Preparation of high density polyethylene

Table 5.1. Typical Conditions for the Preparation of High-Density Polyethylene as Described in the Original Patents...

What are the industrial conditions for preparations of high-density polyethylene Describe the continuous solution process, the slurry process, and the gas-phase process. 

Table 6.1 Typical conditions for some preparation of high-density polyethylene...

On the other hand, the polymer prepared by the embedded catalyst shows T around 130 °C, which is a typical melting temperature of high density polyethylene. There was little activity difference between the polyethylene produced by embedded particles and those by homogeneous catalysts. The results of ethylene polymerization using embedded catalyst and homogeneous catalyst are summarized in Table 1 and Fig. 2,... 

Composite formulations were prepared as follows The straw samples as received from INEEL were ground to 0.69 mm in a hammer mill and oven dried to 1.1% moisture. The dried straw samples were then blended with various amounts of high-density polyethylene (HDPE), lubricants, and maleated polyethylene blends (MAPE) (see Table 2). The mixed formulations were then extruded with a 35-mm Cincinnati Milacron Model CMT 35 counterrotating conical twin screw extruder (Cincinnati Milacron, Batavia, OH), which produced a 9.525 x 38.1 mm2 solid cross-section. Flexural strength, density, and water sorption were measured for the extruded samples according to ASTM Standard Methods (13,14). 

Random ethylene copolymers with small amounts (4-10 wt-%) of 7-olefins, e.g. 1-butene, 1-hexene, 1-octene and 4-methyl- 1-pentene, are referred to as linear low-density polyethylene, which is a commercially relevant class of polyolefins. Such copolymers are prepared by essentially the same catalysts used for the synthesis of high-density polyethylene [241]. Small amounts of a-olefin units incorporated in an ethylene copolymer have the effect of producing side chains at points where the 7-olefin is inserted into the linear polyethylene backbone. Thus, the copolymerisation produces short alkyl branches, which disrupt the crystallinity of high-density polyethylene and lower the density of the polymer so that it simulates many of the properties of low-density polyethylene manufactured by high-pressure radical polymerisation of ethylene [448] (Figure 2.3). 

Fio. 17. The molecular weight distribution of high-density polyethylenes prepared by soluble and insoluble catalysts. The difference in molecular weight distribution is indicated by the difference in slope of the lines. 

J.-L. Shi, L.-F. Fang, FI. Zhang, Z.-Y. Liang, B.-K. Zhu, L.-P. Zhu, Effects of the extractant on the hydrophilicity and performance of high-density polyethylene/polyethylene-b-poly (ethylene glycol) blend membranes prepared via a thermally induced phase separation process. J. Appl. Polym. Sci. 130, 3816-3824 (2013)... 

Kim, J., Hong, S. M., Kwak, S. and Seo, Y., Physical properties of nanocomposites prepared by in situ polymerization of high-density polyethylene on multiwaUed carbon nanotubes , Physical Chemistry Chemical Physics, 2009,11, 10851-10859. Yang, R, Ou, Y. and Yu, Z., Polyamide 6/shca nanocomposites prepared by in situ polymerization . Journal of Applied Polymer Science, 1997, 69, 355-361. 

Other Early Developments. In addition to the breakthrough by Ziegler, two other discoveries of ethylene polymerization catalysts were made in the early 1950s. A patent by Standard Oil of Indiana, filed in 1951, disclosed reduced molybdenum oxide or cobalt molybdate on alumina (13). At the same time, Phillips discovered supported chromium oxide catalysts, prepared by impregnation of a silica-alumina support with Cr03 (14 16). Both the Phillips catalyst and titanium chloride based Ziegler catalysts are widely used in the production of high density polyethylene (HDPE). 

Pourabas and Peyghambardoost [70] prepared positive temperature coefficient composites by using metal-modified and unmodified carbon black in a matrix of high-density polyethylene. Modification with metallic particles led to properties that were related to changing the surface properties of the carbon black. The intrinsic electrical conduction of carbon black also changed after modification. These changes in properties endowed some desirable characteristics to the positive temperature coefficients. 

New catalysts based on Titanium and Hafnium derivatives co-supported on magnesium chloride are actractlng more and more Interest for the preparation of olefin polymers and. In particular, of high density polyethylene (HDPE). 

A quantitative characterization of branching by the means of C NMR was reported by Spevacek [162] in an early study in the case of high density polyethylene (HOPE) and ethylene copolymers of high density prepared by different methods. Correlations between the type of branches and the crystallinity of polyethylene were made. 

In preparing films of high density polyethylene for the fluorination experiments, three methods of preparation have been investigated. In all of these, films were pressed between sheets of clean aluminum foil at the minimum temperature necessary for plastic flow, with a hand press (--200 C). 

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