Plasticizing effect of 1‐butyl‐3‐methylimidazolium bromide content on poly(vinyl alcohol)

Abstract

PVA/IL composites were successfully prepared with an ionic liquid (IL), 1‐butyl‐3‐methylimidazolium bromide and poly(vinyl alcohol) (PVA). The plasticizing effect of IL on PVA was investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and melt flow index (MI) measurements. FTIR analysis indicated that the anion (Br−) of IL could form hydrogen bonds with the hydroxyl groups of PVA. With an increase of IL, –OH absorption peaks of PVA/IL composites shifted to higher wavenumbers. DSC analysis showed that both melt and crystallization temperatures of the PVA/IL composites decreased as IL content increased. XRD analysis showed that the degree of crystallinity of the PVA/IL composites had a decreasing trend with an increase of IL. TGA showed that IL could effectively improve the thermal stability of PVA. The thermal stability of the PVA/IL composites decreased gradually with increasing IL content, but was higher than that of PVA. Thermal processing window (ΔT) analysis indicated that the addition of IL could significantly broaden ΔT of the PVA/IL composites, and their ΔT values first remained basically unchanged and then increased slightly with an increase of IL. In addition, MI analysis presented that the melt processability of the PVA/IL composites was not improved with the addition of IL and it was gradually improved with increasing IL content. In this work, PVA/IL composites with wide ΔT and high melt flow properties were prepared, which will lay a solid foundation for the preparation of high‐performance PVA fibers by melt spinning. © 2022 Society of Industrial Chemistry.

Influence of Complex Plasticizer on Plasticizing Effects and Rheological Properties of Plasticized Poly(Vinyl Alcohol)

“…In addition, the broad peak of OH in DB shifted to higher wavenumbers, which indicated that hydroxyl groups of DM could form intermolecular H-bonds with anions (Br À ) of BMIMBr. [20] In Figure 1b, the characteristic absorption peak for PVA at the wave number of 3269 cm À 1 was ascribed to the stretching vibration of OH. The peaks at 2938 cm À 1 and 2906 cm À 1 were attributed to CH 2 asymmetric and symmetric stretching vibration.…”

“…This was because the reason was same as the T m2 , which destroyed original hydrogen bond interactions of PVA and retarded the crystallization process of PVA. [20] With the increase of DB, the above destructive effect become more and more obvious, which resulted in a decrease in T c1 value. With the further increase of DB (� 30 wt%), there were two crystallization peaks in PVA/DB composites.…”

“…With addition of DB, the T d value of PVA/DB composite was higher than that of PVA, increasing from 241.9 � 1.60 °C to 245.0 � 0.70 °C.This was interpreted in that intermolecular hydrogen bonds were formed among the both hydroxyl groups of DM, anions (Br À ) of BMIMBr and hydroxyl groups of PVA, which retarded the elimination of hydroxyl groups of PVA to a certain extent. [18,20] The T d value of PVA/DB composites increased from 245.0 � 0.70 °C to 277.7 � 1.77 °C with the increase of DB. This was because more newlyformed hydrogen bonds between hydroxyl groups of DM and anions (Br À ) of BMIMBr and hydroxyl groups of PVA further retarded the elimination of hydroxyl groups of PVA.…”

“…Broadening the thermal processing window (ΔT) is the key to realize the thermal processing of PVA. [20,32] The ΔT value of PVA/ DB composites is calculated by the T m2 and T d values and corresponding data are shown in Table…”

“…It was found that with the increase of BMIMBr, the plasticizing effect of BMIMBr on PVA became more significant. [20] Although the thermal processing window of PVA was significantly broadened after the plasticizing modification, the MI value of PVA melt was very small and its melt flow property was very poor, the melt spinning of PVA cannot be realized. The use of compound plasticizer to plasticize PVA could not only obtain good plasticizing effect, but also realize the thermal processing of PVA.…”