High fiber-low matrix composites: kenaf fiber/polypropylene.

Abstract

Considerable interest has been generated in the use of lignocellulosic fibers and wastes (both agricultural and wood based) as fillers and reinforcements in thermoplastics. In general, present technologies limit fiber loading in thermoplastics to about 60 percent by weight of fiber. To produce high fiber content composites for commercial use while maintaining adequate mechanical properties requires innovative processing techniques. A new technique has been developed that allows very high fiber loading. We have processed composites up to about 95 percent by weight of fiber in polypropylene (PP). The process involves some additional processing steps, in addition to conventional compounding techniques, to achieve such high fiber content in PP. Studies on about 85 percent kenaf-PP composites indicates that properties such as flexural modulus and strength are superior to most types of wood particle, low and medium density hard-boards. The fiber orientation is predominantly two dimensionally random for the kenaf-PP composite. The range for the flexural strength (MOR) of medium-density fiberboards (MDF) using phenol formaldehyde as the binding system is typically from 13 to 42 MPa. The flexural stiffness (MOE) range for MDF boards is from 2.24 to about 4.9 GPa. The high range for flexural strength of high-density fiberboards is typically about 70 MPa and the flexural stiffness about 7.58 GPa. The 85 percent kenaf-fiber polypropylene composite, with an MOR of 75 MPa and an MOE of 6.4 GPa, has comparable properties to conventional formaldehyde-based fiberboards. Thermal analysis of the kenaf composites indicates that the crystallinity of the PP in the composites is not affected by the processing.

Citation

Sanadi, Anand R.; Hunt, J.F.; Caulfield, D.F.; Kovacsvolgyi, G.; Destree, B. 2002. High fiber-low matrix composites: kenaf fiber/polypropylene. Sixth International Conference on Woodfiber-Plastic Composites, May 15-16, 2001, Madison, Wisconsin. Madison, WI : Forest Research Society, c2002. Pages 121-124.