Polymer resin sulfur, determination

Chen (29) found that the amount of sulfuric acid directly determines the hardening time in the acid condensation of spent sulfite liquors used in plywood and veneers. However, in general the adhesives based purely on acid condensed lignins have often been found to be an uneconomic and qualitatively inferior alternative to adhesives based on synthetic polymers and phenol or lignin-formaldehyde resins. 

What makes Nafion so useful for catalytic purposes is the superacidity of the acidic form of the polymers. Because the sulfonic acid group is attached to a highly electron-withdrawing perfluoroalkyl backbone, a relatively high polarization of the -OH bond results. Because methods for measuring solution acidity cannot be directly applied to heterogeneous solid materials, determination of the acidity of Nafion-H is difficult. Nevertheless, studies indicate that the acidic character of Nafion-H resin is comparable with that of 100% sulfuric acid, because the estimated Hammett Hq acidity function value of Nafion-H, approximately —12, is comparable with that of 100% sulfuric acid [1]. 

True properties are determined by the polymer and compound formulation and, for synthetic rubbers, additionally by type of curing agents such as sulfur or peroxides and the state of vulcanization. Typical properties for four polymers often used in automotive applications [acetals, nylons, polycarbonates, and unsaturated polyester (vinyl esters)] are shown in Tables 10.1 through 10.4. Typical property data is readily available from resin producers and compounders. Property data for elastomers is found in the chapter on elastomers in this handbook. 

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