Study Of Acicular Powder Preparation And Mechano-chemical Modification Of Wollastonite

Wollastonite is a material of a new industrial mineral, and is widely applied in rubber, plastics and papermaking as filler, besides traditionally applied in porcelain and ceramics, building materials, metallurgy etc. Because of poor miscibility between abio-filler and high polymers, abio-filler is hardly dispersed in polymer. For this reason, wollastonite is required for surface modification to become organic, and increase miscibility and dispersion in polymer.In this paper, fine grinding of wollastonite from Jangxi and Qinghai is connected with surface modification organically. Processing conditions of preparing acicular powder of wollastonite are confirmed about stirred ball mill and vibrational mill. By means of orthogonal tests, main factors affecting ratio of length to diameter of wollastonite are studied. The effect of rotating speed and feed speed of impacting disintegrator on the ratio of length to diameter of product is studied. By modifying surface of acicular powder of wollastonite with stearic acid and cilane in wet and dry, using activation index, diapersion in organic impregnant, surface contact angle, oil adsorption and penetration time to evaluate effect of modification in advance, the effect of dosage of modification medicament, modification time and type of medicament on the modification effect of wollastonite, and ensure processing conditions are determined.The results of research show that ratio of length to diameter L/D of acicular powder prepared by stirred ball mill, vibrational mill and impacting disintegrator is 9~11. It is more advantage that impacting disintegrator ensures shaped character of crystal than other two. After modification of wollastonite, ratio of length to diameter: L/D=5.1~6.3, oil adsorption: wet 44.6~52.4%, dry 34.7 ~ 41.7%, d50 : wet 9.31 ~9.56 urn, dry2.78~3.01 u m, activation index: wet 0.52~0.54, dry 0.69-0.88, penetration time: Wet > 390s, dry > 610s. Dry modification effect is better than wet effect.X-ray diffraction analysis shows that polymorphic transformation of wollastonite occurs because of the mechano-chemical effect in the process of dry and wet fine-grinding. Some defect and diatortion of wollastonite crystal are presented on the surface of powder. Crystal type turns from triclinic Tc intomonoclinic 2M.There are high activation points on the surface of powder and frash surface of powder, and active surface of wollastonite promoting medicament adsorbing, mantletling and chemical bonding on surface.Through research of principle on surface modification of wollastonite by the IR and the SEM, the results are shown that there are hydrocarbons of stearic acid on surface of wollastonite, and other groups, for example, -COO-, -Si-O-, adsorbing or packing on mineral surface. Because of hydrocarbons, wollastonite surface turns into hydrophobic. This results in better miscibility and dispersion in system of wollastonite and polymer.