Extrusion and mechanical properties of highly filled cellulose fibre-polypropylene composites

Abstract This study focused on manufacturing of highly filled cellulose fibre–polypropylene composites and evaluation of the mechanical properties of the composites. Cellulose fibre reinforced polypropylene composites with up to 60 wt% of fibres with and without coupling agent were manufactured by extrusion. In order to achieve consistent feeding of the fibres into the extruder a pelletization technique was used where the fibres were pressed into pellets. Two commercial grades of cellulose fibres were used in the study, bleached sulfite and bleached kraft fibres. Fibre dimension measurements showed that the pelletization process and extrusion at high fibre loading caused the most severe fibre breakage. Flexural testing showed that increased fibre loading made the composites stiffer but reduced the toughness. Addition of maleic anhydride grafted coupling agent (MAPP) increased the stiffness and strength of the composites significantly. In general, there was no significant difference in the mechanical properties between the composites with kraft and sulfite fibres. An interesting finding was that the flexural modulus and strength of the MAPP modified cellulose fibre–polypropylene composites were not higher than what has previously been reported for wood flour–polyolefin composites. Scanning electron microscopy showed that addition of coupling agent improved the interfacial adhesion between the fibres and polypropylene matrix.

[1]  Mohini Sain,et al.  High Stiffness Natural Fiber‐Reinforced Hybrid Polypropylene Composites , 2003 .

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

[3]  E. Sjöström,et al.  Wood Chemistry: Fundamentals and Applications , 1981 .

[4]  G. Daniel,et al.  The influence of hemicellulose on fibril aggregation of kraft pulp fibres as revealed by FE-SEM and CP/MAS 13C-NMR , 2001 .

[5]  G. Thomas,et al.  Wood fibers as reinforcing fillers for polyolefins , 1984 .

[6]  A. J. Michell,et al.  Future prospects for wood cellulose as reinforcement in organic polymer composites , 1989 .

[7]  Paul Gatenholm,et al.  The nature of adhesion in composites of modified cellulose fibers and polypropylene , 1991 .

[8]  G. E. Myers,et al.  Effects of Several Ingredient Variables on Mechanical Properties of Wood Fiber-Polyolefin Composites Blended in a Thermokinetic Mixer , 1992 .

[9]  D. Caulfield,et al.  Low temperature processing of ultra-pure cellulose fibers into nylon 6 and other thermoplastics , 2002 .

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

[11]  L. Matuana,et al.  Surface chemistry and mechanical property changes of wood-flour/high-density-polyethylene composites after accelerated weathering , 2004 .

[12]  E. Gamstedt,et al.  Stiffness Contribution of Various Wood Fibers to Composite Materials , 2006 .

[13]  C. Klason,et al.  The Efficiency of Cellulosic Fillers in Common Thermoplastics. Part II. Filling with Processing Aids and Coupling Agents , 1984 .

[14]  S. Tsai,et al.  Introduction to composite materials , 1980 .

[15]  B. Kokta,et al.  Effect of chemical treatment of fibers on the mechanical properties of polyethylene-wood fiber composites , 1989 .

[16]  P. Zadorecki,et al.  Cellulose fibers as reinforcement in composites: determination of the stiffness of cellulose fibers , 1986 .

[17]  K. Oksman,et al.  Interaction Between Wood and Synthetic Polymers , 1995 .

[18]  P. Gatenholm,et al.  The effect of chemical composition of interphase on dispersion of cellulose fibers in polymers. I. PVC-coated cellulose in polystyrene , 1993 .

[19]  P. Bataille,et al.  Effects of cellulose fibers in polypropylene composites , 1989 .

[20]  B. Kokta,et al.  Use of wood fibers in thermoplastics. VII. The effect of coupling agents in polyethylene–wood fiber composites , 1989 .

[21]  K. Oksman,et al.  Mechanical properties and morphology of impact modified polypropylene-wood flour composites , 1998 .

[22]  B. Kokta,et al.  Influence of coupling agents and treatments on the mechanical properties of cellulose fiber–polystyrene composites , 1989 .

[23]  H. Schreiber,et al.  Thermal degradation of cellulose‐containing composites during processing , 1989 .

[24]  A. Błędzki,et al.  Thermoplastics Reinforced with Wood Fillers: A Literature Review , 1998 .

[25]  J. Simonsen,et al.  Effects of a new compatibilizer system on the flexural properties of wood–polyethylene composites , 2004 .

[26]  J. Sugiyama,et al.  Characterization of the supermolecular structure of cellulose in wood pulp fibres , 2003 .