Biodegradable articles

F. Scheer, Biodegradable nano-polymer compositions and biodegradable articles made thereof, US Patent 7 927 532, assigned to Cereplast, Inc. (El Segundo, CA), April 19, 2011. 

There have been numerous communications on the subject of biodegradation test methods, including aerobic compost (30), anaerobic bioreactor (31), general methodology and future directions (32—34), and a fine review article (24). ASTM (22) and MITI (35) have also set forth standard testing protocols for plastics, as shown in Table 2, whereas OECD test methods (29) are more suited to water-soluble polymers. 

Biodegradation studies of starch blends have not been conclusive where a nondegradable synthetic polymer has been the blend component probably biodisiategration would be a better term to describe these polymers. The principal deficiencies of products based on this chemistry, aside from the incomplete biodegradation, are water-sensitivity of manufactured articles, and the balance of this and biodegradation with the starch level ia the product. 

For color removal, ozonization has achieved the greatest practical importance as seen by the plethora of articles and patents on this method (147—163). Ozonization in combination with treatments such as coagulation, flocculation, carbon adsorption, uv irradiation, gamma radiation, and biodegradation significantly and successfully remove dye wastes and reduce costs (156,164—170). 

For more than 20 years, polymer scientists and plastics technologists have been working to develop plastics materials that would be more acceptable environmentally, and in the third edition of this book, published in 1975, the author devoted a section to photo- and biodegradation of polymers. In spite of such effort, an article in 1992 stated that Degradable plastics are still in the early... 

Compared with tar, which has a relatively short lifetime in the marine environment, the residence times of plastic, glass and non-corrodible metallic debris are indefinite. Most plastic articles are fabricated from polyethylene, polystyrene or polyvinyl chloride. With molecular weights ranging to over 500,000, the only chemical reactivity of these polymers is derived from any residual unsaturation and, therefore, they are essentially inert chemically and photochemically. Further, since indigenous microflora lack the enzyme systems necessary to degrade most of these polymers, articles manufactured from them are highly resistant or virtually immune to biodegradation. That is, the properties that render plastics so durable... 

Such studies have shown that it is the chemical structure and composition that determine whether or not synthetic polymers are biodegradable. On the other hand, the precise rate at which a synthetic polymer will degrade is determined by the specific morphology of the article into which the polymer has been fabricated. 

Biocides are naturally toxic to lower organisms and therefore must be handled with care. Strict government rules control the sale and use of biocides, especially those used in food contact applications. They are added at the fabrication stage. The morphology of the polymer article is important, e.g., high surface area articles, such as foams, biodegrade more rapidly. 

Later work by Suzuki and Tokiwa(55,56,57) in which they evaluated the stability of polyesters to lipases confirmed the work of Potts. Potts(58) demonstrated the biodegradation of polycaprolactone which he used in the fabrication of agricultural articles, such as plant pots. J. P. Kendnck(59) demonstrated that amorphous regions of polyesters were more readily biodegraded than crystalline regions. 

Because enzymes are too big to diffuse into the bulk of a polymer, biodegradation is an erosion process that takes place at the surface of the plastic article [5]. Therefore, the thickness of a plastic article is a decisive parameter in determining the time needed for complete degradation. 

Extrusion is a continuous conversion process via melting and subsequent transformation of granules or powders of biodegradable polymers and additives into semifinished or finished articles like sheets, profiles, tubes, bottles, films, tapes or... 

Yang et al. discussed the basic properties of an implantable or extracorporeal artificial liver. The article focused on implantable devices but other than biodegradability, the properties of implantable devices are also applicable to extracorporeal devices. The focus of the article on implantable devices reveals an unfortunate prejudice on the part of much of the scientific community. Most researchers in this field are working on devices intended to be placed in the body. 

A significant contribution of Raman spectroscopy to the analytical characterization of biomedical issues has been made in the area of biomaterials, especially in the identification of biodegradation and deterioration [1, 2]. The general impact of Raman spectroscopy on the study of biomaterials has been described by this author in three recent review articles [3-5]. In this chapter, the topic of Raman characterization of biomaterials is revisited with particular emphasis placed on those biomaterials widely employed for load-bearing surfaces in artificial joints. Important recent case studies are presented to illustrate the power of the Raman technique to answer key questions of broad medical, scientific, and technological interest. The analytical and physical science lying behind the Raman effect is shown to contribute to the accumulation of a wealth of fundamental information about the medical and technical achievements of prosthesis makers. 

The purpose of this chapter is to provide an update on our understanding of the reactivity of sucrose and the selectivity of its transformations into functionalized derivatives that have become industrial realities because of their biodegradability or biocompatibility. It follows historical accounts on the topic books on sucrose and its chemistry,1 4 a series of books dealing with the use of carbohydrates (in general) as organic raw materials,5 8 and also chapters and review articles.9 24... 

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