Avoiding False Positive Asbestos Analysis in Polymer Matrix Composite Brake Linings

Asbestos has been banned in many countries as industrial material, however the utilization of those fibers in brake linings results in friction properties that are so convenient, that linings containing them are still commercially available. To replace asbestos a large number of mineral phases is utilized in the formulation of polymer based friction material, and it is sometimes difficult to establish if they are present or not in finished brake pads and linings. Several clay minerals have been mistaken for asbestos because they present X-ray diffraction peaks that overlap with the diagnostic asbestos peak. A method to distinguish between the presence of regulated fiber minerals and allowed clay minerals in brake linings is presented using X-ray diffraction in association with a thermal treatment.