On various odd jobs around the car, inside and out, what are the things to consider when choosing the best glue and material to use – contact glue, epoxy glue, super glue, filler paste, fibreglass kits, duct tape, gun gum, wire, string, welding, or what? Stuck.
There are as many different answers as there are different jobs. Cars are made mostly of metal, but also plastic, rubber, fabric, glass, wood, etc. Some things are rigid, others are flexible. Some are static, others move under load.
Some repairs are face-to-face, others span a gap or fill a hollow. Some cover an extensive area, others are tiny, fiddly and preferably invisible.
The shape and size of the repair is sometimes unimportant, but in other instances vital. Some components live at “room temperature”, others have to cope with temperatures at least twice as high as boiling water. Some are in sheltered locations, others are exposed to sun, rain, and a maelstrom of grit.
Many of the repair materials are multi-purpose, but none of them are all-purpose. There are situations where a combination of several of them is the best solution, and other instances where none of them will do an adequate or reliable job.
So, you have to match the properties of the repair material to the requirements of the result you seek.
Contact Adhesives are quick, simple, relatively inexpensive and very multi-purpose. They remain flexible even when they have “dried” but cannot be formed or shaped.
They work best in face-to-face joints, but have limited strength if pushed, pulled or twisted. Because they stick “on contact” between two workpieces, there is little scope for last-second adjustment.
So, good for most things that need to bend (e.g. fabrics) or have a large contact area, but not good as fillers or load-bearers.
Epoxy Adhesives require mixing a resin and a hardener. They are much stronger, allow adjustment time while they chemically “cure” (they don’t need air to “dry”, but get warm as they set), they can be applied in thicker layers and shaped while still soft and/or by filing after they have hardened, they tolerate fairly high temperatures, can fill gaps and sustain some load over a short span, but are not flexible and over time (especially if exposed to sunlight) can get brittle or flake off the non-absorbent surfaces they are applied to.
The surface must be at least micro-scratch roughened to achieve a viable bond, especially with anything very smooth, including plastics. Epoxy glue can be readily reinforced/mixed with things like string, plaster-board tape, wire etc.
Super Glue adheres very firmly and rapidly to most things (including your fingers!) but it has no mechanical bulk strength of its own beyond its super stickiness. Great for “invisible” repairs, strictly surface to surface where there is no flex and minimal load.
If you need to use them as a “bridge” or a “patch” they can be quite versatile if used in combination with a reinforcing material.
You can patch a slit in a rubber grease boot (half-shafts, steering) or fibre-reinforced hose by scratching the rubber surface either side of the cut, sprinkling sandy soil over it, and drenching that with a few drops of superglue.
Or you can use something like the fibre of a cigarette filter to bridge a gap and drench that in the same way. Superglue makes some fibres hot enough to smoulder (!) but in a few seconds the filter is as hard and strong as a wooden peg.
