Unsaturation value

The mixture is kept for 3 hours at 105°C after the oxide addition is complete. By this time, the pressure should become constant. The mixture is then cooled to 50°C and discharged into a nitrogen-filled botde. The catalyst is removed by absorbent (magnesium siUcate) treatment followed by filtration or solvent extraction with hexane. In the laboratory, solvent extraction is convenient and effective, since polyethers with a molecular weight above about 700 are insoluble in water. Equal volumes of polyether, water, and hexane are combined and shaken in a separatory funnel. The top layer (polyether and hexane) is stripped free of hexane and residual water. The hydroxyl number, water, unsaturation value, and residual catalyst are determined by standard titration methods. 

Unsaturation Value. The reaction temperature, catalyst concentration, and type of counterion of the alkoxide affect the degree of unsaturation. The tendency for rearrangement of PO to aHyl alcohol is greatest with lithium hydroxide and decreases in the following order (100) Li+ >... 

Unsaturation value can be determined by the reaction of the akyl or propenyl end group with mercuric acetate ia a methanolic solution to give acetoxymercuric methoxy compounds and acetic acid (ASTM D4671-87). The amount of acetic acid released ia this equimolar reaction is determined by titration with standard alcohoHc potassium hydroxide. Sodium bromide is normally added to convert the iasoluble mercuric oxide (a titration iaterference) to mercuric bromide. The value is usually expressed as meg KOH/g polyol which can be converted to OH No. units usiag multiplication by 56.1 or to percentage of vinyl usiag multiplication by 2.7. 

McNiell has developed a useful technique for the determination of unsaturation using chlorine-36. It is not suggested that the technique should replace existing methods but that it is highly suitable for micro analyses when only small samples are available or for estimation of very low unsaturation values where other methods are not sufficiently sensitive. The superiority of the method for the analysis of butyl rubbers has been demonstrated (61) and it has also been used to measure unsaturation of 0.1—0.01 mole-% of polyisobutene (62). 

Polymer Unsaturation Analysis. Unsaturation is determined routinely by an iodine-mercuric acetate procedure (5). The result of this procedure, iodine number (cgrams of iodine/grams of polymer), was correlated to actual unsaturation by an infrared and an NMR study (4). The infrared study showed that the factor of 0.184 is needed to convert iodine number to % unsaturation. The NMR study showed that a factor of 0.196 is needed to convert iodine number to % unsaturation. [As an example, a piperylene-isobutylene copolymer with an iodine number of 20.7 would have unsaturation values of (20.7) (0.196) = 4.05 mole % (NMR) and (20.7) (0.184) = 3.82 mole % (infrared).]... 

FIGURE 2. (right) Dependence of 1/2 concentration of Dy-HEDTA. a, thylakoid membranes ( ) b, untreated PS-II particles (O) c, NaCl-washed particles (A) d, CaCl2 washed particles ( ). The microwave power at which is one-half of its unsaturated value is taken for a... 

The intensity I = h at which the saturation parameter 5 becomes 5 = 1 is called the saturation intensity. From (7.5) we derive that for 5=1 the population-density difference AN decreases to one half of its unsaturated value AN. The saturation power Ps. is Ps = hA, where A is the cross section of the laser beam at the absorbing molecular sample. 

Because of the saturation by the pump beam, the population Nm decreases from its unsaturated value N to... 

ASTM D2849-69, Standard Methods of Testing Urethane Foam Polyol Raw Materials, describes a number of tests used for analyzing poly(alkylene oxide)s (1). These tests include metals analysis, acid and hydroxyl numbers, unsaturation values, water, suspended matter, specific gravity, viscosity, and color. Many of these tests are well known and will not be described. Those tests dealing with end groups—i.e., the functional groups that are used in the further reaction of poly(alkylene oxide)s—are discussed below. Detailed test procedures can be found in the cited reference and also can be obtained from poly(alkylene oxide) suppliers. 

The frequency of a monochromatic tunable laser is tuned to the center of an atomic transition Ej - E. with transition probability Aj. = 5 x 10 s . Calculate the saturation intensity which depletes the lower level population to 0.5 of its unsaturated value if the only repopulation path is spontaneous emission E - Ej. ... 

Because of this population depletion the absorption coefficient a(o)) = decreases from its unsaturated value aQ(u))... 

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