Synthesis of a Novel Superplasticizer Prepared from Brown Coal

摘要

Poly condensates and polycarboxylates are known to be effective superplasticizers. Here, the synthesis of a novel, brown coal based superplasticizer by grafting acrylic acid (AA) and 2-acrylamido-2-tert. butyl sulfonic acid (ATBS) onto the alkali soluble components of brown coal (lignite) as backbone using free radical copolymerization technique is described. Furthermore, an ATBS-aciylic acid copolymer was synthesized to investigate the influence of the graft chains on the performance of the lignite copolymer. Successful grafting was confirmed by size exclusion chromatography (SEC) and comparison of the adsorbed layer thicknesses of the brown coal substrate and the grafted product. The dispersing performance of the graft copolymer was probed via mini slump tests and compared with that of BNS. Additionally, slump flow retention and sulfate tolerance were determined. It was found that the graft copolymer possesses higher dispersion effectiveness than BNS and exhibits high sulfate tolerance.