Polyethylene process losses

One of the well-known phenomena in high-pressure polyethylene processes is a rapid ethylene decomposition reaction or thermal runaway, known as decomp. At 300°C, ethylene and even polyethylene decompose to carbon, methane, hydrogen, and other hydrocarbon by-products. When the decomposition reaction takes place, the reactor pressure builds up quickly and the reactor must be vented, shut down, and flushed for a long period of time before a new startup is initiated. The resulting economic loss will be quite... 

Surprisingly the water consumption of a starter battery, provided it contains anti-monial alloys, is affected by the separator. Some cellulosic separators as well as specially developed polyethylene separators (e.g., DARAMIC V [76]) are able to decrease the water consumption significantly. The electrochemical processes involved are rather complex and a detailed description is beyond the scope of this chapter. Briefly, the basic principle behind the reduction of water loss by separators is their continuous release of specific organic molecules, e.g., aromatic aldehydes, which... 

Trace analysis has its special hazards for the unwary. The most important of these are loss of material in the analytical process and contamination by outside sources. Everyone realizes that trace constituents can be lost from samples, but few are aware of the many ways in which this can occur. For example, phosphate has been observed to disappear mysteriously from water samples in polyethylene bottles (10). Nitric acid, used to clean plastic vials, has been observed to convert these surfaces to ion exchangers, which readily take up as much as 10 12 moles per sq. cm. of trace metals (16). Lead nitrate solutions unless made distinctly acidic, plate out much of the lead on the walls of glass bottles. While everyone realizes that formation of a precipitate is liable to carry out trace constituents either by adsorption or occlusion, it is not as well-known that vanishingly small amounts of precipitates—amounts likely to be overlooked on casual observation—may also do this. The fly-ash and soot, which seem to be inescapable components of city air,... 

The third side reaction is formation of a small amount of polyethylene during the growth step. The quantity of polyethylene does not represent a significant yield loss, but does present serious processing problems. The polymer deposits on reactor surfaces, inhibits heat transfer, plugs valves, and must be cleaned out periodically. A Conoco patent (9) indicates this problem can be prevented by addition of small quantities of carbon monoxide to the feed ethylene. 

The MQ-filter sandwich was similarly transferred to the filter-rinsing stand, the top 149-jLtm Nitex support was folded back, and three sharpened acrylic tubes were pressed into the filter pair. The MQ-filter area not enclosed by the acrylic tubes was rinsed with several aliquots of deionized water (totaling 200-300 mL) with suction alternately applied from below to reduce sea salt by an order of magnitude this process was required for accurate dry-weight and major-ion determinations. The acrylic tubes were subsequently removed, and the fresh, unrinsed subsamples were preserved for lipid analysis. The remaining filter material was dried at 60 °C for >24 h. Both the MQ and 53-jitm Nitex samples were stored and transported flat in individual polyethylene bags to prevent loss of material. 

The production of polymeric materials is one of the world s major industries. Polymers are utilized in many applications because of their processability, ease of manufacture, and diverse range of properties. Many of the commonest polymers such as polyethylene, polystyrene, and polytetrafluoroethylene (PTFE) are highly hydrophobic materials rendering them unsuitable for many biomedical applications. For applications that require contact with body fluids such as blood or urine, it is necessary for the materials to be hydrophilic and to be capable of maintaining intimate contact with the fluid in question for prolonged periods of time without significant loss of functional performance. 

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