R. G. Raj

Improvement of the mechanical properties of sawdust wood fibre—polystyrene composites by chemical treatment

Abstract The mechanical properties of compression-moulded polystyrenes filled with sawdust wood residue of softwood and hardwood species have been investigated. The tensile modulus at 0.1% strain and the tensile strength, elongation and energy at the yield point are reported. The suitability of sawdust wood residue as a filler for thermoplastics has been tested using two different mesh sizes (20 and 60), as well as by varying the weight percentage of fibres from 10% to 40%. Moreover, to improve the compatibility of the wood fibres with the polymer matrices, different treatments (e.g. graft copolymerization) and coupling agents (e.g. silanes and isocyanates at various concentrations) have also been used. The extent of the improvement in mechanical properties depends on the fibre loading, on the particle size of the fibre, on the concentration and chemical structure of the coupling agents, and on whether special treatments (e.g. coating or grafting of the fibre) are used. The mechanical properties of the composites are improved up to 30% in the case of fibres having a mesh size 60 and when up to 3% of isocyanates was used.

Use of Wood Flour as Filler in Polypropylene: Studies on Mechanical Properties

Abstract Mechanical properties of polypropylene (PP) filled with wood flour was studied. To improve adhesion at the interface, different surface treatments of the fiber were carried out. Polymethylene polyphenylisocyanate (PMPPIC) and silane coupling agents (silane A-172, A-174, and A-1100) were used to pretreat the fiber before it was introduced into the polymer. Increase in tensile strength, with fiber concentration, was found in PP filled with PMPPIC pretreated wood flour. Elastic modulus was unaffected by fiber treatment. Izod-impact strength decreased with increased filler level in the composite.

Polypropylene-Wood Fiber Composites: Effect of Fiber Treatment on Mechanical Properties

Abstract Polypropylene (PP) was reinforced with different wood fibers, chemithermomechani-cal (CTMP) aspen and commercial pulps (Tempure and Temalfa-A). Various chemical treatments on the fiber was carried out to improve the bonding at the interface. Fibres coated with Silane coupling agents Silane A-172 and A-174 (with vinyl and methacryloxy functional groups respectively) upon reinforcement showed poor tensile strength. PP filled with Pre-coated fibers containing maleated propylene wax, polymer and polymethylene polyphenyl isocyanate produced higher tensile strength and modulus. The use of dicummyl peroxide and cummine hydro peroxide as initiators during the coating of the fiber was not effective. Polypropylene reinforced with fibers of lower mesh size gave better tensile properties.

Wood flour as a low-cost reinforcing filler for polyethylene: studies on mechanical properties

Wood flour was used as a reinforcing filler for high-density polyethylene (HDPE). Different fibre treatments were carried out to improve the bonding at the polymer-fibre interface. Wood flour composites coated with alkoxy-silane coupling agents (silane A-172 and A-174) generally showed higher tensile strength and modulus values. A significant improvement in tensile properties was achieved with the addition of polymethylenepolyphenyl isocyanate. The Izod impact strength of the composites decreased with an increase in filler concentration.

The use of Isocyanate as a Bonding Agent to Improve the Mechanical Properties of Polyethylene-Wood Fiber Composites

Abstract Chemithermomechanical pulp (CTMP) of aspen was used as a filler in high density (HDPE) and linear low density (LLDPE) polyethylenes. To improve the bonding between the fiber and polymer, different chemical treatments of the fiber a) treatment with different isocyanates b) coating with maleic anhydride was carried out. Composites with isocyanate treated wood fibers produced higher tensile strength compared to untreated fiber composites. But when compared to diisocyanate, the polyisocyanate treated fibers produced higher gain in strength. HDPE or LLDPE filled with maleic anhydride coated CTMP aspen fibers showed a slight decrease in strength with the increase in filler concentration. Tensile modulus generally increased with filler loading and was not much affected by fiber treatment.

Use of wood fibres as reinforcing fillers for polystyrene

Abstract The suitability of wood (aspen and spruce) fibers in the form of different pulps (e.g. chemithermomechanical and sawdust as reinforcing fillers for polystyrene PS667) have been investigated. The variation in the mixing and moulding temperatures of the composites as well as the effect of different parameters (e.g. fibre loading (10–40 wt.%), particle size of the fibres (20 and 60 mesh size), concentration of coupling agents (0–20%) and nature of the coupling agents (isocyanates) on the mechanical properties (e.g. tensile modulus (at 0.1% strain), tensile strength at maximum point and corresponding elongation and energy) were evaluated. Maximum improvements in the mechanical properties occur when mixing or moulding temperatures reach 175–190°C. Also, a higher percentage of the coupling agent (2 wt.%) and a smaller particle size (mesh size 60) in the composite provide maximum improvement. The polymeric nature of poly(methylene (polyphenyl isocyanate)) as well as the π electron of the benzene ring which is also common to polystyrene make it the best coupling agent in comparison with other isocyanates. After optimization of mixing and moulding conditions, and selecting the suitable coupling agents, composites with 30 wt.% of wood fibres in polystyrene offered improved mechanical properties.

The effect of processing conditions and binding material on the mechanical properties of bagasse fibre composites

Abstract Steam-exploded bagasse fibres (mesh size 60) were used for the fabrication of composites. Polyethylene (high, medium and linear low density) was used as binding material to improve the mechanical properties and dimensional stability of the composites. The effects of variation in processing conditions (compression moulding temperature, mould heating time and moulding pressure) on mechanical properties of the composites were examined. The composities fabricated at high moulding temperature showed improvement in mechanical properties. A binding material (polyethylene 0–20 wt%) was used to improve the fibre adhesion. Significant increases in tensile strength and modulus were observed for the composites of bagasse fibres pretreated with polyethylene as compared to composite without binder.

Compression Molding of HDPE-Wood Fiber Composites: Effect of Processing Conditions on Mechanical Properties

Fabrication of high density polyethylene (HDPE)-wood fiber composites was done by compression molding. The polymer-fiber mixture was compounded in an extruder or roll mill. The effects of compounding (temperature and time) and molding conditions (temperature, pressure, heating and cooling time) on mechanical properties of the composites were examined. Higher tensile strength values were obtained when compounded at 200°C for a short time. Increase in fiber concentration (0-40%) produced an increase in tensile modulus followed by a decrease in elongation and fracture energy.