Thermoplastic waste, disposal

Technology Descriptions The use of thermoplastic solidification systems in radioactive waste disposal has led to the development of waste containment systems that can be adapted to industrial waste. In processing radioactive waste with bitumen or other thermoplastic material (such as paraffin or polyethylene), the waste is dried, heated and dispersed through a heated, plastic matrix. The mixture is then cooled to solidify the mass. 

Advantages The major advantages of the thermoplastic-based disposal systems are by dispiosin of the waste in a dry condition, the overall volume of the waste is greatly reduced most thermoplastic matrix materials are resistant to attack by aqueous solutions microbial degradation is minimal most matrices adhere well to incorporated materials, therefore, the final product has good strength and materials embedded in a thermoplastic matrix can be reclaimed if needed. 

Disadvantages The principal disadvantages of the thermoplastic-based disposal systems are the following (1) expensive, complicated equipment requiring highly specialized labor is necessary for processing (2) the plasticity of the matrix-waste mixtures may require that containers be provided for... 

Additional advantages are obtainable regarding environmental compatibility and electronics waste-disposal regulations. MID technology allows the material mixture of a (conventional) combination of PCB and mechanical parts, which usually consist of a great number of materials, to be replaced by a metallized plastic part (MID). MIDs are made of thermoplastics, which can be recycled and are noncritical in disposal (Franke 1995). 

A number of reviews have been studied on the potential of natural fibers such as sisal, kenaf, hemp, flax, bamboo, and jute for the preparation of thermoplastic composites. In this work, however sisal fiber (SF) has been used as reinforcement due to easily availability and comparatively low cost. The xmtreated and treated SF-reinforced RPP composites have been prepared and investigated their thermal, mechanical, morphological, weathering and impact properties. An improved mechanical, thermal, and morphological property has been observed for chemical treated SF as well as clay loaded RPP. The analysis revealed that SF-reinforced RPP composites with enhanced properties can be successfully achieved which warrants to replace the synthetic fillers-based conventional thermoplastic composites. These SF-based RPP composites can be the material of choice in the field of aeronautic, automobiles, civil engineering, etc., due to its low cost, low density, non-toxicity, recyclability, acceptable strength, high specific properties, and minimum waste disposal problems. 

Another complication in LCI comes from the time horizon considered in the business system. For example, in most developed countries of the world the fate of plastic material is likely to be incineration. Whether the plastic is a disposable or a permanent product, if it makes it to a waste disposal system, it is most likely incinerated. If the plastic is made from petrochemicals and incinerated, then fossil resources are being converted to carbon dioxide emissions. If the plastic is PLA and it is incinerated, then the carbon is converted back to CO2. If the product does not enter the waste disposal system, then the time horizon becomes important. In the case of permanent products, for a relatively short time frame such as a human lifetime, I suppose the products are permanent. For long time horizons, such as hundreds, thousands, or millions of years, then my assumptions regarding permanent products may change. At these longer time scales, I suspect that even permanent thermoplastics may get converted to carbon dioxide. In our LCI analysis, we have used shorter time frames, on the scale of decades, and made conservative assumptions. 

Vesicular films have a honeycomb-like cross-section and are constructed of a polyester base coated with a thermoplastic resin and a light-sensitive diazonium salt. Photopolymer films contain carbon black as a substitute for silver. These films are processed in a weak alkaline solution that is neutralized prior to disposal. As such, they produce a nonhazardous waste. 

Thermoplastic materials for solidification, such as bitumen, polyethylene, and paraffin, are mixed with dried wastes at elevated temperatures. The mixtures solidify when they cool. The hardened mixtures may be placed into containers prior to disposal. One group of materials not suitable for this process, however, includes organic wastes that can dissolve the thermoplastic matrix and thus prevent solidification. Chlorates, perchlorates, and nitrates in high concentrations can deteriorate bitumen. Radioactive wastes can be immobilized by this method. 

In thermoplastic solidification, the initial waste is dried and then combined with bitumen and polyethylene at a high temperature the mixture on cooling becomes a solid. In the second step, the solid waste is thermoplastically coated and then disposed of. This process is used for inorganic and radioactive wastes. 

Polymer encapsulation is an ex situ S/S technique involving the application of thermoplastic resins such as bitumen, polyethylene and other polyelfins, paraffins, waxes, and sulfur-based cements, as opposed to cements and pozzolans. Polymer encapsulation has been used primarily to immobilize low-level radioactive wastes and those waste types that are difficult to immobilize in cement, such as Cl- and SO4-based salts. Bitumen (asphalt) is the least expensive and (hence) used most often. Thermoplastic encapsulation heats and mixes the contaminated soil with the resin at 130 to 230°C in an extrusion machine. Organic pollutants and water boil off during the extrusion and are collected for treatment or disposal. The final product, a stiff yet plastic resin, is then discharged into a drum or other container and land-filled (U.S. EPA, 1997). 

Asbestos wastes may be solidified prior to their landfill burial. This may be achieved by a cementing process such as that using pozzolanic concrete, which contains fly ash or kiln dust mixed with lime, water, and additives (Peters and Peters 1980). Other processes for solidification include thermoplastic and polymeric processes. In the former, a binder such as paraffin, polyethylene, or bitumen is used. In the latter, polyester, polybutadiene, or polyvinyl chloride is used to trap the asbestos fibers or particles over a spongy polymeric matrix. The solidified waste should be disposed of in a licensed hazardous waste dump or disposal site. 

Our society is incredibly dependent on polymers in the form of plastics. Durable and lightweight, plastics are probably the most versatile synthetic materials in existence in fact, their current production in the United States exceeds that of steel. Plastics have come under criticism, however, for their role in the current trash crisis. They make up 21% of the volume and 8% of the weight of solid waste, most of which is derived from disposable packaging and wrapping. Of the 1.5 X 10 kg of thermoplastic materials produced in the United States per year, less than 2% is recycled. 

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