Editing Poly(methyl methacrylate) (section)

=== Production ===
PMMA is routinely produced by [[emulsion polymerization]], [[solution polymerization]], and [[bulk polymerization]]. Generally, radical initiation is used (including [[living polymerization]] methods), but anionic polymerization of PMMA can also be performed.<ref name=Stickler>{{cite book |doi=10.1002/14356007.a21_473|chapter=Polymethacrylates |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Stickler |first1=Manfred |last2=Rhein |first2=Thoma |isbn=3527306730 }}</ref>

The [[glass transition temperature]] (''T{{sub|g}}'') of [[tacticity|atactic]] PMMA is {{convert|105|C|F}}. The ''T{{sub|g}}'' values of commercial grades of PMMA range from {{convert|85|to|165|C|F}}; the range is so wide because of the vast number of commercial compositions that are copolymers with co-monomers other than methyl methacrylate. PMMA is thus an organic glass at room temperature; i.e., it is below its ''T{{sub|g}}''. The forming temperature starts at the glass transition temperature and goes up from there.<ref>{{cite book |last=Ashby |first=Michael F. |author-link=Michael F. Ashby |title=Materials Selection in Mechanical Design |url=https://archive.org/details/materialsselecti00ashb_159 |url-access=limited |publisher=Elsevier |year=2005 |edition=3rd |isbn=978-0-7506-6168-3 |page=[https://archive.org/details/materialsselecti00ashb_159/page/n433 519]}}</ref> All common molding processes may be used, including [[injection molding]], [[compression molding]], and [[extrusion]]. The highest quality PMMA sheets are produced by [[cell casting]], but in this case, the polymerization and molding steps occur concurrently. The strength of the material is higher than molding grades owing to its extremely high [[molecular mass]]. [[Rubber toughening]] has been used to increase the toughness of PMMA to overcome its brittle behavior in response to applied loads.