The tensile properties of polypropylene composites increase as the amount of alignment of the carbon nanofiber additives increases. The strength increases in a reasonably linear manner with fiber volume percentage up to 17%. Also, the strength increases as the fiber length increases.
Top left graph: The predicted ultimate tensile strengths of polypropylene reinforced with 15% volume VGCF as a function of fiber alignment and fiber length. For higher alignment (small values of Z), the ultimate tensile strength is strongly dependant on fiber length.
A method for determining the ultimate tensile strength of partially aligned discontinuous fiber-reinforced composites was tested to determine the effect that fiber length and fiber volume have on the composite strength. It was shown that the composite strength increases as the amount of fiber alignment increases. Also, the strength increases as the fiber length increases. Tensile test specimens containing 0 to 23% fiber volume were tested. The strength increases in a reasonably linear manner with fiber volume percentage up to 17%. It decreased at high fiber loading (23 vol%) which is most likely due to incomplete wetting and infiltration of the VGCF.
Top right graph: The predicted ultimate tensile strength of partially aligned VGCF-reinforced polypropylene as a function of fiber volume fraction (l=10 microns) and degree of alignment. The ultimate tensile strength value is more sensitive to fiber content at a higher degree of alignment.
Bottom left graph: Ultimate tensile strength of partially aligned VGCF-reinforced polypropylene with various fiber volume fractions and various average fiber lengths.
To improve the modulus and strength of polypropylene resin, PPI recommends the following products XXX