Sliding Wear of Polymer – Steel Pairings regarding Flame Retardant Equipped Glass Fibre Reinforced Polymers and (coated) tool steels

The processing of reinforced polymeric materials which are equipped with a flame retardant can cause wear at the plasticating screw, in the mold or in the die. This work deals with tribological long-term tests of 30 wt% glass fiber (GF) reinforced Polypropylene (PP) (PP GF30) as well as 30 wt% GF reinforced and flame retardant (FR) equipped PP (PP GF30FR15) against discs of screw and mold materials (1.2311, 1.2343 and1.8550) and three different physical-vapor-deposited coatings (TiN, TiAlN and CrN, all applied on 1.2343). The tribological measurements were performed utilizing a Pin-on-Disc tribometer and injection mold-ed polymeric pins. The coefficient of friction (COF) is between 0.1 – 0.4. During the experiments the surfaces of almost all discs were roughened or worn. Especially the experiments with the glass fiber reinforced and flame retardant equipped PP pins resulted in a worn surface of all used steel surfaces. The TiN and the TiAlN coated surfaces featured the lowest COF, but both coatings were worn by both modifications. A transfer of material from the coated surface to the pin is shown by EDX measurements. The CrN coating, the nitrided steel and the hot working steel showed the least wear.