Q. There's a crack in my plastics! What do I do?
Q. There were plastics in 1914?
Has Ridout Plastics really been in the plastics business since 1914? Do you
remember the little plastic numbers and letters on grocery shelves (that you used to
switch around)? Originally founded as the Rench Company in downtown San Diego in 1914,
that's how we got our start. In fact, the owner's grandfather and father used
to buy their store supplies from the Rench company in the 1930's! But, for a nice and
informative overview of plastics, specifically, Plexiglas (acrylic), click
here for the
Plexiglas Primer!
Q. What about Speeds, Feeds, and Needs?
Ridout Plastics has a library of the proper machining variables you need for
cutting, machining, drilling, etc. of all plastics. The single biggest problem is the
wrong tool for the wrong job. Email us your request for the type of material and what you need
and we will respond quickly by phone or fax! When in doubt, do not call Tim Taylor
and do not rewire it.....
Q. What are the Working Temperatures of Plastics?
The correct definition for the "working" temperature of a plastic is how hot it can become and still function normally.
Most plastics can go -40 F and retain their physical properties without becoming overly
brittle (except flexible vinyl convertible windows). There are special cryogenic grades
of plastic(G10,UHMWPE) that will go below -400 F ! For the most part, most
plastics will soften or lose their structural properties around 200 F. The
chart below list a few of the most popular plastics and their maximum continuous working
temperatures:
Acrylic 180 F Polycarbonate 240 F Styrene 150 F
ABS 175 F Nylon 220 F Acetal 220 F
Noryl 265 F PEEK 480 F UHMWPE 160 F
Canvas Phenolic 250 F Linen Phenolic 250 F PTFE 500 F
G10 Epoxy/Glass 300 F G7 Silicon/Glas 480 F
Q. Can I Glue Plastic?
One of the really great properties of some plastics are their resistance to
chemicals. Plastics that can be dissolved by a chemical are generally glueable, while
those that are not dissolved, cannot be glued.
A quick test you can do at home: Find some nail-polish remover (acetone) and
test a very small area on the plastic you would like to glue. If it gets sticky, then
Ridout Plastics has a solvent adhesive that will work! If the acetone simply dries up, you have a
problem. Your choices will be: mechanically fasten the plastic, ultra-sonic welding, or
hot-air welding. Most chemical tanks are made of polypropylene or polyethylene and will not
glue. PVC and ABS will glue (like your sprinkler pipes). Engineering plastics for the
most part cannot be glued with adhesive, unless a contact adhesive is acceptable for your
application. Please talk to our sales people about our Adhesive Cross-Reference
chart that will help you select the right adhesive for your application!
Q. Is 1/4" Plastic Really 1/4" Thick?
Depends on what kind of plastic you buy. Most engineering plastics (Nylon,
Delrin, PTFE, etc.)are sold "thick" - standard tolerances are -0.0", +5% because the
machinist needs the extra material for exactness. This is also true of the rod
and tube in these grades. However, there are many plastics that are sold in metric
thicknesses with english width and length! Yikes!
Acrylic, such as Plexiglas, is sold this way. The table below should help you
be more informed about what you are getting. Please be aware that some plastic
companies in the U.S. may substitute .098" for .118" and .220" for .236". If you receive a
price quote substantially lower than ours, you may want to measure the sheet they
are selling...
1/10" = .098" 1/4" = .236" 3/4" = .708"
1/8" = .118" 3/8" = .354" 1" = .944"
3/16" = .177" 1/2" = .472"
7/32" = .220" (looks like 1/4"!)
Q. Does acrylic (Plexiglas, Lucite) yellow in the sun?
Since the beginning of the creation of plastics, many myths have been
perpetuated about the longevity of plastics, especially outside in the elements. All
plastics come from petroleum and natural gas. Sunlight, especially ultraviolet radiation, has
a disastrous effect on most plastics. Some plastics, like polyethylene (PE) milk
jugs, degrade quickly in the sun - in a matter of months. PE can easily be recycled.
Many children's toys are made from PE and get brittle and crack when left outside.
Acrylic (Plexiglas, Lucite,and Acrylite) comes from natural gas and is
completely inert when in solid form. American-made acrylic does NOT yellow in the sunlight.
Witness the protective canopies and bubbles in the World War II bombers - they are
still clear after 50 years in the sun! There are three other clear plastics that do yellow
in the sun and get confused with acrylic - Styrene, PETG, and Polycarbonate. They have
their respective qualities that make this an acceptable trade-off. Ask your Ridout
Plastics salesperson for information on all of these plastic solutions.
Q. What about Expansion & Contraction of Plexiglas?
Thermal Expansion and Contraction - All materials expand and contract to a
greater or lesser degree due to changes in temperature and humidity. Allowances must be
made for these changes in the construction and fabrication of products; for example, the
expansion joints in cement sidewalks and on steel bridges. Acrylic sheet is subject to
greater dimensional change, due to thermal expansion and contraction, than other
materials with which it is used in construction.
Comparison of Co-Efficient of Thermal Expansion
Acrylic Sheet vs. Other Materials
Inches/Inch/F
Acrylic Sheet .0000410
Aluminum .0000129
Plate Glass .0000050
For indoor applications where temperature normally remain the same (+/- 20
degrees F), acrylic sheet does not generally require special considerations for expansion
and contraction other than providing for a snug rather than tight fit since its
movement is approximately .00984" per foot length for each 20 degrees of
temperature change.
Degree of Size of Temperature Change for Plexiglas
10 15 20 30 40 50 60
12" 1/16 1/16 1/16 1/16 1/16 1/8 1/8
24" 1/16 1/16 1/16 1/16 1/8 1/8 1/8
36" 1/16 1/16 1/16 3/8 1/8 3/16 1/4
48" 1/16 1/16 1/8 1/8 3/16 1/4 1/4
60" 1/16 1/16 1/8 1/8 1/4 1/4 3/8
72" 1/16 1/8 1/8 1/8 1/4 5/16 3/8
84" 1/8 1/8 3/16 3/16 5/16 5/16 1/2
96" 1/8 1/8 3/16 1/4 5/16 3/8 1/2
Q. Help....My Plastic Is Scratched!!?
When your beautiful piece of Lucite acrylic scratches, you can fix it quickly!
If you can't feel the scratch with your fingernail, then Novus#2 or #3 should restore
the finish. Otherwise, you will need to sand and buff the area that is scratched to
return the shine (see next paragraph). It's the same way we polish the edges of thick pieces
of acrylic here at Ridout Plastics - it works! This procedure ONLY works on acrylic. It
does not work on styrene (like the colored boxes we sell) or on polycarbonate (Lexan,
Tuffak, Cyrolon). They both look clear, but they cannot be restored. Ask about our
Abrasion Resistant coatings...
Solution: Sand the affected area with 400 Wet/Dry, then 600 Wet/Dry. Use a
buffing wheel on your drill with the Plastic Buffing Compound or White Diamond as Rouge is too fine, to restore the shine. Let
the compound do the work - do not press hard or you will "burn" the compound into
the plastic. Ask a salesperson to show you the helpful products on our shelves.
Q. What adhesives work with Plastics?
One of the really great properties of some plastics are their resistance to
chemicals. Plastics that can be dissolved by a chemical are generally glueable, while
those that are not dissolved cannot be glued.
A quick test you can do at home: Find some nail-polish remover (acetone) and
test a very small area on the plastic you would like to glue. If it gets sticky, then
Ridout Plastics has a solvent adhesive that will work! If the acetone simply dries up,
you have a problem. Your choices will be: mechanically fasten the plastic, ultra-sonic
welding, or hot-air welding. Most chemical tanks are made of polypropylene or
polyethylene and will not glue. PVC and ABS will glue (like your sprinkler pipes).
Engineering plastics for the most part cannot be glued with adhesive, unless a contact
adhesive is acceptable for your application.
Please talk to our sales people about our Adhesive Cross-Reference chart that
will help you select the right adhesive for your application!
Q. Hey - This Sticker Won't Come Off My Plastic!?
Don't you just hate it when those price tags don't come off a plastic item?
The problem is that the adhesive either dries out or the wrong kind of adhesive on the
price tag was used.. In any case, you need to find a way to get the darn thing off your
plastic!
Solution:
The simple way to lift a "tight" sticker off of plastic is by moistening the
price tag with Lighter Fluid - which is actually a very refined grade of kerosene! This will
not bother
Acrylic, Styrene or Polycarbonate plastics which will be 90% of the types you
will be dealing with. If in doubt, test the fluid on a small part of the plastic. Look
at it in 24 hrs. OK? Remember that you could scratch the plastic when rubbing the
price tag loose. Easy does it....
Q. I am worried about Junior falling through railing!?
One of most appealing plastic solutions around the home is the installation of
Plexiglas or Lucite along railings and fences to prevent small children and pets from
passing through the railing uprights. Remember, Plexiglas is 50% lighter than glass of
equal thickness. In 1/8" thickness, it is 17 times stronger. If Plexiglas breaks, you
will find only large, rather blunt pieces that you can handle with your bare hands. You
will not find shards of material scattered like a mine field!
Installation of Plexiglas is incredibly simple. Using a special drill bit, you
can drill small holes on either side of the railing in strategic places and use plastic cable
ties. If you are renting, or simply don't want a permanent installation - it's quick and
effective.
Q. Are The Edges of Your Plexiglas Too Sharp?
Our saws and routers leave nice chip-free edges on the pieces of Plexiglas we
cut. They can be quite sharp if the edge will be exposed to the touch. While this
edge is not sharp like glass, if you run your hand down the edge quickly, and with
pressure, you may get a "paper-cut" type of injury.
Solution : Use 100 grit sandpaper and a
sanding block. Just pass the sandpaper over the edges at a 45 angle a few
times. Use your fingers to test the edge. When it feels good, stop!
Q. There's a crack in my plastics! What do I do?
There is nothing more frustrating than a crack in a piece of Plexiglas or
Lexan. Both of these materials are "notch sensitive". By the way, so is glass! That's why you
can scribe and break glass (and Plexiglas) along the scribe. These materials have
no grain and therefore cracks can travel as they please.
However, cracks can be stopped with a simple procedure. Using a very small
drill bit, 1/16" or so, drill a hole through the material at the end of the crack. That's
it. If it is a long crack, you might be able to inject some IPS WeldOn #3 (methylene chloride)
into the crack to partially seal it. If the plastic is on a sign, and therefore most
likely opaque, you should glue a 1" strip of 3/16" Plexiglas to the back side to
reinforce the cracked area.
