Incineration, of PET

At present it seems that most problems arising during incineration of PET can be resolved however, quite a few residual hurdles will have to be taken before an economically feasible and ecologically accepted industrial technical process will be available. 

Several processes have been developed [41-43] to overcome the technological drawbacks of plastics incineration cited above. These include continuous rotary-kiln processes a process for glass-reinforced PET a combined system for wood fiber and PET to provide steam to power equipment and a fluidized system for pyrolysis, in combination with silver recovery from photographic film. Incineration of photographic film raises the additional problem of the formation of toxic halogenated compounds due to the presence of silver halides. 

Finally, the most heavily contaminated PET-shreds have to be incinerated. Here, however, economics may not be favorable enough for industrial development. As an alternative, those PET-shreds are brought to a landfill. Perhaps in future more attention will be given to modification of PET-films in such a way that they may become biodegradable, if the process can be accelerated or if a real breakthrough becomes available. 

DuPont offers a family of biodegradable polymers based on polyethylene terephthalate (PET) technology known commercially as Biomax. Proprietary monomers are incorporated into the polymer, creating sites that are susceptible to hydrolysis. At elevated temperatures, the large polymer molecules are cleaved by moisture into smaller molecules, which are then consumed by naturally occurring microbes and converted to carbon dioxide, water and biomass. Biomax can be recycled, incinerated or landfilled, but is designed specifically for disposal by composting. 

Organic polymers can also be incinerated as a means of disposal, (a) What products are formed on combustion of polyethylene (b) What products are formed on combustion of polyethylene terephthalate (c) Are these reactions exothermic or endothermic (See Sections 6.4 and 29.3 for related reactions.) (d) Propose a reason why HOPE and PET must be separated from poly(vinyl chloride) prior to incineration. 

The Danish minister of environment in 1988 announced that within a few years the manufacture and use of polyvinyl chloride (PVC) products had to be reduced as much as technically and economically possible due to their environmental impacts of production, use, and disposal. This preventive environmental policy was mainly based on the emission of hydrogen chloride and dioxins from waste incineration. A study of the technical, economic, and environmental consequences of a substitution was initiated by the National Agency of Environmental Protection. The goal was to collect background data for the upcoming negotiations between the environmental authorities and PVC-industry and manufacturers of PVC products in Denmark. The environmental assessment focused on PVC and 11 alternative materials, such as polyethylene (PE), polypropylene (PP), polyethylene terephtalate (PET), polystyrene (PS), polyurethane (PUR), synthetic rubbers (EPDM, CR and SBR), paper, impregnated wood, and aluminum. ... 

Environmental concern with reference to PVC and the fact that burning (possibly as a distinction from controlled incineration) may generate obnoxious acid fumes has created pressure on the pharmaceutical industry to move away from PVC. The alternative materials which have been considered include PET (polyester) and PP (polypropylene). Both require higher softening temperatures than PVC and good heat control, which can be more readily achieved with modem equipment with an effective preheat system. However, this only applies to certain selected and special material grades. Although these materials can be coated with PVdC to improve the moisture barrier, there are pressures to ban PVdC as it also contains a chloride component. Suffice it to say that the replacement of PVdC and its associated barrier/heat seal features may not be easy to achieve. Current opinion is that PVC will not be replaced. 

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