Wood flour filled polypropylene composites: Interfacial adhesion and micromechanical deformations

Abstract

Polypropylene/wood flour composites were prepared in a wide composition range from 0 to 80 wt% filler content. The adhesion of the components was modified by two maleic anhydride functionalized polypropylenes (MAPP) with different maleic anhydride content and molecular weight. The components were homogenized in an internal mixer and then compression molded to 4 mm thick plates. Tensile properties were measured and micromechanical deformation processes were followed by acoustic emission as well as volume strain measurements. The detailed analysis of the results identified four micromechanical deformation processes in the matrix and the composites, respectively. The matrix polymer deforms mainly by shear yielding, which basically does not emit sound. The presence of wood flour initiates particle related processes in the composites. Debonding dominates in the absence of coupling agent. Pull‐out of fibers may follow the debonding of large particles at an intermediate stress level. The introduction of functionalized polymer increases interfacial adhesion considerably and completely changes the deformation mechanism; the fracture of wood particles becomes the dominating process in this case. Further improvement of composite strength is possible only by the increase of the inherent strength of the wood. POLYM. ENG. SCI., 47:1246–1255, 2007. © 2007 Society of Plastics Engineers

Ecotoxicity and fungal deterioration of recycled polypropylene/wood composites: Effect of wood content and coupling

“…yield stress and tensile strength, depend very much on interfacial adhesion (Dányádi et al, 2007a;Dányádi et al, 2007b;Dányádi et al, 2006;Renner et al, 2009). This is demonstrated well by Fig.…”

“…Wood fibers reinforce PP considerably, stiffness increases from the initial value of 1.3 GPa to around 4 GPa. Composites without coupling agent and with MAPP have practically the same modulus proving that the strength of interfacial adhesion does not influence stiffness much (Dányádi et al, 2007a;Dányádi et al, 2007b;Renner et al, 2009). On the other hand, the correlation obtained for the composites containing MAEPDM deviates from that of the other two sets of materials indicating a slight degree of embedding in this case.…”

“…Since the surface energy of wood is relatively small, such particles easily debond from the surface under the effect of external force (Móczó & Pukánszky, 2008;Pukánszky & Vörös, 1993;Renner et al, 2009). To prevent debonding and achieve sufficient reinforcement, the fibers are usually coupled to the matrix polymer by functionalized polymers, mostly by maleated PP (MAPP) in polypropylene Bledzki et al, 2002a;Dányádi et al, 2007a;Dányádi et al, 2010;Dányádi et al, 2007b;Ichazo et al, 2001).…”

Wood flour filled PP composites: Compatibilization and adhesion

“…The stiffness of the composites is not influenced significantly by the presence of the functionalized polymer [3,17,27], but strength usually increases considerably [2,3,17,19,27,28]. The tensile and flexural strength of polymers usually decreases with increasing filler content in the absence of coupling [2,19,28,31], but the correlation can be turned around and considerable increase can be achieved with the help of functionalized polymers.…”

“…In previous papers we presented the effect of various factors on the deformation and failure of wood flour filled PP composites [31,33]. We found that the dominating 5 micromechanical deformation mechanism is debonding in these materials, indeed.…”