The cavitation development of poly(4‐methyl‐1‐pentene) casting films studied by in situ small angle X‐ray scattering

Abstract

In this paper, the on‐line small angle X‐ray scattering/wide‐angle X‐ray scattering (SAXS/WAXS) characterization method was adopted to study the morphology evolution of poly(4‐methyl‐1‐pentene) casting films during stretching. In this process, the lamellae structure was destroyed. And “bridge structure” was generated in the amorphous region. The scattering pattern changed obviously before and after cavities orientation. Stretching temperature and stretching speed mattered for the size of micropores. Low temperature helped generate more and larger voids. The faster stretching speed can improve the generation of cavities, enlarged cavitation number and helped its reorientation. These results provide the basic knowledge of how to produce poly(4‐methyl‐1‐pentene) microporous membranes with high electrochemical performance.

Influence of crystal orientation on stretching induced void formation in poly(4‐methyl‐1‐pentene) investigated by in‐situ small‐angle and wide‐angle X‐ ray scattering

“…For the P4MP1 precursor film, the optimum annealing temperature and time were 205°C and 20 min, and the best cold and hot stretching temperatures were 70 and 180°C 23 . In the later work by Yin et al, 24–26 P4MP1 precursor film with different draw ratios was obtained and the optimum annealing parameters and stretching parameters were discussed. It was found that the crystallinity of the precursor film declines with increasing draw ratios.…”

“…During extrusion, a larger molecular weight, higher extrusion speed, and a larger quench height promote the formation of planar stacked lamellar texture and higher main-chain crystalline orientation factor. 21 For the P4MP1 precursor film, the optimum annealing temperature and time were 205 C and 20 min, and the best cold and hot stretching temperatures were 70 and 180 C. 23 In the later work by Yin et al, [24][25][26] P4MP1 precursor film with different draw ratios was obtained and the optimum annealing parameters and stretching parameters were discussed. It was found that the crystallinity of the precursor film declines with increasing draw ratios.…”

“…In the stretching stage, low temperature and faster stretching speed resulted in more voids and larger void sizes. 26 In spite that the influence of processing parameters of MEAUS on the porosity of microporous P4MP1 membrane was discussed, the development of voids in P4MP1 during stretching remains not fully understood, which inhibits the better control of the pore size and size distribution in the membrane. To figure out the initiation and evolution of voids in P4MP1 during stretching, the in-situ ultra-small angle X-ray scattering (USAXS) method was employed to monitor the structural evolution of compression-molded P4MP1 plates.…”

“…The variation of the optimum annealing condition is of great possibility caused by the different molecular weight and extrusion parameters. In the stretching stage, low temperature and faster stretching speed resulted in more voids and larger void sizes 26 …”