What is a good material to adhere plastic to plastic?

Plastic is a flexible material, but it can be difficult to repair. Many common adhesives don’t work well with it. That’s because plastics tend to have smooth surfaces. The lack of roughness and porosity makes it difficult for glues to adhere. Certain adhesives can even damage plastic.

However, there are some types of adhesives that are safe to use with plastic. Finding a good one is a matter of finding the right one for your needs.

Types of plastic

Many different types of plastic are used in commercial applications. Each one has its own distinct properties. The first thing you need to know is what plastic you are using. The easiest way to do so is to check the recycling number on the packaging. The number will appear inside a three arrows symbol.

1. PET (Polyethylene Terephthalate): used for water and soft drink bottles.
2. HDPE (High-Density Polyethylene): used for detergent bottles and plastic buckets.
3. PVC (Polyvinyl Chloride): used for toys and plastic pipes.
4. LDPE (Low-Density Polyethylene): used for squeezable bottles and furniture.
5. PP (Polypropylene): used for bottle caps, drinking straws and pill bottles.
6. PS (Polystyrene): used in model kits and to make disposable cups and cutlery.
7. Polycarbonate, BPA, and Other Plastics: used for some food containers.

Choosing the right glue to adhere plastic

Once you know the type of plastic, you need to choose a suitable adhesive. Category 1, 2, 4 and 5 plastics are the most difficult to adhere. Common adhesives will not work on them. You might need an adhesive specific for polyethylene or polypropylene.

1. PET: Certain cyanoacrylate glues can be used, in combination with a primer. However, some PET plastics might be impossible to bond.
2. HDPE: Use plastic cement, cyanoacrylates or epoxies. For hard plastics try Loctite Plastic Bonding System. It’s a two-part cyanoacrylate glue. It’s water-resistant, sets in seconds and dries clear.
3. PVC: Use plastic cement, cyanoacrylates or epoxies. Two-part primer and PVC solvent cement is commonly available.
4. LDPE: This category has low surface energy. Using glue is not recommended. You can try a glue for flexible plastics such as Loctite Vinyl, Fabric & Plastic Flexible Adhesive. You will probably need surface preparation.
5. PP: Like the one above, this category has low surface energy. The same indications apply. Look for an adhesive specific for polypropylene.
6. PS: Use epoxies or spray adhesives.
7. Other plastics: The best glue depends on the type of plastic. For polycarbonate, use an epoxy. Acrylic requires an acrylic solvent adhesive. Cyanoacrylates may also work.

Tips to adhere plastic

1. Clean the surface. Use soap or a plastic cleaner. You can also soak the plastic in isopropyl alcohol. Dry thoroughly before applying glue. 
2. Roughen the surface. This will improve adhesion. You can use sandpaper or steel wool. Two-part adhesives use an activator to roughen the surface.
3. Apply glue precisely. You can use a small paintbrush or the tip of a needle.
4. Seal pieces tightly. Use a clamp, tape, or elastics to hold parts together while glue dries. Check curing times: they can range from a few minutes up to 24 hours.
5. Cleanup. Remove any excess uncured glue or spillage immediately using isopropyl alcohol or denatured alcohol.

Conro Electronics offers a wide choice of adhesives from major manufacturers such as Henkel Loctite.

We’ll show you how to improve product reliability while increasing performance and lowering costs. Our team of technical support specialists will provide your company with dependable global supply, unrivalled efficiency, and superior technical support.

Feel free to contact us on 0208 953 1211 or send us an email to info@conro.com