How do I bond plastic?
Bonding plastic ā but how? Many people try to bond plastics using so-called āall-purpose adhesivesā. However, plastics require specialised adhesives ā and itās not only the adhesive that matters, other factors also play an important role.
Pay attention to the type of plastic
Prepare the surfaces properly
Select the right adhesive
Follow the bonding steps carefully
Why are some plastics difficult to bond?
There really is no such thing as an all-purpose adhesive, and this is especially true for plastics. When bonding plastics, the adhesive must be carefully matched to the type of plastic. It is therefore very important to know which material a component is made from. Often, a small material marking on the back or underside of the product can provide this information. A key factor is the surface tension of the plastic. Materials with low surface tension, such as PE, PP or PTFE, do not allow adhesives to bond easily. Plastics with higher surface tension, on the other hand, are much easier to bond. The following overview shows how well different plastics can be bonded based on their surface tension:
| Material | Short designation | Surface tension (mN/m) |
|---|---|---|
| Low surface tension (difficult to bond) | ||
| Polyamide | PA 6.6 | <40 |
| Polyethylene | PE, HDPE | 31 |
| Polyetheretherketone | PEEK | 38 |
| Polyester | PET | 40 |
| Polypropylene | PP | 29 |
| Polystyrene | PS | 38 |
| Polytetrafluoroethylene | PTFE | 19 |
| Recycled plastic | Recycled materials | <40 |
| Thermoplastic elastomer | TPE | 35 |
| High surface tension (easy to bond) | ||
| Acrylonitrile butadiene styrene | ABS | 42 |
| Carbon fibre | CFK | 40 |
| Fibre glass | GFK | 40 |
| Polyester | PBT | 42 |
| Polycarbonate | PC | 46 |
| Phenolic resin | PF | 42 |
| Acrylic | PMMA | >40 |
| Polyoxymethylene | POM | 42 |
| Polyurethane | PUR | 43 |
| Polyvinyl chloride | PVC | 41 |
| Styrene acrylonitrile | SAN | 41 |
Surface preparation
How to prepare surfaces properly for bonding
The successful use of WEICON adhesives depends on careful surface preparation, as this is the most important factor for overall success. Dust, dirt and moisture have a negative impact on adhesion.
For a reliable bond, the surface often needs to be prepared as follows:
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clean and dry bonding surfaces
ā
lightly roughen the surface with a fine abrasive fleece
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clean and degrease using WEICON Surface Cleaner
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use adhesives specifically designed for plastics
Select the right adhesive
Once the plastic has been identified and the surface prepared, the next crucial step follows: selecting the right adhesive. Depending on the type of plastic and the application, different groups of adhesives are used. They differ in curing time, strength and area of application. The following overview helps you choose the appropriate type of adhesive:
| Type of plastic | Recommended WEICON āTopā products | Properties | Benefits |
|---|---|---|---|
| ABS / PBT / PF / POM / PUR / PVC |
2-component adhesive Easy-Mix Epoxy Minute Adhesive, S 50, Plastic Bond, RK-7100 1-component cyanoacrylate adhesive VA 8406, VA 1401, VA 2500 HT, Contact Gel |
Easy to use, strong adhesion to the most common industrial plastics and high resistance to ageing. | Simple application, process-reliable and reproducible results even under adverse conditions. |
| GRP (fibreglass) / CFRP (carbon fibre) |
2-component adhesive Easy-Mix HT 180, RK-7100 Black, RK-1300, S 50 1-component cyanoacrylate adhesive VA 30 Black, VA 250 Black, VA 2500 HT |
Good adhesion to fibre-reinforced composites, non-damaging to the material and no adverse effect on material properties. | Adhesives and composite materials with equally high performance levels ā a perfectly matched material combination |
| PMMA / PC / SAN |
2-component adhesive Easy-Mix PU Crystal, RK-7200, Easy-Mix N 5000 1-component cyanoacrylate adhesive VA 1403, VA 1408, VA 1460 |
Transparency and brilliance are retained, with no stress cracking, discolouration or blooming at the bond line. | Special adhesives for bonding transparent and sensitive plastics with high aesthetic requirements. |
| PA6.6 / PE / PP / PEEK / PET / PS / PTFE / TPE / Recycled materials |
2-component adhesive Easy-Mix PE-PP 50, PE-PP 45, RK 7300 |
Perfect for difficult-to-bond plastics: rapid strength build-up, extreme impact resistance, and can be used without primer. | The top solution for bonding low surface energy plastics. It delivers high-strength and durable bonds without the need for a primer. |
Bonding process
Once the type of plastic and adhesive have been selected, correct application determines whether the bond will last. With just a few but important steps, a strong and reliable plastic bond can be achieved.
Bonding plastic properly ā hereās how itās done:
1. Lightly roughen the bonding surfaces using a fine abrasive fleece.
2. Immediately afterwards, thoroughly clean away dust using WEICON Surface Cleaner, which is very gentle on materials.
3. Apply the adhesive correctly, in a thin and even layer across the bonding surface.
4. Fit the components together precisely and hold them under light pressure until the adhesive has fully cured.
Our tip: You can always find the exact application instructions and curing times in our technical data sheets.
Useful tips
A few basic rules will ensure that a plastic repair is not just a temporary fix, but remains stable in the long term. Many problems are not caused by the adhesive itself, but by small mistakes in application.
Tips for a strong bond:
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Do not subject parts to load until the adhesive has fully cured
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Protect the bond from weather conditions and moisture until the adhesive has fully cured
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Maintain a constant temperature of 20 Ā°C during curing
Avoid common mistakes:
ā Using all-purpose adhesive instead of a suitable plastic adhesive
ā Failing to clean or prepare the surface
ā Loading the bond too early
Application examples
The following examples show typical applications for plastic adhesives in different areas. They illustrate how damaged or broken plastic parts can be reliably repaired. Each application takes you directly to the appropriate product solution.
Bonding a camera to a bicycle helmet using WEICON Easy-Mix PE-PP 50
Repairing a parasol using WEICON Easy-Mix PE-PP 50
Repairing a lawnmower using WEICON Plastic Bond
Bonding a broken-off suitcase wheel using WEICON RK-7300
Repairing a water tank
Contact & Support ā Weāre here to help
If you have any questions about our adhesives, the WEICON team is always at your disposal. Our support team will advise you on product selection, provide application recommendations and assist you with any technical questions. This ensures you achieve the best possible results when using our products.
