Why Are Plastics Like PP and PE Difficult to Bond?
Polypropylene and polyethylene make it difficult for many adhesives to wet enough due to low surface energy. The adhesive is collected like drop and the bond area remains limited if it does not emit. The problem is not only to find 'strong adhesive', but to manage the surface-stick interface.
What does low surface energy mean?
It is necessary to spread liquid adhesive on the surface and contact with microscopic irregularities. Many formulations are beads because the surface energy is low in polyolefins such as PP and PE. Mold release, oil, dust and additives can make this situation more difficult.
Surface preparation options
Cleaning is the first step; but it does not permanently upgrade the surface energy to wipe it alone with solvent. Coronary can activate plasma or flame treatment surface; adhesives for special primarys or polyolefins are another way. The effect of the process should be checked for the time between activation and bonding as it can be reduced over time.
Load design and geometry
The connection in low-energy plastics constantly increases the risk of exposure to peeling load. Grow the overlay area, turn the load to slip, reduce the sharp edge and reduce the demand on the adhesive that add mechanical locking. The stretch of the part and different thermal expansion should also be included in the test plan.
What should be considered in the test?
Sample should be prepared using real resin grade, pigment, mold separator and production surface. After aging, temperature, humidity and chemical contact breakout mode is saved. The sustainability and process control method of surface change between lots should not be transferred to mass production without determining.
Application control list
- Verify full class and additives of plastic.
- Separate surface activation with cleaning.
- Standardize activation-structure time.
- Disconnect the bond geometry to slip instead of peeling.
- Evaluate the break mode after aging.
Conclusion
It is possible to glue PP and PE; but special product requires controlled surface preparation and correct connection design. Accidental success with general purpose is not sustainable.
Manstechnic approach
Manstechnic tests a combination of product-weight-equipment using surface specimen and serial production conditions.