Plateau modulus determination methods

Figure 10.3 Mean molecular mass between chemical crosslinks and trapped chain entanglements Mc+e in a cured mixture of a poly(ethylene glycol) diacrylate (PEGDA) and 2-ethylhexyl acrylate (EHA) as a function of the EHA content [52]. Mc+e values were determined from (1/T2s)max and the plateau modulus (see Figure 10.2). A substantial difference in Mc+e value, as determined by these two methods at low crosslink density, is caused by the effect of network defects which decrease volume average network density determined by DMA (see Section 10.3). The molecular mass of PEGDA (Mn = 700 g/mol) is indicated by an arrow. The molecular mass of network chains in cured PEGDA is about three times smaller than that of the initial monomer. The molecular origin of this difference is discussed in Section 10.3...

Dynamic spectroscopy (this method is more sensitive to Tg modifications) characterized cured MTI as polymer networks. The existence of the high-elasticity plateau typical for cross-linked organic polymers makes it possible to determine values of high elastic modulus in the pseudoequilibrium zone. Systems based on oligoethers and mixtures with oligoesters are characterized by E values of 5.0 and 8.5 MPa, respectively, which comply with adhesion strength data. 

The oscillatory measurements were carried out to investigate visco-elastic properties of binary HPMC/SDS mixtures, as well as of the separated coacervate phase in ternary HPMC/NaCMC/SDS systems. The amplitude sweep method was used. The oscillating frequency was 1 Hz. Plateau values of elastic, G , and viscous modulus, G , were determined from the linear visco-elastic region with the confidence band of 95%. Relative contribution of viscous to elastic component of the investigated structured systems was evaluated by means of the tanS value ... 

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