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This work presents selected properties of polypropylene-based (PP) composites modified with an organic filler, namely walnut shells (NUT). Two series of composites were prepared via a twin-screw extrusion process, followed by injection molding. The first series, named PP/NUT, contained 10, 20 and 40 wt% of walnut shell powder, while the second, abbreviated PP/NUT/MAPP, apart from nut filler included polypropylene-graft-maleic anhydride (MAPP), which was intended to promote adhesion between the polymer and filler. The following measuring techniques were applied: differential scanning calorimetry, thermogravimetry, dynamic-mechanical thermal analysis, and scanning electron microscopy. The measurements showed the filler to have a significant influence on the properties of the PP/NUT composites in comparison with unmodified polypropylene. It was also shown that the addition of polypropylene-graft-maleic anhydride to the formulation enhanced interfacial bonding between the polymeric matrix and filler. Moreover, the introduction of organic filler to the polymeric matrix increased its stiffness without altering the crystallization kinetics of polypropylene. [ABSTRACT FROM AUTHOR]

Wood-polymer composites based on high-density polyethylene and two types of pine-wood filler were investigated. It is shown that the addition of long wood fibres to common polyethylene leads to a substantial increase in stiffness, i.e. from 504 MPa for PE-HD up to 1526 MPa for PE-HD with 60% wood fibres. Moreover, morphological investigations revealed that superficial wood particles were sufficiently embedded in the base polymer ensuring protection against higher moisture uptake rates. [ABSTRACT FROM AUTHOR]