Monday, March 30, 2009

Surfboard Donor Board in Plexiglass

The California Surf Museum was recently renovated - completely. It's located in Oceanside, just a short paddle up the coast from our facility. Being a life-long surfer, I whothey called on me to help out with the donor recognition boards. I was honored.

So I met with the architect who supplied small pieces of glass tile that were part of the color theme. We matched these tiles to a PMS color chart we use in creating custom colored plexiglass sheet. This chart is rather magical as it allows for solid, transparent, translucent, and frosted sheets. Wow.

We decided to go with a blue tint with a frosted surface on 1 side. Oh - did I say how BIG they wanted these to be? 8ft tall. It required 3/4" thick material to make the boards stiff enough. Check this picture out. The public rarely sees the gasket used in manufacturing the sheets - but asked for it to be left on to maximize the available material that was cast for the project.

Next, we had to create a surfboard shape that was a blend of the old 60's longboard and an all-around "fun board" shape. I stopped shaping surfboards in 1975, but I have been designing skateboards my whole life (and continue to produce and sell a line of, yes, fiberglass plastic skateboards and clear skateboards too). So I was honored to create these donor boards.

Here's the machines cutting out the shapes.

As soon as I get a great photo of the boards installed at the museum, I will add that.

Friday, March 27, 2009

Plexiglass Acrylic Chuppah Mandap Mundap Gazebo on the Beach

OK - we have made some interesting things to go in interesting places. When one of our event planner customers based in San Jose del Cabo asked us to build an acrylic Mundap (or Mandap) or acrylic CHUPPA for Jewish wedding ceremonies.... we said "How Big do you want it?"

They said "Oh - maybe 8 ft high and 10ft wide" and "we want the top struts to be open, so we can put fresh flowers in" and a few other requests.

And a few more requests.... make sure YOU click on these pictures for a full size view of these clear Plexiglass gazebos. (I use the term gazebo loosely of course)

We said "You realize that not only do we have to build this, but we have to ship this 1200 miles to you - without breaking - and you have to be able to assemble and disassemble this many times!" And with our "When Others Can't - We Can" attitude, we figured out the "how" and put this together. It breaks down into 8 pcs and has adjustable sliders for assembly on uneven ground.

Nice. A bit of Jewish tradition : The wedding ceremony takes place under the chuppah (canopy), a symbol of the home that the new couple will build together. It is open on all sides, just as Abraham and Sarah had their tent open all sides to welcome people in unconditional hospitality. I think that's pretty cool.

Update June 2009: here's a link to the company that makes these Acrylic Plexiglass Chuppa Mandaps.

Thursday, March 26, 2009

Formed Plexiglass Wall for Koi Pond

Click to Enlarge this pictureThis is one of those fun jobs we get to do every now and then. A customer who is re-landscaping the backyard decided he wanted some clear Plexiglass walls to see the water and the koi fish. For a really BIG pond. So we had to take a couple of 48x96 sheets of Plexiglas that were 2" thick and bend them into an arc about 15ft across. Then we needed to put a hand rail on top. Make sure you Click to Enlarge this picture.

There are a lot of challenges to fabricating this part. First of all, there is no 16ft long sheet, and if there was, there are not too many 16ft long ovens to heat it up! So the fabrication method is to form 2 pc, and then chemically bond the 2 sections with liquid acrylic resin. That bond is almost as strong as the sheet itself.

Cutting the toprail is another challenge as the customer wanted one continuous piece. Again, we cut 2 pc and bonded together and then to the "wall". It takes a lot of practice to use this adhesive and achieve bubble free bonds - which give the appearance of 1 contClick to Enlarge this pictureinuous piece.

But wait - now that we have created this 16ft monster, how do we get this out the door and in the backyard of the customer? Even though the destination was 30 miles away, packing for transport was intricate: we had to completely support the entire piece underneath - and put this on a custom pallet. At the job site it took 8 people to carefully lift and place it in the final position.

Pretty cool! Make sure you Click to Enlarge this picture.

Wednesday, March 25, 2009

Corrugated and Flat Fiberlass Sheet Panels

Corrugated Fiberglass Sheets and Panels are cool. They are clear or colorful. They remind me of the 50's, yet designers are still calling out for them in modern applications from skylights, fences, wall partitions, to patio covers. Fiberglass is relatively cheap, chemical resistant, hold up to sunlight, has a great R-value, is strong and easy to cut.

There are over 500 profiles of corrugation made over the past 50 years. (I happen to have access to most of these older profiles, but you'll need 8000sf to crank up the machines). In the 21st century, only a handful are still being produced. Most of what you see as a consumer is what's called "2-1/2" corrugation. There are wood filler strips to match a cross section and strips for the ends - even aluminum nails to batten down the panels. There are several other options that I will discuss - from "R" panels, to metal building products, to something we call "Tred-Safe" - a corrugated roofing panel you can walk on.

Flat and Corrugated Fiberglass panels are rated by their "weight per square foot". The material is made from polyester resin, chopped fiberglass fibers, and sometimes acrylic modifiers are added for clarity and longevity in the sun - say for greenhouse applications. These panels are made by basically pouring the resin onto a conveyor, sprinkling the chopped fibers over the resin, and then laying a top sheet of mylar material over it. (Ok - that was really simplistic, but you get the idea) The trick is to sprinkle enough fibers on the sheet to hold it together. The more fibers, the higher the weight per square foot. At 6 or 8 ounce, it's thicker than a credit card.

Thing is, most of the panels in the big box stores are so thin they'll break before you get them on your patio cover. What a waste. Gives them a bad name. You have to go to a plastic supply center to find the good stuff. I have also seen some quality hardware chains carry them, and some specialty lumber yards offer them. You should be asking for "6 ounce" or higher. The cheapie panels are about 3 ounce. Maybe less. They typically run 26" wide (so you can overlap) x 96" long. The better 6 ounce and 8 ounce sheets come longer - 144" and more - but the shipping gets crazy on the 192" long sheets - so size does matter.

Now - for you industrial types it gets far more interesting. There are panels are DURABLE - and some so thick you can walk on them, with specific corrugations for metal building sides and skylight panels. There are "R-panels" and cooling tower panels. The sheets are typically wider - from 36" to 52" wide and thicker 8 ounce type material. But wait - there's more! You can only sprinkle so much fiber on the sheet - to go beyond the 8 ounce, you have to add fiberglass cloth and rovings! And yes. like the picture shows, you can walk on it - carefully. That's about 12 ounce material in the picture.

Fiberglass sheets and panels last a long time. There used to be a plant here in town that was made with corrugated panels. After about 40 years, the panels were still performing - even though they looked weathered. Panels 6 ounce and up usually have a warranty of 20 years - pro rated of course. I know of a customer that called about the warranty on his panels. We went out, got on the roof, and sure enough, the panels needed replacing. When asked when they were purchased, he said "Oh, I think about 35 years ago" to which we said - "Well, I guess you got 15 bonus years for free!"

Which makes me think that Fiberglass Sheets - whether corrugated or flat - will play a BIG part in helping us develop better application for solar heating of water and spaces.

Note: Fiberglass Liner Panels - for walls and ceilings - are on a future blog (yet to be written).
Note: Fiberglass sheet - structural sheet and high pressure
laminated NEMA G10 and FR4 - are on a future blog (yet to be written).

re: fiberglass sheets, panels, sheet, corrugated fiberglass panels, tube, roof panels, rod, tubing, sheeting, reinforced panels, flat, roofing, clear, pipe, greenhouse, angle, wall panels, liner panels

Tuesday, March 24, 2009

Plexiglass (Plexiglas) vs Glass

Thanks to my friends at Evonik Industries,
aka DeGussa, Cyro, makers of Plexiglas® brand acrylic everywhere but the USA where Plexiglass is known as ACRYLITE® acrylic sheet....

You ask: Why should I use ACRYLITE® acrylic sheet in place of standard glass?

Unsurpassed beauty, warmth and elegance! Creative design flexibility!
Caring Performance! There are so many compelling reasons to use ACRYLITE® acrylic sheet in place of glass.

Glass is tried and true - it has been around for hundreds of years. Using glass has made it possible to bring the warmth of daylight into our homes and buildings while keeping the bitterness of weather outside. We owe much thanks to this hard working material.

While properties like transparency, stiffness, and strength have helped to make glass successful, it has been limited by other properties. Its brittleness and heavy weight as well as the difficulty of cutting, shaping, coloring, and decorating glass have imposed limitations on designers, builder and architects, alike. Fortunately, there is an alternative - acrylic sheet. Acrylic is much tougher than glass, at half the weight, is easy to fabricate and form into a variety of shapes, comes in hundreds of colors and is readily decorated. It provides a new level of flexibility and allows ideas to take shape. It sets designers free!

Why use ACRYLITE acrylic sheet in place of glass?

Because acrylic sheet offers a number of significant advantages:

Performance! Acrylic is often used where safety and ease of handling are concerns. It is many times more impact resistant than conventional plate glass and has similar impact strength compared to tempered glass. If it does break, acrylic sheet will usually crack or fracture into large pieces
with edges that are much less sharp than those of broken glass. In addition to its excellent impact strength, acrylic sheet of the same size and thickness is half the weight of glass. High impact strength and light weight make acrylic sheet the choice of people who care! (personally, I am scared of glass and have several scars to prove it)

Impact and Weight: Acrylic vs. Glass

Plexiglass is HALF the weight of glass!
Plexiglass is up to 17 times more impact resistant than glass!
(use the figure of 1.5lb per SF for 1/4" thick Plexiglas.

Warmth! Acrylic feels warm to the touch, not cold like glass, because it is a better heat insulator. Compared to glass it has a lower coefficient of thermal conductivity.

Typical values for the Coefficient of Thermal Conductivity
Acrylic: 1.3 BTU/(hr-ft2)(F/inch)
Glass: 5.3 BTU/(hr-ft2)(F/inch)

Beauty and Elegance! Acrylic has crystal clarity, pure water-white edges and unmatched light transmission. The dull grey or green edges of glass cannot match the
sparkle and elegance of acrylic. Unlike glass, colorless acrylic sheet has essentially zero absorption of visible light.

Creative Design Flexibility! ACRYLITE acrylic sheet is available in a nearly unlimited array of standard, custom and designer colors. Smooth and etched surface finishes can be combined with eye grabbing colors to produce thousands of unique and exotic looks. CYRO Industries can custom match almost any color in ACRYLITE® GP acrylic sheet when modest minimum order quantities are met.

Acrylic can be cold formed into modest radii or thermoformed into flowing curves and shapes. Acrylic's excellent thermoforming properties will help ideas take shape.

Custom sizes and unusual shapes need not be a concern. Acrylic sheet is readily cut, routed or machined into intricate shapes and sizes using typical woodworking equipment. CYRO Industries can provide expert advice on appropriate blades, tooling and procedures to insure success.

Acrylic is easily decorated. It can be painted, engraved, or hot stamped.

There is no need to accept the limits of glass, with acrylic, ideas are set free!!

Where can acrylic be used in place of glass?

Acrylic is used in hundreds of different applications. Some of the more common applications where acrylic is used in place of glass are listed
below along with the benefits of acrylic.

Architectural Glazing:
* thermoformability
* easy cut to size
* impact strength
* low thermal conductivity

Fixtures, Displays and Furniture:
* sparkling water white edges
* unlimited color
* fabrication ease
* decorating
* impact strength
* light weight

* impact strength
* conservation grades (UV Filtering)
* non-glare grades
* reduced breakage in shipping

Transportation Glazing:
* light weight
* impact strength
* thermoformability
* color availability

Stadium and Wind Break Fence Glazing:
* light weight
* impact strength
* crystal clarity
* easy cut to size

Are there other considerations when replacing glass with acrylic? The properties of acrylic are different than glass. This leads to its exceptional impact strength and lightweight, for instance. However, in some situations these differences may require design changes or even make acrylic substitution infeasible. The checklist below highlights some important considerations when
substituting acrylic for glass. CYRO's Technical Service Department can also provide assistance.

* Mechanical strength and stiffness.

Acrylic has lower tensile strength and stiffness than glass. When used in glazing, the requires thickness will usually be 1.5 - 2.5 times greater than that required for plate glass to withstand the same wind loads. When used for shelving the required thickness to support the same weight will beat least 2.5 times greater than that required for plate glass; however acrylic will offer much greater impact strength. CYRO's TechnicalService Department can provide design assistance.

* Expansion and contraction allowances.

Acrylic expands and contracts more than glass due to temperature and humidity changes. Its coefficient of thermal expansion is about 8 times greater than that of glass. Proper allowances must be made to permit expansion and contraction. CYRO's Technical Service Department can provide assistance.

* Scratching.

The surface of acrylic is not as hard as that of glass. Therefore, it is more prone to scratching and abrasion. If resistance to scratching and abrasion is important, then specify ACRYLITE® AR Abrasion Resistant sheet.This revolutionary acrylic sheet has a "glass-like" coating on one or both surfaces that resists scratching.

* Chemical Resistance.

Acrylic is not as chemically resistant as glass. Many glass cleaners cannot be used to clean acrylic sheet. If this is a concern, then specify ACRYLITE® AR
Abrasion Resistant Sheet. This revolutionary acrylic sheet has a "glass-like" coating on one or both surfaces that resists many
chemicals. Standard glass cleaners can be used to clean the coated surfaces of ACRYLITE AR acrylic sheet.

* Flammability.

Acrylic is a combustible thermoplastic. Be sure to consider all applicable building code regulations before substituting acrylic for glass.

* Codes and Regulations.

CYRO's ACRYLITE acrylic sheet products have been tested for compliance with many codes and regulations. A few of these are listed below. Exact compliance may vary
with product type and thickness. Check with CYRO's Technical Service Department for details

BOCA Evaluation Services., Research Report #96-75
SBCCI PST & ESI Evaluation Report #95112B
ICBO Evaluation Services, Inc., Evaluation Report #3715 - CC2
* City of Los Angeles, Research Report #RR 24392
* NY City MEA #144-80-M or 145-80-M
* Wisconsin Material Approval Report #950043-L
* ANSI Z 97.1 for Safety Glazing Materials used in Buildings
* Federal Motor Vehicle Standard 2-5, Safety Glazing (FMVSS205)
* ANSI Z26.1, AS-4, 5, 6 & 7 for Safety Glazing Material for
Glazing Motor Vehicles and Motor Vehicle Equipment Operating on Land and Highway
* Federal Motor Vehicle Standard 302 for Flammability of Interior Materials
* Underwriters Laboratories Recognized Component, File #E54671
* Underwriters Laboratories Flammability Rating: 94HB in all thicknesses
* ACRYLITE GP 1.25" sheet is UL listed (UL752) as a Bullet Resistant Glazing Material, Level 1

Monday, March 23, 2009

Plastic Thermal Expansion & Contraction

So, today I spent some quality time at a potential customer's factory. They would like to replace some plastic and metal panels with higher performing plastic sheet material. They have a great business and a line of great products that are designed to be used on pickup trucks. You can imagine that the temperature extremes the product encounters are extreme - potentially from -50F to well over 130F (surface temp of the plastic could be 175F).

Everything that exists has a "coefficient of thermal expansion". Materials like glass have a very low rate - metals have a larger rate - and plastics have many different rates.

The application is a 3 ply laminate of plastic, metal, and EPS foam. All three materials expand and contract at different rates. That said, over the length of the pickup truck bed, which can be 8ft, materials can grow and shrink from 1/8" to 1/4". The fact is, even a change of 1/32" can deform a panel in a frame.

It looks like from initial discussion that a thermoset plastic, such as FRP, or fiberglass reinforced plastic, will not only reduce the amount of movement, but offer a higher impact resistance and make for a heavier duty product.

The point is: when you are using Plastics in an environment with large temperature swings, you will have a plastic part that will grow, and shrink, with the the temperature changes. Some typical coefficients of thermal expansion can be found on and a cool chart to figure this at You can see that Plexiglas move about 10 times more than glass. For a list of a range of materials, check this link.

Friday, March 20, 2009

Plexiglass sheets - sheet sizes to please everyone

Plexiglass (Plexiglas) comes in a wide variety of sheet sizes. Like a lot of materials, when you purchase the REAL stuff - there is a difference. Forget everything you saw at the big box home stores. You know, the film masked stuff jammed in a few slots in between the fence posts and bags of cement. Oh - you need it cut?

Plexiglas sheet (and other brands) are made from a machine that is over 8ft wide. They can run any length (until they run out of room) as a sheet. You can also get a ROLL of Plexiglas in certain thicknesses (not for the casual user). But the fact is: you can get Clear Plexiglass sheet in 4x8, 5x8, 6x8, 4x10, 4x12, 6x10 and so forth. Keep in mind - you might need several people to pick the sheet up! But a quality Plexiglas Distributor should have this available AND be able to trim the sheet to the final size you need.

Big is not always better - these really large sheets have specific applications. And the shipping cost to bring it to you is pricey - not every truck on the road can handle the largest sheets.

Most people will find the 48"x96" and 72"x96" sheet sizes to give the best yields for cutting. But if your company has an odd size and needs a LOT of them (say 2000 lbs or more), you qualify for custom run to size programs to eliminate waste. Pretty cool.

What about thickness? Is it really metric? Yes. While the width and length are in INCHES, the thickness is actually made in MILLIMETERS. Here's a little cross reference:

Inches mm fraction
0.060 1.5 1/16
0.080 2.0
0.118 3.0 1/8
0.177 4.5 3/16
0.220 5.5 1/4 (what you find as 1/4" at most shops)
0.236 6.0 1/4
0.354 9.0 3/8
0.472 12.0 1/2
0.708 18.0 3/4
0.940 25.0 1.0"

Wednesday, March 18, 2009

Repairing a Crack in Plexiglass

Your Plexiglas is cracking.

You're thinking... hey, it's the Plastic Genius, there must be a solution to this! Well, there is and here's the basic idea.

1. Stop the crack NOW. You do this by drilling a teeny hole at the end of the crack. Teeny will be defined as the smallest drill bit you have laying around. From 1/16" to 1/8" will work fine. You don't need the special Plexiglas drill bit for this one since the Plexiglas is already cracked. (otherwise, you really DO need those bits for NEW holes).

2. The hole drilled at the end of the crack will STOP the crack from propagating any further. Depending on the severity of the crack, this might be all you need. I had a patio table top that cracked in 2000 when the wind blew over the table and the umbrella pole jammed the hole. I had a 3 inch crack. Drilled a 1/8" hole in it. With a metal drill bit. I finally replaced the top last summer in 2008. Not because I wanted to, but I was getting grief from my wife about having a plastics company and I really had no excuses left - 8 years was a solid test of my fix.

3. Filling in the crack. This is tricky AND you may have some success if this is a display case, window, or other stationary object. The water thin adhesives such as WeldOn #4 will "wick" into the crack by capillary action, and probably spill out around the crack (wipe off with Kleenex quickly). I generally do not recommend. If there is vibration (like a camper window) it will open up again - but the crack will not get longer.

4. Airplanes, gliders, and other aerospace cracking. Drill a hole. Normally, the plexiglass acrylic used in plane windows and windshields is different than the plexiglass used in displays and windows. It's chemical resistant and the regular #4 glue won't work. It may or may not be "stretched" or "pre-shrunk" acrylic. I don't know FAA regs, but I doubt slapping on a strip over the hole will pass inspection. However, that said, you "could" do that by using another glue such as WeldOn #16 or better, WeldOn #40 and a small piece of CAST plexiglass sheet (not extruded).

5. Preventing Cracks. Most cracks propagate from holes or from edges that have not been smoothed after cutting. When you get plexiglass from a "real" dealer (not HD or Lowes) they have the equipment to cut sheet correctly. When you DIY, you might have some chips from your cutting. That's OK - just sand down the chips with 80-100 grit sandpaper. Trust me on this - it makes ALL the difference in the impact resistance of the final piece. BTW, the same goes with polycarbonate (Lexan) - it is also "notch sensitive" (like glass too) and WILL break at the chip. Now a lot of cracks come from the HOLE that was drilled. First - make sure you use a Plexiglas drill bit (the head is reshaped to a 60 degree angle and carves through - metal bits punch out the backside of the plexi and cause chipping). Second - make sure the hole is BIGGER than the screw or bolt. Why? The expansion and contraction of the plexiglass will put stress on the hole. Overstressing causes cracking. This can also happen in a window where something impacts against it - and Boom, there's a crack in your sheet. According to Cyro Industries (Evonik): When drilling holes to support sheet by point fastening, there are two rules that apply. First, the bolt hole diameter should be at least 2 times the diameter of the bolt. This allows for adequate clearance for thermal and moisture expansion and contraction. Second, the distance from the hole center to the edge of the sheet should be at least 1.5 times the diameter of the drilled hole. Please see the picture below for a detailed diagram.

6. Preventing Cracks - Part 2 - while we are on the discussion of holes, try NOT to countersink. Countersinking basically STOPS the ability of the sheet to move. This causes cracking. It is always best to drill a hole slightly larger than the bolt or pan-headed screw and use a washer to disperse the energy of an impact. That said, NEVER tighten a bolt or screw "all the way". Hand tighten and then back off 1/4 turn. This allows for expansion and contraction too.

Attention Boat Owners: I know, you have to countersink that 1/2" thick hatch cover with screws every 5". But the difference is you are also using a flexible sealant underneath, and impact is usually in the form of a wave which spreads the energy. Don't forget to back off 1/4 turn though.

Tuesday, March 17, 2009

Plexiglass sheet - my clear Plexiglas blog

Plexiglass. Crystal clear acrylic PMMA sheet.
It's a beautiful thing when you take a sheet of acrylic, cut it, polish the edges and peel the paper off. It's light - half the weight of glass. It's friendly. Glass breaks into a gazillion pieces. Plexiglas breaks into a few dull edged chunks - if it does break at all. I feel safe near Plexiglas. I am scared of all glass. Except maybe a wine glass.

Clear Plexiglass sheet is made in 2 basic ways.

1. The original process, and still used today, is the cell casting method. I think it's a classic way of making acrylic, much less any material. A chemist mixes all the right chemicals in a large pot and pours the liquid between 2 sheets of glass. The production team must keep the sheets evenly spaced - whether the casting is vertical or horizontal. This casting is then placed in an autoclave and cooked for a couple of days. If all went right, the sheets of glass are separated and a sheet of acrylic is removed. The gasket used to seal in the liquid between the sheets still surrounds the finished sheet - which is cast larger than the final dimension required. (a 48x96 might start out as a 52x102 sheet and then trimmed down). The gasket is trimmed (except on the largest sheets like 72x120 to protect the edges) and the sheet is masked with a heavy paper or polyethylene film. Cell Casting produces a sheet with the highest molecular weight - making it more chemical resistant and a bit harder surface than extruded acrylic sheet. Due to the method of casting, there are wider tolerances on the thickness throughout the sheet. The middle of the sheet is typically thinner than the edges by up to 15%. In most applications, this is not an issue. Textures are created in the cell cast method by using glass sheet with that texture. Different thicknesses of acrylic are cast by changing out the gaskets. Of course, as the sheets get thicker, it takes specialized equipment to handle the weight of these sheets. Sheets up to 4" thick are regularly made here in the USA. Castings of acrylic even thicker are made by special order.

2. The most efficient manufacturing processes, and most common, is extrusion of Plexiglas sheet. You need a pretty big "room" to do this right. At one end will be a silo of dry acrylic pellets about the size of rabbit food. At the other end is a traveling cutoff saw and stack of pallets. What happens in between is proprietary to each manufacturer - but goes something like this: after the pellets leave the silo they enter a pipe with a large heated screw that turns the solid pellets into liquid acrylic. This pipe may be up to 10-12 inches in diameter. It passes through several filters to remove particulates in the resin and dumps out into a series of highly polished metal rollers where the liquid is spread from side to side - creating a waterfall of liquid acrylic sheet. This ribbon of plexiglass sheet winds it way in, out, and around 4-6 rollers before it cools enough to head horizontally down the final stretch toward the saw. The rollers are temperature controlled to cool the acrylic. The rollers play a very important part in the extrusion process. Highly polished rollers produce crystal clear sheet. A roller with a texture can produce non-glare sheet, textures for patio tables, or frosty textures. With the latest equipment, plexiglass acrylic sheet can be extruded up to 1" thick (which is really 25mm or .940"). Extruded sheet has a lower molecular weight as a function of the manufacturing process.

OK - now that you know all this fascinating data... why should you care? It depends. Since the predominant material out there is extruded acrylic sheet, it is perfectly fine to use with 98% of the applications out there - windows, machine guards, display cases, brochure holders, cages, trays, etc. You MUST use cell cast sheet wherever there will be continual stress on sheet. Like say, an aquarium or vacuum chamber. Experienced plexiglas fabricators know this and it's not a choice - that's what they will use. Remember - higher molecular weight plastic materials always perform better than their extruded counterparts.

General Purpose extruded grades: Plexiglas MC from Arkema, Acrylite FF from Evonik (Degussa), Optix from Plaskolite, Lucite CP from Plaskolite

General Purpose cell cast grades: Plexiglas G from Arkema, Acrylite GP from Evonik, Polycast GP from Spartech

Interesting formulas you might be interested in:

Acrylic is a derivative of natural gas: see chart below.

(Natural Gas)-->>(Propane) -->>(Propylene)-->>(Isopropyl Alcohol) -->>(Acetone)

+ hydrogen cyanide -->>(Acetone Cyanohydrin)

+ sulfuric acid -->>(Methacrylamide)

+ methanol -->>(Methyl Methacrylate)-->> (Acrylic Plastic) Plexiglas, Lucite, Acrylite

Monday, March 16, 2009

UHMW Polyethylene - the Slickest Plastic of the Bunch

I remember when UHMW was introduced to the market - Ultra High Molecular Weight Polyethylene was supposed to replace Teflon in every "wear" application. It was supposed to last longer. The scientists had no idea what they had created and what an industry would be spawned. The first UHMW was called Pactene and was green. It's naturally white, but some marketing guru decided that if they made it green, and trademarked it, everyone else would have to sell white to compete. That was a pretty smart guy. Turns out UHMW has allowed many industries to be much more efficient in their production. Funny thing is... UHMW doesn't wear out very fast and after it was first introduced and all that Teflon was replaced, sales of UHMW fell. Until we all thought of some more places it could be used.

Keep in mind, UHMW does not glue to itself. Or to anything. It's one of the group of plastics that are so chemical resistant that they don't bond with solvent adhesives. LDPE, HDPE, UHMW, Polypropylene, UHMW polyethylene.... so you have to mechanically fasten, or use contact cement or 2 sided tape to stick it down. There is a product out there called "Slick Strips" with adhesive already applied to the sheet for wear applications. Peel and Stick.

UHMW also has some amazing physical properties - with a density of 0.96 it could float, and can take extremely cold temperatures. Cryogenic.

UHMW is used around the world in 1000's of applications. It has the lowest coefficient of friction for a plastic. And it's extremely chemical resistant. That means that metal chains can rumble over a wear guide of UHMW without wearing down. In the mining industries, gravel and ore can travel over UHMW plates easily (insteadof metal which will either wear or decompose - or both). In the marine industry, dock bumpers are made from thick UHMW so boats from dinghies to aircraft carriers can bump against the docks. My first use was a wear plate under the mast of my Hobie Cat to replace the Teflon disc that came with it. I made a toboggan for my kids by heating and wrapping the front end. That thing was out of control. Literally. Why do we love sliding on snow so much? To get on AFV? I digress. Now there are special formulations for specific industries - even formulas to make it even slicker! More on that below...

Know your UHMW! Here's a legend to some of the formulas:
Virgin UHMW Polyethylene - this means you are getting the original resin in your sheet. It can be made 2 ways: Extruded (most common) and Compression Molded (less common). Extruded will always be cheaper and has a lower molecular weight. For most applications, it's fine. Compression Molding offers a sheet that has far less internal stress from production and a modestly higher molecular weight. If you need to do a LOT of machining to the sheet, ask for compression molded UHMW. It is worth the investment.
Reprocessed UHMW Polyethylene - this is the most common form and the least expensive. The low bidder is usually quoting this. If it is white, then only white scraps are ground and added to the extrusion. This is OK for many applications - like bumpers or other plates that get hit, bumped and scuffed. If the repro UHMW is black, then there is typically a mix of scraps in the formula. Not recommended for a wear application.
Exotic UHMW Formulas - OK, maybe not exotic, but there are a lot of formulas available that will perform in a superior way for your application. Specific grades are made for very specific applications. Not only is the density a variable, but the molecular weight is a variable. There are fills with silicone, oil, fiberglass and mysterious proprietary additives the manufacturers guard like the Coke recipe that change the physical properties - and that may make the particular formula work better or worse for your application. ASK questions and make sure you get a spec sheet from the company - so you get what you asked for. The best plastic companies will ask you lots of questions about your application and exactly what you are trying to achieve by using UHMW.

Parting thought: I have seen customers try to use HDPE instead of UHMW. It may come from the same family, but everything is different about the 2 plastics. They cut and machine differently. The form different. They have completely different properties and pricing. As they say - you get what you pay for. While the short term performance of HDPE might seem like a cost savings, long term detriments will more than cancel out the savings - and if you have a brand to protect, try to remember how hard you worked to build the brand....

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.

Saturday, March 14, 2009

Welcome to my blog - the Plastic Genius

Plastic genius. My company mantra is "When Others Can't - We Can." We're not primadonnas - we are life long learners and we have answers to your questions - solutions to your requirements. My family entered plastics distribution and fabrication in 1968. Did Dad listen to the guy in "The Graduate"? You know the line "Just One Word -are you listening? PLASTICS." I was barely a teen, and excited that I had access to a shop-full of tools and Plexiglass, Lexan, fiberglass, resin, Micarta, foam, architectural and engineering plastics. Dad always encouraged experimentation on the shop floor, in marketing, and in building a business.

41 years later you'd think I had seen it all, but that's not true - I am still learning and still working with customers on new applications in a new millennium. So I decided to blog. About plastics. All kinds of plastic sheet, rod, and shaped materials. A brain dump of what I know, tell some stories, and upload postings of new materials as they become available in the market.

Since we are all so wired and connected via the web - it's my sincere hope that one of your searches for plastic will parse through this blog - and you'll either get your answer or get pointed to a site I know that has your answer. Yes - I have a plastics company but this is not a shameless blog to get your business. If you find that my company can help you - great! The internet is full of paths to multiple answers. Of course, I would hope that a conversation with my team at is more rewarding to you and your company.

So here we go!