Glass Transition in Rubbery Materials

Abstract

When the perturbation frequency imposed on a rubber falls within the glass transition zone of its viscoelastic spectrum, energy absorption is maximized. This phenomenon is the operative mechanism for various applications of elastomers requiring large energy dissipation. Nevertheless, a fundamental understanding of the glass transition is lacking. The diversity of properties that depend both on chemical structure and thermodynamic conditions makes modeling difficult and a first principles theory perhaps unachievable; indeed, the number of models for the glass transition seems to be inversely proportional to their ability to accurately describe the myriad behaviors. The progress made at quantifying the role of the thermodynamic variables temperature, T, and density, q, on the dynamics is described. An important aspect of the work was the discovery that relaxation times and viscosities of molecular liquids and polymers superpose when plotted against the scaling variable T/q c

Understanding the Influence of Oligomeric Resins on Traction and Rolling Resistance of Silica-Reinforced Tire Treads

“…22 One possible explanation for this T g shift is related to the previously discussed question about the solubility/compatibility of the three resins in the basic compound. 11 It is useful to use the approach of Fox to calculate the resulting T g of two mutually soluble components with different individual T g s. The well-known Fox equation 23 is expressed as…”

Isomorph theory of physical aging

“…Experimental confirmations of isomorph-theory predictions have been presented in Refs. 71 and 22, 72-75. In particular, the density-scaling relation obeyed by many glass-forming liquids [76][77][78][79] -as well as the so-called isochronal superposition property [33,74,80,81] -are both consequences of the theory [23].…”

Electrical and Dielectric Properties of Rubber

“…At temperatures near the glass transition, the dynamics of liquids and polymers becomes much slower, reflected in large increases in viscosities and relaxation times. 3,61 This slowing down of the molecular and segmental dynamics is a consequence of growing cooperativity, as motion of a molecule or segment increasingly requires adjustments of neighboring species; that is, the motions exert reciprocal influences. 88 Quantification of these space-time correlations is essential to understanding the dynamic properties of liquids and polymers close to T g .…”