Utilization of Recycled Polypropylene, Cellulose and Newsprint Fibres for Production of Green Composites

Abstract

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.

Waste Paper as a Valuable Resource: An Overview of Recent Trends in the Polymeric Composites Field

“…However, WP-ON presented the highest mechanical properties for flexural strength (25%) [ 71 ]. Recycled PP filled with WP as newspaper (WP-N) was compared with better quality and more expensive filler: cellulose with a special bleaching pretreatment [ 69 ]. The results showed an improvement in tensile strength (26% and 56%) and stiffness (47% and 16%) for WP-N and cellulose, respectively, compared to recycled PP.…”

Effect of Agricultural Biomass Residues on the Properties of Recycled Polypropylene/Polyethylene Composites

“…One factor which affects mechanical properties is crystallinity. In the literature, two opposite trends may be found: the crystallinity degree (Xc) increases due to the fibers acting as nucleating agents [ 23 ] or the crystallinity degree does not change much with increasing fiber content [ 24 ]. In the case of the investigated composites, it was found that the fibers induced crystal nucleation of the polymer matrix.…”

Leaching and VOC Emission Tests of Polymer Composites Produced from Post-Consumer Waste in Terms of Application in the Construction Sector

“…For environmental tests, secondary raw materials obtained from the recycling of beverage bottles-rPE and rPP-newsprint (NP) and the composites produced from them were used; see Table 1. The paper [25] presents a method for producing the secondary raw materials and their properties. The thermoforming process developed under the Ceplafib project [22] was used to obtain polypropylene matrix composites reinforced with cellulose fibres (rPP/NP) and polyethylene-based composites reinforced with cellulose fibres (rPE (HD:LD 50:50) + NP, rPE (HD:LD 70:30) + NP).…”

“…The characteristics of the rPE/NP and rPP/NP composites, including mechanical, thermal and morphological properties were published by Fajs P. et al [24] and Bogataj V.Z. et al [25].…”