Effect of Crosslink Density on Elastic and Viscoelastic Properties

Effect of Crosslink Density on Elastic and Viscoelastic Properties 

This chapter is devoted to a short deseription of low-strain mechanical properties of polymers in the sohd state and in the glass transition region, with an emphasis on the effeet of erosslinking on these properties. There are three degrees of complexity in the description of this behavior, depending on the number of variables taken into account in the constitutive equations under consideration. 

Lowest Leyel. At the lowest level, these equations could involve only two variables, the stress a and the strain e  

This means that the mechanical behavior is regarded in relatively sharp intervals of time and temperature. Then, engineering moduli are generally sufficient to describe the material s behavior at low strains. They are interrelated by the following relationships  

E can be determined from a uniaxial tensile (E = a/s), or a uniaxial compressive test, or a flexural test (Fig. 11.1a and Chapter 12) G can be determined from a shear test, G = s/y, where s is the shear stress and y is the shear strain (Fig. 11.1c) K can be determined from a compressibility test. 

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