Three modes of dissociation of H bonds in hydrogen-bond dominated solids

Abstract

ICE, paper and regenerated cellulose, Nylon (unstretched and lightly stretched), and to a certain extent natural cellulose, lignin and wool are typical examples of hydrogen-bond dominated solids (whose mechanical properties are mostly controlled by the density and characteristics of the hydrogen bond). Previously¹ I have shown that for these materials, Young's modulus E is related to N, the effective number of H bonds per cm³ responding to unidirectional stress, by E = kN^1/3. For cellulosics k is ∼ 8 × 10² when E is in Pa. Two major rheological characteristics of hydrogen-bond dominated solids are their ready softening by water and their relaxation of stress with time under constant strain. Thus, E_W/E₀, the ratio of the modulus at w g H₂O/g solid to the modulus at w= 0, drops to very small values for paper at saturation. Similarly, E_t/E₀, the modulus at time t to E at t = 0 in a stress relaxation experiment, drops to small ratios at high values of t. I postulate that both types of loss in E arise from reductions in N, through H-bond dissociation. I find this dissociation can be in one of three modes: I, II and III.