Editing Poly(methyl methacrylate) (section)

== Synthesis and processing ==

=== 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.

=== Recycling ===
Plexiglass can be broken down with [[pyrolysis]] at a temperature of at least {{Convert|400|C}}. The recovered monomers then are purified, but the costs and complexity have prevented this from becoming the norm.<ref name=":0">{{Cite web |last=Coxworth |first=Ben |date=2025-03-03 |title=Simple technique may allow for almost complete recycling of Plexiglass |url=https://newatlas.com/materials/simple-technique-complete-recycling-plexiglass/ |access-date=2025-03-05 |website=New Atlas |language=en-US}}</ref>

Another approach binds monomers to the ends of long polymer chains. Those monomers detach when heated, triggering the chain to disassemble, with monomer yields of up to 90%, although the presence of dyes reduce this number. However, polymers produced by this technology require special machinery and lack thermal stability.<ref name=":0" />

A third approach adds a chlorinated dichlorobenzene solvent to crushed Plexiglass. The mixture is heated to a modest {{Convert|90-150|C}} and exposed to [[ultraviolet light]]. The light splits a chlorine radical from the solvent, which breaks the polymer into monomers, which are purified via distillation, yielding virgin-grade stock. Even in the presence of additives, yields are 94 to 98%.<ref name=":0" />