The Influence of Excess Coupling Agent on the Microdeformation Processes and Mechanical Properties of Poly(propylene)/Wood‐Flour Composites

Summary: It is well known that coupling agents improve the adhesion between poly(propylene) and wood fillers leading to an increase of the composite mechanical properties. Above a certain concentration limit of the coupling agent, however, deterioration of the mechanical properties often occurs, and little attention has been directed so far towards finding out the reasons for that behavior. Transmission electron microscopy and high‐voltage electron microscopy were used in this work to study the morphology and microdeformation behavior of PP/wood‐flour composites modified with high amounts of maleated poly(propylene) as a coupling agent. It was found that the coupling agent containing a higher concentration of grafted maleic anhydride forms a separate phase in the poly(propylene) matrix, influencing the mechanical properties of the composites. HVEM micrograph of the deformation structure of wood‐filled poly(propylene) composite showing fibrils stretching between the coupling agent domains and the PP matrix. magnified image HVEM micrograph of the deformation structure of wood‐filled poly(propylene) composite showing fibrils stretching between the coupling agent domains and the PP matrix.