Facile way of dynamically tailoring microporous structures in polyvinylidene fluoride films prepared by thermally induced phase separation

Abstract

Polyvinylidene fluoride (PVDF) films were prepared via thermally induced phase separation (TIPS) using diphenyl carbonate as the diluter in an attempt to disclose the competitive relationship between crystal growth and droplet growth during phase separation process. By varying the quenching temperature different temperature gradient fields were established, which were theoretically evaluated via enthalpy transformation method. The effects of polymer concentration and quenching temperature on evolution of hierarchical morphologies in TIPS films were systematically investigated. According to the morphological characteristics, the cross‐sectional morphology of the films with lower polymer concentration (ΦP = 25%) could be divided into three layers; while that of higher polymer concentration counterpart (ΦP = 55%) only presented a bi‐layered structure. The reason for this could be ascribed to the effect of cooling rate on both crystal growth and droplet growth during TIPS process, which further determined the formation of the hierarchical structure in microporous films. With an increasing quenching temperature, both pore size and porosity of PVDF films increased, accompanied by an improvement on both thermal stability and dynamic mechanical thermal property. The present study could insightfully supply a facile route to fabricate structure‐controllable microporous films of crystalline polymers via an appropriate regulation of the TIPS quenching parameters.

Enhanced Thermally Conductive and Microwave Absorbing Properties of Polymethyl Methacrylate/Ni@GNP Nanocomposites

“…In Figure , the three-dimensional temperature fields of the composites with varied filler contents as functions of the position and heating time were quantitatively acquired via an enthalpy transformation method (ETM), in which enthalpy ( H ) is treated as a dependent variable in addition to temperature ( T ) with the energy equations discretized into a set of equations containing both H and T , and ETM has been proven to be fairly suitable for the generalized multi-dimensional phase-change issues. − …”

“…The parameter D was a characteristic parameter reflecting the internal structure of composites, which was generally related to the type, content, and dispersion state of fillers, as well as whether a filler network structure was constructed. The FPM equation has been proven to be useful for studying the heating/cooling process of polymers and their composites. − …”

Selective Distribution of Filler in PMMA/PLA/BN Thermally Conductive Composites: Theoretical Prediction and Experimental Investigation

“…Figure displays the three-dimensional temperature field of the composites with various BN contents (quantitatively obtained using an enthalpy transformation method, − ETM) as a function of position and heating time. In ETM treatment, the enthalpy ( H ) should be regarded as a dependent variable other than temperature ( T ), with the energy equation discretized into a set of equations solely containing H and T .…”

Hierarchical structure and properties of high‐density polyethylene (HDPE) microporous films fabricated via thermally‐induced phase separation (TIPS): Effect of presence of ultra‐high molecular weight polyethylene (UHMWPE)

“…The latent heat released during polymer crystallization also reduced the cooling rate greatly. As a result, the temperature for positions close to the glass plate nearly remained stable at the polymer crystallization temperature because of the latent heat released from crystallization being equal to the heat transmitted outwardly via heat conduction 31–34 . As far as the isothermal platform was concerned, the closer to the glass plate, the more obvious isothermal platform, since the closer to the glass plate, the less easily the latent heat transferred away.…”

“…wardly via heat conduction. [31][32][33][34] As far as the isothermal platform was concerned, the closer to the glass plate, the more obvious isothermal platform, since the closer to the glass plate, the less easily the latent heat transferred away. On the side of the films close to the cooling medium (X = 0), isothermal platforms were invisible, because of the latent heat released from crystallization process quickly transferred away without any accumulation of excessive heat.…”