QUESTION:

What causes the rubber blooming?

A manufacturer of thermal processing units for modified color pigments needed analytic support in a rubber blooming troubleshooting case. After thermal processing of these pigments, bigger lumps of unknown origin were found by one of his customers. We were asked to determine the composition of these lumps and to possibly identify the origin. The requester suspected a cleaning cloth to have caused the contamination.

APPROACH:

Analysis of samples and thermal processing units

We obtained ‘lump’ samples, processed reference material and the neat components (filler and pigments). After examination with 2 complementary analytical techniques (Pyrolyse-GC-MS and FTIR), we identified a specific petroleum fraction in addition to the known pigments and fillers. Seemingly, this aliphatic contamination acted as glue and thus induced the formation of pigment lumps.

Based on these intermediate results, the cleaning cloth could be excluded as the origin of the contamination. After discussion of these findings with the customer, the ball bearings in the thermal processing units came into the focus. And indeed, we identified the same petroleum fraction on the outer face of the ball bearings that were used in the processing machine. We also found that the grease from the inner part of the ball bearing was not causing the problem.