TPGOA Technical Insights
Bonding Polypropylene with Industrial Adhesive
Polypropylene plastic is a favorite substrate among goods manufacturers. It is low-cost, tough with some degree of flexibility, and has excellent chemical resistance. Certain blends can even rival ABS (acrylonitrile butadiene styrene) in terms of performance. High-density and low-density polypropylene surfaces can be quite difficult to bond or print onto. This is due to low surface energy or poor “wettability” – typically only 29 mN/m (normally to achieve “wetting” or adhesion a surface energy above 36 mN/m is required).
Many goods manufacturers use welding techniques (e.g. friction welding, ultrasonic welding, lasers etc.). As well as being expensive, welding is normally not suitable when bonding polypropylene to other substrate materials. Also, if parts are an awkward shape. then welding cannot be considered.
Surface Preparation for Bonding Polypropylene
Due to the low surface energy of polypropylene, it is recommended to pre-treat surfaces prior to bonding. There are several ways of pre-treating surfaces for bonding polypropylene:
- Flame Treatment: This is normally done with specialized equipment - it is important to have the set up optimized so parts are the correct distance from the flame and pass through at the correct speed; over-treating the surface will result in similar bonding results to untreated surfaces, i.e., the adhesive will not stick! Be careful if manually attempting this because results will be inconsistent. Flame treatment is more suited to flat, uniform surfaces rather than complex shapes. Professional equipment can be quite bulky.
- Corona or Plasma Treatment: This is good for intricately-shaped components - it involves an electronic discharge over the surface of the parts which helps activate surface electrons and makes them more receptive to bonding. However, equipment can be quite costly.
After the surface energy has been improved, the material is ready for bonding and most industrial adhesive types can be considered – allowing for plenty of choice to suit the production process.
TPG makes every effort to insure that the information contained herein is accurate - however, we accept no liability for the content of this piece, or for the consequences of any actions taken on the basis of the information provided.
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