Nuclear magnetic resonance structure investigations on crosslinked polyesters
Styrene-crosslinked mixed polyesters derived from maleic anhydride, 2,2-di(4-hydroxypropoxyphenyl)propane, oligo(propylene oxide) and 1,2-propylene glycol were investigated by high-resolution solid-state 13C-NMR spectroscopy. The structural modifications accompanying crosslinking were characterized in terms of spin-lattice relaxation times as a function of unsaturated polyester composition. Copolymerization and crosslinking (Fig. 4) effects were individually evaluated and the latter effect was related to variations in crosslinking density associated with the chemical structure of the unsaturated prepolymer. As the crosslinking effect is suppressed, the mechanical properties undergo expected changes, e.g., impact strength is increased and modulus of elasticity in tension is decreased (Table 2, Fig. 5).
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