Polymer coatings, both with and without pigments, have been subjected to solar radiation and water spray weathering. degrees of penetration of the weathering effects have been measured by injecting positrons of varying energy, i.e. to variable depths, into the films and observing the Doppler broadening of the annihilation radiation. The The method is capable of detecting changes due to weathering effects at very early stages, long before visual examination reveals degradation. AS little as one week of exposure caused measurable changes in the polymer structure, which were reflected in the Doppler broadening. could possibly become a useful complement to the other methods of determining weatherabilities of protective polymer coatings.

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A great deal of effort has been directed toward the development of new polymer blends and interpenetrating polymer networks in recent years. This approach has emerged as an important means of developing new polymeric materials and improving properties such as sound damping. The thermodynamic models that best describe polymer-polymer interactions have an important free volume contribution. Until recently, however, there was no technique that could make a direct, nondestructive measurement of the molecular free volume. Using the free volume microprobe (FVM), it is now possible to characterize both the average free volume site size and the relative number of free volume sites. Thus it is possible to make some assessment of the total free volume as well as the free volume distribution. The basic theory of the FVM technique will be presented as well as some supporting data from a series of miscible, immiscible, and partially miscible polymer blends.

Buried potable waterpipes are susceptible to permeation by organic solvents. In studying piping made of PVC, asbestos/cement, and ductile iron, full‐pipe assemblies and laboratory bench techniques were employed. Elastomeric gaskets for all three systems become permeated, at least under exaggerated conditions. Results show that thermodynamic activity, as opposed to concentration, is the driving force. At solvent activities well above those encountered in typical soil, PVC is seen to be an effective barrier against permeation.

An approach has been developed to estimate the solubility and diffusivity of toxic phosphonofluoridates in high molecular weight polymeric matrices based upon experimentation with nontoxic simulants. This approach is based on Gee's relation for estimating solubility (equilibrium swelling) from knowledge of the solubility parameters for the polymer and the simulant liquids concerned and on Van Krevelen's relation between diffusivity and activation energy of diffusion. The latter is interpolated from a standard plot of activation energy of diffusion against penetrant molar volume. Equilibrium swelling values and diffusivities for toxic alkyl phosphonofluoridates in styrene‐butadiene rubber (SBR) and low density polyethylene (LDPE) were estimated from results of swelling measurements (as a function of time and at three different temperatures) involving the two polymers and a series of nontoxic liquids, similar to the toxic alkyl phosphonofluoridates.