Plastic Bonding Techniques
Plastic Bonding – Secure Adhesion for Every Type of Plastic
Bonding and joining plastic
Plastic bonding is one of the material bonding processes. During the bonding process, adhesive is applied to the surfaces to be bonded either selectively or over the entire surface and cured. The resulting bond in plastic bonding is form-fit and permanent, and must be able to withstand mechanical and thermal loads depending on the area of application. In the case of plastics, it is essential that the selected plastic has an adhesive surface. This makes it possible to bond the thermoformed parts together.
Key Factors to Consider When Bonding Plastics
Pre-Treatment for Adhesion
Certain plastics, such as polyolefins (PP, HD-PE), have low natural adhesion and require pre-treatment through thermal, electrical, or chemical processes to ensure a strong bond.
Surface Cleaning Before Bonding
Plastics must be free from contaminants like oils, greases, and dust. Maintaining a clean workspace is essential to achieve optimal adhesion.
Consulting Experts for Specialized Applications
For specialized plastic bonding applications, expert consultation with adhesive manufacturers ensures that bonded thermoformed parts meet specific performance requirements.
Advantages of Plastic Bonding
High Mechanical Strength & Durability
Bonded plastic components withstand high mechanical pressure and temperature variations. Adhesive bonding prevents unintended movement of parts during further processing. Acrylic-based adhesives, in particular, offer excellent adhesion and fast curing under UV light.
Efficient & Cost-Effective Alternative to Welding & Screwing
Bonding can replace traditional joining techniques such as welding and screwing. While expertise is required, adhesive bonding is often faster and more cost-effective than these methods.
Sealing & Additional Functional Benefits
Beyond joining, adhesive bonding provides additional benefits such as electrical insulation, gas and liquid sealing, vibration damping, corrosion protection, and the ability to accommodate material movement.
The Plastic Bonding Process
Clean the surface before bonding plastic
Before bonding plastic, the surface must be degreased. This can be achieved with organic solvents or by convection heating in an oven.
Mechanical pre-treatment for bonding plastics
Roughened surfaces are easier to bond. Techniques such as sanding, brushing and sandblasting are used when bonding plastics. This changes the surface roughness and size, which is crucial for the effectiveness of the bond. At the same time, loosely adhering reaction products, polishing agents, lubricants and stabilizers are also removed.
Subject the plastic to physical pre-treatment before bonding
Thermal processes, such as flame treatment, can also improve the bonding of plastic surfaces. These processes cause a chemical and physical change to the surface. When flaming plastics, an open flame is passed over the surface of the part to be joined at a defined distance and speed.
The flame can be either reducing or oxidizing, depending on the type of plastic to be treated. This leads to an increase in energy on the component surface and ensures that the plastic parts can be bonded better. The surface can also be influenced by adding chemically reactive substances.
Chemical pre-treatment for better bonding of plastic parts
Pre-treatment with acidic or alkaline substances also has a positive effect on how easily the plastic can be bonded. This process creates a new structural boundary layer with a significantly higher polarity through oxidation or phosphating. Wet-chemical pre-treatment, for example with chromium sulphuric acid, can be used to treat components with a wide variety of shapes.
Plastics Suitable for Adhesive Bonding
Find out which plastics can be bonded so that you can start your thermoforming project straight away.
Plastic Bonding Adhesives – Overview
How they work
The curing of the adhesive is initiated by a reaction mechanism that is triggered by the addition of a catalyst in the form of energy or solvent.
Influencing variables
- Reaction time: Time to reaction mechanism
- Temperature: Heat often has a positive effect on the reaction time
- Pressure: The application of pressure often has a positive effect on the reaction time
- Concentration of the catalyst
Other Joining Techniques for Thermoformed Plastics
Want to explore additional joining techniques for thermoformed plastics? Learn more about:
