Effect of Virgin Heterophasic Pp Copolymer Content on Moisture Absorption, Thermal and Mechanical Properties of Recycled Polyethylene Wood Flour Composites

Abstract

The effect of virgin heterophasic PP copolymer (vPP) content on moisture absorption, as well as on thermal and mechanical properties of recycled polyethylene/ wood flour composites was investigated. The polymer matrix of recycled post-consumed plastic waste (rPE) was composed of a matrix of LDPE and a part of PP. Wood flour of Pinus radiata was used as filler at a constant loading of 45 wt.%. rPE/vPP blends and their composites were manufactured by melt blending, and then by injection molding. The morphology of the blends and composites was analyzed by means of scanning electron microscopy. The addition of vPP improved tensile and flexural moduli and flexural strength of wood plastic composites (WPC). The highest increase of these properties was observed for a WPC sample with a rPE/vPP ratio of 19. WPC made with higher virgin PP content (rPE/vPP ratio = 9 and 5.7) showed lower increase of mechanical properties compared to polymer matrix and WrPE samples. The moisture uptake of WPC made of rPE/vPP blend was higher than those of rPE, and their mechanical properties were more adversely affected by immersion in water. TGA results indicate that rPE are thermally more stable than rPE/vPP blends. The incorporation of heterophasic PP copolymer into the recycled polymer matrix of WPC delays the starting of wood flour degradation.

Thermoplastic Recycling: Properties, Modifications, and Applications

“…The effect of wood flour of Pinus radiata as fillers at a constant loading of 45 wt.% of recycled post-consumed plastic waste reported to be influenced by virgin PP [43]. In the report, the addition of virgin PP improved tensile and flexural moduli and flexural strength of wood plastic/LDPE composites (WPC).…”

“…The improvement in rheological morphology does not indicate an improvement in compatibility as well as mechanical properties [71]. Modification of recycled HDPE with treated natural fiber using NaOH, SLS, acetic anhydride, CaCO 3 filler, and zeolites as well as synthetic fibers is characterized with improvement in polymer dispersion, even distribution of fibers, interfacial adhesion, fiber tearing, micro-crack formation, modifier content and size, nature of the modifier, and reduction in void formation [20,43,[72][73][74][75]. This indicated the enhanced compatibility which corroborates the improvement in physical, mechanical, and thermal properties of the modified recycled thermoplastics and dictates its applications.…”

Properties of High-Density Polyethylene-Polypropylene Wood Composites

“…Many studies investigated the potential of the polyolefin recycled matrix components for WPC [10,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Chtourou et al [21] showed that municipal waste plastics composed of 95% PE and 5% PP and pulp fibers produced WPC with average tensile properties compared to virgin polyolefin.…”

“…Catto et al [31] showed that recycled polyolefin is a viable alternative due to its comparable physical and mechanical properties to virgin polyolefin. Adding virgin PP to recycled HDPE improves WPC properties [32]. De Oliveira Santos et al [33] showed that using recycled PET below the melting temperature could enhance the composites processing and mechanical properties.…”