A study of plastic plateau disappearance in stress-strain curve of annealed polypropylene films during stretching

Lei, Caihong; Shuqiu, Wu; Xu, Ruijie; Xu, Yang; Peng, Xinlong

doi:10.12989/amr.2013.2.2.111

Cited by 11 publications

(15 citation statements)

References 8 publications

(8 reference statements)

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“…Figure 9 presents the DSC curves of samples at different stretching stages. With the increase of drawing ratio, the endotherm plateau formed during annealing disappears progressively, in agreement with the former results given in our previous articles [18,19]. As can be seen, from Sample A to Sample E, the DSC curves for PP-B and PP-G do not show much difference.…”

Section: Properties Of Precursor and Annealed Filmsupporting

confidence: 92%

Influence of low molecular weight tail of polypropylene resin on the pore structure by room‐temperature stretching

Lei

Shuqiu

et al. 2013

Polymer Engineering & Sci

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Two polypropylene resins with approximate weight‐average and z‐average molecular weight but differing in low molecular weight tail content were used for the fabrication of microporous membrane based on melt‐stretching mechanism. The precursor film with row‐nucleated crystalline structure, annealed film and cold‐stretched film were prepared and characterized. It was found that the existence of the low molecular weight tail resulted in higher lamellar thickness in precursor film and more perfect grown crystalline part during annealing. During stretching under room temperature, within the plastic region in stress–strain curve, these grown parts were pulled out and converted to bridges connecting separated lamellae. Higher content of connecting bridges existed in the cold‐stretching film with low molecular weight tail. In addition, the polypropylene resin with low molecular weight tail showed more pronounced stain‐hardening behavior in stress–strain curve, indicating crystallization occurrence of stretched tie chains, resulting in more stable connecting bridges and less deterioration to formed pore structures. Therefore, it can be seen that for polypropylene resin with certain high molecular weight chains, the existence of low molecular weight tail is important to the formation and stabilization of pore structure during the fabrication of microporous membrane by stretching. POLYM. ENG. SCI., 53:2594–2602, 2013. © 2013 Society of Plastics Engineers

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Section: Properties Of Precursor and Annealed Filmsupporting

confidence: 92%

Influence of low molecular weight tail of polypropylene resin on the pore structure by room‐temperature stretching

Lei

Shuqiu

et al. 2013

Polymer Engineering & Sci

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“…In our previous work, it was found that the DSC curves of annealed film showed an endotherm plateau before the main melting peak, similar to the DSC curves of the heat‐set microporous membrane in Fig. .…”

Section: Resultssupporting

confidence: 77%

“…As to the second stage—the annealing process—the annealing temperature, annealing time and tension level (percent extension) control the annealing effect . In our previous work we found that, during cold stretching, the low‐temperature endotherm plateau in the DSC curves and the plastic plateau in the stress–strain curves of annealed films disappeared progressively and their disappearance corresponded to the formation of an initial bridge structure connecting separated lamellae. Recently, we have found that, compared with that formed only through cold stretching, more connecting bridges were initiated during hot stretching .…”

Section: Introductionmentioning

confidence: 99%

Influence of heat-setting temperature on the properties of a stretched polypropylene microporous membrane

et al. 2013

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The influence of heat-setting temperature on the stress-strain curves, differential scanning calorimetry (DSC) curves and properties of a stretched polypropylene microporous membrane was studied. It was found that with an increase of heat-setting temperature, a plastic plateau region in the stress-strain curves and a melting endotherm plateau in the DSC curves became apparent. The permeability and porosity firstly increased with the temperature to 145 • C and then decreased. The pore structure arrangement showed similar changing trend. On the one hand, higher heat-setting temperature could decrease the shrinkage of the microporous membrane. On the other hand, the crystallization of some chains around separated lamellae during heat-setting was unfavorable to the properties of the microporous membrane. The occurrence of crystallization during heat-setting explained the origin of the plastic plateau. For the fabrication of microporous membranes based on the meltstretching mechanism with good dimensional stability, heat-setting is necessary, but too high a heat-setting temperature can destroy the permeability.

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“…In the works by Carreau group in the field of PP microporous membrane, the roomtemperature stretching ratio was set at 35-40 % [7][8][9][10][11] , based on the direct comparison of structure and properties of stretched microporous membrane. In our previous work [14][15][16] , to follow the changes induced by room-temperature stretching, the room-temperature stretched films were heat-set at 145 °C for 10 minutes to decrease their shrinkage. This is since the annealed films show higher elastic recovery and the stretched film by only room-temperature stretching will recover to its unstretched state after the stretching stress is relieved.…”

Section: Introductionmentioning

confidence: 99%

The study of room-temperature stretching of annealed polypropylene cast film with row-nucleated crystalline structure

Chen

Xie

et al. 2016

Polymer

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The room-temperature stretching process of polypropylene annealed film with rownucleated crystalline structure was studied by in-situ small-angle X-ray scattering (SAXS) setup and off-line wide-angle X-ray scattering (WAXS), temperature-modulated differential scanning calorimetry (TMDSC) and stress-strain curves testing. The formation process of initial connecting bridges and pores was clarified. For the annealed film, except for the initial lamellae structure, the recrystallized part formed by the melting and crystallization of imperfect crystals during annealing, tie chains connecting the lamellae structure among the amorphous region, secondary crystals from the crystallization of tie chains during annealing and daughter crystals from the special cross-hatched crystalline structure of PP coexist. It was found that 10 % stretching lead to the pronounced increase of long period and the appearance of a few initial connecting bridges. The stretching of daughter crystal and recrystallized part contributed to the formation of initial bridges. At stretching ratio of 30 %, uniform distributed connecting bridges were observed and the stretched film showed maximum structure periodicity. At this stretching ratio, except for the stretching of daughter crystal, the stretching of tie chains and secondary crystals within the amorphous region lead to the formation of more connecting bridges. At higher stretching ratios into the strain-hardening region and beyond the second yield point, except for the stretching of the above mentioned crystalline

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A study of plastic plateau disappearance in stress-strain curve of annealed polypropylene films during stretching

Cited by 11 publications

References 8 publications

Influence of low molecular weight tail of polypropylene resin on the pore structure by room‐temperature stretching

Influence of low molecular weight tail of polypropylene resin on the pore structure by room‐temperature stretching

Influence of heat-setting temperature on the properties of a stretched polypropylene microporous membrane

The study of room-temperature stretching of annealed polypropylene cast film with row-nucleated crystalline structure

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