Editing Polycarbonate (section)

==Properties and processing==
Polycarbonate is a durable material.  Although it has high impact-resistance, it has low scratch-resistance. Therefore, a hard coating is applied to polycarbonate [[eyewear]] [[corrective lens|lenses]] and polycarbonate exterior automotive components. The characteristics of polycarbonate compare to those of [[polymethyl methacrylate]] (PMMA, acrylic), but polycarbonate is stronger and will hold up longer to extreme temperature. Thermally processed material is usually totally amorphous,<ref>{{cite journal|last1=Djurner|first1=K.|last2=M??nson|first2=J-A.|last3=Rigdahl|first3=M.|title=Crystallization of polycarbonate during injection molding at high pressures|journal=Journal of Polymer Science: Polymer Letters Edition|volume=16|issue=8|year=1978|pages=419–424|issn=0360-6384|doi=10.1002/pol.1978.130160806|bibcode=1978JPoSL..16..419D}}</ref> and as a result is highly [[Transparency (optics)|transparent]] to [[visible light]], with better light transmission than many kinds of glass.

Polycarbonate has a [[glass transition temperature]] of about {{convert|147|C|F|abbr=on}},<ref>[https://web.archive.org/web/20100210070124/http://www.bayermaterialsciencenafta.com/faq_pcs/index.html Answers to Common Questions about Bayer Polycarbonate Resins]. bayermaterialsciencenafta.com</ref> so it softens gradually above this point and flows above about {{convert|155|C|F|abbr=on}}.<ref name="city">{{cite web |title=Polycarbonate |publisher=city plastics |url=http://www.cityplastics.com.au/materials-polycarbonate/ |access-date=2013-12-18 |archive-url=https://web.archive.org/web/20181016161442/http://www.cityplastics.com.au/materials-polycarbonate |archive-date=2018-10-16 }}</ref> Tools must be held at high temperatures, generally above {{convert|80|C|F|abbr=on}} to make strain-free and stress-free products. Low [[molecular mass]] grades are easier to mold than higher grades, but their strength is lower as a result. The toughest grades have the highest molecular mass, but are more difficult to process.

Unlike most thermoplastics, polycarbonate can undergo large plastic deformations without cracking or breaking. As a result, it can be processed and formed at room temperature using [[sheet metal]] techniques, such as bending on a [[Brake (sheet metal bending)|brake]]. Even for sharp angle bends with a tight radius, heating may not be necessary. This makes it valuable in prototyping applications where transparent or electrically non-conductive parts are needed, which cannot be made from sheet metal. [[Poly(methyl methacrylate)|PMMA/Acrylic]], which is similar in appearance to polycarbonate, is brittle and cannot be bent at room temperature.

Main transformation techniques for polycarbonate resins:
*[[extrusion]] into tubes, rods and other profiles including multiwall
*extrusion with cylinders ([[calender]]s) into sheets ({{convert|0.5|-|20|mm|in|abbr=on}}) and films (below {{convert|1|mm|in|abbr=on}}), which can be used directly or manufactured into other shapes using [[thermoforming]] or secondary [[Manufacturing|fabrication]] techniques, such as bending, drilling, or routing. Due to its chemical properties it is not conducive to laser-cutting. 
*[[injection molding]] into ready articles

Polycarbonate may become [[Brittleness|brittle]] when exposed to ionizing radiation above {{nowrap|25 [[Gray (unit)|kGy]] (kJ/kg).}}<ref>{{cite book |author1=David W. Plester |date=1973 |chapter=The Effects of Radiation Sterilization on Plastics |title=Sterilization Technology |chapter-url=http://infohouse.p2ric.org/ref/27/26567.pdf |archive-url=https://web.archive.org/web/20150512042131/http://infohouse.p2ric.org/ref/27/26567.pdf |archive-date=2015-05-12 |s2cid=18798850|quote=Polycarbonate can satisfactorily be given a single-dose sterilization exposure (22) but tends to become brittle much above 2.5 Mrad. |page=149}}<!--https://scholarworks.rit.edu/cgi/viewcontent.cgi?article=1802&context=theses Mechanical properties of polymeric packaging films after radiation sterilization 1990--></ref>

[[File:Polycarbonate water bottle.JPG|thumb|A bottle made from polycarbonate]]