This work investigates the feasibility of using the recycled polypropylene (rPP), cellulose (CF) and newsprint (NP) fibres in polyolefin reinforced composites. Recycled PP filled with 40 wt.% of cellulose (rPP/CF) or newsprint (rPP/NP), with the addition of impact modifier (IM) and compatibilizing agent (CA), have been prepared with extrusion melting and injection moulding. Melting and crystallization behaviour of plain matrix and composites were measured by differential scanning calorimetry (DSC). Morphological and mechanical properties were also studied using scanning electron microscope (SEM) and tensile testing, respectively. Thermal stability of composites was similar to neat rPP for both types of the filler used. Though, the crystallinity was progressively decreased with the addition of CF or NP. The DSC further revealed an occurrence of the two distinct melting transitions, meaning that the examined materials were not based on pure polypropylene (PP), but are rather blends of high-density polyethylene (HDPE) and PP, what has been confirmed also by the Fourier transform infrared spectroscopy (FTIR). The largest single source of contaminations in recycled PP comes from HDPE since both polymers are identified by a similar density and can be accidentally mixed during the conventional physical separation process. Composites reinforced with CF have shown better mechanical performances than those based on reclaimed NP fibres, what can be attributed to the initial fibre quality. Tensile strength of the composites filled with CF and NP fibres was 36 MPa and 29 MPa, respectively, in disparity to 23 MPa measured for neat rPP. The fibre addition further resulted in substantial increase in Young modulus of the composites. The addition of CF and NP fibres lead to an improved modulus of elasticity by 16 and 47%, respectively. Waste paper in the form of recovered cellulose or reclaimed newsprint fibre can thus meet all the technical requirements to become an alternative to inorganic fillers in thermoplastic composites.

This study investigates the mechanical, thermal and morphological properties of rHDPE (Recycled High Density Polyethylene) and a mixture of rPE HD/LD (High and Low Density Polyethylene), both reinforced with rNP (Reclaimed Newsprint Paper) fibres. To enhance the composite properties, the addition of highly grafted maleic anhydride polyethylene wax, as CA (Coupling Agent), and semi crystalline copolymer of propylene and ethylene, as IM (Impact Modifier), was included into the material formulation by a twin-screw extruder. Mechanical and morphological properties were studied on tensile test specimens, prepared by injection moulding, by tensile testing machine and SEM (Scanning Electron Microscope), respectively. Thermal properties, i.e. melting and crystallization behaviour, were investigated by DSC (Differential Scanning Calorimetry). Mechanical analysis showed that the addition of rNP in both composites increased the young modulus and significantly decreased the elongation at break. The DSC results revealed that the addition of the rNP in the rHDPE matrix led to a substantial decrease of crystallinity, which consequently affects the tensile strength of the composite (17 MPa) in contrast to the neat rHDPE (25 MPa). On the contrary, fibre addition in rPE HD/LD matrix had no specific impact on the crystallinity index, but did contribute to the increased tensile strength (26 MPa) when compared with neat rPE HD/LD (16 MPa). SEM photomicrographs of the impact fracture surfaces demonstrated a solid adhesion bond between the natural fibres and the rPE HD/LD matrix. Reclaimed newsprint fibres can thus be considered as a perspective alternative to the inorganic fillers in the rPE HD/LD composite.