Effects of microgel content and n‐methylolacrylamide on the properties of microgel composite hydrogels prepared by postcrosslinking method

Abstract Acrylamide co 2‐acrylamido‐2‐methylpropane sulfonic acid microgel composite (MC) hydrogels were prepared by heating MC polymer with 50% water content. Crosslinking reaction occurred in the heating process and reactive microgels with hydroxymethyl groups introduced by N‐methylolacrylamide (NMA) were used as postcrosslinkers. Microgel swollen size is influenced by NMA content. Both microgel and its NMA content affect MC hydrogel properties, which relates to the crosslinking chain length and the crosslinking density. The tensile strength of MC hydrogels increases and their elongation decreases as the microgel content increases from 0.1 to 0.5 g. Both the tensile strength and the elongation decrease as the microgel content further increases from 0.5 to 1.1 g. The MC hydrogel tensile strength increases and the elongation decreases as the NMA content of microgels increases from 5.0 to 14.8%. However, they both decrease when the NMA content of microgels exceeds 14.8%. Although the crosslinking chains υ calculated from tensile stress–strain curves were very high, MC hydrogels were elastic and had the highest tensile strength of 127 kPa and considerably moderate elongation of 427%. Their excellent mechanical properties attributed to their unique structure crosslinked by microgel particles. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers