Disintegration, biodegradation

Nickel K, Neis U (2007) Ultrasonic disintegration of biosolids for improved biodegradation. Ultrason Sonochem 14 450 -55... 

U. Neis, K. Nickel, and A. Tiehm, Ultrasonic disintegration of sewage sludge for enhanced anaerobic biodegradation. Advances in Sonochemistry, 6, Theme issue — Ultrasound in Environmental Protection,... 

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... 

At this point little is known about the interrelationships between composition, structure, starch-degradation and physical disintegration properties of starch-plastic composites. Continued work towards development of a laboratory assay for biodegradability will eventually result in the establishment of a sufficient database to elucidate these relationships, allowing development of a host of starch-containing plastic products for both existing and new markets. 

A frequently cited merit of biodegradable plastics is their lack of persistance in an intact state "environmentally friendly" is a widely used vernacular phrase, but there has also been speculation in the popular press that degradable plastics will release potentially harmful additives into the environment when the plastics degrade or disintegrate. An ideal biodegradable plastic will leave no undegraded polymeric residues, and for these materials, the persistance of additives as well as the polymers must be considered. In this case, the issue is not whether or not the additive... 

Apart from the pure process-driven requirements of the disintegration within a defined time span and the proof of ultimate biodegradability, it is necessary to make sure that there is no negative impact of degradation products or intermediates of the degradation process on the environment. Adequate information has to be provided for a comprehensive assessment of environmental and toxicological safety. 

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. 

Biodegradation studies of starch blends have not been conclusive where a nondegradable synthetic polymer has been the blend component probably bio disintegration 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 in the product. 

Laboratory tests have to be performed for materials, intermediates and additives. In these tests the chemical properties are checked, the ultimate biodegradability is verified and the disintegration properties are determined. Chemical testing serves to ensure that neither harmful organic substances, such as polychlorinated biphenyl (PCB) and dioxins, nor heavy metals, such as lead, mercury and cadmium, pass into the soil via the compost. 

In June 2004, Treofan introduced its new biodegradable and compostable Biophan film made from polylactic acid supplied by NatureWorks LLC. According to the company, Biophan offers exceptional transparency and gloss, the ability to transmit water vapour, and outstanding sealing properties. Biophan is also printable, resistant to oil, fat and alcohol, and is thermoformable. Biophan disintegrates completely into water and carbon dioxide within 45 days. 

At lower starch contents (i.e., less than 60%) the starch particles act as weak links in the plastic matrix and become sites for biological attack. The polymer matrix can therefore disintegrate into small fragments, but this does not mean that the entire polymer structure will actually biodegrade. 

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