Study On Surface Modification And Mechanism Of Wollastonite Powder

Wollastonite,due to its special fibrous structure,has excellent characteristics such as high resistance,low dielectric constant and low oil absorption.Compared with other non-metallic mineral materials,Wollastonite has a wide application value in the fields of ceramics,plastics,rubber,paper making,coatings and so on.It is a kind of new industrial raw material that attracts much attention.Wollastonite is an inorganic filler,if it is directly filled in the polymer,due to the difference of interface properties,the compatibility between the two is poor,the dispersion is not uniform,but leads to the decline of the matrix material properties.Therefore,wollastonite was selected as the main research object in this paper.The optimal surface modification conditions of wollastonite were explored through single factor influence experiment and orthogonal experiment.The wollastonite before and after modification was characterized by XRD,FT-IR,TG-DSC and SEM,and the modification mechanism of different modifiers was analyzed.The modified wollastonite was filled with polypropylene to prepare the composite material.The results of single factor experiment showed that the optimal modification conditions of the four modifiers were obtained.The optimal modification conditions of stearate were zinc stearate,and the optimal modification conditions of silane coupling agent were KH-570.The characterization results show that the modification mechanism of the two modifiers is as follows:COOH in stearate forms coordination bond with the surface Ca of wollastonite;The oligosiloxane obtained by hydrolysis and condensation of silane coupling agent is bonded with OH~-on the surface of wollastonite in the form of chemical bond.The orthogonal experiment results showed that the optimal modification conditions of wollastonite were as follows:zinc stearate was selected as modifier,modification time was30min,modifier dosage was 4%,slurry concentration was 10%,and modification temperature was 60℃.It has been proved that the contact Angle and activation index are the optimal values under this condition.The results of particle size measurement and fractal dimension calculation show that the smaller the fractal dimension of wollastonite,the finer the particle size is,the better the modification effect is.Under this condition,the contact angle is 117.250°,and the activation index is 98.9%.Compared with pure polypropylene(PP),the tensile strength of the modified wollastonite/PP composites is reduced by 13%,the elastic modulus,elongation and impact strength are increased by 53%,56%and 39%,respectively,and the bending strength is increased by 3%.