## 2 Results and Discussion
### Properties of Composites
#### 2.2.3 Analysis of Dynamic Mechanical and Deformation Mechanism  
As shown in Figure 8a, in the unmodified system, the G\({}^{\prime}\) of unmodified WrP was consistently the highest across the tested temperature range. This was attributed to the molecular chain segments being in a \"frozen\" state at low temperatures, while the G\({}^{\prime}\) of the composites was mainly contributed by the stiffness of the reinforced matrix and wood flour [22]. As the temperature increased, the kinematic activity of the matrix molecular chain segments increased, and weak interfacial bonding caused a rapid decrease in the G\({}^{\prime}\) of WrP. Its value fell below those of WrPMD and WrPM at approximately 3 \({}^{\circ}\)C and 20 \({}^{\circ}\)C, respectively. In the WrPMD system, good interfacial compatibility and the branched structure of the matrix molecular chain showed a positive contribution to the composite's modulus, resulting in a maximized G\({}^{\prime}\) at high temperatures. Following the addition of OBC, its lower modulus resulted in the G\({}^{\prime}\) value of WrPOM being the lowest, consistent with the trend observed in flexural modulus changes. The additional incorporation of DVB enhanced matrix strength and interfacial compatibility, partially offsetting the negative impact of OBC on modulus [33]. As a result, the G\({}^{\prime}\) of WrPOMD exceeded that of WrP at elevated temperatures. The magnitude of the loss modulus G\({}^{\prime\prime}\) primarily reflected energy dissipation from the movement of molecular chains at the composite interface (Figure 8b). As the temperature increased, energy dissipation from matrix molecular chain relaxation increased the G\({}^{\prime\prime}\) of the composites. The loss modulus showed two transition peaks around 0 \({}^{\circ}\)C and 80 \({}^{\circ}\)C. The relaxation peak at 0 \({}^{\circ}\)C was primarily associated with the polymer's glass transition. The differences in the glass transition relaxation peaks at low temperatures were small. This was attributed to interface interactions, which restricted chain segment movement. The relaxation peak at 80 \({}^{\circ}\)C corresponded to molecular chain movement in the crystalline region of rPP. With increasing temperature, rPP molecular chain mobility improved after activation. In WrP, weak interfacial bonding increased rPP chain relaxation, while friction with wood flour in the interface increased G\({}^{\prime\prime}\) due to increased energy dissipation. After MAH grafting modification, chain movement restriction reduced at higher temperatures, thereby enhancing the short-chain mobility in rPM. This facilitated movement in the crystalline matrix, shifting the onset and peak relaxation to lower temperatures. In addition, after DVB co-grafting modification, both onset and peak relaxation of the composites shifted to higher temperatures compared with WrPM. After MAH grafting modification of the rPP matrix, the G\({}^{\prime\prime}\) of both WrPM and WrPOM decreased. This indicated that improved interfacial compatibility effectively restricted molecular chain movement at the interface, reducing energy loss. In the MAH/DVB co-grafted system, as the number of MAH groups in the matrix molecular linkages increased and branched structures formed, the movement of molecular chains at the interface became more difficult, leading to a decrease in G\({}^{\prime\prime}\) for WrPMD and WrPOMD. The tan\(\delta\) of unmodified WrP was consistently the largest (Figure 8c). This phenomenon could be attributed to the poor dispersion of wood flour and weak interfacial bonding between the components, resulting in significant energy dissipation within the weak interfacial layers and defects in the composites [40]. The co-grafting of modified rPP with MAH and DVB improved interfacial compatibility and reduced defects, resulting in lower tan\(\delta\) values for the composites WrPM and WrPMD.