| As important inorganic materials with reinforcement and fire-retardant effects,basic magnesium sulfate and magnesium hydrate whiskers were widely applied in various fields such as plastics,chinaware,dope,metal,chemical,aviation spaceflight and so on.However,such products were still in the stage of research and development in China.Compared to the United States and Japanand other developed nations,our country had a large gap.In view of this situation,this paper researched the preparation,modification and application of both basic magnesium sulfate and magnesium hydrate whiskers on the base of previous studies.Took magnesite as row material and calcinated it for 3 hours at 700℃,basic magnesium sulfate whiskers were prepared by hydrothermal synthesis method with the activity magnesia for 4.0% of slurry,the reaction temperature of 200℃,the reaction time of 4 hours,and the stirring speed of 400r/min.Took sodium hydroxide and basic magnesium sulfate whiskers as raw materials,magnesium hydrate whiskers were prepared by hydrothermal synthesis method with the basic magnesium sulfate whiskers for the 4.0% of slurry,the reaction temperature of 180℃,the reaction time of 4 hours,the stirring speed of 100r/min,and equivalent weight ratio of sodium hydroxide to magnesium sulfate whiskers for 1.4:1.By means of single factor tests,basic magnesium sulfate and magnesium hydrate whiskers were modified by surface modification agents such as fatty acid,titanate,silane, aluminum esters and so on.The experimental results indicated that sodium stearate and zinc stearate were the most excellent modifiers for basic magnesium sulfate whiskers and magnesium hydrate whiskers individually.The contact angle,the activate index and the oil-adsorbed value of modified basic magnesium sulfate and magnesium hydrate whiskers were 111.85°,99.28%,186ml/100g and 126.38°,99.05%,354ml/100g respectively. The dispersion and fluidity of whiskers had evident improvement.Apart from the physical absorption,there were firmly chemical adsorption between the surface of whiskers and stestic acid salts.Added the modified basic magnesium sulfate and magnesium hydrate whiskers to polypropylene,the impact strength and the oxygen index increased and the tensile strength and the elongation at break decreased of both MOS/PP and MH/PP composite materials with addition of whiskers.The impact strength,the tensile strength, the elongation at break and the oxygen index of PP were 62J/m,25.8MPa,83.5% and 19.2%.When the increasing amount is 50%,these indicators of MOS/PP composite were 79.67J/m,20.6 MPa,9.7% and31.5%,and these indicators of MH/PP composite were 75J/m,21MPa,7.2% and 32.8%.Integration mechanics property and fire-retardant property of composite increased.In this paper,basic magnesium sulfate and magnesium hydrate whiskers toughness and flame retardant action mechanism for polypropylene were researched.The results indicated that the surface of whiskers and resin formed a new plastic interface layer after contacting and infiltrating,when the stress did its work,the plastic interface layer could deform to alleviate stress concentration and make composite system absorb more energy,so that the toughness of composite material can be enhanced.The final decomposition products of them were magnesia and water. The water could absorb a large amount of calories and dilute the concentration of oxygen.The magnesia was a nicer fireproof material which can cover the surface of polymer so as to prevent the entry of oxygen and heat,so it could serve the purpose of fire retardant.Achievements in this paper had a certain guiding significance for the large-scale production and application of basic magnesium sulfate and magnesium hydrate whiskers.
|
PDF Full Text Request