In this study, mechanical and morphological properties of composites made up of recycled highdensity polyethylene (HDPE) filled with calcium carbonate and fly ash (FA) were studied. Interfacial interactions were modified to improve the filler compatibility and mechanical properties of the composites by surface treatment of the FA filler with 3-amino propyl triethoxy silane. The composites were prepared by using a Thermo Haake Rheomixer. Effect of filler loading and treatment of FA with silane coupling agent on mechanical and morphological properties were investigated and it was found that silane treatment indicated significant improvements on the mechanical properties of the HDPE-FA composites. The improvement with silane treatment of FA was also confirmed by applying the Pukanszky model. Scanning electron microscopy on the fracture surface of composites had given direct evidence of better interfacial adhesion via silane treatment.

In this study, Wood Plastic Composites (WPCs) were produced from post-consumer bulky wastes of recycled plastic and wood in order to minimize waste, decrease environmental effects of plastics, reserve natural resources, and support circular economy for sustainable production and consumption. Five different types of polypropylene (PP) or polyethylene (PE) based recycled plastics and wood obtained from urban household bulky wastes were used in the production of recycled WPC composites, r-WPCs. Virgin WPC (v-WPC) and r-WPC compounds were prepared with wood flour (WF) and maleic anhydride grafted compatibilizer (MAPP or MAPE) to evaluate the effect of recycled polymer type and compatibilizer on the mechanical properties. It was found that tensile strength properties of r-WPCs produced from recycled PP (r-PP) were higher than that of the r-WPCs produced from mixed polyolefins and recycled PE. r-WPCs containing anti-oxidants, UV stabilizers, and compatibilizer with different WF compositions were produced from only recycled garden fraction PP (PPFGF) to determine the optimum composition and processing temperature for pilot scale manufacturing of r-WPCs. Based on tensile, impact, flexural, and water sorption properties of r-WPC compounds with different formulations, the optimum conditions of r-WPC compounds for industrial manufacturing process were determined. Surface morphology of fractured surfaces as well as tensile, flexural and density results of r-WPC compounds revealed the enhancement effect of MAPP on interfacial adhesion in r-WPCs. r-WPC products (crates and table/chair legs) based on bulky wastes were produced using an injection molding process at industrial scale by using 30 wt% WF-filled r-WPC compound. This study demonstrated that r-WPC compounds from recycled bulky plastic and wood wastes can be used as a potential raw material in plastic as well as WPC industry, contributing to circular economy. Graphic AbstractKeywords Wood plastic composite · Recycling · Bulky plastic waste · Mechanical property · WPC manufacturing

Polypropylene (PP) is one of the most important commercial polymers due to its superior properties such as high chemical resistance and low density. Fillers (CaCO 3 , Mg(OH) 2 , talc, mica, etc.) or reinforcing agents (glass fibre) are used in many applications of PP such as in household, automotive and packaging industry to enhance the properties of PP (stiffness, gas permeability, heat resistance, flame retardance, etc.), and to reduce the cost. In spite of the advantages of the fillers, the incorporation of the hydrophilic fillers into PP leads to the loss in the mechanical properties and also the changes in the thermal properties of PP. However, the mechanical properties of polymer composites can be improved by using silane coupling agents as those reported in the literature [1][2][3][4][5][6][7].Also, the previous study done by our group on the effects of interfacial interactions on the mechanical properties of PP-natural zeolite composites has indicated that silane coupling agents provide significant improvement in the mechanical properties of the composites [8]. Furthermore, although there are many studies related to the effects of silane coupling agents on the mechanical properties of polymer composites [1][2][3][4][5][6][7][8], the number of studies related to the effects of filler modification on the thermal properties of the composites is limited [9][10][11].Thermal behaviour of polymer composites is important in the determination of end use applications and processing methods of polymer articles. Generally, thermal degradation and crystalline properties of polymer composites can be analyzed by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) [12][13][14]. In this study, it was aimed to investigate the effect of silane coupling agents and natural zeolite on the thermal properties of PP using DSC and TG. Particularly, non-isothermal crystallization kinetics of the natural zeolite filled PP composites was investigated to determine the effect of cooling conditions on crystallization properties. The crystallization properties affect mechanical and transport properties of polymer composites [15][16][17]. Because of the importance of crystallization process, non-isothermal crystallization kinetics also was investigated using Avrami and Kissinger models for the determination of spherulite growth rate and crystallization activation energy, respectively. Theory Characterization of polymer composites by TGTG is based on the mass loss of a sample due to the formation of volatile products as a function of temperature. TG is used to characterize the decomposi- Analysis and Calorimetry, Vol. 94 (2008) 3, 757-765 The thermal characterization of polypropylene (PP) composites containing untreated and treated zeolite with different silane coupling agents was carried out using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) to investigate the effects of natural zeolite and surface modifiers on melting, crystallization and degradation behaviour of PP. 3-aminopro...