Physico-chemical analysis of flexible polyurethane foams containing commercial calcium carbonate

Abstract

Calcium carbonate (CaCO 3 ) is a filler often utilized by the Brazilian mattress factories in the production of polyurethane foams. The filler allows the substitution of part of the polymeric agents, conferring dimensional stability and hardness to the foams. However, in agreement with experimental data, it is observed that the excess of commercial CaCO 3 utilized in industry causes the increase of hysteresis, possibly causing permanent deformations and damaging the quality of the final product. In the present work, the physico-chemical analyses of the flexible polyurethane foams with different contents of CaCO 3 were performed. The foams are submitted to the morphological, mechanical and positron analyses to verify the alterations provoked by the progressive introduction of this filler.

Rice-like hollow nano-CaCO 3 synthesis

“…This process causes the recrystallization of the particles leading to close up the edges of the hollow CaCO 3 particles with an empty It is important to understand the chemistry behind formation and close-up of the hollow structures in nano-CaCO 3 synthesis. We have reported in our previous paper that the solubility values for Ca(OH) 2 and CaCO 3 are about 20 mM and 0.1 mM, respectively [29]. Therefore, the solution was initially undersaturated with respect to Ca(OH) 2 and supersaturated with respect to CaCO 3 .…”

“…We have reported in our previous paper that the solubility values for Ca(OH) 2 and CaCO 3 are about 20 mM and 0.1 mM, respectively [29]. Therefore, the solution was initially undersaturated with respect to Ca(OH) 2 and supersaturated with respect to CaCO 3 . However, the supersaturation conditions can change through the progress of the crystallization leading to the dissolution of the newly synthesized CaCO 3 particles and/or close-up of pores as a result of recrystallization.…”

“…The remaining undissolved CO 2 bubbles was allowed to be purged from the surface of the solution to the atmosphere. The newly formed CaCO 3 crystal particles around the CO 2 bubbles were removed as quickly as possible from the crystallization region into the Ca(OH) 2 solution by mechanical stirring. The CO 2 bubble-free region of the reactor is called the "stabilization region".…”

“…It could be possible to produce CaCO 3 from its natural mineral sources by crushing, grinding, and sieving processes. However, calcite produced from natural sources are in micron sizes and they have inhomogeneous size distribution [2]. Therefore, production of nano calcite can be achieved by recrystallization; such that the mineral CaCO 3 is converted to calcium oxide (CaO) by calcination, hydrated to calcium hydroxide (Ca(OH) 2 ) and recrystallize by carbon dioxide (CO 2 ) [3][4][5][6].…”

“…However, calcite produced from natural sources are in micron sizes and they have inhomogeneous size distribution [2]. Therefore, production of nano calcite can be achieved by recrystallization; such that the mineral CaCO 3 is converted to calcium oxide (CaO) by calcination, hydrated to calcium hydroxide (Ca(OH) 2 ) and recrystallize by carbon dioxide (CO 2 ) [3][4][5][6]. Obtaining CaCO 3 particles in nano sizes with homogeneous size distribution and different morphologies is difficult due to agglomeration of newly synthesized clusters [7][8][9][10], which is related to the surface potential of the colloidal CaCO 3 particles [11][12][13][14].…”