Interfacial adhesion mechanisms of ultra-highly filled wood fiber/polyethylene composites using maleic anhydride grafted polyethylene as a compatibilizer

[Display omitted] •Ultra-highly filled wood fiber/polyethylene composites (UH-WPCs) was successfully fabricated using maleic anhydride grafted polyethylene (MAPE) as matrix or compatibilizer.•Only 25% and 30% MAPE was grafted on wood fiber at 80 wt% loading using MAPE as matrix and compatibilizer, respectively.•Mechanical properties of the compatibilized UH-WPCs were not positively correlated with the absolute content of MAPE grafted on wood fiber.•The esterification is not the key determinant for the interfacial adhesion mechanisms using MAPE as compatibilizer in UH-WPCs. To investigate whether the esterification reaction was the dominant factor that improved the interface compatibility of wood-plastic composites and accordingly their performances, ultra-highly filled wood fiber (WF)/polyethylene composites (UH-WPCs) was fabricated using maleic anhydride grafted polyethylene (MAPE) as compatibilizer or matrix with WF content of 60–85 wt%. The FTIR and TGA results confirm the absolute content of MAPE grafted on WF was 4.5% and 0.9% for the UH-WPCs with 80 wt% WF using MAPE as matrix and compatibilizer, respectively. The UH-WPCs using MAPE as matrix or compatibilizer exhibited considerable higher mechanical properties, better creep resistance, and lower water absorption compared to the uncompatibilized ones. Compared with the uncompatibilized composites with 80 wt% WF, the tensile and flexural strengths were increased by 187% and 186% for using MAPE as matrix, and 224% and 189% for using MAPE as compatibilizer, respectively. These results reveal that the mechanical properties of the UH-WPCs with MAPE were not positively correlated with the absolute content of MAPE grafted on WF. The above findings confirmed that the esterification was not the key determinant for interfacial adhesion mechanisms using MAPE as compatibilizer in UH-WPCs, and some other more important factors may exist.