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Author Topic: The right glue for the right job!  (Read 7030 times)
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« on: May 20, 2011, 06:26:28 AM »

This write-up is courtesy of MillenniumFalsehood, a member of the community.

"Here's my personal guide for different glues and their uses:

CA has great tensile and compression strength, but poor sheer strength. Use it in low-load conditions, such as attaching photoetch to the surface of a model. If you make a mistake, don't panic. Simply freeze it overnight and then, with a dull eXacto, work it loose and pop the part free. Avoid superglue de-bonder. It'll eat some types of plastic and softer styrenes.

Epoxy is the strongest, but it can be tricky to use and *must* be mixed thoroughly. Use in high-load conditions, such as the connection between the saucer and dorsal in a Federation ship. Unlike CA, you can't debond this stuff easily, unless the surface is unusually shiney. Luckily, you have plenty of time to realize your mistake, pull the components apart, and clean the bonding surfaces.

Welders, like Plastruct and Ambroid, are not glue. They melt the plastic and fuse it, so provided the joint isn't disturbed until the welder has evaporated and you got the welder all the way into the joint, the resulting bond will be as strong as the plastic the kit is made from. This is only true of styrene and ABS kits. Other substances will not be touched by the stuff, so if you need to bond dissimilar materials (wood-to-styrene, metal-to-styrene, etc.), use CA or epoxy.

White glue is a special case. It isn't that strong, but it has a quality about it that makes it ideal for gluing canopies and other clear plastics: it won't craze the plastic. Welders and CA are made from and will outgas harsh chemicals that will alter the physical properties of the plastic, making it opaque, and so are not suitable for gluing clear plastics. White glue however uses stickiness to bond materials, and it's perfectly non-toxic, so it's great for bonding canopies. You could theoretically use epoxy, but white glue is again better suited because you can clean it up without damaging the plastic and if you want to work on the cockpit again you can remove the glue with a little soapy water.

Something else: certain plastics, like polyethylene and polypropylene, CANNOT be glued by any means. This is no accident; they're designed to be chemically inert, so welders won't touch them and glues can't get a hold of them, even if you rough up the surface. These plastics are easy to identify. They typically have a waxy texture, and are often use in food packaging and plumbing. Avoid these plastics, but if you simply MUST have a part that's made from this stuff, cast it in resin first. Then use either CA or epoxy as usual."

"Of all the things I've lost in life, I miss my mind the most."
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