Biodegradability, wood-polymer

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. 

It is difficult to make a distinct classification of biodegradable polymers. Many authors have classified them according to their origin as natural or synthetic polymers. Both of these are subdivided into different classes based on the main linkages present in their structure. Thus completely biodegradable natural polymer subclasses include polysaccharides, polypeptides, polyesters, lipids, natural rubber and natural composites (wood). Partially biodegradable synthetic polymer subclasses include polyesters, polyur eas, polyurethanes, polyamides, poly( vinyl alcohol) and poly (ethylene glycol). 

Deka BK, Mandal M, Maji TK (2012) Effect of nanoparticles on flammability, UV resistance, biodegradability, and chemical resistance of wood polymer nanocomposite. Ind Eng Chem Res 51 11881-11891... 

Hazarika A, Maji TK (2014c) Strain sensing behavior and dynamic mechanical properties of carbon nanotubes/nanoclay reinforced wood polymCT nanocomposite. Chem Eng J 247 33-41 Hazarika A, Maji TK (2014d) Thermal decomposition kinetics, flammability, and mechanical property smdy of wood polymtar nanocomposite. J Therm Anal Calorim 115 1679-1691 Hazarika A, Mandal M, Maji TK (2014) Dynamic mechanical analysis, biodegradability and thermal stability of wood polymer nanocomposites. Compos Part B 60 568-576 Hetzer M, Kee D (2008) Wootl/polymer/nanoclay composites, environmentally friendly sustainable technology a review. Chem Eng Res Des 86 1083-1093 Hill CAS, Abdirl KHPS, Hale MD (1998) A study of the potential of acetylation to improve the properties of plant fibres, frrd Crops Prod 8 53-63 Hoffmann MR, Martin ST, Choi WY, Bahnemann W (1995) Environmental application of semiconductm photocatalysis. Chem Rev 95 69-96 Huda MS, Drzal LT, Misra M, Mohanty AK (2(K)6) Wood-fiber-reinforced poly(lactic acid) composites evaluation of the physicomechanical and morphological properties. J AppI Polym Sci 102 4856-4869... 

Lu, X., Zhang, M.Q., Rong, M.Z., Shi, G., and Yang, G.C. (2003) All-plant fiber composites II. Water absorption behavior and biodegradability of unidirectional sisal fiber reinforced benzylated wood. Polym. Compos., 24, 367-379. 

It will be evident from the applications discussed above that a primary requirement for agricultural plastics is a variable and controllable period of stability in the environment. Oxo-biodegradable synthetic polymers, as was seen earlier, biodegrade in much the same way as natural rubber and lignocellulosic materials such as straw, twigs, wood chips, bark, etc. These... 

Sugar cane waste is another raw material that can be treated in a hot solution of concentrated acetic acid in hydrochloric acid solution. After re-concentration, the lignin is then precipitated in warm water and finally recovered by dissolution in acetone. Due to all this complex chemistry, the major commercialised wood polymers are blends. These plastics contain wood powder, starch or lignin. The presence of lignin as a filler in other polymers improves the quahty of the biodegradation. Some of those products are reinforced with flax or hemp. 

Cellulose, which is more fibrous than wood flour, is used as a filler for urea and melamine plastics. Melamine dishware is a laminated structure consisting of molded resin-impregnated paper. Starch and soybean derivatives are biodegradable, and the rate of disintegration of resin composites containing these fillers may be controlled by the amount of these fillers present in polymers. 

Disposables are also considered to be an environmental threat. Only some of the materials used in the diapers are biodegradable (the wood pulp and SAP). The polyethylene and polyester sheets are not biodegradable neither is the elastic used for better fit, nor the polypropylene used for the tape that is employed as a fastener. Disposable diapers account for up to 2 percent of the total volume of landfills in the United States. The lifetime of the diaper in the landfill depends on several environmental factors soil condition, groundwater flow, and the presence of other materials in the soil. see also Matertals Science Polymers, Synthetic. 

---