Measurements on Liquids in Solid Matrices

Brief mention may be made of some methods in which apparatus designed for viscoelastic solids is applied to study of viscoelastic liquids compounded with solid matrices. Such measurements usually provide the loss tangent only and are not appropriate for absolute measurements of viscoelastic properties, though they can give a semiquantitative view of changes in properties over wide ranges of temperature. 

In the method of Illers, 2o the liquid is dispersed as droplets in a block of polymeric solid which experiences very little mechanical loss in the range of frequencies and temperatures to be investigated. Then, in measurements of the type described in Chapter 7, observed losses may be largely ascribed to the liquid phase. Experiments may be carried through the temperature range in which the liquid experiences transition from fluid to glasslike consistency. 

In the so-called torsional braid analysis,the liquid is absorbed in a long strip of soft braided thread or filter paper which has very slight torsional stiffness, and torsion pendulum measurements are made by the methods of Chapters 6 and 7. Both storage and loss components of the dynamic torsional response may be attributed primarily to the viscoelastic liquid, and examined on a relative basis, although absolute measurements are not possible. Care must be taken that a contribution from the braid does not lead to erroneous conclusions about the properties of the viscoelastic liquid.25a. a flexural braid method has also been utilized. 

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