Semi-crystalline shear modulus

The conditions under which a particular deformation mode (coarse shear banding or deformation in a diffuse shear zone) predominantes seem to depend mainly on the ambient temperature, T, as compared to the glass transition temperature, T, of the material. This hypothesis can be deduced from a diagram of shear modulus G vs. ratio T/T for the tested polymers (Fig. 32). The amorphous PS as well as the semi-crystalline polymers PP and PB-1 exhibit a tendency to formation of coarse shear bands when the ratio of T/T is distinctly smaller than 0.75. There exists a... 

Figure 3.2 Shear storage modulus plot for semi-crystalline Nylon 6,6 demonstrating a, 3 and y transitions. Sonrce Anthor s own files...

Figure 13.4 Shear storage modulus - temperature plot for semi-crystalline 6,6 Nylon demonstrating alpha, beta and gamma transitions. Source Author s own files)...

In the case of elastically-isotropic solids there are only two independent elastic constants, Cn and Cn because 2c44 = Cu - C12. Since glassy polymers and randomly oriented semi-crystalline polymers fall into this category it is worth considering how the stiffness constants can be related to quantities such as Young s modulus, E, Poisson s ratio v, shear modulus G and bulk modulus K which are measured directly. The shear modulus G relates the shear stress 04 to the angle of shear 74 through the equation... 

Equation 1.16 can be used for the description of the temperature dependence of displaying one principal difference from the filled polymers. As the G value for amorphous and semi-crystalline polymers, the macroscopic shear modulus should be used instead of its value for a loosely packed matrix. This is explained so that, contrary to the value, the G value for the polymer amorphous state is determined by the structure of both quasi-phases [35]. The truth is that the application of the G value in Equation 1.16 only for a loosely packed matrix would mean determination of the cluster property (x ) from properties of another structure component only, which is physically meaningless. 

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