Impact modification of wood flour reinforced PP composites: Problems, analysis, solution

Polypropylene (PP)/elastomer/wood flour composites were prepared from two PP reactor blends. The detailed analysis of the deformation and failure of the composites has shown that several local deformation processes take place during loading which differ considerably in terms of energy consumption. These processes may even interact with each other, sometimes resulting in an antagonistic effect on impact resistance. The shear yielding of the matrix consumes energy the most efficiently. The presence of wood decreases shear yielding by hindering overall deformation and initiating other local processes like debonding. The role of debonding is controversial; it may increase, but also decrease plastic deformation and impact resistance. The fracture of wood does not consume much energy and thus does not contribute to impact resistance. PP cannot be reinforced with wood flour, if impact resistance is an important aspect. Other methods are more suitable in such cases, like the addition of synthetic fibers.

Automated summary

The deformation and failure analysis of PP/elastomer/wood flour composites reveals that various local deformation processes occur during loading, with different energy consumption. These processes can interact and even result in an antagonistic effect on impact resistance. Shear yielding of the matrix is the most energy-efficient process. The presence of wood decreases shear yielding by hindering overall deformation and initiating other local processes such as debonding. The role of debonding is controversial as it may increase or decrease plastic deformation and impact resistance. Wood fracture does not significantly contribute to impact resistance. If impact resistance is important, PP cannot be reinforced with wood flour, and other methods like adding synthetic fibers are more suitable.