What are the Characteristics of Acrylic (PMMA)?
Now that we know what it is used for, let’s examine some of the key properties of Acrylic. PMMA is classified as a “thermoplastic” (as opposed to “thermoset”), and the name has to do with the way the plastic responds to heat. Thermoplastic materials become liquid at their melting point (160 degrees Celsius in the case of Acrylic).
A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like Acrylic liquefy, which allows them to be easily injection molded and then subsequently recycled.
By contrast, thermoset plastics can only be heated once (typically during the injection molding process).
The first heating causes thermoset materials to set (similar to a 2-part epoxy) resulting in a chemical change that cannot be reversed.
If you tried to heat a thermoset plastic to a high temperature a second time it would simply burn.
This characteristic makes thermoset materials poor candidates for recycling.