No abstract

Thermally expandable microspheres (TEMs) employing poly(methyl methacrylate) (PMMA) as shell and sodium bicarbonate (NaHCO 3 ) as core were prepared by a simple method of thermally induced phase separation (TIPS). The addition of NaHCO 3 improved the foaming properties of TEMs. The effects of preparation parameters on the morphology, amount of encapsulated NaHCO 3 , and foaming properties of TEMs were studied; the parameters investigated included the quench rate, the molecular weight (M w ) and amount of PMMA, and the amount of NaHCO 3 . The results show that when 0.5 g of PMMA 50k, 3 g of NaHCO 3 , and 50 g of ethanol were used, with quenching temperature at 0 8C, the TEMs were fully spherical and the maximum expansion volume of TEMs was about 3.8 times the original volume. The expansion volume of TEMs increased with increasing amount of encapsulated NaHCO 3 , and the foaming onset temperature and temperature of complete bursting of TEMs were related to the M w of PMMA.

No abstract

The formation mechanism of TEMs via TIPS was investigated. It was supported by calculation, the effect of quench rate and stirring speed.