Polyethene high molecular weight

Whereas, as mentioned above, aluminum trialkyls oligomerize ethene under pressure, cationic compounds of the type [ AlMe X- and [(L2AlMe)2(/r-Me)]+X [L = benzamidinate anion, X = MeB(C6F5)3] give high molecular weight polyethene under mild conditions.32... 

Elliott (1978) in a brief communication reported that more than 70% of the aluminium in blood was present in the plasma compartment. In normal subjects, they reported that a very small proportion of the plasma aluminium was ultrafiltrable. These findings were not consistent with thos of Lundin et al. (1978). In the study of (1978) the tendency was for the ultrafiltrable fraction to decrease as the total plasma aluminium concentration fell below 200 fiQlL. At high plasma aluminium levels, studies using polyethene glycol and direct ultrafiltration indicated that 60-70% of the aluminium was bound to high-molecular weight proteins, 10-20% was bound to albumin, and 10-30% was ultrafiltrable. 

Anderson, J C. "High Density and Uirra-High Molecular Weight Polyethenes", Trib. Int. Vol No 1, 43-47, 1982. 

Apparently, soluble catalysts are obtained by reaction of Ti(OR)4 with AIR3 [144]. High-molecular-weight polyethene is obtained in variable amounts, with Al/Ti ratios ranging between 10 and 50. Similar results are attained by replacing titanium alkoxide by Ti(NR2)4 [145]. Soluble catalytic systems are also obtained by reaction of Ti(acac)3 [146] and Cr(acac)3 [147] with AlEts as well as by reaction of Cr(acac)3 and VO(acac)2 with AlEt2Cl in the presence of triethyl phosphite [121]. With vanadium catalysts the activity reaches its maximum at Al/V ratio = 50. Under these conditions up to 67% vanadium is in the bivalent oxidation state. Bivalent and trivalent compounds will be active. 

Table 2 shows polymerization conditions for the high-pressure process and density, molecular weight, and weight distribution of the polyethene (LDPE). Bunn [54] was the first to study the structure of polyethene by x-ray. At a time when there was still considerable debate about the character of macromolecules, the demonstration that wholly synthetic and crystalline polyethene has a simple close-packed structure in which the bond angles and bond lengths are identical to those found in small molecules such... 

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