Partial biodegradation

Owing to the above reasons, some biopolymers have been used directly or after modification, to replace the conventional fillers leading to partial biodegradation. A number of studies have been carried out with an aim to maximize the proportion of renewable resources used while retaining acceptable material properties. 

Polymer blends, particularly olefins with biodegradable polymers, are gaining popularity as an approach to degradable packaging plastics. The materials are at best only partially biodegraded, but will lose form and bulk as the plastic disintegrates. This may be sufficient in landfill as volume diminishes, leaving room... 

These kinds of products are normally used in mulch films, bags and packing. Other systems have been investigated. The combination starch/ polyester has been claimed to be fully biodegradable (Tokiwa et al., 1993). Others are partially biodegradable, like starch/polyethylene/poly-e-caprolactone blends (Corp, 2001) and their derivatives or combinations of starch and modified polyesters. 

TBA was clearly more easily biodegraded than MTBE or ETBE. Nevertheless, there was a case where no TBA degradation occurred (site 14). Even if partial biodegradation of MTBE or ETBE takes place, TBA would accumulate in the aquifer and the use of adapted microorganisms or microcosm material with TBA degradation capacity would be required to clean up the site. 

Production of cis,cis-muconic acid by partial biodegradation of benzoic acid (three enzymatic steps) with a mutant of Pseudomonas putida (Mitsubishi Kasei Corporation). Productivity is >70 g 1 1 d 1.This process still requires further development. 

In conclusion, it was said [3] that partial biodegradation of rubber leading to potentially useful products is technically feasible. Economically, such an approach will have to wait for significant changes in the present needs for the products of this type of process. 

ARV 99] Arvanitoyannis I.S., Totally and partially biodegradable polymer blends based on natural and synthetic macromolecules preparation, physical properties, and potential as food packaging materials , Journal of Macromolecular Science - Reviews in Macromolecular Chemistry Physics, vol. C39, no. 2, pp. 205-271, 1999. 

Wu, D. Q., Qiu, F., Wang, T., Jiang, X. J., Zhang, X. Z. Zhuo, R. X. (2009) Toward the development of partially biodegradable and injectable thermoresponsive hydrogels for potential biomedical applications. Acs Applied Materials Interfaces, 1, 319-111. 

Other attempts at fully or partially biodegradable starch-filled plastics were studied such as starch/poly(8-caprolactone) (PCL) [23], others which are partially biodegradable, starch/poly(vinyl chloride)/poly( -caprolactone) (PCL) [24] or starch/modified polyesters [25]. In all these cases, starch granules are used to increase the surface area available for attack by micro-organisms. 

Generally speaking, bio-based plastics include starch-based plastics, protein (soybean protein) based plastics, and cellulose-blended plastics. They can also be blended with conventional plastics such as polyethylene (PE), polypropylene (PP), and poly(vinyl alcohol). However, such bio-based plastics are only partially biodegradable. The residual petroleum-based plastics remain as broken pieces, creating additional pollution. In addition, these plastics have intrinsic thermal and mechanical weaknesses, and they are now discouraged for applications. 

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). 

It is environmentally important to perform a life cycle assessment analysis, not only for non-biodegradable polymers but also for partially biodegradable or even completely biodegradable polymers. Life cycle analysis (LCA) is a tool which helps in understanding the environmental impact associated with the products, processes and activities throughout the life of a polymer. The life cycle of vegetable oil-based polymers is shown in Rg. 2.6. Thus a complete LCA would include three separate but interrelated components, an inventory analysis, an impact analysis and an improvement analysis. 

Is it possible to transfer a synthetic non-biodegradable polymer to a partially biodegradable polymer If so, how may this be done ... 

Except in the vicinity of phosphate rock deposits, phosphorus is usually present only in topsoil, and below a depth of about a metre its concentration diminishes rapidly. The ploughed layer of soils usually contains about 0.1-1.5% N and 0.02-0.5% P (Table 12.5), but not all of this nitrogen and phosphorus is in a form which is available for plant growth. In unfertilized soils, nearly all the nitrogen and about half the phosphorus are present as organic compounds. These are partially biodegradable into... 

Nakamura EM et al. (2005) Study and development of LDPE/starch partially biodegradable compounds. Journal of materials processing technology. (162-163) 236-241. 

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