Real-Time NMR Experiments

Two practical aspects are of importance in vulcanising rubber compounds  

1) the crosslinking kinetics, which determine the production cycle time or throughput, and 

2) the crosslink density, which partly determines the mechanical and elastic properties of the vulcanisate. 

The crosslinking kinetics and the final state of cure are commonly studied with the aid of rheometers. NMR relaxation experiments can offer several advantages for the characterisation of the crosslinking kinetics in complex materials because of high method selectivity with respect to the rubbery chains/phases in polymer blends, filled and oil extended rubbers. 

Network structures have been quantitatively determined by means of real-time XH NMR T2 relaxation experiments for several polymers [174-178]. The effect of the curing conditions on sol and gel fractions and the spatial heterogeneity of the network structure has been studied for polyethylene [174], polyacrylamide [175], PDMS [176], BR [177], epoxy resins [178] and EPDM [179]. 

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