Polyethylene processing data

This relationship has been central to commercial catalyst manufacture for half a century. Notwithstanding its importance, however, the underlying science was not explained [500]. Both activity and MW are affected by pore volume, but the data of Figure 49, and also many other related data, show that it is not certain that the two relationships are necessarily identical. That is, activity depends on catalyst fragility, but it is not obvious how catalyst fragility could control chain transfer. Thus, the connection between MW and porosity may or may not involve fragility. The influence of pore volume is seen in all polyethylene processes— slurry, gas phase, and solution. No satisfying explanation has yet been proposed to account for this relationship. 

Their data yielded Henry s constants from 130 to 300 to 600 atm. These results are useful for the design of separation equipment in the high-pressure polyethylene process. 

Table 3.14 shows an overview of the production costs for the processes described for the production of polyethylene. All data have been standardised for the different processes by using USD 600/t as the feedstock price for both ethylene and butene-1. As can be seen for all processes, the impact of the feedstock price is about 80 %. All data used are based on ChemSystem (1996/97 for LDPE and LLDPE, 1999/2000 for HDPE) data for new large scale plants. 

Most thermal analysis methods for studying polymeric stabilizer systems are based on the antioxidant s ability to delay the oxidation process. Usually a sample is heated to a specified temperature and the induction time, or period of time before the onset of rapid thermal oxidation, is determined [see discussion of oxidative induction time (OIT) in Section 3.4.2 of this chapter]. The end of the induction period is marked by an abrupt increase in the sample s temperature, evolved heat, or mass and can be detected by DTA, DSC or TGA, respectively (Bair 1997). The effect of antioxidant structure and its concentration on prolonging a sample s induction period can be used to determine the most effective antioxidant system for a polymer such as polyethylene. Extensive data have shown that thermal information such as this can be used successfully to estimate the lifetime of polyethylene at processing temperatures (Bair 1997). 

Depending upon the extent of process data available, a comparison may be made of the carrying capacities of the various solvents. Table 14-4, which is based on the data of Buck-lin and Schendel (198.S), presents gas solubility data for three different processes Fluor Solvent (propylene carbonate), Selexol (polyethylene glycol dimethyl ether), and Purisol (n-methyl-2-pyrrolidone). Solubilities of CO2 and H2S as well as hydrocarbons and other gases are shown, with all data collected at 25°C. The solubilities shown are single component data. In real systems there can be substantial interactions between the solutes, the net effect of which is usually to decrease the CO2 and H2S solubilities and to increase the hydrocarbon solubilities. Also, since all processes do not operate at the same temperature, the relationship between solubility and temperature must also be included in the evaluation. 

Figure 2.5 Shearing force per unit area versus shear rate. The experimental points are measured for polyethylene, and the labeled lines are drawn according to the relationship indicated. (Data from J. M. McKelvey, Polymer Processing, Wiley, New York, 1962.)...

The cooling requirements will be discussed further in Section 8.2.6. What is particularly noteworthy is the considerable difference in heating requirements between polymers. For example, the data in Table 8.1 assume similar melt temperatures for polystyrene and low-density polyethylene, yet the heat requirement per cm is only 295 J for polystyrene but 543 J for LDPE. It is also noteworthy that in spite of their high processing temperatures the heat requirements per unit volume for FEP (see Chapter 13) and polyethersulphone are, on the data supplied, the lowest for the polymers listed. 

In the process of inhibition polypyrocatechin borate interacts with polyethylene macroradicals to form the B—O—C bonds. This is confirmed by the fact that the absorption spectrum of polyethylene inhibited with polypyrocatechin borate revealed the bands in the region of 1350 cm" characteristic for the B—O—C bond. There is no such a band in the spectrum of pure polypyrocatechin borate after heating under the same conditions. Chemical analysis of boron in polyethylene provides support for the IR-spectroscopy data concerning the presence of chemically bonded boron in polyethylene after destruction. 

Measurement by gel permeation chromatography in 0.2 M phosphate buffer pH 7.0 with polystyrenesulfate or polyethylene glycols ([5] in the case of aureobasidium sp. A-91) as molecular weight standards. Data processing as de.scribed in Ref. [II]. 

By permission, Norton Chemical Process Products Corp., Bull. SI-72 and Bull. PTP-1 other manufacturer s data are equivalent, f Also available in polypropylene (including glass reinforced) high density polyethylene, rigid PVC, fluorinated vinyls. 

L. L. Blyler and T. K. Kwei processed their own experimental data in an incorrect way polyethylene melts with dissolved nitrogen have the same viscosity as pure melts. Dissolved nitrogen cannot change the value of the free volume of the PE melt hence, L. L. Blyler s and T. K. Kwei s formula is incorrect. 

Both Odian and Silverman models satisfactorily explain most of the observed results in all solvents (Tables I-III, VI) used in the present study, however there are some exceptions especially when solvents other than the alcohols are used (Table VI). Thus the Odian mechanism is not consistent with the DMF data nor can the Silverman model account for the acetone results. In addition, in further preliminary studies with grafting of styrene to polyethylene (10) in solvents other than those reported here both Odian and Silverman mechanisms are deficient. The problem is that possible contributions from the radiation chemistry of the components in the grafting reaction need to be considered in formulating a complete mechanism for the overall process. 

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