Polyethylene process preheating

Starch and cellulosic materials are frequently used as fillers in degradable materials. The addition of starch to LDPE in combination with a pro-oxidant increases the photooxidation rate and the formation of hydroperoxides and carbonyl groups. Starch alone does not increase the photooxidation rate. The addition of starch to LDPE increases its stability in 80°C water. Slower degradation in water is due to leaching out of the pro-oxidant. The addition of starch causes biodegradation process under soil burial conditions. Further increase in the degradation rate can be achieved by preheating polyethylene filled with starch. ... 

During the winter of 1991, bulk mustard was drained from preheated (20°C) 1 ton containers into heavy-walled, polyethylene-lined cardboard boxes and allowed to freeze under cool conditions (<0°C). The boxes containing frozen mustard were then placed in sealed metal cargo containers and immediately transported to the incinerator site. The boxes were then off-loaded and processed via the rotary kiln solids feed system. All bulk mustard (3 tonnes) was destroyed in this manner as part of the incinerator test bum program (see below). 

Thicker plastics generally need to be blanked at elevated temperature. Acrylic, cellulose acetate, cellulose nitrate, ethyl cellulose, polyethylene, polystyrene, vinyl butyral, and polyvinyl chloride can commonly be blanked. The process is accurate to about 1/64 in. Allowance must also be made for thermal shrinkage when the material has been preheated. 

Extruder Drives The higher specific heat requirements of SPS and lack of preheating through drying necessitates extruder drive with greater capability. On a theoretical basis, extrusion of SPS requires 2.5-2.75 times the drive horsepower typically needed to process a preheated polyethylene terephthalate (PET). For preheated PET extrusion, extruder drives are designed for approximately 12.01b/h/hp room temperature SPS would require approximately lOlb/h/hp [13]. 

ArCom XL polyethylene is produced in a multistep process that has been described in the literature [8]. Rods of GUR 1050 are isostatically molded and gamma irradiated at room temperature with a nominal dose of 50kGy. The rods are preheated to 130°C and then hydrostatically extruded with a diametral compression ratio of 1.5. The hydrostatic extrusion produces orientation of the UHMWPE and mechanically anneals the material. The rods are then stress relieved at 130°C prior to machining into components, which are terminally gas plasma sterilized. 

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