Network characterization of phenolic-based coatings

Phenolic-based coating systems incorporating typical binding resins such as epoxies or polyesters were prepared along protocols mimicking relevant application conditions and are investigated using methods which are fairly standard in an industrial environment. Following a pragmatic approach, gravimetric analysis along with spectral analysis by FTIR spectroscopy of the insoluble gel fraction and liquid 1H NMR spectroscopy for the soluble fraction were used in a quantitative way to investigate proven binder/crosslinker systems over a range of compositions. Furthermore, a close analysis of the soluble fraction data has been conducted following the statistical mean-field model of Miller-Macosko with proper adjustments to account for the investigated systems where the phenolic resin can crosslink with itself and with the binder, whereas the binder mainly links to the crosslinker in conjunction with chain extending end-end couplings. For the linear precursors considered here, end and side functions were treated as chemically distinct in the model. The soluble and insoluble fractions of phenolic-based coating systems are characterized by gravimetric and spectral analysis after curing at elevated temperature. The soluble fraction is compared to statistical model predictions obtained following the recursive method of Miller-Macosko. The chemical coupling mechanisms controlling the insoluble gel formation for resole-epoxy and resole-polyester systems are successfully identified. [Display omitted]