Strain Hardening and Network Density

Although understanding of the deformation behavior of amorphous polymers is well established in terms of molecular structure, as described in Section 18.2, the deformation behavior of semicrystalline polymers, in particular, large-strain behavior. 

it is observed that the strain hardening is same for amorphous PET and cold crystallized PET, although the crystalline phase is developed by cold crystallization. Eor example, the slope at large strain is used to define the strain-hardening modulus and the lines are parallel and thus strain-hardening modulus values are the same for PET with 0%, 22%, and 29% 

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