Evidence for the Shift of the Glass Transition near the Particles in Silica-Filled Elastomers

Abstract

Filled elastomers exhibit complex dependence of their viscoelastic modulus, both as a function of temperature and frequency. Otherwise, recent observations on thin polymer films have shown that their glass transition temperature depends on their thickness. Based on these recent results, and on a recent model, we propose that the mechanical behaviour of the filled elastomer is strongly influenced by a gradient of the glass transition temperature in the vicinity of the particles. This allows us to suggest a specific temperature-frequency superposition law for filled rubbers. This law seems to apply very successfully on two systems with different dispersion qualities, revealing the existence of a glass transition temperature gradient in the vicinity of the particles.

Enthalpic relaxation of silica–polyvinyl acetate nanocomposites

“…This seems in contradiction with the thesis of existence of glassy layers around the filler. 5,7,8 If there were glassy layers around the filler, their effects on the ageing of the material should have been immediately felt. If one argues that such effects are beyond the detection limit of the instrument or the technique employed, then the same argument should hold at the intermediate and longer annealing periods.…”

“…[1][2][3][4] The presence of a glassy layer at the filler surface as the underlying mechanism of reinforcement has been proposed by several authors. [5][6][7][8] The model states that a glassy layer or layers with a gradient of glass transition temperature persists near the walls of the filler even if the temperature is above the glass transition Correspondence to: S. Amanuel (E-mail: amanuels@union. edu) temperature of the neat or composite material.…”

“…More recently, NMR measurements indicate a decrease in chain mobility and some ordering of chains near filler surfaces. [6][7][8] Of major importance is the issue of whether or not a decrease in mobility necessarily implies the formation of a glassy layer, and if it does, whether or not the glassy layer is of sufficient extent and stiffness to account for the very high reinforcement values observed above the glass transition temperature. In this regard, there are several observations that have been made in filled elastomers well above the glass transition temperature that suggest alternate explanations to the formation of a glassy layer.…”

A review on the role of interface in mechanical, thermal, and electrical properties of polymer composites

“…The relaxation time was mainly measured using dielectric spectroscopy [183,184], NMR spectroscopy [185][186][187][188][189][190][191][192], and neutron scattering [193,194]. T g was determined using dynamic mechanical spectroscopy [195][196][197][198][199], calorimetry [191,[200][201][202], and dilatometry [184,203] techniques. Since the mobility of the polymer chains around the fillers is related to the interfacial interaction, the presence of the interaction and their strength can be estimated by measuring T g and relaxation time [11,204].…”

Reduced-mobility layers with high internal mobility in poly(ethylene oxide)–silica nanocomposites

“…1 The unique reinforcement has been explained theoretically 2,3 as well as experimentally [4][5][6] by filler networking, where filler-filler contacts are mediated by adsorbed and thus immobilized polymer species. The characterization of such adsorbed layers is challenging, as the traditional solvent-leaching technique ("bound rubber determination") largely overestimates the amount of polymer being part of the actual reduced-mobility layer.…”