Editing Materials science (section)

===Polymers===
{{Main|Polymer}}
[[File:Polypropylene.svg|thumb|left|upright=0.9|The repeating unit of the polymer polypropylene]]
[[File:Expanded polystyrene foam dunnage.jpg|thumb|Expanded polystyrene polymer packaging]]
[[Polymer]]s are chemical compounds made up of a large number of identical components linked together like chains.<ref>{{Cite web |date=2017-10-13 |title=Explainer: What are polymers? |url=https://www.snexplores.org/article/explainer-what-are-polymers |access-date=2024-05-02 |language=en-US}}</ref> Polymers are the raw materials (the resins) used to make what are commonly called plastics and [[rubber]]. Plastics and rubber are the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form. Plastics in former and in current widespread use include [[polyethylene]], [[polypropylene]], [[polyvinyl chloride]] (PVC), [[polystyrene]], [[nylon]]s, [[polyester]]s, [[acrylic resin|acrylics]], [[polyurethane]]s, and [[polycarbonate]]s. Rubbers include natural rubber, [[styrene-butadiene]] rubber, [[chloroprene]], and [[butadiene rubber]]. Plastics are generally classified as ''commodity'', ''specialty'' and [[engineering plastic|''engineering'' plastics]].

Polyvinyl chloride (PVC) is widely used, inexpensive, and annual production quantities are large. It lends itself to a vast array of applications, from [[artificial leather]] to [[electrical insulation]] and cabling, [[packaging]], and [[Food storage|containers]]. Its fabrication and processing are simple and well-established. The versatility of PVC is due to the wide range of [[plasticiser]]s and other additives that it accepts.<ref>{{Cite journal |last1=Bernard |first1=L. |last2=Cueff |first2=R. |last3=Breysse |first3=C. |last4=Décaudin |first4=B. |last5=Sautou |first5=V. |date=2015-05-15 |title=Migrability of PVC plasticizers from medical devices into a simulant of infused solutions |url=https://www.sciencedirect.com/science/article/pii/S037851731500246X |journal=International Journal of Pharmaceutics |language=en |volume=485 |issue=1 |pages=341–347 |doi=10.1016/j.ijpharm.2015.03.030 |pmid=25796128 |issn=0378-5173}}</ref> The term "additives" in polymer science refers to the chemicals and compounds added to the polymer base to modify its material properties.

[[Polycarbonate]] would be normally considered an engineering plastic (other examples include [[PEEK]], ABS). Such plastics are valued for their superior strengths and other special material properties. They are usually not used for disposable applications, unlike commodity plastics.

Specialty plastics are materials with unique characteristics, such as ultra-high strength, electrical conductivity, electro-fluorescence, high thermal stability, etc.

The dividing lines between the various types of plastics is not based on material but rather on their properties and applications. For example, [[polyethylene]] (PE) is a cheap, low friction polymer commonly used to make disposable bags for shopping and trash, and is considered a commodity plastic, whereas [[medium-density polyethylene]] (MDPE) is used for underground gas and water pipes, and another variety called [[ultra-high-molecular-weight polyethylene]] (UHMWPE) is an engineering plastic which is used extensively as the glide rails for industrial equipment and the low-friction socket in implanted [[hip joint]]s.