The characteristics of the new chiral stationary phase heptakis(2,3-di-O-met hyl-6-0-tert-butyldimethylsilyl)-fl-cyclodextrin are outlined and compared with permethyl-and perethyl-P-cyclodextrins. Column C: . T b 7 20 25 min. 20 25 min.Figure 6 Separation of the enantiomers of lavandulyl acetate on columns A and C (coated with 15 and 5 0 % of DIME-6-TBDMS-P-CD in OV-1701-vi, respectively): conditions as for Figure 3.phases. Figure 7 shows a test for chiral GC separations on a micro preparative scale, the separation of 1-(2-methoxypheny1)ethanol on a 0.54 mm i.d. fused silica wide bore column. In this instance SE-52 was used as solvent for the modified cyclodextrin. ConclusionThe introduction of the bulky TBDMS groups slightly changes, but does not reduce, the chiral selectivity, and it is, furthermore, evident that the chiral selectivity and versatility of this new chiral stationary phase are at least as high as those of PME-P-CD.

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A method for determining the abrasion resistance properties of reinforced vulcanizates was required for evaluating new GR-S type elastomers and carbon blacks developed for use in automobile tire treads. In spite of the fact that past experiences revealed that most laboratory machines are unsatisfactory for testing GR-S vulcanizates, a program for evaluating several machines was undertaken. A Lambourn abrader similar to the one recently adopted by the British Standards Institution for testing elastomer vulcanizates appeared to be most promising, for which reason efforts were expended on constructing a similar machine. The abrader that was constructed and operated to simulate wear brought about by a tire slipping on road surfaces embodied the following four modifications of the British machine: 1. All parts and accessories were either obtained or fabricated in the United States. 2. The electrical eddy current type of brake used in the original Lambourn machine was replaced with a hydraulic, gear pump braking system. 3. Intermittent talcing of the test wheel during operation was specified. 4. A revolution counter equipped with a friction drive wheel, one foot in circumference, was installed to ride on the test wheel for the purpose of conveniently determining test run distances. The conditions for testing vulcanizates were standardized to obtain abrasion loss values that could be expressed in terms of loss in cubic centimeters per 3000 feet of running at 24 per cent slip. Adjustments were made in calculating abrasion ratings from volume loss values to bring them more in line with reported service test ratings.

A study of factors which affect the results obtained with the constant slip abrader in evaluation of abrasion resistance properties of GR-S vulcanizates has revealed the following : 1. As might be expected, abrasion losses decrease with increase in 300 per cent modulus. 2. Losses increase approximately logarithmically as the amount of slip between the test and abrasive wheels increases. 3. The abrasion losses decrease with increase in talcing rate, due to “lubrication” of the abrasive wheel by the talc as long as the rate is sufficient to keep the wheel free of loose abraded material. 4. Indications are that abrasion losses may increase with increase of coefficients of friction of test wheels against the abrasion wheel. 5. In a study of the effect of ambient temperature on constant slip abrasion losses, the losses increased as the temperature was raised from −10 to 30° C for GR-S 1500, GR-S 1503, and for high Mooney-viscosity GR-S 1500 extended with a naphthenic extender oil, and the losses remained essentially constant for the Resin-731 extended high Mooney viscosity GR-S 1500. The Resin-731 extended stock changed only slightly with temperature and, consequently, its comparative rating increased rapidly with rise of temperature. It was noted in photomicrographs of the wheel surfaces that the abrasion pattern which was evident at normal temperatures was absent or at best poorly defined at the lower temperatures, indicating a possible difference in kind of abrasion at low temperatures than at normal temperatures. 6. Latex masterbatches of oil and black that had been premixed by several different methods gave vulcanizates with constant-slip abrasion resistance superior to similar masterbatches prepared in the usual manner. 7. The constant-slip abrader was found to be useful in evaluating new SAF blacks and in the evaluation of the effect of using dispersing agents in carbon black and extender-carbon black masterbatching by the latex procedure.

Studies were made of the influence of a number of polymerization variables on the tensile strength of vulcanized evaporated films from low-temperature high-solids GR-S latexes. Previous reports of film tensiles on the order of 3000 pounds per square inch for latexes of 70/30 butadiene-styrene charge ratio were confirmed. The levels of accelerator necessary for optimum vulcanized properties were found to be considerably lower than those normally used, particularly for latexes shortstopped with dithiocarbamate salts. Microscopic coagulum found in some latex samples had a pronounced effect in decreasing film tensile of vulcanizates. Cured films from latexes emulsified with mixtures of fatty acid and rosin soap possessed considerably better tensile strengths than those from latexes using all fatty acid soap emulsification. Wide variations on Mooney viscosity had relatively little effect on ultimate film tensiles. Incorporation of small amounts of lignin into the latex as the ammonium or sodium salt decreased cure rates of films and aided in giving more reproducible tensile results. Both lignin and the sodium salt of cresyl monosulfide improved the aging characteristics of films.