Periodically micro-patterned viscose fiber-reinforced polypropylene composites with low surface friction

• Influence of micro-patterning on friction behavior of polypropylene/viscose fiber composite.
• Micro-pattern shortened the run-in period with composite surfaces.
• Sliding friction of composites was affected by micro-patterning and fiber loading.
• High fiber content coupled with low-density micro-pattern resulted in very low friction levels.

Polypropylene/viscose fiber (PP/VF) composite with a surface pattern consisting of periodic, micro-scale cylindrical pillars were manufactured and the effect of fiber loading and micro-patterning on the friction and wear properties of the composites was studied. The micro-patterned viscose fiber composite surfaces were prepared via melt compounding and injection molding. SEM studies showed that the fiber dispersion within the micro-bumps was influenced by the fiber loading and high aspect ratio (300–1200) of viscose fibers. With higher fiber loadings the fiber content of the micro-bumps was prominently higher than with lower fiber loadings of the composites. The wear and friction behavior of the patterned composite series were evaluated by sliding the fabricated surfaces against rough and smooth steel surfaces with a pin-on-disc type tribometer. It was noted especially in the case of a smooth counter surface that while both high fiber content and sparse micro-bump coverage individually decreased the sliding friction, their synergetic effect produced a dramatic drop in friction coefficient.