Effect of inorganic salt additives on the viscosity of cellulose acetate solutions

Poly(p-phenylene terephtalamide) (PPTA), a high-performance polymer with high modulus and good hydrophilicity, is often used as a reinforced material. However, due to its high crystallity, micro-phase separation often occurs in the blends. In this paper, PPTA/poly(vinylidene fluoride) (PVDF) compatible blend solution was synthesized by in situ polycondensation. Blend ultra-filtration membrane was prepared through the immersion phase inversion process. In order to obtain desired pore structure, the effects of different additives including hydrophilic polymer (polyethylene glycol (PEG)), inorganic salt (lithium chloride (LiCl)) and the surfactant (Tween-80) on the morphology and performance of PPTA/PVDF blend membranes were studied. The membrane formation process was investigated through ternary phase diagram (thermodynamics) and viscosities (kinetics) analysis. It was found that, with the increasing of LiCl content, a porous membrane structure with long finger-like pores was formed due to the accelerated demixing process which resulted in the increase of porosity and pore diameter as well as the enhancement of water flux and the decline of PEG rejection. When Tween content increased to over 3 wt%, dynamic viscosity became the main factor resulting in a decreased phase separation rate. The transfer of PEG and LiCl molecules onto membrane surface increased the surface hydrophilicity. The effect of Tween content on membrane hydrophilicity was also correlated with the compatibility of blend components.

show abstract

“…This network structure gradually developed with the increasing of LiCl content. Consequently, the viscosity significantly increased [25].…”

Section: Kinetics Of Membrane Formationmentioning

confidence: 99%

Effects of Additives on the Morphology and Performance of PPTA/PVDF in Situ Blend UF Membrane

Shi

Zhang

et al. 2014

Polymers

View full text Add to dashboard Cite

show abstract

“…This can be attributed to the slow solvent transfer rate in the sublayer caused by the high viscosity of the casting solution. The electrostatic attraction between cationic TpEB and negatively charged PAN chains results in the formation of the PAN matrix consisting of PAN chains with cationic TpEB as “pendant” groups, which significantly increases the viscosity of the casting solution. , After the rapid penetration of water molecules through the membrane surface into the sublayer, the movement is hindered by the high viscosity of the bulk of the casting solution. Thus, the exchange rate of the solvent and nonsolvent decreases and the PAN precipitates more slowly in the sublayer.…”

Section: Resultsmentioning

confidence: 99%

In Situ Growth of Cationic Covalent Organic Frameworks (COFs) for Mixed Matrix Membranes with Enhanced Performances

2020

View full text Add to dashboard Cite

Covalent organic frameworks (COFs) are increasingly utilized as doping agents for the design of advanced ultrafiltration mixed matrix membranes, thanks to their prominent nanoporosity and excellent polymer compatibility. However, current strategies are largely limited in the complicated postaddition of neutral COF particulates. Herein, cationic COFs, namely, TpEB, with sizes down to ∼39 nm are in situ synthesized in polyacrylonitrile (PAN) solution as crystalline fillers for the production of highly permeable TpEB−PAN ultrafiltration membranes. After the condensation of monomer pairs, the growth of cationic TpEB crystallites is restrained due to the electrostatic interaction with negatively charged PAN chains, leading to the formation of a homogeneous TpEB-incorporated casting solution. During the subsequent nonsolvent-induced phase separation process, TpEB crystallites facilitate exchange between the solvent and the nonsolvent because of their hydrophilic and nanoporous nature, accelerating the rate of phase inversion to form a highly porous membrane surface. Thus-prepared TpEB−PAN membranes deliver a tight rejection of BSA with water permeance of up to 380 L m −2 h −1 bar −1 , which is 35.6% higher than that of the original PAN membranes prepared without TpEB. The TpEB−PAN membranes also exhibit enhanced operation stabilities and fouling resistances. This in situ growth strategy suggests a new avenue for the preparation of advanced mixed matrix membranes.

show abstract

“…The results of rheological measurements reflect structural features of the polymer [1,4,5]. It is known that the polymolecularity of CNs is caused both by the polymolecularity of the initial cellulose and by the heterogeneity of esterification [6][7][8][9][10]. The chemical structure of CNs is formed at the stage of esterification of cellulose by "structural synthesis", the nature of which makes it possible to judge the chemical homogeneity and inhomogeneity of the CNs [11].…”

Section: Introductionmentioning

confidence: 99%

Features of the Structure and Rheology of Nitrocellulose Solutions

Kostochko

Валишина

Шипина

2013

International Polymer Science and Technology

View full text Add to dashboard Cite

show abstract

Effect of inorganic salt additives on the viscosity of cellulose acetate solutions

Cited by 6 publications

References 6 publications

Effects of Additives on the Morphology and Performance of PPTA/PVDF in Situ Blend UF Membrane

Effects of Additives on the Morphology and Performance of PPTA/PVDF in Situ Blend UF Membrane

In Situ Growth of Cationic Covalent Organic Frameworks (COFs) for Mixed Matrix Membranes with Enhanced Performances

Features of the Structure and Rheology of Nitrocellulose Solutions

Contact Info

Product

Resources

About