D. Maldas

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.

Composites of Polyvinyl Chloride-Wood Fibers. I. Effect of Isocyanate as a Bonding Agent

Abstract Various parameters concerning the performance of isocyanate as a coupling agent have been discovered. Greater premixing time (e.g., 20 min) leads to an improvement in the mechanical properties of the composites. the isocyanate solution is more efficient in comparison with undiluted isocyanate. Moreover, the chemical structure of isocyanate, which provides a better interaction with thermoplastics, results in superior properties. the reactivity of different isocyanates decreases in the following order: PMPPIC, TDIC, HMDIC, EIC. Again, isocyanate can act as a promoter or as an inhibitor, depending on the concentration of isocyanate used. For example, with a moderate concentration, it promotes maximum mechanical properties, while with a higher concentration, mechanical properties deteriorate. In addition, the nature of the pulp (e.g., CTMP, cotton, or sawdust) and fiber loading percentage as well as different grades of polymer supplied by different companies also play an important role in the mechani...

Interfacial adhesion of lignocellulosic materials in polymer composites: an overview

Cellulosic materials have long been used as cost-cutting fillers in the plastic industry. Among the various factors which determine the final performance of the composite materials depend, to a large extent, on the adhesion between the polymer matrix and the reinforcements, and, therefore, on the quality of the interface. In fact, the majority of cellulosic raw materials are lignocellulosics of different polarity to plastics, and due to this divergent behavior, the adhesion between cellulosic materials and polymer matrices is very poor. However, a sufficient degree of interaction or adhesion between the surface of the cellulosic materials and matrix resin is usually desired to achieve an optimum performance of the end-product. In many cases surface modification of the cellulosics or the matrix resins, using various additives, vinyl monomers, or coupling agents, are considered to be essential to achieve this goal. The present paper surveys research work published in this field with special emphasis on the ...

Improving adhesion of wood fiber with polystyrene by the chemical treatment of fiber with a coupling agent and the influence on the mechanical properties of composites

—The mechanical properties of polystyrene filled with chemithermomechanical pulp and wood residues of softwood and hardwood species, which were precoated with phthalic anhydride and various polymers, e.g. polystyrene and PVC, have been investigated. The extent of improvement in the mechanical properties of the composite materials depends on the coating composition, the concentration of phthalic anhydride, the nature of the coated polymers, as well as the concentration of fiber, the nature of the wood species, and the nature of the pulps. Experimental results indicate that phthalic anhydride acts as a coupling agent, but when its performance was compared to that of poly[methylene (polyphenyl isocynate)], it seemed inferior to the latter.

Role of Coupling Agents on the Performance of Woodflour-Filled Polypropylene Composites

Abstract Composite materials were prepared from waste woodflour and polypropylene (PP). In order to enhance the chemical affinity between hydrophilic woodflour and hydrophobic polymer, the surface of the filler was modified by coating with a mixture of PP and a polymeric isocyanate, while PP was mixed with two types of maleated PP, before being mixed the woodflour with polymer. The effects of coupling agents (i.e., individually or their mixtures) on the mechanical properties and void content of the composites have been evaluated. In the presence of coupling agents the composites showed superior mechanical properties compared to those of non-treated composites and to those of unmodified polymer. The extent of improvement in mechanical properties depends on the nature, addition levels, and compositions of coupling agents. As far as mechanical properties of the composites were concerned, the mixtures of coupling agents showed better performance compared to those of coupling agents used individually.

Effect of reactive additives on the performance of cellulose fiber-filled polypropylene composites

The role of boron compounds on the flame retardance characteristics of unmodified as well as surface-modified wood fiber-filled polypropylene composites is discussed. The effect of three different additives, m-phenylene bismaleimide (BMI), BMI-modified polypropylene (BPP), and a mixture of borax and boric acid, on the mechanical properties of various cellulosic fiber-filled polypropylene composites was also investigated. BPP showed the greatest effect on composite strength. The combination of BPP with a 35/65 (weight ratio) explosion fiber/polymer resulted in a composite with greater tensile strength in comparison with virgin polypropylene. Although the addition of BMI to the filled composite marginally decreases the strength of the virgin polymer, the performance of these modified composites is much better compared with that of unmodified ones. Overall, these findings indicate that BPP and BMI impart some degree of interaction between the cellulosic filler and polypropylene, particularly in the interfaci...

Surface modification of wood fibers using maleic anhydride and isocyanate as coating components and their performance in polystyrene composites

The effect of surface modification of various wood fibers [e.g. woodflour and chemithermomechanical pulp (CTMP) of hardwood aspen, and woodflour of softwood spruce] by precoating with only maleic anhydride (MA) and/or poly[methylene (polyphenyl isocyanate)] (PMPPIC) in the presence of benzoyl peroxide (BPO) on the mechanical performance of modified fiber-filled polystyrene (PS 201 and PS 525) composites has been studied. The effects of the concentration of fiber, MA, PMPPIC, and BPO on the mechanical properties of the composites have also been evaluated. As opposed to unmodified fiber-filled composites, most of the mechanical properties of the modified fiber-filled composites increased with an increase in the concentration of BPO, MA, and/or PMPPIC up to a certain limit, and then either decreased or levelled off. The properties improved even more when both MA and PMPPIC were used as compared with the use of only one of them. The optimum concentrations of BPO, MA, PMPPIC, and fiber vary according to the wo...

LIQUEFACTION OF SEVERAL BIOMASS WASTES INTO PHENOL IN THE PRESENCE OF VARIOUS ALKALIS AND METALLIC SALTS AS CATALYSTS

In this study, several biomass wastes, e.g., mainly birch (Betula maximowicziand Regel) wood meal and so on, were liquefied into phenol by using various alkalis (e.g., mainly sodium hydroxide [NaOH] and so on) and various alkaline/acidic salts. The effects of a variety of reaction parameters on the liquefaction yield (i.e., the amounts of unreacted biomass residue and combined phenol) flow properties of the liquefied biomass, and flexural properties of the liquefied biomass molding materials were investigated. The results showed that various alkalis and metallic salts (acidic or basic) were effective catalysts in the liquefaction of wood into phenol at an elevated temperature (250°C) in sufficiently low amounts of unreacted biomass residue. These compounds were not effective catalysts, however, from the standpoint of a sufficiently high amount of combined phenol. Among the alkalis and acidic salts, NaOH was found to be the most efficient catalyst in the dissolution of biomass into phenol. The lowest amount of residue and combined phenol was obtained for birch wood meal, but the highest amounts of combined phenol and the lowest unreacted phenol were obtained for bleached Kraft lignin. Moreover, other biomass, such as aspen wood meal, unbleached TMP, cotton, jute fiber, and kenaf plant, were determined as convenient biomass for liquefaction into phenol by using NaOH as a catalyst. The flow properties of NaOH-catalyzed liquefied wood were,quite close to those of commercial novolak resin. Furthermore, NaOH-catalyzed liquefied wood mixed with HMTA was easily formed into molding materials, and the flexural properties of the materials were determined to be lower than those of commercial novolak resin.

Phenolic resol resin adhesives prepared from alkali-catalyzed liquefied phenolated wood and used to bond hardwood

Wood-based resol resins were prepared from both water- and sodium hydroxide (NaOH)-catalyzed liquefied phenolated wood. The effects of various reaction parameters, e.g. the concentrations of phenol and formaldehyde, temperature, and time, on the extent of yield, free phenol content, molecular weight as well as the gluability of the resol resins have been evaluated. As far as the yield, free phenol content, and molecular weight are concerned, the optimum conditions of resol resin preparation were found to be a phenol : wood weight ratio of 4 : 6, a formaldehyde : phenol mole ratio of 1.5 : 1, a temperature of 82.5°C, and time 3 h. However, these optimum conditions changed when the performance of the adhesives was considered in terms of the adhesive bond strengths for plywood joints. The yield, molecular weights, polydispersity, and gluability of resol resins prepared from water-catalyzed liquefied wood were lower compared with those prepared from NaOH-catalyzed ones. In most cases, the dry-bond strengths o...

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.