Polar surface energy

Typically, the polar surface energy component of polymers used for release coatings is relatively small and the work of adhesion can be written simply as... 

To solve this equation the adsorption isotherm needs to be measured over a wide range of partial pressures and integrated. As a result the work of adhesion Wa, the free energy JG and the dispersive and polar surface energy, y s and y s can be obtained. 

The equilibrium wetting behavior of simple liquids (including low MW polymers) on low polarity polymer surfaces is well documented and consistent with Gibbsian thermodynamics within specific constraints. Empirical relationships have been established between observed contact angles and polymer surface chemical composition. Predictive relationships have been established between contact angles and polymer substrate surface chemistry based on the theory of fractional polarity surface energies can be factored into dispersion and polar components. These relationships seriously break down with increasing polarity of either the liquid or solid surface. 

Jute fibre treatment Water/arr contact angle Polar surface energy (mJ m ) Flexural strength of polyester composites (MPa)... 

Later, it was realised that polar interactions could also play a role in wetting and adhesion. The surface energy was divided into non-polar and polar components and new equations were then proposed to allow for the possibility of polar interactions across the interface (Equation 8.7). From that equation it can be expected that maximal adhesion will occur when the ratio of polar to non-polar surface energy is the same for the adhesive and the adherand. 

Fig. 7 Correlation between polar surface energy with percentage of oxygen on sample surface as analysed by XPS,...

Overall Surface Energy Polar Surface Energy Component... 

Fig. 11 Overall and polar surface energies measured by the Owens-Wendt technique (with Washburn absorption) for various types of Toray TGP-H paper GDLs. Values in white boxes represent the total aerial loading of PTFE for each sample. AA plain, BA 5 wt% substrate/0 wt% MPL, BC 10 5wt% substrate/10wt% MPL, BC 5wt% substrate/23wt% MPL, DA 20wt% substrate/0 wt% MPL, DC 10 20wt% substrate/10wt% MPL, DC 20wt% substrate/23 wt% MPL...

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