 105–130 °C |
| Polyetheretherketone (PEEK) | 143 °C | 343 °C |
| Polyetherketoneketone (PEKK) | ||
| Polyetherimide (PEI) | ||
| Polyethersulfone (PES)- see Polysulfone | ||
| Chlorinated Polyethylene (CPE) | ||
| Polyimide (PI) | ||
| Polylactic acid (PLA) | 50–80 °C | |
| Polymethylpentene (PMP) | ||
| Polyphenylene oxide (PPO) | ||
| Polyphenylene sulfide (PPS) | ||
| Polyphthalamide (PPA) | ||
| Polypropylene (PP) | 160 °C | |
| Polystyrene (PS) | 240 °C | |
| Polysulfone (PSU) | ||
| Polytrimethylene terephthalate (PTT) | ||
| Polyurethane (PU) | ||
| Polyvinyl acetate (PVA) | 32 °C | |
| Polyvinyl chloride (PVC) | 80 °C | |
| Polyvinylidene chloride (PVDC) | 40 °C | 185 °C |
| Styrene-acrylonitrile (SAN) | 115 °C |
Read more about this topic: Thermoplastic
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