Waste rubbers biodegradation

Renewable raw materials are made or derived from short-term renewable sources (one to a few years or a few tens of years) such as plants, trees, wood wastes and other agricultural products. Not all these materials are necessarily biodegradable. Natural rubber, for example, comes from the latex of a tree (Hevea brasiliensis) and is not biodegradable. Renewable materials are often considered as opposites to fossil sources such as petroleum that are not renewable on a human timescale. On the other hand, some synthesized plastics such as certain polyesters are biodegradable. 

The Sesame is designed so that molders can use a smaller runner and sprue, which gives them more control over the amount of plastic and pressure used to form the part itself. A smaller runner and sprue also means less material waste. While screw-and-barrel systems waste as much as 99.7% of the shot material, the Sesame wastes less than 80%. This is particularly important when molding expensive materials like biodegradable plastics, which cost as much as 10 per gram. The Sesame can handle any type of moldable plastic, as well as silicone rubber. Super-small medical parts that have been molded by the machine include ... 

Patit P. Kundu is Professor in the Department of Polymer Science Technology at Calcutta University, India. He obtained his PhD in 1997 from IIT, Kharagpur, India. He has 67 research papers to his credit in international journals along with ten papers in national/international conferences, contributed 2 book chapters, and one patent. His research interest centers on the fields of synthesis and characterization of oil based rubber and nano-composites, microbial fuel cell, direct methanol fuel cell, microbial biodegradation of waste polyolefin fUm, tissue engineering and gene therapy. 

Tires are one of the most durable technological products manufactured today. They are a resilient, durable composite of fabric, steel, carbon black, natural rubber, and synthetic polymers. The qualities that make tires or other engineered rubber products a high-value item create a special challenge of disposal. Tires and other rubber products, such as conveyor belts and hydrauUc hoses, are not biodegradable and cannot be recycled like glass, aluminum, or plastic. Four potential applications for such products entering the solid waste stream have been identified ... 

Currently the world s consumption of plastics is growing in this regard there are difficulties in disposing of large amounts of household plastic waste. The solution is to develop biodegradable polymers with a specific expiration date. This work is dedicated to the creation of biodegradable composite material based on LDPE, wood flour and rubbers of different nature. 

One reason that synthetic polymers (including rubber) are so popular as engineering materials is their chemical and biological inertness. On the down side, this characteristic is really a liability when it comes to waste disposal. Most polymers are not biodegradable and, therefore, do not biodegrade in landfills major sources of waste are from packaging. 

In this process, which has been in existence as a concept for at least 30 years and is often referred to as a microbial process, chemolithiotrophic bacteria in aqueous suspensions in the presence of oxygen can be nsed to selectively attack the sulfur crosslinks in the snrface of waste rnbber crumb particles. The process can also be regarded as a type of biodegradation process, the by-prodncts of which can inclnde elemental sulfur, sulfates, sulfides and snlfnric acid. Specific examples of the bacteria that have been used to devulcanise rubber in this way inclnde species of Thiobacillus, e.g., T. thiooxidans. 

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