Annealing of Oriented PP/PE Double-layer Film within the Melting Range of PE: the Role of Partial Melting and Self-nucleation

The effect of roll temperature from 60 to 120°C on the crystalline structure and properties of oriented polypropylene (PP) cast films and the stretched microporous membrane was studied. It was found that the long period, the thickness of the crystalline and amorphous phase increase with the increasing roll temperature. And the regularity of the lamellar structure also improves with the increasing roll temperature. In comparison, the lamellae lateral dimension is nearly unchanged at 50 nm. The orientation of the lamellar structure slightly decreases from 0.81 to 0.76 with increasing roll temperature. The increase of the long period and the improvement of the regularity of the lamellar structure lead to the increase of the elastic recovery value of PP cast film. The corresponding microporous membrane also shows a smaller thickness of lamellar clusters, larger pores, better air permeability and better thermal shrinkage resistance. The higher roll temperature is beneficial to the perfection of the lamellar structure, obtaining the higher‐performance microporous membrane.

Section: Introductionmentioning

confidence: 99%

Effect of roll temperature on the structure and properties of oriented polypropylene cast film and stretched microporous membrane

Chen¹,

Chen

Yin

et al. 2023

Annealing improves the mechanical properties in poly(butylene succinate) films with oriented lamellar structure: The effect of metastable lamellae

Xie,

Xu,

Hwang

et al. 2024

The application range of biodegradable Poly(butylene succinate) (PBS) is highly dependent on its mechanical properties, which can be improved by the annealing process. In this study, the mechanical properties and microstructure of PBS films with oriented lamellar structures annealed at different temperatures were characterized. It was found that the annealing process effectively improves the elastic modulus and yield strength of the oriented PBS film with the increase of annealing temperature, which is completely different from the previous results of other oriented semicrystalline polymers such as PP, PMP, PE, and PVDF. The long periods, lateral dimensions and orientation of the lamellae of the oriented PBS film increase with the increasing annealing temperature. Meanwhile, the low‐temperature endothermic plateau in the DSC curve and the g1,r/Q in the SAXS experiment decrease with annealing temperature, indicating that increasing annealing temperature would reduce the thin and metastable lamellae in the PBS films. Compared the annealing results of oriented PBS films and that of other‐oriented semicrystalline polymers, we suggested the annealing process for the oriented PBS films would reduce the thin lamellae and form thicker lamellae, resulting in an increase in the elastic modulus and yield strength of the annealed PBS films. This study clarifies how the annealing temperature affects the microstructure and mechanical properties of the oriented semicrystalline films.

Cavitation behavior of poly(4‐methyl‐1‐pentene)/polypropylene/poly(4‐methyl‐1‐pentene) tri‐layer film: Influence of annealing and stretching temperature

Shi,

Chang

et al. 2024

In this work, poly(4‐methyl‐1‐pentene)/polypropylene/poly(4‐methyl‐1‐pentene) tri‐layer films were prepared. The microstructure of the film was adjusted by annealing in the temperature range of 150–237.5°C. Afterward, the influence of annealing and stretching temperature on the cavitation behavior of the film was investigated by small‐angle x‐ray scattering (SAXS). Results showed that for the “butterfly” scattering in the early stage, the radius of gyration () and maximum dimension () of voids were ca. 75 and 200 nm, which were hardly influenced by annealing. Whereas, the volume fraction of voids was enlarged obviously, suggesting that more voids were formed; for the “streak” scattering in the late stage, the length of voids () grew gradually with stretching, and the ultimate value of was 432.5 nm for un‐annealed film and 176 nm for film annealed at 230°C. Simultaneously, the misorientation of voids was reduced from 0.33 to 0.18. As the stretching temperature was elevated from 30 to 45 and 60°C, and maintained at 75 and 200 nm, and was enlarged to 434 and 432 nm. At the same time, the number of voids was reduced obviously. As the stretching temperature was 90°C, the voids were suppressed.