Preparation of small particle diameter thermally expandable microspheres under atmospheric pressure for potential utilization in wood

Abstract Small particle diameter thermally expandable microspheres (TEMs) were obtained for potential utilization in wood, with special attention on their particle diameters and expansion properties. The revolving speed of homogenization (RS) of 800 ~ 3000 r min −1 was applied in suspension polymerization under atmospheric pressure to prepare TEMs, with n ‐hexane as core material and the copolymer of acrylonitrile, methyl acrylate, and vinyl acetate as shell. (a) The effect of the RS on the particle diameters of TEMs presented a negative correlation at low RS and remained stable at high RS, (b) When the RS was 1900 ~ 2100 r min −1 , the optimized TEMs with average particle diameters of 3.82 ~ 4.06 μm were prepared, possessing expansion ratios of 3.4 ~ 4.3 and an expansion temperature of 112°C, (c)The optimized TEMs had core‐shell structure and high encapsulated content of alkane, and (d) The TEMs with small particle diameters could be impregnated into wood and expand successfully in wood cell lumens.