Polymer wood

To prepare polymer wood, wood is degassed and then loaded with a suitable monomer. The monomer is then polymerized. For polycondensations, the preferred monomers are those that do not eliminate volatile components during polymerization (diisocyanates). Both ring-containing monomers (epoxides) and monomers with carbon-carbon double bonds can be polymerized. In the case of the latter, polymerization can be initiated by y-irradiation, peroxides, redox systems, etc. Not all monomers are suitable for the manufacture of polymer wood. Poly(acrylonitrile), for example, is insoluble in its own monomer. In wood, therefore, the precipitation polymerization leads to powdery deposits and not to a continuous phase. The same problem occurs with vinyl chloride, and in this case the boiling point of the monomer (—14 C) is too low. Poly(vinyl acetate) has too low a glass-transition temperature. In addition, monomers with low G values (see Section 21.2.1) need high doses of y rays to initiate polymerization. Commercially used polymers include, e.g., copolymers of styrene and acrylonitrile, poly(methyl methacrylate), and unsaturated polyesters. 

It is probable that some grafting occurs during polymerization, since electron spin resonance studies show radicals in both the cellulose and the lignin after irradiation. In addition, part of the polymer cannot be extracted. This nonextractability, however, cannot originate from cross-linking of the polymer chains since the extracted portion is unbranched, and branched chains would be found in the extract in the case of a cross-linking reaction. 

Polymerization is inhibited by substances present in the wood. For example, the quercitin found in wood transforms under the action of oxygen into a quinone, which acts as an inhibitor (see Section 20.3.6)  

This unavoidable inhibition can be counteracted by suitable choice of initiator, e.g., through the use of a mixture of rapidly and slowly decomposing initiators. 

Polymer wood has improved mechanical properties compared to wood. It is used for window frames, sports equipment, musical instruments, and boats. A parquet floor of polymer wood does not require subsequent sealing. The polymer content of such woods varies, of course, from one type of wood to another, but is usually between 35% and 95%. 

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Natural polymers are far more complex materials, being exclusively "organic", that is, products of life (cellulose, proteins, DNA,...). Nevertheless, as nature seems to have formed (size, weight, hardness, etc.) several natural polymers (wood, bones, ivory, etc.) in such a way as to be almost immediately usable by our ancestors, they were most probably the bases of the first human tools. The commonly widespread conception that polymers are the youngest "materials" in the historical world is not true, but, strictly speaking, only applies to synthetic polymers, which were discovered about 100 years ago, early in the XXth century. 

Harvey GR (1972) Absorption of chlorinated hydrocarbon from seawater by a crosslinked polymer, Woods Hole, MA, USA... 

Sebe, G. and Brook, M. (2001). Hydrophobization of wood surfaces covalent grafting of silicone polymers. Wood Science and Technology, 35(3), 269-282. 

Petrella, V., The mass burning rate of polymers, wood and liquids. Journal of Fire and Flammability 1980, 11, 3-21. 

The potential use of cellulose graft polymers to compatibilize the linking of a natural polymer (wood) with a synthetic polymer (polystyrene) is based on... 

Several reports on the activation of lignocellulosic surface by corona discharge, microwave plasma, and ozone treatments have been published (120-22). Strong bonds were produced between thermoplastics and wood by corona treatment of wood surfaces and particularly by treatment of polyethylene and polystyrene surfaces. With 5-min treatment wood—polymer—wood bonds of over 569 psi... 

Use Organic synthesis, particularly of adipic acid and caprolactam (about 95%), polyvinyl chloride and its copolymers, and methacrylate ester polymers wood stains paint and varnish removers, spot removers degreasing of metals polishes leveling agent dyeing and delustering silk lubricating oil additive solvent for cellulosics natural and synthetic resins, waxes, fats, etc. 

Most of all, in daily life, shelter, clothing, food, education, and recreation depended, and still depend, essentially on the use of natural polymers—wood, cotton, fur, wool, silk, starch, leather, paper, rubber, and a variety of resins, glues, and coatings. Around each of these materials a highly sophisticated art developed—entirely empirical and without any basic knowledge and, in fact, in most cases, without any concern about the material s composition and structure. 

U.S. Pat. No. 6,942,829 [72] discloses a method of forming a polymer-wood composite material comprising 20-80% by weight of cellulose filler such as hardwood fiber, softwood fiber, hemp, jute, rice hulls, and wheat straw, 20-80% of a thermoplastic polymer such as polypropylene, polyethylene, polyamides, polyesters, and other polymers, 0.1-10% of a blend of a nonionic compatibilizer and a lubricant. 

Canadian Pat. No. 2,178,036 (December 1996). K.V. Seethamraju, N.J. Beaverson, K.E. Heikkila, and M.J. Deaner. Advanced compatible polymer wood fiber composite. 

Quantitative XRF is used in virtually every industry for almost any type of liquid or solid sample. XRF is used daily to analyze minerals, metals, paper, textiles, ceramics, cement, polymers, wood, environmental samples, food, forensic samples, cosmetics and personal care products, and more. Only a few examples will be given here. 

Hamstad MA (1997) Improved signal-to-noise wideband acoustic/ultrasonic contact displacement sensors for wood and polymers. Wood and fibre science 29 (3) 239-248... 

Porous materials are two-phase structures composed of a continuous solid/liquid phase and either continuous or discontinuous gaseous phase [2,4,6,7], As explained before, it is possible to find various materials with a porous structure (polymers, wood, metals, ceramics, etc). Porous structures can be classified according to their topology on one hand would be the open pore foams, which show continuity of the gas and solid phases, and on the other hand would be the closed pore foams, in which the gas is enclosed in the pores (ie, continuous solid phase and discontinuous gas phase). 

The properties of polymer-wood materials based on virgin and recycled low density polyethylene (LDPE), PS, and their blends (LDPE-PS) were studied [21] and it was found that reactive groups in recycled polymers bring about chemical and specific interactions at the polymer-wood and polymer-polymer interface, thus improving the mechanical properties of these materials. 

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