Plastic is a ubiquitous material, used in a wide range of sectors — from automotive and electronics to industry and model making. Its durability, lightness and corrosion resistance make it an excellent and versatile construction material. However, it is worth bearing in mind that due to these specific chemical properties, effective bonding of plastic elements requires the use of equally effective adhesives. When choosing them, various factors must be taken into account — i.e. the type of polymer, the flexibility of the bond, temperature resistance or the working environment. So, how do you choose the best adhesive for bonding plastics? What are the characteristics of a good plastic adhesive? What is worth bearing in mind and what mistakes should be avoided?
How does plastic adhesive work?
In simple terms: a product is applied to a given surface, then the water/solvent gradually evaporates, causing the adhesive to dry, bonding the parts together.
At this point, however, it is worth distinguishing between several main types of adhesives — i.e. solvent-based adhesives, water-based adhesives, reactive adhesives and hot melt adhesives, each using different mechanisms of adhesion and cohesion.
- Solvent-based and water-based adhesives
Solvent-based and water-based adhesives work by evaporating the carrier (organic solvent or water), leaving a thin layer of binder on the surface to bind the elements together. In the case of solvent-based adhesives, there may additionally be partial dissolution of plastic surfaces, which increases adhesion (the phenomenon of one surface sticking to another). - Reactive adhesives
Chemically curing adhesives i.e. cyanoacrylate (so-called “superglue”) or epoxy, use chemical reactions to cure the bond. Cyanoacrylates polymerise when exposed to moisture from the air, forming strong and rigid bonds. Epoxy adhesives, on the other hand, consist of two components — a resin and a hardener — which react with each other, leading to the formation of cross-linked polymer structures with high mechanical strength. - Hot melt adhesives
Hot melt adhesives work by heating and cooling the polymeric binder. When heated, the adhesive becomes liquid, allowing application to the surface, and then solidifies as it cools to form a permanent bond.
Types of plastic adhesives and their properties
1. Cyanoacrylate (CA) adhesives
Cyanoacrylates are single-component adhesives that undergo anionic polymerisation in the presence of moisture from the air or trace amounts of water on the plastic surface. The bond is created by the formation of long polymer chains, which ensures high bond strength. Their main properties are very fast curing (on the order of seconds), high mechanical strength and the brittleness of the bond.
- Applications: bonding of polycarbonates, acrylic glass (PMMA), polystyrene (PS); limited effectiveness on low surface energy substrates (e.g. polypropylene (PP)).
2. Epoxy adhesives
Epoxy adhesives consist of an epoxy resin and a hardener, which react through a chemical cross-linking process. The epoxy reaction results in a cross-linked structure with high mechanical and chemical resistance. It is distinguished by its high tensile and shear strength, resistance to chemicals and temperature.
- Application: Bonding of ABS, PC, PS, PVC as well as composites and metals to plastics.
3. Polyurethane (PU) adhesives
Polyurethane adhesives can be one-component (reactive with moisture) or two-component (reaction of isocyanate with polyols). Once cured, they form flexible, weather-resistant bonds, hence their main properties, i.e. good flexibility, vibration and temperature resistance, hydrophobicity.
- Application: bonding of thermoplastics such as PVC, ABS, PU, as well as applications in the automotive and construction industries.
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4. Solvent-based adhesives
These adhesives work by dissolving plastic surfaces and re-bonding them through the evaporation of the solvent. They contain volatile organic compounds (e.g. acetone, dichloromethane) and their properties are based on good surface penetration and high chemical resistance after drying.
- Applications: bonding of PVC, PS, ABS; used in the model making and chemical industries.
5. Hot melt adhesives
These are polymer adhesives that become liquid when heated and solidify when cooled, forming a mechanical bond. They are most often based on EVA (ethylene-vinyl acetate) copolymers or polyamides. Properties: no solvent emissions, high bonding speed, moisture resistance.
- Applications: packaging (https://www.products.pcc.eu/en/k/packaging/), furniture, electronics, bonding of PE and PP films.
6. Acrylic adhesives (MMA)
Methacrylate structural adhesives contain two components: an initiator and a catalyst, which activate radical polymerisation to form a durable and strong bond. They are distinguished by their high dynamic strength, impact resistance and good adhesion to low surface energy substrates.
- Applications: bonding of polypropylene (PP), polyethylene (PE), PTFE and carbon fibre composites.
How to choose the right adhesive for a particular type of plastic?
In order to select the right plastic adhesive, it is first necessary to identify the type of plastic. Some, such as polyethylene (PE) and polypropylene (PP), are resistant to bonding due to their low surface energy and require the use of specialised adhesives or adhesion enhancers. Others, such as PVC or polystyrene, bond more easily, allowing the use of standard solvent-based adhesives.
In a nutshell, it can be considered that:
- Cyanoacrylate adhesive (“super glue”, i.e. strong adhesive) is effective for many hard plastics.
- Two-component epoxy adhesives are suitable for a wide range of plastics, including PE and PP.
- Polyurethane adhesives are ideal for outdoor applications.
- Solvent-based adhesives work well for bonding PVC and polystyrene.
How to apply plastic adhesive correctly?
Step 1: Identify the plastic. Before you start, make sure you know what type of plastic you are dealing with.
Step 2: Clean the surfaces. Thoroughly clean the surfaces to be joined. Remove any dirt, dust, oil or grease. You can use isopropyl alcohol or a special degreaser to ensure better adhesion.
Step 3: Sand the surface. If possible, it is a good idea to lightly roughen the surface with a sander or fine sandpaper.
Step 4: Apply the adhesive. Spread the adhesive evenly on one or both surfaces, depending on the manufacturer’s instructions. Once the adhesive has been applied, gently press the surfaces together. Make sure they are carefully aligned and do not move.
Leave the glued parts for the time recommended by the adhesive manufacturer. This time can vary from a few seconds (for cyanoacrylates) to several hours (for epoxy adhesives).
Step 5: Clean. After gluing, remove excess adhesive with a cloth soaked in solvent or alcohol, preferably before the adhesive has completely set.
The most common mistakes when bonding plastic and how to avoid them
Mistake 1: Poor surface preparation. Contaminants — oils, grease — can significantly reduce the bond’s efficiency, resulting in non-permanent bonding of the glued elements. Therefore, the surface should be thoroughly cleaned before the adhesive is applied, preferably with isopropyl alcohol or another suitable solvent.
Mistake 2: Wrong adhesive for the surface type. For example, using an all-purpose adhesive for polyethylene, which requires specialised adhesives that improve adhesion.
Application of plastic adhesives in different industries
Electronics industry
In the electronics industry, plastic adhesives are essential for assembling device housings, attaching components to printed circuit boards, packaging, insulating, and protecting delicate electronic components. At the same time, these adhesives must meet stringent requirements for electrical conductivity and thermal resistance, and often also minimise the risk of component damage by electrostatic discharges (ESD).
Construction industry
In the construction sector, adhesives are used to install PVC components, i.e. pipes, windows, profiles. These adhesives must be highly resistant to changing weather conditions, vibration and weight, ensuring long-term stability and tightness of the joints.
See more: https://www.products.pcc.eu/en/k/construction-sector/
Furniture industry
Typically, adhesives are used to bond decorative elements, i.e. laminates and veneers, as well as to attach various plastic components. Here, adhesives must offer high adhesion to a variety of materials and an aesthetically pleasing finish so as not to negatively affect the appearance of the finished product.
See more: https://www.products.pcc.eu/en/k/furniture-industry/
Automotive manufacturing
Plastic adhesives in automotive production are used to assemble interior components, bumpers, body panels and other plastic components. As in other industries, they must meet special requirements — such as mechanical strength, resistance to oils, fuels and extreme temperatures — which are crucial for the safety and durability of vehicles.
In each of these sectors, the right choice of adhesive for industrial applications is critical to ensure optimum product performance and durability.
- Hanyż, B., & Gajewska-Kobus, I. (2001). Kleje poliuretanowe nowej generacji. Izolacje, 6, 24-25.
