THE PROCESS OF THE EMULSIFIER-FREE POLYMERIZATION IN THE PRESENCE OF BARIUM SULFATE POWDER

The process of emulsifier-free copolymerization of the Styrene-Butyl Acrylate-K_sS_sO_s-water in the presence of Barium Sulfate(BS)powder was investigated under varied conditions within the range of BS powder quantity,initiator concentration and reaction temperature.Experimental results showed that the rate of polymerization is proportional to 0.3-power of the BS quantity and 1.3-power of the initiator concentration.There is a linear relationship of 2/3-power for the conversion and time.A process for the polymerization is propose to explain the experimental results.

SOAPLESS EMULSION COPOLYMERIZATION IN THE PRESENCE OF BARIUM SULFATE POWDER

To investigate soapless emulsion copolymerization in the presence of a solid phase, copolymerization experiments were carried out for the styrene-butyl acrylate-K_2S_2O_8-water system by using barium sulfate powder,which is assumed to be chemically inert.Reaction conditions were varied with respect to barium sulfate powder quantity,initiator concen- tration and temperature.These factors were investigated with respect to the effect on reaction rate and conversion,polymer particle number and diameter,and latex stability.

EDTA-type Polymer Based on Diazacrown Ether as the Solubilizer of Barium Sulfate to Water

The EDTA dianhydride reacted with diazacrown ethers to obtain the water-soluble EDTA-diazacrown ether polymers 1~3. The effects of crown ether ring in the polymer chains including its cavity size on the solubilization of barium sulfate to water were investigated by comparison with the crown ring-free analogue 4. The result shows that the polymer 2 is the efficient solubilizer of BaSO4 and the highest solubilization efficiency of the BaSO4to water is up to 72.5%.

Surface Modification of Barium Sulfate Particles

In this study, surface modification of barium sulfate was investigated using several model molecules for chemical treatment: ethanesulfonic acid, butyric acid, trimethoxy(propyl) silane and phosphoric acid 2-hydroxyethyl methacrylate. Samples were characterized by FT-IR and TGA to check the capability of these model molecules to interact with BaSO4 surface. The results pointed out the presence of an organic layer around the surface after the chemical treatment even after several washings to remove all species in excess. Model molecules were grafted onto BaSO4 surface and grafted density was determined. It reveals that phosphoric acid and carboxylic acid are the best candidates for the modification of BaSO4 surface. Both can be used as anchoring groups to modify the hydrophilic balance of barium sulfate surface in order to avoid the formation of aggregates and to improve the compatibility of this filler within hydrophobic polymer matrix.

Fabrication of submicron barium sulfate aggregates in the presence of ethylenediaminetetraacetic acid anions

Barium sulfate aggregates with an average size of 0.5μm were synthesized at pH 7, directed by ethylenediaminetetraacetic acid （EDTA） anions. The particle morphology, chemical composition, and size distribution of the BaSO4 aggregates were characterized. The as-synthesized BaSO4 particles were spherical and comprised many interconnected nanoballs, of which the surface properties were affected by the EDTA anions. The adsorption of EDTA anions reversed the charge and weakened the surface polarity of BaSO4, instigating the formation of aggregates by a self-assembly and transformation process. The resulting BaSO4 particles at pH 9-10 were ellipsoidal and featured smooth surfaces. Based on the zeta potential of BaSO4, variations in the morphology induced by changes in pH were closely related to the adsorption of mono- and multi-valent anions onto the electrical double layer of BaSO4.

Effect of barium sulfate modification on the SO2 tolerance of V2O5/TiO2 catalyst for NH3-SCR reaction

Sulfur poisoning of V_2O_5/BaSO_4–TiO_2（VBT）,V_2O_5/WO_3–TiO_2（VWT） and V_2O_5/BaSO_4–WO_3–TiO_2（VBWT） catalysts was performed in wet air at 350℃ for 3 hr,and activities for the selective catalytic reduction of NO_x with NH_3 were evaluated for 200–500℃.The VBT catalyst showed higher NO_x conversions after sulfur poisoning than the other two catalysts.The introduction of barium sulfate contributed to strong acid sites for the as-received catalyst,and eliminated the redox cycle of active vanadium oxide to some extent,which resulted in a certain loss of activity.Readily decomposable sulfate species formed on VBT-S instead of inactive sulfates on VWT-S.These decomposable sulfates increased the number of strong acid sites significantly.Some sulfate species escaped during catalyst preparation and barium sulfate was reproduced during sulfur poisoning,which protects vanadia from sulfur oxide attachment to a great extent.Consequently,the VBT catalyst exhibited the best resistance to sulfur poisoning.

Effect of BaSO_(4) on phase composition and sintering process of iron ore fines

Iron ore containing BaSO_(4) may have a series of effects on the quality of the sinter and performance of the blast furnace.Thus,the effect mechanism of BaSO_(4)(0-6.0 mass%)on the compressive strength,mineral composition,and microstructure of the sinter was investigated.The experimental results show that the compressive strength of the sintered samples initially increases and then decreases when the BaSO_(4) content increases from 0 to 6.0 mass%,reaching a peak value of 12.78 kN with a BaSO_(4) content of 1.0 mass%.Thermal analysis indicates that BaSO_(4) initially decomposes to produce BaO at 1468 K in the presence of iron ore.BaO combines with Fe_(2)O_(3) forming barium ferrite(Ba_(2)Fe_(6)O_(11)),which exists in the sintered sample with a granular form.BaO also dissolves in calcium ferrite and slag to promote the formation of calcium ferrite and barium glass,respectively.The content of needle-like calcium ferrite gradually increases and then decreases with the increase in BaSO_(4) content.Hematite exists in a plate-like form.The generation of dicalcium ferrite is promoted by increasing the BaSO_(4) addition from 2.0 to 6.0 mass%.