Polymer concentration dependence of the gel point for chemically modified biopolymer networks using small amplitude oscillatory rheometry

摘要: Solutions of xanthan gum form a strong gel upon the addition aluminium ions (Al(III)). We have previously reported on stoichiometric (ratio crosslinker to polymer present) dependence thermal point and final strength. The results presented here expand previous work, presenting gelation characteristics for range concentrations different stoichiometries. limiting ratio, below which does not occur, is found be independent concentration. relaxation exponent shown decrease with increasing concentration, whilst temperature T-g, increase. 'gel strength' measured at complete extent increase concentration defined effective stoichiometry, r(e), becomes less pronounced. For systems constant stoichiometry varying concentrations, storage modulus follow power law relationship an approximately two. All observed trends support proposed mechanism xanthan-Al(III) provide new insight into in presence metal ions. (C) 2001 Elsevier Science Ltd. rights reserved.