## 1 Introduction  
About 6.5 billion tons of plastic and rubber wastes [1], which constitute mainly plastic bags, masks and water bottles, are constantly produced [2] and disposed of around the world every year [3]. Consequently, the food chain of marine life and terrestrial animals have been interrupted due to the difficulty of degrading these wastes in nature [4, 5]. At present, there are several conventional attempts to solve plastic pollution, including unsupervised landfill and incineration or development of degradable plastic as a substitute for use in daily life [6, 7, 8, 9]. However, these methods would probably cause secondary pollution or waste residues during the production of degradable plastics [10, 11]. Hence, the transformation of plastic wastes into wood plastic composites (WPC) could be one of the promising alternatives to avoid secondary pollution [12].  
WPC represents a kind of biocomposite with high hydrostability that is prepared by the combination of wood fiber and plastic wastes. The production process of WPC includes injection molding, extrusion molding, compression molding and hot pressing molding [13]. Compared with the traditional adhesive-bonded biocomposites, WPC demonstrates the advantages of being glue-free and having zero formaldehyde emission during the preparation process [14, 15]. As early as the 1990s, many countries have begun to use waste plastics in daily life to manufacture WPC [16]. In recent years, numerous studies were reportedon the properties of wood flour-based WPC prepared with a different proportion of wood flour and plastic wastes. [PERSON], [PERSON] et al. studied the mechanical properties of WPC prepared with different proportions of Paulownia elongata wood and polypropylene [17]; [PERSON] et al. studied the possibility of using decayed wood and polyvinyl chloride to prepare wood plastic composites with excellent properties [18]. However, the performance comparison of WPC prepared with several plastic wastes (i.e., PE, PP, PVC, ABS, HDPE) under different proportions of wood flour and plastic wastes are limited. Hence, it was innovative to compare the properties of WPCs prepared by different plastics combined with different proportions to formulate the optimum WPC with the best performance.  
The objective of this study was to prepare wood plastic composites with different types of plastic waste as raw materials and different ratios, and to study the effect of the ratio on the properties of the materials, so as to find out the nonadhesive composite which is suitable to replace MDF and HDF. The prepared WPCs were first characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Then, the WPCs were further analyzed on the mechanical properties using a mechanical testing machine to study its water stability and other properties by hot molding (Figure 1a,b). WPC with desirable characteristics such as high mechanical properties, good hydrophobicity and environmental friendliness was successfully prepared at a lower cost (Figure 1c) than the medium-density fiberboard (MDF) and high-density fiberboard (HDF).