The Stress-Strain Curve at High Elongations

Most elastomers are amorphous in use. Indeed, significant crystallinity deprives the polymer of its rubbery behavior. However, some elastomers crystallize during strains such as extension. The most important of these are cis-polybutadiene, m-polyisoprene, and cK-polychloroprene. Crystallization on extension can be responsible for a rapid upturn in the stress-strain curves at high elongation see Figure 9.5. 

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