In situ POM and FTIR investigation on quiescent phase transition of polybutene‐1 from form II to form I

Abstract

Despite extensive investigations in the past decade, the factors affecting the phase transition of polybutene‐1 (PB‐1) form tetragonal form II to hexagonal form I were not clarified completely. In this study, quiescent phase transitions of PB‐1 within different morphological of crystals at different temperatures were investigated employing polarized optical microscopy and Fourier transform infrared spectroscopy. Results indicate that the phase transition depends not only on intercrystalline links but also on the lamellar thickness. The phase transition always occurs spontaneously first in thick form II lamellae. The intercrystalline links have opposite effects in the early and later stages. In the early stage, it can promote form I nucleation in some form II clusters, where these clusters were subjected to inward tensions of intercrystalline links. While in the later stage, it retards form I growth since subjecting to outward tensions of intercrystalline links. This study helps to identify more effective method to accelerate forms II‐I phase transition.

Microstructural Change of Poly(1-butene) during Crystallization, Phase Transition, and Melting Revealed by Synchrotron Small-Angle X-ray Scattering

“…To accelerate phase transition, we employed two-step annealing method suggested by Men et al, i.e., lower-temperature annealing first for form I nucleation and then high-temperature annealing for form I growth. It was reported that employing such a method could reduce the phase transition time greatly. , According to the literature, , −10 and +40 °C were employed as nucleation temperature and growth temperature, respectively. Nucleation time and growth time were 120 and 230 min, respectively.…”

“…A plausible explanation is that the form II to form I phase transition occurs first in thick lamellar crystals. Poly­(1-butene) normally forms a broad thickness distribution of lamellar crystals . The thick form II lamellar crystal has a lower folded-surface free energy in an unit volume, which favors a form II to form I phase transition.…”

“…It was reported that employing such a method could reduce the phase transition time greatly. 49,50 According to the literature, 48,49 −10 and +40 °C were employed as nucleation temperature and growth temperature, respectively. Nucleation time and growth time were 120 and 230 min, respectively.…”

“…As mentioned above, employing the scattering before crystallization has another aim, that is, truncating Porod scattering with the scattering of crystal embryos. As form I is hard to form directly from crystallization, 49 we cannot assume that form I crystal embryos exist in the free melt. The above aim was not achieved.…”

“…Poly(1-butene) normally forms a broad thickness distribution of lamellar crystals. 49 The thick form II lamellar crystal has a lower foldedsurface free energy in an unit volume, which favors a form II to form I phase transition. Therefore, a form II to form I phase transition most likely initials from thick lamellar crystal and then occurs in thin lamellar crystals, as proposed by Zhang recently.…”