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The dynamic mechanical moduli of slightly (0-16 wt96) plasticized poly(vinyl chloride) were measured by the method of free damped oscillation in the temperature range from -180 to + 100°C. The added plasticizers are tricresyl phosphate (TCP), butyl benzyl phthalate (BBP), dioctyl phthalate (DOP), dibutyl sebacate (DBS) and dioctyl sebacate (DOS). Two dispersion regions (a and /3) are observed in the case of poly(vinyl chloride) and they are influenced by addition of plasticizers. The a-dispersion shifts to the lower temperature side and broadens with increasing plasticizer content. These effects are mainly dependent upon the plasticizer species, and of the above plasticizers their plasticizing ability decreases in the order of DOS> DBS>DOP>BBP>TCP. The /3-dispersion, whose activation energy was estimated to be 14.3 kcal/mo!, first begins to disappear from the higher temperature side with increasing plasticizer content and ultimately vanishes. This effect scarcely depends upon the plasticizer species.Young's moduli of these samples were measured at -20-+40°C from observing the tensile stress relaxation. The modulus vs. plasticizer content curve shows a maximum. This is an example of "antiplasticization." The ability of additives to provoke antiplasticization decreases in the reverse order of plasticizing ability, that is, in the order of TCP>BBP>DOP>DBS>DOS.KEY WORDS Antiplasticization / Poly(vinyl chloride)/ Plasticizer/ Viscoelasticity / Polymer

The rate of micelle dissociation in a surfactant solution has been investigated by several techniques, such as stopped flow, pressure jump, temperature jump, and ultrasonic absorption. In the first three of them, the system to be examined is brought suddenly into a state of non-equilibrium. The process of self-adjustment of the system to its thermodynamical equilibrium is traced by some means, such as light absorption at a definite wave-length, electrical conductivity, temperature change, and, in a special case, lightscattering.Except for the stopped-flow method, the studies usually deal with rate phenomena that are close to equilibrium. Unless otherwise stated, the later discussion will be concerned with this case. One or more relaxation times are obtained in principle, although it is not easy to separate relaxation times of the same order of magnitude.In the ultrasonic absorption method, the system is perturbed by a continued irradiation of sound. The whole system is considered to consist of many small elements, each being contained in an imaginary wall-less vessel. The pressure in each vessel varies periodically with the frequency of the sound, in contrast with the case of pressurejump method where the pressure is changed suddenly from a value to another definite value. At any moment except some particular ones, the actual concentrations of coexisting chemical species do not agree with their equilibrium concentrations which should be realized under the pressure at that moment. The actual concentrations vary periodically with the sound frequency but with a lag of phase with the equilibrium concentrations which also vary with the same frequency. The lag of phase evokes the absorption of sound energy. Measuring the sound absorption at several frequencies, one can obtain the relaxation time (s).Assuming a suitable reaction model, one evaluates the rate constants of micelle dissociation and formation from the relaxation time (s). The same method of analysis can be applied, irrespective of the technique by which the relaxation time has been obtained. The above four methods may be called "relaxation method" en bloc. The reaction models adopted were usually such as a number of surfactant molecules (reactant) reacted reversibly with themselves to form a micelle (product) according to the mass-action law.On the other hand, several workers have applied "magnetic method", viz. NMR or ESR technique to investigate the dynamical behavior of micelles on a somewhat different standpoint. In a solution of a surfactant whose concentration is higher than its critical micelle concentration (cmc), some Of the surfactant molecules associate to form micelles and the others are monomolecularly dispersed in the bulk water phase. If these two species display NMR signals at different positions (different chemical shifts), the rate of exchange of a surfactant molecule between micelles and the surrounding water can be estimated by the analysis of NMR signal shape. Provided the surfactant is a stable radical, the rate is evaluated by an anal...

Ultrasonic velocity measurements have been made on a series of dilute aqueous solutions of n-alkanols and α,ω-alkane diols by means of the sing-around method. The apparent molal adiabatic compressibilities, φK have been derived, and the φ°K at an infinite dilution has been estimated. The φ°K values per CH2 and CH3 groups were estimated from the additivity of the φ°K value for each group. The values are negative at low temperatures and markedly decrease with a decrease in the temperature. This fact suggests that the iceberg formation makes a negative contribution to the φ°K.

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