Simple method for preparation of thermally expandable microspheres of PMMA encapsulating NaHCO₃via thermally induced phase separation

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.

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

“…Except for the Group 2, and Group 12 ~ 14, which had an expansion ratio of 3.4 ~ 4.3, the volumes of the rest groups expanded merely 1.4 ~ 2.6 times as compared with the unheated TEMs. Although the favorable expansion ratios of 3.4 ~ 4.3 were lower than the TEMs prepared under high pressure, 22,24 the values in the present study were still close to the result from Zhou et al 16 who used atmospheric pressure technology. The specific expansion temperature could be measured only for Group 1 ~ 2 and Group 12 ~ 14.…”

“…The preparation of TEMs was carried out by suspension polymerizations with six steps. Part of this preparation was conducted according to previous literature, 19,29,33 with considerable conditions being optimized in this study. The main processes of the experiments are stated below and partly illustrated in Figure 1.…”

“…To obtain the TEMs for wood modification with high efficiency, more investigations on the preparation of TEMs become crucial. A few innovative approaches of TEMs preparation have been put forward nowadays, especially the way of thermal-induced phase separation, 15,16 however, suspension polymerization is still a relatively mature method concerning TEMs preparation. In most of the investigations, the particle diameters of TEMs were generally 20~50 μm, [17][18][19] while the smallest particle diameter of TEMs was around 10 μm 20 , yet still not small enough to be impregnated into wood effectively.…”

Synthesis and characterization of high temperature resistant thermal expansion microsopheres with P(acrylonitrile/methacrylic acid/N,N-dimethylacrylamide/n-butylacrylate) shell

“…TEMs are generally prepared by Pickering suspension polymerization to disperse the oil phase in the water phase containing a nano inorganic dispersant [6]. According to the maximum expansion temperature, TEMs can be divided into three categories: low temperature (< 120 °C), medium temperature (between 120 and 180 °C) and high temperature (higher than 180 °C) TEM S [7][8][9]. At present, there are few reports on the preparation of high temperature resistant TEMs.…”

Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology

“…The investigation shows that the crystallization of PLA was impeded at high quenching temperatures due to the nucleation and growth process, resulting in the absence of foam formation. The effects of quenching temperature on foam morphology have been discussed by Akbarzadeh et al, Zhuo et al, and Nam et al [49][50][51] .…”