Polytetramethylene glycols

Figures 13.25-13.28 show the ultrahigh resolution separations in chloroform of polystyrene standards, polytetramethylene glycol, urethanes and isocyanates, and epoxy resins, respectively. Multiple column sets of anywhere from two to six columns in series have been used for well over a year with no apparent loss of efficiency. The 500- and 10 -A gels can easily tolerate 15,000 psi or more. In fact, the limiting factor in the number of columns that can be used in series is generally the pump or injector in the FIPLC system. A pump capable of 10,000 psi operation should allow the use of a column bank of 10-12 50-cm columns with a total plate count of 500,000 or more.

There is still much work to be done in clearly defining the mechanism of initiation and the gegenions formed in the in situ preparation of trialkyl oxonium salts. Clearly, however, for theoretical studies of the polymerization the use of preformed trialkyl oxonium salts is to be preferred. For the preparation of polymer, on the other hand, the more convenient in situ method may be preferred, particularly if the desired product is a polytetramethylene glycol. 

Polyether diols form a very important segment of the diols used in the manufacture of polyurethanes. The normal route is by addition polymerization of the appropriate monomeric epoxide. The most important polyethers are polypropylene glycol (C3) and polytetramethylene glycol (C4). The manufacturing route is given in Figure 2.10. 

PTMEG PU (R) Purging Polytetramethylene glycol. An abbreviation for polyurethane. Process of expelling an unwanted gas or vapor from a system through the introduction of a different gas or vapor until all traces of unwanted gas or vapor have been removed. 

Preparation of KP-13. A pre-polymer of KP-13, which has isocyanate groups at it s both terminal group, was synthesized with polyethylene oxide, polydimethyl-siloxane, polyethylene oxide, polytetramethylene glycol and 4,4 -diphenylmethane diisocyanate in the presence of diazobicycloundecene catalyst at 50 °C for 1 hour in the... 

Three types of PUs were prepared, based on polytetramethylene glycol(PTMG) of molec.wt. 2000, 1000 and 650. The prepolymers were prepared by reacting PTMG with MDI and were then extended with diethylene triamine(DETA) or DETA/hydrazine mixture to form the PU polymers. The polymers were then grafted with epichlorohydrin and further reacted with different... 

Polytetramethylene glycol of molecular weight 2000 was freeze-dried from benzene in a vacuum. The bromoethylated prepolymer was obtained by reaction of the glycol, first with adipoyl chloride, then with ethylene bromohydrin (Table II) and precipitation in water and n-hexane. Nitromethane solution of the poly-THF dioxolenium salt was prepared after filtration of silver bromide from the reaction product of bromoethylated poly-THF with silver perchlorate in nitromethane. 

The abrasion loss of PU elastomers is markedly improved with the MW increase of the oligo-glycol. PU elastomers based on polytetramethylene glycols and on polyfethylene adipate) glycols have the lowest abrasion loss. Polypropylene glycols (obtained in anionic catalysis) lead to PU elastomers with poorer abrasion resistance [2],... 

A critical factor in the success of a particular separation in an ABS may be the choice of polymer. The polymer not only affects the distribution of the solute between the phases but also has a considerable effect on the physical characteristics of the phases. It may be possible to fine-tune the polymer-rich phase by choosing from a variety of commercially available polymers whose hydrophobicity increases as PEG < Pluronic [block PEG/ polypropylene glycol (PPG) copolymers] < PPG < polytetramethylene glycol (Fig. 3 [36—40]). PPG-2000 is essentially water insoluble (and thus can be utilized neat) but is included for comparison with the ABS systems. The Pluronic polymer used, L64, has a very narrow range of usefulness [41], At low polymer and salt concentrations it forms a monophasic system. If the concentration of polymer and salt is too high, the polymer tends to foam out of solution. 

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