Note to the reader: Chemistry not your style? Why not try our California Valley Girl version?
It’s back to school, and we’re heading to Chemistry Class! Didn’t you just love mixing those chemicals and watching a yellow and a transparent liquid combine to form a blue compound? These colour changes can have practical applications; for example, they’re used in breathalyzers to detect the quantity of alcohol in one’s breath. On the topic of Chemistry and alcohol, you’ll recall that the chemical formula of alcohol is C2H5OH. And you probably still remember the easiest Organic Chemistry formula: CH4 for methane. But did you ever learn about (C5O2H8)n? Now this one’s a stumper, eh?
Here’s a clue: just look around. Look at the windows, light fittings, a fish-bowl, drinking glasses or eyeglasses Ð heck, look at your mobile-phone’s screen Ð and you’re sure to see (C5O2H8)n. That’s because it’s the
formula for acrylic; ubiquitous, cant-do-without, acrylic. In the trade, acrylic is known as ‘PMMA’ which is an abbreviation of its chemical name, Polymethyl-Methacrylate. The ‘n’ in the chemical formula means ‘many’ and that accounts for the ‘poly’ Ð ‘many’ or ‘multiple’ Ð in the scientific name. Just C5O2H8 is Methyl-Methacrylate or ‘MMA’.
Acrylic is one of the thermoplastics and is a member of the acrylic-based resin family. Its mode of production and quality differ by materials and method: it is composed of one or another of two materials, and is manufactured using one or another of two methods.
Acrylic is a petroleum-based polymer so its materials may be sourced directly from fossil fuels or derived from recycled acrylic. Fossil fuels-based production results in a superior product whereas recycled materials make for an inferior type of acrylic which can be prone to clouding, brittleness, and ageing. The method of production is either extrusion or casting, with the latter method producing the higher-grade acrylic. In extrusion, the cheaper method, liquefied acrylic is passed Ð ‘extruded’ Ð through rollers. Thus, it is pressed into sheets while it is cooling and hardening. Casting, on the other hand, requires semi-liquid acrylic to be put into moulds, where it is pressed and temperature-treated. Cast acrylic is harder, more temperature-resistant, more transparent, and simply looks cleaner and better than most extruded acrylic.
Acrylic possesses quite a striking combination of properties which make it exceedingly useful and practical for a vast variety of uses Ð and then some. These key properties are impact- and shatter-resistance, light transmission, low weight, and slow ageing. Based on these criteria, an acrylic versus glass head-to-head will often result in favour of acrylic, depending on the desired usage.
One of acrylic’s main selling points is its unmatched flexural strength. Its coefficient of rupture is 700kg/cm2 Ð that’s ten times more than the strongest glass. Think about it: only over 1500 pounds of pressure exerted on an area smaller than the smallest coin will rupture acrylic. It is for this reason that acrylic is preferred for windshields, aircraft windows, riot police shields, and Ð of course Ð bullet-proof protective enclosures. Even when acrylic shatters, it breaks into large pieces with blunt edges that do not hurtle at high velocity Ð exactly the opposite of glass shards.
Acrylic is very light-friendly. It transmits 92 percent of light in the visible spectrum, thereby making it an ideal choice for windows, skylights, and storefront displays Ð one can enjoy a sunlit interior while being unsusceptible to most breakages. Unlike glass, which refracts or even reflects oblique and parallel rays, acrylic will transmit about 92 percent of transverse, oblique and parallel rays. The icing on the cake is that harmful UV rays cannot pass through acrylic so you get the best of all worlds with acrylic windows.
Only half as dense as glass, acrylic, consequently, also weighs about half as much as glass. This is a massive advantage when it comes to hoisting, and fitting or joining, large sheets. Large glass panes, both heavy and prone to breakage, require specialized equipment and careful handling while acrylic sheets can be handled in a more simple, straightforward manner.
Acrylic sourced from fossil fuels and manufactured using the casting method has a long life Ð reputable manufacturers typically provide 30-year guarantees. So long as it is not exposed to excessively high temperatures, i.e. over 80 degrees Centigrade (176 degrees Fahrenheit), good quality acrylic will neither cloud nor degrade in sunlight or rough weather. Unlike high-quality glass, acrylic is not scratch-proof; however, it is scratch resistant. Specially-made chemical cleaners can ‘lift’ scratches from most acrylic products.
As a consequence of these properties Acrylic is big business, so much so that one trademarked brand-name has entered the lexicon and a second has started to recur in common usage: Plexiglas and Lucite, respectively. Plexiglas Ð frequently misspelt ‘plexiglass’ and called just ‘plexi’ Ð is associated in most people’s minds with the shatter-resistant and protective properties of acrylic. It is a product of Rohm & Haas of Germany, now owned by Dow Corning. Lucite, on the other hand, is typically associated with acrylic’s decorative and visually appealing attributes. It is made by Lucite International which supplies the building-block for acrylic, the Methyl-Methacrylate (MMA) monomer, to other manufacturers. Perspex is another well-known acrylic brand. It is Lucite International’s budget-friendly offering.
Though this article is about acrylic and not Rohm & Haas, a word about Otto Rohm is in order because . . . he’s the inventor of acrylic! His accidental discovery of acrylic and its properties is similarly serendipitous to that of Marie Curie’s discovery of radium and X-Rays, and 3M’s discovery of the mild, reusable adhesive that brought about Post-It Notes with their distinctive stick-unstick-restick feature.
Rohm was a German acrylics chemist who wanted to create an acrylic-based adhesive that would cohere Ð permanently stick together Ð two panes of glass so as to make them shatterproof. In 1933 he succeeded in polymerizing the Methyl-Methacrylate monomer, creating PMMA or acrylic, and prepared his tri-layer ‘sandwich’. Unexpectedly, his ‘sandwich’ fell apart! The two panes of glass slid off, not having adhered to the new polymer, leaving behind a sparkling, crystal-clear pane Ð the world’s first acrylic sheet! Three years later in 1936, Rohm perfected his technique and trademarked his product under the brand-name ‘Plexiglas’.
That was waaay back in the 1930s. “You’ve come a long way, baby” is a phrase that springs to mind when thinking about acrylic today, for it has become the beauty queen among the resins and thermoplastics Ð we may veritably accord acrylic the title ‘Miss Resin-ThermoplasticÕ! Because it can be coloured, all the way from delicate tints through to solid, opaqe colours, and can be shaped and moulded, it is used to make attractive and visually-appealing products. Tableware with deep rich hues and frosted wineglasses; etched, design-imprinted ice buckets and unsexy, solid-coloured soap-dishes Ð they’re all made of acrylic. One of the latest fashions (‘Acrylic Fashions’!) has to do with photography. Specialty photography shops offer a service in which the photo of your choice is ‘printed within’ a premium acrylic tile or block. This technique results in a cutting-edge memento: a slab of ‘glass’ encasing an image that looks translucent, luminous, and three-dimensional at one and the same time! Thank you Mr. Rohm; thanks, acrylic!
Want to hear more about acrylic and her many charms? Just hang around till tomorrow, mate. Someone will have discovered a crackling new use for acrylic by then!