Choosing the right glue for the right plastic
It's important when gluing plastic onto anything to know what kind of plastic you're dealing with. If you get it wrong, in the most extreme cases, the glue can disolve the plastic rather than bond to it, but in normal use even, not identifying the type of plastic and matching that to the glue will need to bonds that rapidly come unstuck.
The key to getting this right is to:
- Find the plastic type logo on the thing you want to bond.
- Read the info sheet on the glue you want to use.
- Make sure it explicitly recommends it's use with that specific type of glue.
Finding the plastic logo
These are usually embossed into the plastic item at the time of manufacture. They look like a triangle with a number in it.
You may have to look around for it, but in most countries it's a legal requirement to have this standardised logo present on anything made predominantly of plastic.
The different types of plastic
- PET (Polyethylene Terephthalate)
- Mostly used in water bottles, soda/pop bottles and packaging. Generally a single use plastic.
- Glues to consider: Hot glue, super glue and foaming polyurethane.
- HDPE (High-Density Polyethylene)
- A stiffer plastic used in detergent bottles, oil bottles and most plastic toys.
- Glues to consider: Plastic cement, cyanoacrylates or epoxies.
- PVC (Polyvinyl Chloride)
- A flexible plastic used in the likes of cooking oil bottles.
- Glues to consider: cyanoacrylates or UV Curable adhesives.
- LDPE (Low-Density Polyethylene)
- A very low density sheet plastic used for example on dry-cleaning bags and shrink-wraps.
- Glues to consider: Plastic cement, cyanoacrylates or epoxies
- PP (Polypropylene)
- A heat-resistant plastic that's quite tough and gives a barrier to grease and chemicals. Mostly used in butter tubs and to seal in food.
- Glue to consider: hot melt glue that's made of polypropylene
- PS (Polystyrene)
- A very light-weight plastic used in disposable foam cups, clamshell food containers and the like.
- Glues to consider: PVA (white craft glue, wood glue), Hot glue.
- Other (BPA, Polycarbonate and LEXAN)
- A tough general use category. This is the sort of plastic used in baby bottles, car bumpers and water-cooler bottles. -= Glues to consider: Methyl Methacrylate (quite hard to find), Superglue, Epoxy, Polyurethane glue.