Study Of Preparation And Application Of Calcium Sulfate Whisker

As one of the high-tech industries in the21st century, new material industry is thebasis and foothold of the rapid development of modern industry. Whiskers which areused as fillers and reinforcing agents in the composite materials field have high strength,high hardness, high temperature resistance, corrosion resistance, light weight and goodperformance, however, because of the high price and the complexity of the preparationprocess, the whiskers including silicon carbide whisker, silicon nitride whisker,alumina whisker limit the expansion of its application. With the advantage of rich rawresources, the simple preparation process and inexpensive, calcium sulfate whisker asa cost-effective and green material has broad application prospects and practical valueand it often used as enhanced material, friction material, environmental filter materialand coating paper filling material.Hydrothermal synthesis of calcium sulfate whisker is one of the main methods ofresearch and production, gypsum as raw materials. This method is lower cost and theproduct has good dispersion. However hydrothermal method requires high temperatureand pressure, this leads to high energy consumption, high equipment requirements. Itis difficult for this method to be used in industry because of the low length-diameterratio, low dispersion of whiskers obtained.To solve the above technical problems, a new preparation of calcium sulfatewhisker of acidification has been proposed as under the conditions of lowertemperature and normal pressure. The building gypsum has chosen as the raw materialand sulfuric acid as the main accelerator the purity of calcium sulfate hemihydratewhiskers is higher than96%, the diameter is0.5-2μm,the length is70-100μm, theaspect ratio is50-70. the material could be directly applied in the reinforcement ofpolymer composites below200℃. The main contents and conclusions of this study are as follows.The main accelerator is sulfuric acid, the reaction temperature reduce from140℃to70℃in the traditional preparation process, meanwhile, the product iscalcium sulfate hemihydrate whisker, without hydrothermal reaction condition, themethod of lower temperature water bath overcome the shortcomings of thehydrothermal equipment requirements and improve the safety of performance.The building gypsum is the raw material, the sulfuric acid and alum as theaccelerant; it greatly improved the whisker morphology uniformity and aspect ratio,which is in line with the industrial application requirement.The optimum condition of calcium sulfate hemihydrate whisker is follows：Themass proportion of gypsum and water is1:20, the mass proportion of gypsum andsulfuric acid is1:6. The alum is9%, the dosage dropping is2mL·min-1, the water bathtemperature is70℃,the aging time is1h,The purity of calcium sulfate hemihydrate whisker is higher than97.6%, theaspect ratio is50-70. The purity of anhydrous calcium sulfate whisker, which has beencalcined in250-300℃, is higher than96.3%, the aspect ratio is30-50.In addition, the explorative experiment on calcium sulfate whisker reinforcedcomposites is launched, the results showed the anhydrous and calcium sulfatehemihydrate whisker modified enhance the group fill the PE resins, the PE/CSWcomposite material mechanical properties improved effectively such as notched impactstrength and elastic modulus.