Dimensional stability wood-polymer composites

Furuno, T. and Goto, T. (1979). Structure of the interface between wood and synthetic polymer. Xll. Distribution of styrene polymer in the cell wall of wood-polymer composite (WPG) and dimensional stability. Mokuzai Gakkaishi, 25(7), 488 95. 

Simonsen, J. (1998). Lack of dimensional stability in cross-linked wood-polymer composites. Holzforschung, 52(1), 102-104. 

The book opens with a paper on the structure and composition of wood to define the material under discussion and then considers molds, permeability, wood preservation, thermal deterioration and fire retard-ance, dimensional stability, adhesion, reconstituted wood boards such as fiberboard and particleboard, plywood, laminated beams, wood finishes, wood-polymer composites, and wood softening and forming. A final paper treats the common theme of wastewater management. Only one of the papers presented at the meeting is not included in this volume, and its subject of conventional wood preservation methods is adequately treated in detail elsewhere (e.g., Nicholas, D. D., Ed Wood Deterioration and Its Prevention by Preservative Treatments, 2 vols., Syracuse University Press, 1973). 

Fifteen years ago, when wood-plastic composites were first introduced many people predicted that this process would solve the problem of wood dimensional stability and great claims were made for its future use. Now that the physical properties of wood-polymer composites are better understood, specific commercial products are being produced which take advantage of the desirable aesthetic appearance, the high compression strength, increased hardness and abrasion resistance and improved dimensional stability. Future use of wood-polymer composites will depend upon the imagination of the producer and the market place. 

JL HE POLYMERIZATION OF VINYL MONOMERS in the void spaces of bulk wood results in wood—polymer composites of increased strength properties and dimensional stability see Chapter 6). Because the different environmental conditions expose in-service timber to attack by numerous wood-deteriorating microorganisms, it is desirable to enhance the biodegradation resistance of wood, with simultaneous improvements in mechanical behavior. This chapter summarizes the formation of bioactive wood-polymer composites (1-4). The basic approach is still in situ polymerization of vinyl monomers in wood, with the appropriate choice of a bioactive, toxic, functional group incorporated in the monomer, and with other modifications based on wood-polymer reactions. 

The impregnation of wood by polymers with TBT functional groups offers a viable route to the preparation of bioactive wood— polymer composites with a number of advantages. Polymer impregnation may be expected to improve the strength properties and dimensional stability of wood in water. The controlled release of the toxic TBT moiety, chemically linked to the polymer located within the wood, can increase the service life of wood while ensuring min-... 

Analog-to-glass fibers silanes are used as coupling agents for natural fiber polymer composites. For example, the treatment of wood fibers with product A-175 improves wood dimensional stability [53]. In contrast, a decrease of mechanical properties was observed for coir-UP composites after a fiber modification with di-chloromethylvinyl silane [54]. The treatment of mercer-... 

Fujimura, T. and Inoue, M. (1992). Improvement of the durability of wood with acrylic high polymers IV. Effects of bulking on the dimensional stability of composites. Mokuzai Gakkaishi, 38(3), 264-269. 

It may also be possible to eventually extend this bonding concept to the preparation of flakeboards and other wood-base composite materials. If plastics like polystyrene are incorporated into the composite matrix, and successful bonding between the wood and plastic is developed through the graft polymers, the three-dimensional network of plastic material throughout the composite matrix may lead to enhanced physical and mechanical properties as well as improvements in dimensional stability (Figure 2). 

Historically, the use of cellulose fibers in polymer matrix composites has been mainly as a cheap filler in the form of wood flour [2]. Although wood flour does increase the dimensional stability of a polymer composite, it does not significantly increase the shength of the composite, due to its relatively low degree of cellulose fiber refinement. In addition, cellulose is hydrophilic because of its many hydroxyl groups and ether links, and this leads to high moisture uptake. Moisture adsorption tends to lower the mechanical shength of cellulose composites over time. 

Some of the composites have also been in the consumer market for some time. In addition to plywood, homebuilders and furniture makers are making extensive use of particle board (woodchips in a polymer matrix) because of its superior dimensional stability. Often it is laminated to a wood veneer for use as furniture. Decorative vinyl-clad steel or aluminum panels are used in office buildings. Generally, the more advanced composites such fiber-reinforced metals and ceramics have been too expensive for... 

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