Client request
In the world of injection molding, even a small residual stress in a component can cause an unexpected failure. This was the problem a client brought to us: they needed to verify the quality of a part molded from polysulfone (PPS/PPSU), a material known for its excellent resistance to heat and many chemicals, such as aqueous solutions of metal salts.
The part in question, a cylinder, had been produced with two different injection molding procedures. The objective was to compare these two procedures to identify the one that ensured the lowest accumulation of residual stress, in order to optimize the quality and durability of the final component.
The solution proposed by Plastanalisi
To address this challenge, we suggested using the phenomenon of Stress Cracking, a specific analysis technique for polymers. This test is based on a simple principle: a material can crack if it is simultaneously exposed to a mechanical tension and a specific chemical substance. By removing one of the two factors, the problem does not occur. In our case, we immersed a sample of the cylindrical part in a specific solvent for a short duration, applying an external factor to highlight internal tensions. If stress is present, cracks will be observed on the material’s surface. This method allows for a quick and effective evaluation of the different injection molding procedures.
Analysis results
Plastanalisi technicians subjected the samples produced with the two procedures to a solvent immersion test. The results were clear:
The part produced with Procedure 1 showed obvious signs of cracking after just 60 seconds, indicating the presence of residual stress.
In contrast, the part obtained with Procedure 2 showed no alteration after the test, demonstrating the absence of residual tensions and thus confirming the effectiveness of this second molding method.
Thanks to this analysis, the client was able to identify and adopt the optimal procedure, ensuring stress-free and higher-quality components.