The Surface Modification Of Magnesium Hydroxide By Oleic Acid And Its Application In EVA

In this thesis, Magnesium hydroxide was modified by dry and wet processes respectively, using oleic acid(an-ionic surfactant) as modification. The optimal modification conditions of wet and dry processes were examined through in the single-factor experiments. After analyzing the activation index, adsorption rate and carbon content, the optimal conditions of wet process were found to be as follows: 35%magnesium hydroxide in slurry, 2.0% oleic acid used as modification agent, 2, 200rmp(stirring rate), 50℃(modification temperature), and 40min(modification time), while the optimal conditions of dry process were: 160℃(modification temperature), 2.5%oleic acid used for modification, 15 min(modification time) and 2, 500rpm(stirring rate). According of the results of contact angle measurement and settlement curve it was suggested that the surface of the modified magnesium hydroxide was “hydrophobic” on the surface. After comparing the modification results of dry and wet processes, it was found that the hydrophobic properties were better for magnesium hydroxide modified by wet process. Besides, the magnesium modified with oleic acid was characterized by SEM, XRD, FT-IR and TGA-DTG. The XRD and FT-IR showed that the oleic acid was esterified and chemisorbed on the(001) surface of magnesium hydroxide. After SEM analysis, it was discovered that modified magnesium hydroxide was more dispersible,and the TGA indicated that the heat resistance of magnesium hydroxide was somewhat improved after modification.The impacts of modification conditions upon rheological properties of processed MH/EVA blends were explored with a torque rheometer. The results suggested that the modification conditions were consistent with the characterization results of modification effects when the rheological properties were optimum for processing, and the magnesium hydroxide modified by oleic acid would be easier to process composites.Furthermore, a composite material of EVA and MH was prepared by the melt-bet blending process. After examining the composites, their mechanical properties were found to apparently improve and the flame retardancy was discovered to increase to certain extent. By comparing the modification effects of dry and wet processes, the wet process was more favorable for improving rheological properties of processed composites, increasing the elongation at break and strengthening the flame retardancy,while the dry process was more helpful for increasing the tensile strength of composites.