Rheological properties of methylcellulose aqueous gels under dynamic compression: Frequency sweep and validity of scaling law

Abstract

AbstractThe aqueous methylcellulose (MC) gels are characterized with a dynamic mechanical analyzer (DMA) under dynamic vertical compression. During the frequency sweeps of MC gels at different temperatures, the storage modulus is observed to be higher than loss modulus at lower frequencies. Both of the storage and loss modulus increases with frequency, but the rate of increase is higher for loss modulus. This leads to the first crossover between E′ and E″ during the frequency scan. For the frequency scan at a high temperature (80°C), a higher rate of increase is observed in storage modulus beyond the first crossover frequency. This leads to the second crossover between storage and loss modulus. Optical microscopy results indicate the presence of core–shell microstructure in aqueous MC gels. The first crossover is possibly due to the shell–sol transition, whereas the second crossover is due to the sol–shell–core transition. The validity of scaling laws at and around the first‐crossover point (shell–sol transition) is checked. The scaling law is valid at the first‐crossover point, but it is invalid around it. Alternate scaling equations based on reduced parameters are also used to check the universality. Irrespective of temperature, scaling laws are valid for reduced parameters. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010