When making complicated shapes or constructing large objects, it’s necessary to join two pieces of acrylic together, or join acrylic with plastic, glass and wood. Different kinds of adhesives work for different situations and materials.
Before gluing any plastics, care should be taken to make the edges as smooth and flat as possible. Fine sandpaper is good for this. Then, both edges should be wiped with isopropyl alcohol in order to remove any fragments of dust or dirt. Even the oil from your skin can interfere with the process and cause a bad join.
If you are using solvents, be sure to work in a well-ventilated space.
Acrylics are not actually glued: they are chemically ‘welded’ together using a special cement. Acrylic cement does not stick the surfaces to one another – instead, it bonds them permanently.
Tensol 12 is a single component cement, ideal for bonding cast acrylic pieces where strength isn’t so important. Because it’s viscous, it fills gaps well without running. This means Tensol 12 is good for hand-machined or sawed acrylic as it is more forgiving with rough edges. It’s also very straightforward to use because it doesn’t need to be mixed with anything before it can be applied, and it dries quickly too. Other thick cements suitable for imperfect edges include WeldOn 16 and Acryfix 192.
Tensol 70 is a water-thin catalyst cement which is well suited to larger pieces which need a stronger bond. It comes in two parts and must be mixed before being applied to the acrylic, then squirted between them with a fine syringe. The surfaces to be joined must be very smooth to allow the cement to flow evenly between them. Once all the cement is in place, pressure is applied to bond the two edges together.
Tensol 70 is completely clear in colour and will evaporate when dry, so don’t attempt to wipe away any spills or leaks. When applying the cement, use a syringe without a rubber plunger as the solvent can cause rubber to degrade.
WeldOn 40 is a two-part product which is mixed and used to bond acrylic and PVC together. It can also be used to bond acrylic with wood. Clear PVC cement can be used to bond acrylic with plastic in some cases, although it is not as strong.
Bostik Titan Bond Plus is great for bonding glass pieces with acrylic. Silicone adhesives can be used in some cases, but again, they are not as strong and may not be watertight.
Polypropylene, ABS, HIPS and PETG plastics can be bonded to acrylic using a solvent or thermoplastic adhesive such as Acri-Bond 120. Delrin (a type of Nylon) and Acetal can be bonded with acrylic using Loctite Epoxy or Bondit. However, the joins will generally be weaker than with other types of plastic.
Never use superglue to bond two pieces of acrylic: the chemicals in the glue can cause the acrylic to turn white.