Isotactic polypropylene–1,2,4,5-tetrachlorobenzene: porous bodies via thermally induced phase separation
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Using recently constructed experimental phase diagram isotactic polypropylene–1,2,4,5-tetrachlorobenzene (TeCB), we formulate a physically consistent scenario of the mixture evolution under thermally induced phase separation and predict the morphology of capillary-porous bodies that are formed after cooling down the binary system and removal of the low molecular mass component. This approach allows us to interpret the experimental data obtained by optical microscopy, scanning electron microscopy, and differential scanning calorimetry on the system with two crystallizable components. At any composition, TeCB forms needle-like crystals of nearly square section. Increasing polymer content affects crystal growth by limiting their length and by generating another population of small TeCB crystals of irregular shape and close to log-normal size distribution, located in the amorphous polymer regions. Finite rate of cooling the system leads to a hysteresis, when the values of characteristic temperatures and compositions in the phase diagram appear to be considerably shifted to lower temperatures and higher polymer contents. Combination of structural and calorimetric data provides an opportunity to characterize polymer–solvent systems from both thermodynamic and technological standpoints.
KeywordsPhase diagram Crystallization DSC Optical microscopy Scanning electron microscopy
This work was carried out using the equipment of Shared Research Centers of TIPS RAS and FSRC “Crystallography and Photonics” RAS. It was supported by the Ministry of Science and Higher Education of Russia within the State Assignment of ISC RAS, TIPS RAS, and FSRC “Crystallography and Photonics” RAS.
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