Property spectrum of SR-PP composites

The layered structure of fiber composites made exclusively of polypropylene enables numerous attractive and balanced properties, which are not attainable for unreinforced polymers or conventional fiber composites [72], 

First and foremost, the very low density of SR-PP composites should be highlighted. The formation of cavities in the amorphous areas during the stretching of the original tapes causes the density to decrease (experimentally) to values as low as 0.77 g/cm in unidirectional composites [26,73]. Due to the micro-cavities, which are usually closed during hot-compaction [20], a density of 0.91 g/cm is usually achieved for self-reinforced fiber composites. This value equals approximately that of the original, unreinforced PP-material. 

Klimke [43] estimates a directly attainable weight reduction of about 30% in comparison to a PP-GF30. In addition, the balanced property profile of the materials also makes it possible to reduce the component wall thickness by 20 to 30%. In sum, a weight reduction of around 50% is realized. The component properties remain constant and, consequently, an excellent lightweight potential for plain components results. 

However, self-reinforced PP-fiber composites are exceedingly efficient with regard to their absolute mechanical and physical properties. 

Compared to glass fiber and other foreign fiber reinforced polypropylenes, prominent characteristics are an exceptionally high impact strength and resistance to perforation [26,76]. These are caused by an efficient absorption of energy by self-reinforced fiber composite systems. 

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