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ACRYLIC: The Wonder Plastic

19 September 2016

Amaury Picard

Poly(methyl methacrylate) — or 'PMMA' — is a transparent thermoplastic with untold numbers of applications. It's sold under the brand names Acrylite, Altuglas, Cyrolite, Lucite, Optix, Oroglas, Perspex, Plexiglas, R-Cast and Zylar, and it's used to make everything from spectacles to paint.

What is a 'thermoplastic'?

Thermoplastics are more properly called 'thermosoftening plastics', and the clue is in the name: They're a class of polymer that becomes soft and malleable when heated above a certain temperature but remain tough and hard when cool. This means that a single piece of plastic can be made and remade multiple times — you heat it up, you do what you want with it, you wait for it to cool and then if you don't like it you can heat it up again to 'reset' it and start over. There are hundreds of these thermoplastics in the world, but one of the best known and most utilised is poly(methyl methacrylate) —more commonly known as acrylic.

What sets acrylic apart?

Acrylic is special mostly because it's so versatile. It's a great replacement for glass in situations where safety is of absolutely paramount concern, meaning that it's often used in aquariums and for viewing ports in submarines and aeroplanes. It's good for making lenses with and has been used in lighthouses and on automobiles as well as to make ordinary glasses. Architects can use its light-reducing and -controlling properties to great effect in building design, while artists of other kinds have used it to frame paintings and to design furniture from. Salvador Dali used to paint on it as though it were canvas! Acrylic paint is, of course, a favourite of children everywhere. Dentists use it as a form of cement, as well as to build dentures — and over the years the medical uses of this remarkable plastic have been many and varied. You have only to glance at the 'applications' section of the website for one of acrylic's best-known brand names to see how versatile it is.

What can't it do?

All materials have their drawbacks, and acrylic is no exception. It's difficult to know how most plastics will break down over time because they simply haven't been around — or outside — long enough to find out, but early investigations of the Futuro house have indicated that it seems to be biodegrading. This is good news for the environment in many ways, but bad news for the longevity of PMMA and other thermoplastics. Acrylic is also quite flammable, and was partially indicated in the Summerland Disaster on the Isle of Man in 1973.

The most important drawback from an engineering perspective, however, is acrylic's tendency toward brittleness. It can't be used as a load-bearing material, and it's important to be careful using it in any situation where pressure may be applied. The good news is that some of this problem can be mitigated with the use of rubber toughening, a process by which many polymers can be made better able to cope with load and pressure by simply adding rubber to them. This makes them bend a little and removes some of their stiffness — which in turn decreases brittleness.

All sorts of thermoplastics and engineering plastics are used in a variety of industries because of their versatility.

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