Introducing water-redispersible powderable acrylic adhesives using Persian gum

Abstract

Persian gum (PG), as a recently-highlighted carbohydrate natural polymer, was introduced both as a powder adhesive in its pristine form, and as a water-redispersing agent for water-incompatible acrylic adhesives. Blends of PG and poly(methyl methacrylate-co-butyl acrylate) containing 30 wt. % methyl methacrylate (MBC) were molecularly incompatible at PG contents below 50 wt. % due to the large difference in their Hildebrand solubility parameters (calculated to be 37.49 and 19.71 J1/2/cm3/2 for PG and MBC, respectively). However, further increase in the PG content evolved the system toward miscibility through intensified intermolecular hydrogen bonds. Addition of PG to MBC at compositions of more than 50 wt. % PG also provided it with powderability. Swelling of slabs of the blends in water followed a pseudo-Fickian mechanism and the equilibrium swelling ratio of the blends was a reciprocal power function of ternary interaction parameter (χ1(23)). Furthermore, increase in the PG content from 0 to 90 wt. % improved the adhesion strength of the blend adhesives. Ultimately, the blend containing 90 wt. % PG presented 52 times and 34 times enhancement in the adhesion strength to fabric and wood substrates compared to the pristine acrylic adhesive, respectively.