Wood flour filled PP composites: Adhesion, deformation, failure

Poly(propylene) (PP) wood composites were prepared in a wide composition range from 0 to 70 wt% wood content. Matrix/wood adhesion was improved by the introduction of two maleinated polypropylenes (MAPPs) with different molecular weights and functionality. MAPP/wood ratio changed from 0 to 0.25 in 0.05 steps. Mechanical properties of the composites were characterized by tensile testing, while their fracture resistance was determined with instrumented impact measurements. Micromechanical deformation processes were followed by acoustic emission and volume strain measurements, which were supported by scanning electron microscopy done on the broken surface of fractured samples. The results show that stiffness increases with wood content and it does not depend very much either on the type or the amount of the functionalized polymer used. However, ultimate tensile properties are strongly influenced by the amount and properties of MAPP; larger molecular weight and smaller functionality are more advantageous both for strength and impact resistance. The optimum MAPP/wood ratio was found to be around 0.05 in accordance with some literature data. Because of their large size, wood particles debond very easily from the matrix leading to volume increase and catastrophic failure at small deformations. When adhesion is improved by the introduction of MAPP, large wood particles fracture thus also contributing to the failure of the composite. At large wood content considerable aggregation of the particles may take place leading to inferior strength.

[1]  Qinglin Wu,et al.  Wood‐fiber/high‐density‐polyethylene composites: Coupling agent performance , 2005 .

[2]  B. Pukánszky,et al.  Interfaces and interphases in multicomponent materials: past, present, future , 2005 .

[3]  A. Błędzki,et al.  Creep and impact properties of wood fibre–polypropylene composites: influence of temperature and moisture content , 2004 .

[4]  J. Balatinecz,et al.  Surface modification and adhesion mechanisms in woodfiber-polypropylene composites , 1999 .

[5]  A. Błędzki,et al.  A comparison of compounding processes and wood type for wood fibre—PP composites , 2005 .

[6]  B. Kokta,et al.  Interfacial adhesion of lignocellulosic materials in polymer composites: an overview , 1993 .

[7]  H. Choi,et al.  Analysis of the debonding process in polypropylene model composites , 2005 .

[8]  Qinglin Wu,et al.  Chemical Coupling in Wood Fiber and Polymer Composites: A Review of Coupling Agents and Treatments , 2000 .

[9]  Jürgen Bohse,et al.  Acoustic emission characteristics of micro-failure processes in polymer blends and composites , 2000 .

[10]  R. Kahraman,et al.  Effect of epolene E‐43 as a compatibilizer on the mechanical properties of palm fiber–poly(propylene) composites , 2004 .

[11]  B. Kokta,et al.  Use of Wood Flour as Filler in Polypropylene: Studies on Mechanical Properties , 1989 .

[12]  Bumjae Lee,et al.  Water absorption behavior and mechanical properties of lignocellulosic filler–polyolefin bio-composites , 2006 .

[13]  A. Błędzki,et al.  Composites reinforced with cellulose based fibres , 1999 .

[14]  V. Hristov,et al.  Impact fracture behavior of modified polypropylene/wood fiber composites , 2004 .

[15]  B. Lauke,et al.  Acoustic emission of debonding between fibre and matrix to evaluate local adhesion , 2003 .

[16]  G. Michler,et al.  Modified polypropylene wood flour composites. II. Fracture, deformation, and mechanical properties , 2004 .

[17]  J. Karger‐Kocsis,et al.  Comparison of the fracture and failure behavior of polypropylene composites reinforced by long glass fibers and by glass mats , 1995 .

[18]  I. Mondragon,et al.  Mechanical Behavior of Wood/Polypropylene Composites: Effects of Fibre Treatments and Ageing Processes , 2003 .

[19]  Mohini Sain,et al.  Interface Modification and Mechanical Properties of Natural Fiber-Polyolefin Composite Products , 2005 .

[20]  J. Kenny,et al.  Mechanical characterization of polypropylene–wood flour composites , 2003 .

[21]  A. Błędzki,et al.  Wood Fiber Reinforced Polypropylene Composites: Compression and Injection Molding Process , 2004 .

[22]  Pht Peter Vollenberg.  The mechanical behaviour of particle filled thermoplastics , 1987 .

[23]  L. Matuana,et al.  Effectiveness of Maleated and Acrylic Acid-Functionalized Polyolefin Coupling Agents for HDPE-Wood-Flour Composites , 2003 .

[24]  Pht Peter Vollenberg,et al.  Experimental determination of thermal and adhesion stress in particle filled thermoplasts , 1988 .

[25]  R. Li,et al.  A FRACTURE MECHANICS STUDY OF POLYPROPYLENE–WOOD FLOURS BLENDS , 2001 .

[26]  Carmen Albano,et al.  Polypropylene/wood flour composites: treatments and properties , 2001 .

[27]  A. Błędzki,et al.  Physico-mechanical studies of wood fiber reinforced composites , 2002 .