Preparation of ammonium polyacrylate thickener via inverse emulsion polymerization: paste forming ability and rheological property

Abstract

In this work, ammonium polyacrylate (NH4PAA) thickener was synthesized by the inverse emulsion polymerization method with acrylic acid and ammonia water as the aqueous monomer, C16–C31 n-alkanes (5# white oil) as the continuous phase, Span 80/Tween 80 as composite emulsifiers, and Tween 80 as the phase inversion agent, under the action of ammonium persulfate-sodium bisulfite initiation (APS-NaHSO3) and N, N’-methylene-bis-acrylamide (MBA) crosslinking. Gel permeation chromatography and Fourier transform infrared spectroscopy provided evidence for the synthesis of NH4PAA, with a molecular weight of 232,000. The carboxylic content and nitrogen content of the NH4PAA thickener are 23.5% and 3.37%, respectively. A response surface analysis and single factor experiment showed that the optimum synthesis conditions of the NH4PAA thickener were pH 6.5, monomer dosage 38.49 wt%, reaction temperature 45.5°C, initiation system APS and NaHSO3 (weight ratio 1:2) 0.34 wt%, MBA dosage 0.15%, and reaction time 3.2 h. The viscosity of the NH4PAA thickener is 15.7 Pa·s (under the condition of using a rotary rheometer for testing, the mass fraction of the thickener is 3 wt%), which exceeded the corresponding viscosity of diPh-2-CUM-O, SAMXG8 reported in the literature and commercial thickeners. Transmission electron microscopy showed that the NH4PAA thickener presented spherical morphology. Dynamic light scattering showed that the particle size was concentrated at 78.8 nm. A rheological test showed that the NH4PAA thickener was a pseudoplastic fluid with good thixotropy. The NH4PAA thickener gave nylon carpet good printability after jet printing. This work provides a theoretical basis for the development of high-quality thickeners for carpets in jet printing.