Preparation of cationic poly(acrylamide)/bentonite nanocomposites from in situ inverse emulsion copolymerization and their performance in papermaking

This study examined the effects of acryl-grafted bentonite (AGB) in cationic poly(acrylamide) (CPAAm)/AGB nanocomposites on the flocculation and retention of micrometer-sized talc and ground calcium carbonate (GCC) suspensions used for papermaking. The AGB was synthesized by reacting Na ⁺-bentonite with (3-acryloxypropyl)trimethoxysilane. The graft yield measured by thermogravimetric analysis was ca. 24%. Different concentrations (0, 1.0, 2.9, and 4.9 wt%, designated as CPAAm/AGB-0, -1, -3, and -5, respectively) of AGB were then added to the in situ inverse emulsion copolymerization of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride to produce the CPAAm/AGB nanocomposites. The nanocomposites improved the flocculation of the GCC suspension model significantly in an AGB concentration-dependent manner. Dynamic drainage analysis revealed a decrease in dewatering time and turbidity from 11.2 s (pure CPAAm) to 8.7 s and from 349 to 33 NTU, respectively, at the same concentration (0.3 wt%) of nanocomposite. The results of the fabrication of handsheets revealed significant improvement (up to 2-8%) in the total retention yield and ash retention yield with increasing AGB concentration at the same GCC content.