Wood fibers as reinforcing fillers for polyolefins

Abstract

Wood pulp fibers possess strength and modulus properties which compare favorably with glass fibers when the differences in fiber densities are considered. Softwood pulp fibers with fiber aspect ratios near 100 are readily dispersed into highdensity polyethylene or isotactic polypropylene with the aid of carboxyic dispersing agents to form mixtures containing 50 weight-percent wood pulp which can be readily injection molded. The mechanical properties of the molded specimens were similar for all types of pulp including Kraft (bleached and unbleached), mechanical and chemical-mechanical pulps, waste pulps, and reclaim newspapers. Comparisons of the stiffness/weight efficiencies revealed that pulp composites equal or exceed the stiffness of most traditional materials of construction including steel, aluminum, glass-fiber composites, and talcfilled polyolefins, while retaining a major material cost advantage. The measured strength values of the pulp composites were less than the theoretically predicted values due to the presence of voids created by the formation of volatiles during processing. Mechanical pulps which were available in dry form were preferred because of lower cost and ease of handling. Wood fibers are non-abrasive so that relatively large concentrations may be incorporated into polyolefins without causing serious machine wear during mixing and fabrication.

Tensile and impact properties of three-component PP/wood/elastomer composites

“…Reports in the literature indicate that impact resistance often decreases as an effect of wood reinforcement [38][39][40][41][42][43][44] similarly to many particulate filled composites [45][46][47][48][49][50][51].…”

Effectiveness of Maleated and Acrylic Acid-Functionalized Polyolefin Coupling Agents for HDPE-Wood-Flour Composites

“…The rule of mixtures only holds under certain conditions [18,19]: (i) the fibers are continuous, that is they extend for the length of the composites, (ii) the fibers are aligned in a single direction, (iii) the load is applied parallel to the direction of fibers, and (iv) there is perfect interfacial bonding between the fiber and the matrix. Accordingly, the tensile strength of the composites will increase with the fiber fraction beyond the critical fiber 1 Composites were made of 60% HDPE and 40% wood flour based on the total weight of composites.…”

Thermal, mechanical and morphological properties of polypropylene/clay/wood flour nanocomposites

“…The addition of wood flour to neat thermoplastics can greatly stiffen them, but makes them more brittle at the same time [2,6,7]. Compatibilizers such as maleated polyethylene (MAPE) and maleated polypropylene (MAPP) played an important role in improving the compatibility and bonding strength between hydrophilic wood flour and hydrophobic thermoplastics [8][9][10]. Composites with structure and composition at the nanoscale exhibit highly improved mechanical properties and high temperature endurance [11][12][13][14].…”