Surface Energy Of Polymers Research Articles

Relaxation of the surface energy of solid polymers

The surface energy of a polymer can be increased by compression moulding against a metal substrate. After removal of the substrate relaxation to the equilibrium value sets in. We determined the rate of polymer surface energy relaxation as a function of temperature. For a vinyl chloride-vinyl acetate copolymer we determined an activation energy of the relaxation process that could be correlated to segmental motions in this polymer. For a plasticized polyvinylchloride we found a lower activation energy and a larger rate of relaxation, which is the result of the action of plasticizers on segmental motions. In the case of polyethylene the results indicate segmental motions in amorphous regions in the polymer. With polyethylene the activation energy drops when nearing the melt temperature. The movements of molecular segments correspond to a desorption process at the polymer surface, after removal of the substrate. This agrees with the adsorption during compression moulding, as repotted in earlier work.

Polymer polarity and surfactant adsorption

AbstractThe effect of polymer polarity on surfactant adsorption from aqueous solution is discussed. The analysis assumes that surfactant adsorption at the polymer–water interface follows a Langmuir‐type adsorption isotherm and the free energy of adsorption is controlled by the interfacial tension of the interface. Saturation adsorption given by the area per molecule of surfactant at the critical micelle concentration (CMC) of the surfactant is related to the polymer–water interfacial tension and the polarity of the polymer surface, calculated from the polar and dispersion contributions to the polymer surface energy. Available data on the area per molecule of sodium lauryl sulfate on various polymer surfaces have been used to test satisfactorily the above analysis. The analysis is used to interpret some of the observations relating to surfactant adsorption encountered in the emulsion polymerization of polar monomers and particle size determination of latexes by the soap titration method. Further, potential utility of such area per molecule data to characterize the nature of polymer surfaces is also discussed.

The determination of solubility parameters of solvents and polymers by means of correlations with other physical quantities

AbstractCorrelations of solvent solubility parameters with molar attraction constants and with properties like surface tension, dipole moment, and index of refraction have been explored. From relations found to be valid for solvents, it is possible to calculate the solubility parameters for polymers. A relation between the dispersion contribution to the surface energy of polymers (a measurable quantity) and the dispersion solubility parameter of polymers has been found which is similar to a relation established for low molecular weight substances.

Reactions and wetting properties of 1:1 perfluoroalkyl allyl and methallyl ether–maleic anhydride copolymers

AbstractPolymers with fluoroalkyl side‐groups on three of every four carbon atoms along the polymer main chain were made by treating 1 : 1 copolymers of perfluoroallyl (or methallyl)ethers and maleic anhydride with SF4, and then esterifying the resulting acid fluoride groups with 1H, 1H‐pentadecafluorooctanol. Surface wettability of these polymers by polar and non‐polar liquids was studied. The critical surface tension (γc) was found by Zisman's method. The dispersion force component of polymer surface energy (γsD) and the polar component of surface energy (γsp) were calculated by the respective methods of Fowkes and Owens. The γc values for several of the highly fluorinated polymers were lower than previously reported for any fluoropolymer but not so low as has been observed for the surface of an oriented perfluoroacid monolayer. In the range 11.4–18.5 dyne/cm, γc approximates γsD for the fluorinated surfaces; however at lower γc values, considerable difference between γc and γsD was noted.