## 1 Introduction  
Biocomposites have recently experienced significant advancements in both academia and industry due to their favorable specific mechanical properties and eco-friendly characteristics [1, 2]. Biocomposites can efficiently utilize natural lignocellulosic resources and plastic waste as important raw materials to produce high-value and sustainable products [3]. However, recycled plastic wastes, such as polypropylene (PP), polyethylene (PE), and polystyrene (PS), exhibit poor miscibility, and fully separating the individual components is technically difficult and uneconomic [4]. Additionally, most recycled plastic waste is a hydrophobic mixture and is incompatible with hydrophilic lignocellulosic particles [5]. The mechanical performance of the resulting waste plastic-based biocomposites generally fails to meet the performance requirements in structural and other engineering fields, particularly regarding impact strength, due to interphase incompatibility [6, 7, 8]. To better meet performance requirements and expand applications in emerging fields, various strategies for enhancing interfacial adhesion in biocomposites containing plastic waste have been extensively researched [9; 10; 11]. Coupling agents are an effective means to improve interfacial adhesion and mechanical properties in biocomposites [12]. However, the partial enhancement of the interface layer still falls short of the impact strength requirements for structural applications. Low impact strength, particularly at higher lignocellulosic loadings (above 50 wt.%), remains a major drawback of biocomposites [13]. Consequently, this severely reduces the end-of-life performance of biocomposites. Incorporating strong hybrid fibers into biocomposites is an alternative strategy to enhance both stiffness and impact strength [14]. However, some drawbacks exist, such as poor interfacial compatibility between components and severe abrasion of processing equipment. Furthermore, reinforcing fibers, like carbon fiber, glass fiber, and Kevlar fiber, are not recyclable [15; 16; 17]. Blending modification with polyolefin elastomers or their maleated derivatives to improve impact strength has been a traditional, yet active, area of research, particularly for polyolefin-based biocomposites [18; 19; 20]. Extensive efforts devoted to elastomer-toughened polymer/filler composites have focused on achieving excellent toughness with minimal strength and modulus loss or even improvement [21; 22; 23]. In these multicomponent systems, two types of structures may form: elastomer and filler either separately distributed within the polymer matrix or the elastomer encapsulates the filler, forming an embedded structure [24; 25]. [PERSON] et al. [26] chose two compatibilizers, maleated polypropylene (MAPP) and maleated ethylene-propylene-diene elastomer (MAEPDM), to prepare wood plastic composites separately. They found that only MAPP led to separate distribution of the components, whereas embedding was promoted by the introduction of MAEPDM. [PERSON] et al. [27] conducted a systematic study on composites with embedded structures, investigating their effects on stiffness and toughness. They reported that the stiffness of these composites is determined by the degree of embedding, while toughness increases can result from either an embedded structure or separate distribution. The toughness of these multicomponent systems is primarily determined by the dominant micromechanical deformation processes. Therefore, proper structural design is essential for developing high-performance materials [28; 29; 30]. Additionally, optimizing the composition, component type and content, and molding technology is a potential strategy to achieve greater stiffness and toughness in the final composites. The structure-property relationships of PP/wood flour/elastomer composites prepared using a twin-screw extruder were reported in a previous study [31]. Polymer matrix modification with polar monomers can be used to control the structure of multicomponent composites.