Preparation And Application Of Ultrafine Barium Sulfate In Microemulsion System

As a basic chemical raw material,barium sulfate（BaSO₄）is widely used in composite material synthesis and material function optimization due to its excellent characteristics.BaSO₄ has the advantages of high whiteness,hard texture,acid and alkali resistance,and stable chemical properties.It is used in coatings,inks,plastics,papermaking and other industries.Because it is non-toxic and barium element core can reduce the X-ray transmittance,so it plays an important role in medical imaging and radiation protection materials.However,it still has shortcomings such as large specific surface energy,easy agglomeration,poor compatibility with the matrix,and irregular morphology,which limit the application of BaSO₄.Therefore,the preparation of BaSO₄with hydrophobic surface,high dispersion,small and uniform particle size,and regular morphology is the key.In this paper,ultra-fine BaSO₄ particles were prepared by the microemulsion method.BaCl₂ and Na₂SO₄ were used as reaction materials,and oleic acid and glyceryl monostearate were selected to establish a microemulsion system（Surfactant-belong microemulsion-SBME）.Through the pseudo-ternary phase diagram method,the best stable state of the SBME system was determined:the mass ratio of compound oleic acid to glycerol monostearate 1:1,compound surfactant:co-surface active agent（n-butanol）:oil phase（cyclohexane）:water phase 7.59:12.34:25:25.The temperature of the system was 60℃,the pH value was 8.In the stable state of the system,ultrafine BaSO₄ particles are synthesized.The optimal reaction conditions are explored through experiments:the concentration of BaCl₂ and Na₂SO₄ 0.6 mol/L,reaction time 45 min,aging time 90 min,stirring speed 450 r/min.The ultrafine BaSO₄ with an average particle size of 90.42 nm,an activation degree of 82%,a sedimentation volume of 4.3 m L/g and good dispersibility was obtained on this condition.The use of surfactants increases production cost and causes certain pollution to the environment.A new type of Surfactant-free microemulsion-SFME system（Surfactant-free microemulsion-SFME）was established through the pseudo-ternary phase diagram method to determine the components and proportions of the SFME system,the mass ratio of amphiphilic solvent（isopropanol）:oil phase（Cyclohexane）:water phase 3.2:6.8:36,the concentration of reactant BaCl₂ 0.6 mol/L,and the concentration of Na₂SO₄ 0.5 mol/L.The temperature of the system was 60℃,and the pH was 5.In the stable state of the system,ultrafine BaSO₄ particles were synthesized.The optimal reaction conditions are explored through experiments,the reaction time 30 min,the aging time 60 min,the stirring speed 400 r/min.The ultrafine BaSO₄ with an average particle size of 160.27 nm,an activation degree of 75%,a sedimentation volume of 3.7 m L/g and good dispersibility was obtained on this condition.The two kinds of ultrafine BaSO₄ particles were characterized separately,and they were applied to water-based coatings as inorganic fillers,and the coatings were characterized and tested to obtain the optimal addition amount.When the addition amount of ultrafine BaSO₄ particles prepared by SBME system was 4%of the mass of the matrix,the hardness and adhesion of the coating were both 3H,the bending strength was 2 mm,and the rockfall impact test height was 95 cm.At this time,the performance of the coating reached optimal.