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

In this work, ammonium polyacrylate (NH 4 PAA) 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-NaHSO 3 ) and N, N’-methylene-bis-acrylamide (MBA) crosslinking. Gel permeation chromatography and Fourier transform infrared spectroscopy provided evidence for the synthesis of NH 4 PAA, with a molecular weight of 232,000. The carboxylic content and nitrogen content of the NH 4 PAA thickener are 23.5% and 3.37%, respectively. A response surface analysis and single factor experiment showed that the optimum synthesis conditions of the NH 4 PAA thickener were pH 6.5, monomer dosage 38.49 wt%, reaction temperature 45.5°C, initiation system APS and NaHSO 3 (weight ratio 1:2) 0.34 wt%, MBA dosage 0.15%, and reaction time 3.2 h. The viscosity of the NH 4 PAA 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 NH 4 PAA thickener presented spherical morphology. Dynamic light scattering showed that the particle size was concentrated at 78.8 nm. A rheological test showed that the NH 4 PAA thickener was a pseudoplastic fluid with good thixotropy. The NH 4 PAA 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.