Water content polyethers

Other important tests are for acid and alkalinity number and for water content (266), because water content and alkalinity of the polyether glycol can influence the reaction with isocyanates. The standard ASTM test for acid and alkalinity number, ASTM D4662 (267), is not sensitive enough for the low acidity and alkalinity numbers of PTMEG, and special methods have been developed. A useful alkalinity number (AN) has been defined as milliequivalents KOH per 30 kg of PTMEG, as titrated in methanol solution with 0.005 N HC1 (268). Other useful nonstandard tests are for heavy metals, sulfated ash, and peroxide. The peroxides formed initially in oxidations are quickly transformed into carbonyl groups, which are detectable by infrared spectroscopy. On oxidation, a small C—O peak develops at 1726 cm-1 and can be detected in thick (0.5-mm) films. A relative ratio of this peak against an internal standard peak at 2075 C—O is sometimes defined as the carbonyl ratio. 

For weakly hydrophilic polymers like polyethers and polymethacrylates the same relationship between D0 and ED is valid like that between the simple gases. With increasing water content the diffusion coefficient in this case also decreases significantly due to the clustering of the water molecules about the polar groups, leading to relatively immobile water molecules. In contrast to Eq. (9-29), here ... 

The less hydrophilic polymers such as polyethers and polymethacrylates form the other extreme. Here the diffusivity markedly decreases with increasing water content. This is explained by the increasing "clustering" of water in the polymer (at polar "centres" or in micro cavities) so as to render part of the water comparatively immobile. In this case the influence of water can be approximated by the expression ... 

The presence of water in starters or in monomers (PO, EO or BO) always leads to polyether diols. The control of water content in the raw materials, used for polyether polyol synthesis, has a great practical importance for two reasons ... 

Additionally, polyesters and polyethers may contain several impurities derived from their methods of manufacture and being polymeric materials may vary in molecular weight and type of end-group. For routine analysis of raw materials, a determination of hydroxyl value, acid value and water content is usually sufficient. The reactivity of polyesters of the same chemical type can vary widely and for this reason it is sensible that an activity test be performed similar to that for diisocyanates using a diisocyanate of standardized activity. 

The effect of moisture on the p relaxations in amorphous phenylene polymers is well documented (93-95) for many of the systems cited previously. For example, Allen and co-workers (93) determined that both the dielectric and mechanical P relaxations in polysulfone, polycarbonate, polyphenylene oxide, and polyether sulfone were dependent on the water content of the samples. In addition, the amount of water absorbed depended on the polarity of the molecule. The effect of moisture on the dielectric p process in these polymers appears to be greater than for the mechanical loss process, as illustrated in Figures 41 and 42 (93). 

Fig. 9. Water melting enthalpy as a function of water content of polyether/LiCl/water systems.

The static moduli, failure stresses and dynamic moduli of an unfilled and filled polyether-urethane were measured over a range of equilibrium water contents and the results obtained compared with those for dry controls. Fillers employed were barytes (and small amounts of fumed silica and carbon black) or iron oxide. A quantitative relationship between water content and mechanical properties was established and the mechanics of the water/ polymer/filler interaction assessed. (Tenth Annual Meeting of the Adhesion Society Inc., Williamsburg, Virginia, USA, 22-27 Feb. 1987). 4 refs. 

Features Leads to f ne homogeneous foams with a high content of closed cells and a regular distribution of the foam density chemically stable in the polyethers commonly used for rigid foam suitable for formulations with a high water content Properties Lt, brn, liq, completely misc, with water dens. 1.05 g/ml vise. 500 mPa S vapor pressure < 1 hPa flash pt, > 94C ref. index 1.449 95% NV Use Level 0,5-2,0%... 

Polyallylamine (Mw = 70 000 g/mol) and polystyrene sulfonate (M, = 70 000 g/mol) were obtained from Aldrich. PAH was used as received, while PSS was purified from low molecular weight impurities by dialysis (Polyether-sulfone membranes, MW cut off 10 000 g/mol, Millipore) against ultra pure water and freeze dried. All water used for preparing solutions or for dialysis was purified by a Purelab Plus UV/UF, Elga Lab Water system and had a resistivity smaller than 0.055 xS/cm and a total organic content between 2 and 12 ppb (parts per billion). 

A very simple method to obtain polymeric dispersions in liquid polyethers is to make a mixture between a polyether polyol and a polymeric latex, such as the azeotropic copolymer styrene - ACN (StACN copolymer), obtained by emulsion copolymerisation, having around 20-40% solid content. The water is eliminated step-by-step by vacuum... 

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