Uniaxial cold drawing of plastic - What happen to the material's modulus?

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SUMMARY

The discussion focuses on the effects of uniaxial cold drawing on polybutylene succinate, a semicrystalline polymer. It is established that strength and elongation at break increase along the machine direction (MD) with higher draw ratios, while modulus slightly decreases. In contrast, along the transverse direction (TD), strength decreases, elongation at break increases, and modulus significantly rises from 500 MPa to 750 MPa at the highest draw ratio. This behavior contradicts typical expectations regarding modulus reduction along the TD, prompting inquiries into the underlying mechanisms.

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  • Understanding of uniaxial cold drawing processes
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  • Familiarity with polybutylene succinate characteristics
  • Basic principles of material science related to crystallinity
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Material scientists, polymer engineers, and researchers studying the mechanical properties of semicrystalline polymers, particularly those involved in processing and application of polybutylene succinate.

yijing84
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Hi all.
I am now working on the uniaxial cold drawing on the plastic sheet (polybutylene succinate, a semicrystalline polymer).
After uniaxial cold drawing, as expected, strength increased along the drawing direction/ machine direction (MD).
Strength and elongation at break drastically increased with increasing draw ratio along the MD.
However, modulus slightly reduced with the draw ratio.

Along the transverse direction (TD), strength reduced as expected with the draw ratio.
However, elongation at break slightly increased with draw ratio.
Furthermore, modulus significantly increased with draw ratio from 500MPa to 750MPa at the highest draw ratio along the TD.

According to most of the study, modulus should reduce along the TD with draw ratio as the less regid molecular bond along the TD as compared to along the MD (rigid covalent bond). However in my case, it is totally different.
I am here kindly ask for any possible explanation on this phenomena on the modulus along the TD?
Thank you so much.
 
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