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

Poly(vinyl alcohol) (PVA) was modified using D-mannitol (DM) and 1-butyl-3-methylimidazole bromide (BMIMBr) as the complex plasticizer (DB), and PVA/DB composite was prepared. The plasticizing effect of DB on PVA was studied by Fourier transform infrared spectroscopy (FT-IR), differntial scanning calorimetry (DSC), thermos gravimetric analysis (TGA) and melt flow indexer (MI). FT-IR analysis indicated that Br- of BMIMBr and OH of DM could form H-bonds with OH of PVA. With the increase of DB, the melt temperature (Tm2) and crystallization temperature (Tc1) of PVA/DB composite decreased, the initial thermal decomposition temperatures (Td), thermal processing window (Delta T) and MI values increased respectively. Based on above studies, the influence of DB content on rheological properties of PVA/DB composite was investigated by the capillary rheometer. The result displayed that apparent viscosity of PVA/DB composite decreased with increasing DB content, shear rate and measured temperature. The non-Newtonian index (n) increased and structural viscosity index (Delta eta) decreased with the increase of measured temperature and DB. The viscous flow activation energy (E eta) decreased as the shear rate and DB content increased. When the measured temperature, DB content and shear rate were in the range of Tm2+30 -Tm2+35 degrees C, 40-50 wt% and 764.8-1504.9 s-1, respectively, the spinnability of PVA/DB composite was optimal, which will lay a theoretical foundation for the exploration of melt spinning process in the future. In our work, we describe the plasticization mechanism of the D-mannitol (DM) and 1-butyl-3-methylimidazolium bromide (BMIMBr) on poly(vinyl alcohol) (PVA). The both hydroxyl groups of DM and anions (Br-) of BMIMBr could form intermolecular hydrogen bonds with the hydroxyl groups of PVA, destroying the original intra-or intermolecular hydrogen bonds of PVA. This work will lay a theoretical foundation for the exploration of melt spinning process in the future. image