Sunday, March 15, 2009
Plexiglass is really spelled PLEXIGLAS....
Plastic. Kinda like saying "wood" or "metal". There's a lot of variety out there. So, let's be specific and talk about ACRYLIC - a clear or colored thermoplastic known as Plexiglas, Plexiglass, Plex, Plexi Glass, Flexi Glass, Perspex, Polycast, Lucite, Optix, Acrylite, .... and for the legal eagles, Plexiglas® is a registered trademark of Arkema, Inc. And since the common mis-spelling is "plexiglass" I will interchange the spelling throughout the blog (no disrespect to Plexiglas).
Acrylic IS the generic name for clear methyl methacrylate resin. PMMA as all the scientists say. The formula is natural gas based and requires a lot of acetone. It is truly one of the most beautiful of the thermoplastic materials. And along the way I have heard many myths about Plexiglas - and what is does, and does not do.
"Plexiglas yellows" - it doesn't. Plexiglas transmits 92% of visible light and over 10 years in the harshest sunlight will lose about 2% - which you can't really detect with your own eyeballs. In fact, Plexiglas is SO clear you can look through the edge of a thick sheet and read a business card easily - even 4ft away! So... As far as I can tell, this myth started because there were a lot of clear styrene sheets sold (as a plexiglass look-alike) in the old days (50's and 60's) and they sure DID yellow. Fast. And Plexiglas? Never. Like a lot of technological developments, it was World War II aircraft manufacturing that really catalyzed the production of acrylic sheet - and those old planes have been sitting in the sun for 60 years. Plexiglas is still clear. But, let me ramble a bit more here. There have been some differences in the quality of acrylic sheet over the years - and the domestic manufacturers in the USA (and NAFTA plants) have been making the best products that do not yellow - as compared to certain plants in Asia which I have seen discolor after 5-10 years. In buying acrylic sheet - ask where it's made. I like Plexiglas, Acrylite, Optix, Polycast, and Lucite. Here's what the guys at Plexiglas said about yellowing:
Plexiglas G's (that's general purpose) ability to withstand the effects of weather, sun, and a wide range of temperatures in outdoor use. This permanence derives from the acrylic resin's inherent stability. A large number of clear samples, after more than 10 years' outdoor exposure in Pennsylvania, show an average of more than 90% light transmission, which represents a loss of only 2%. Inspection reveals that very few test samples exhibit any obvious damage due to weathering.
In other tests, samples of colorless Plexiglas G sheet exposed outdoors in Arizona, Florida, and Pennsylvania for 20 years or more show no significant discoloration, crazing, surface dulling, loss of light transmission, or development of have or turbidity. Although these samples were Plexiglas G sheet, ongoing weathering studies have shown Plexiglas MC sheet to behave in a similar manner.
In these tests the samples were mounted on outdoor racks at a 45-degree angle facing south. Angling the racks in this manner increases the rigors of exposure significantly. Actual outdoor applications ordinarily involve less severe conditions.
"Plexiglas scratches" - it does. It can also be re-polished rather easily. Most scratching occurs because people use their bare hands to wipe off the dirt or dust. You would
not do that to a fine piece of furniture - you would use some Pledge and a soft cloth. Do the same with the Plexiglass.
I like the Brillianize and Novus #1 and #2 series for cleaning and light scratch removal.
"Plexiglass is Bullet Proof" - uh, yes, well it is "bullet resistant" in thicknesses of 1.25" and up. Look for a stamp on the material stating that fact. Bullet Resistant Sheet is known as Plexiglas® SB Cell Cast Acrylic Sheet and has US Patent No. 4.505.972. Comes in 4x8, 5x8, and 6x8 sheets. Plexiglass looks great with its clear edges and crystal clear beauty. On another level, there are some really effective "containment grade" and "bullet resistant" grades of Makrolon Hygard sheet that will stop some serious firepower. What is nice is these materials can be cut and shaped to replace glass panels easily. They will stop all kinds of weapon fire - and are rated by UL from Level 1 to 6. But no material is bullet proof...given enough bullets.
"Plexiglass is bad for the Earth - you can't recycle it" - not true. Most of us in the industry have a source for recycling our scrap. It is not curbside yet so if you have some plexiglass to toss, check with your local plastic distributor to see if they will let you drop it off. We have a local recycler at the city dump AND a regional recycler that picks up our large bins weekly. At the manufacturer level, all of our suppliers recycle all scrap in-house. Try this Google search.
Posted by Plastic Genius at 1:15 PM