Bonding Polypropylene with Industrial Adhesive
Polypropylene plastic is a favourite 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 29mN/m (normally to achieve “wetting” or adhesion a surface energy above 36mN/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 specialist equipment, it is important to have the set up optimised 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. 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 plenty of choice to suit the production process.
Primer: Special chemical primers can be used to activate the surface for bonding. Permabond offers Permabond POP Polyolefin Primer – this can only be used in conjunction with a cyanoacrylate adhesive. This offers a simple solution for customers looking for an instant bonding solution.
Remember: for consistent results, bond surfaces as soon as possible after pre-treatment.
Can’t do Surface Preparation?
Don’t worry, there are industrial adhesive products available for bonding polypropylene without treated surfaces. Permabond has two new products TA4610 and TA4620 which have good adhesion to untreated polyolefins as well as other substrate materials.
For more information on bonding polypropylene or other industrial adhesives, please contact the Permabond technical team here.