摘要：

    Reinforcement of rubber with fillers such as carbon black and silica produces an increase in both the elastic and viscoelastic behaviour. While the increase in elastic modulus with particulate volume fraction is well understood in terms of hydrodynamics, dynamic filler networking and occlusion of rubber matrix by the filler agglomerates, the temperature-dependent changes in viscoelastic behaviour are less well understood. This is partially due to the complexity of studying filled rubber systems. For example, the fillers do not homogeneously disperse throughout the rubber matrix with the extent of particulate aggregation depending upon the filler type and the detailed processing conditions. Understanding the behaviour is also complicated by chemical crosslinking varying between filled samples despite the use of equivalent curing systems as the crosslinking chemistry is affected by the presence of highly active, high surface area filler particles. This also makes a direct comparison between samples with differing volume concentrations difficult.
    Under conditions of small dynamic strains (typically < 0.1 %) many of the issues associated with the Payne Effect non-linearity, such as filler structure breakdown, are not encountered; which permits a simplified study of the reinforcement. Working at small strains, in the linear viscoelastic region allows viscoelastic parameters (tanδ, G’, G’’) of filled rubbers to be understood in terms of three effects:
1. How active-surface particles alter the chemical crosslinking processes and how this might alter the dynamic properties (G’, G’’) of the rubber matrix in filled systems.
2. How the dispersion of the filler phase (as well as the filler volume fraction) might determine both the extent of hydrodynamic amplification of the modulus (G’) and any non-linear filler structure breakdown.
3. How an interphase polymer region at the filler interface where the labile attachment of the polymer to the filler surface affects both the magnitude of the hydrodynamic reinforcement (G’) and viscous dissipation losses in the bulk material (G’’).
Model filled rubbers prepared using a variety of filler particles of various surface areas, morphologies and surface activities are characterised to help understand the effects of each of these on the viscoelastic properties.
 

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