Plastic Trim, Repairs, Plastic Welding

[<mail@xxxxxxxxxxxx>]

Resending this.  The original did not make it through the list process, 
apparently.
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Ralph Ausmann  -  Hillsboro, OR - > <ralph.ausmann@xxxxxxxxx>

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I came across this company in an article some time back and here they have a
web site now.  It loks like they have a system useful system for 
restorations.

http://www.northwestpolymers.ca/welders.html

I will paste that article on below also.  It may have some ideas for your
projects.

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(Taken from Farm and Country March 15, 1999)
UNDER THE HOOD

By Keith Berglind

When duct tape doesn't cut it...

A plastic Welding Primer

I can suggest taking a quick inventory of all the plastic parts on your farm 
machinery, but I bet it'll take a while. No doubt you'll find plastic 
tractor hoods and fenders, plastic water and chemical tanks on the sprayers, 
plastic fuel tanks, plastic grain hoppers and a lot of plastic pipes and 
lines.

And I'll bet another thing - duct tape isn't the permanent repair you're 
looking for to fix damage to these items. Most of us learned metal welding 
watching dad on the farm. As an adult, I found it tough to figure out how to 
repair plastic pieces, let alone try to build anything with sheets of 
plastic. There are just too many kinds of plastic in use.

Like most people, I started using the crazy-glue type chemicals to fix 
plastic pieces. At best I fixed a few kids' toys. Nothing lasted, if it 
stuck at all. I was always looking for something better. And, being busy in 
business all these years, I didn't have time to take a proper plastic 
welding program.

I won't bore you with tales of my failures trying to weld plastic with large 
hot air guns, small hot air guns, propane torches, soldering guns, fluxes 
and strange plastic welding rods. These all work - to some degree and in 
some special cases - but they're not for the average farm repair shop. 
Here's what does work and what you need to know.


The basics

There are three elements to a plastic weld repair:

 * Knowing what kind or type of plastic you're about to weld
 * Having the correct plastic welding rod or wire
 * Having the best plastic-weld tool (welder)
For example, if you identify that the plastic fender from your four-wheeler 
is ABS plastic, and you select the ABS welding rod, then when you heat the 
fender and feed the ABS welding rod through the welder you will have a 
secure repair. ABS is a thermoplastic that may be heated and reshaped with 
heat. It's hard to do it wrong if these three steps come together at the 
same time in a welded repair.

However, if the fender is thermoset-plastic (which cannot be softened and 
reshaped with heat, or heat-welded) then you will need to select the correct 
external bond/patch repair method to glue it together, or bond a fiberglass 
reinforcement strip over the break to form a secure repair.


Identifying the plastic

The first step is to identify the general group or chemical range the broken 
part falls into. There are several common tests for type of plastic. The 
Society of Plastics Industry of Canada recommends this sequence of tests:

 1) Check appearance and texture
 2) Check density
 3) Perform flame test
 4) Check melting temperature in oven
 5) Perform solubility test
 6) Send to test lab for analysis
These steps may seem complicated, so let's take a few short cuts.  An easy 
step is to look for two or three letters embossed on the back of the part. 
You may see the letters ABS, PP or PE or something similar. These are the 
common and easy-to-weld plastics.

With some practice under your belt, you may want to try a burn or flame 
test. Take a slice or hidden part of the piece and burn it with a small open 
flame. Start a note-book of your observations. For example, if you have a 
small plastic part kicking around, and it says PP or ABS on the back, when 
you burn a sample of this note the colour of the flame, colour of the smoke 
(if it smokes), whether it burns alone, drips, if the drips burn, and what 
is the smell of the burning.

Here are some observations I've made:

 * PE (polyethylene) burns with no smoke, smells "waxy" and has bluish 
flame
 * PP (polypropylene) burns with no smoke, smells acrid and has orange 
flame
 * PVC (polyvinyl chloride) will not burn when flame is removed
 * TPU (polyurethane) burns with black smoke and a "sputtery flame"
 * ABS (acrylonitrile butadiene styrene) has very carbon-like or sooty 
smoke that smells slightly sweet

You probably recognize ABS, PVC and PP as letters on common plastic piping. 
This is a great way to practise, as the plastic identification is very 
obvious. Practice by burning and welding some cheap ABS sewer pipe. Be sure 
to write down what you see.    Northwest Polymers' Robert Decloedt - 
designer and builder of the welder I use - usually tells me to try a sample 
test weld on an out-of-the-way section.

For example, if you try a PP welding rod on ABS, once the weld cools it will 
pull off easily with pliers. I have had a couple of repairs that I couldn't 
identify, so I tried several pieces of welding rod until one stuck 
perfectly.


Test strips

When I first got serious about welding plastic, I wanted some "official" 
tests that I could rely on. After a little research I discovered the Society 
of Plastics Industry of Canada (905) 678-7748. I bought one of their plastic 
identification kits (about $50), which included a booklet with charts on 
identifying plastics and a set of 12 labeled six-inch long plastic strips. 
These are for test burning. When I'm not sure what burning ABS looks like, I 
select the ABS strip and burn the end a bit. Very little is lost each time.


Welder kit

The plastic welder I use is manufactured and distributed by Northwest 
Polymers Inc. The basic kit includes a variable temperature hot-tip welder, 
a large selection of the various plastic welding wires or rods and several 
chemical adhesive repair compounds. NWP has been supplying these products to 
auto body shops and bumper repair shops for years.

In the meantime, for information on the plastic welder, you can contact 
Northwest at 1-800-361-3002. Next column, I'll demonstrate, in detail, how 
to use this tool.

 Keith Berglind is a licensed heavy-duty mechanic and all-round fix-it 
expert
 © copyright 1999 Agricultural Publishing Company Limited.
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