Thermally expandable microspheres of poly (acrylonitrile/ethyl methacrylate/methacrylic acid) with fast thermal response property

Purpose The purpose of this paper was to synthesise a thermally expandable microsphere (TEMS) with fast thermal response property and small expansion temperature range, and investigate the factors affecting the expansion properties of the microspheres. Design/methodology/approach A new kind of TEMS with fast thermal response property was synthesised by suspension polymerisation method, using acrylonitrile, ethyl methacrylate and methacrylic acid as the main monomers; Mg(OH) 2 as the main dispersing agent; and isooctane or n -hexane or n -pentane as the blowing agent. Findings The TEMS possessed the best expansion capacity when encapsulated isooctane and n -hexane were about 18.5 Wt.%. The expansion process of the TEMS could be finished by raising the temperature to 18°C from the expansion onset, much less than the reported 30-50°C. The morphology of the TEMS turned from sphere to irregular concave shape following the content increase of the blowing agent. Originality/value A new kind of TEMS composed of acrylonitrile/ethyl methacrylate/methacrylic acid as the polymer shell was synthesised. These TEMS showed the fastest thermal response speed reported.