Crystallization behavior of isotactic polypropylene containing a fibrous nucleating agent in a flow field

2023

Polymers

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The effect of shear history on structure development during post-processing annealing was studied using poly(lactic acid) PLA. Since PLA shows a low crystallization rate, quenched films had no crystallinity. Moreover, molecular orientation was not detected in the films. During the annealing procedure beyond its glass transition temperature, however, molecular orientation to the flow direction occurred with the crystallization growth in the films having an appropriate shear history. This peculiar crystal growth during the annealing was most probably attributed to the crystallization from extended chain crystals generated during the applied shear history, although the amount of extended chain crystals was low. The results obtained in this study should be noted because the molecular orientation proceeded due to the annealing history applied. Furthermore, this phenomenon will be used to suppress dimensional change and increase product rigidity.

Section: Resultssupporting

confidence: 90%

Role of Shear Flow on Structure Development during Post-Processing Annealing for Poly(lactic acid)

2023

Polymers

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“…A camera was set up on the other eyepiece to investigate the morphology. The details and some experimental results obtained by this machine were reported in our previous papers 36,37 . Figure 1 illustrates the experimental protocols for temperature and shear.…”

Section: Measurementsmentioning

confidence: 99%

Optimum processing conditions for the maximum crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Janchai

et al. 2023

Sci Rep

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The effect of thermal and shear histories on the crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was studied. As with other crystalline polymers, the shear history greatly affected the crystallization rate when the shear rate was beyond a critical value, i.e., the inverse of the Rouse relaxation time. Even after the formation of extended chain crystals, spherulite texture was clearly discernable. It grew from certain points on the extended chain crystals. Consequently, a row of spherulites appeared along the flow direction. The resin temperature in the molten state was also significant. When the sample was heated to 170 °C, which is beyond the main melting peak in the differential scanning calorimetry curve, unmolten crystals did not affect the linear viscoelastic properties. They acted as effective nucleating agents for the rest of the polymer during cooling. Therefore, the shear history hardly affected the crystallization rate and the number of spherulites.

“…A camera was set up on the other eyepiece to investigate the morphology. The details and some experimental results obtained by this machine were reported in our previous papers [24,25]. Figure 1 illustrates the experimental protocols for temperature and shear.…”

Section: Measurementsmentioning

confidence: 94%

Optimum Processing Conditions for the Maximum Crystallization Rate of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Janchai

et al. 2022

Preprint

Self Cite

The effect of thermal and shear histories on the crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was studied. As with other crystalline polymers, the shear history greatly affected the crystallization rate when the shear rate was beyond a critical value, i.e., the inverse of the Rouse relaxation time. Even after the formation of extended chain crystals, spherulite texture was clearly discernable. It grew from certain points on the extended chain crystals. Consequently, a row of spherulites appeared along the flow direction. The resin temperature in the molten state was also significant. When the sample was heated to 170°C, which is beyond the main melting peak in the differential scanning calorimetry curve, unmolten crystals did not affect the linear viscoelastic properties. They acted as effective nucleating agents for the rest of the polymer during cooling. Therefore, the shear history hardly affected the crystallization rate and the number of spherulites.