Preparation And Properties Of Polypropylene/ Wollastonite Composite

Polypropylene(PP) is a kind of thermoplastic synthetic resin with high performance, which has a wide range of applications in the automotive industry, household electrical appliances, electronic, agriculture, building packaging, and building materials furniture. Not only can the wollastonite filler enhance the mechanical properties of polypropylene, but it can reduce production cost, so the researches on it has a great significance. In this paper, Stearic acid, Isopropyl trioleyl titanate(NDZ-105), polymethylmethacrylate(PMMA) coating were used to modify wollastonite respectively, polypropylene/wollastonite composite with excellent mechanical performance was successfully achieved when the modified wollastonite was used as a filler. The main research work is as follows:First, reaction conditions of the stearic acid modified wollastonite were studied. The results showed that when the dosage of stearic acid was 2%, the reaction time to 20 min, the reaction temperature was 90 ℃, the stirring speed of 800 r/min, the modification effects of wollastonite was best, the activation index was 89.93%, water contact angle of 143.2°, FTIR and TG analysis showed that the wollastonite was successfully modified by stearic acid, modification mechanism was that stearic acid hydrolyzed firstly, then reacted with calcium on the surface of the wollastonite. Stearic acid was coated on the surface of wollastonite by chemically bonded moiety.Secondly, reaction conditions of(NDZ-105) modified wollastonite were studied. The results showed that the best modification effect was acheived when the dosage of titanate coupling agent was 4%, the reaction time for 40 min, the reaction temperature was 80 ℃, stirring speed of 800 r/min. the activation index could be 61.31%, the water contact Angle reached 125.2 °.Compared with stearic acid modified wollastonite, although the activation index and water contact angle was reduced, the goal to modification was achieved.Thirdly, PMMA/wollastonite composite particles were prepared by soap-free emulsion polymerization, the influence of reaction conditions on the the modification effects of wollastonite were investigated.then the composite particles were characterized by using FTIR, SEM, TG-GTA and so on.Results showed that the maximum clad ratio of 31.57%, and water contact angle of 130.1 °was reached when the mass ratio of PMMA/wollastonite is 8:10, initiator dosage is 0.4%, and reacted at 70 ℃ for 2 h. The lipophilicity of modified wollastonite surface increased significantly, FTIR, SEM and TG-DTA measurements indicate that PMMA coated on the wollastonite particle surface by forming chemical bond.and compared with PMMA, the thermal decomposition temperature of the composite particles increased from 200 ℃ to 260 ℃, reaction mechanism of PMMA coating wollastonite was also studied.Finally, by contrast, when the dosage of filler was 10%, the wollastonite modified with stearic acid /polypropylene composites had the best optimum impact strength and bending strength, which could be 14.21 kJ?m?2,49.25 MPa respectively, were 105.8% and 34.5% higher than that of pure PP, PP/PMMA coating wollastonite had the best tensile strength of 34.56 MPa, was about 10.5% higher than that of pure PP, the vicat softening point of which was increased from 140.5 ℃to 154.9 ℃, the thermal stability of the composite was improved. Thus, different modifiers can improve PP/wollastonite composite different mechanical properties, so selecting different modifier should be based on the actual need.SEM analysis showed that the stearic acid to improve the dispersion of wollastonite in the pp matrix was the best, the compatibility between PMMA coating wollastonite and polypropylene was the best, NDZ-105 was worst; XRD analysis showed that adding wollastonite did not change the crystal type of polypropylene, but crystallite size became smaller, which increased the impact strength of composites, adding modifier can improve the dispersion of wollastonite in polypropylene, stearic acid in the aspect of improving wollastonite dispersion is best. The conclusions are consistent with the SEM and mechanical properties. We also found that the melt blending process caused the fracture of wollastonite, which was the main causes limited the improvement of mechanical properties of PP/ wollastonite composite, so how to solve the fracture problem of wollastonite in melt blending is the focus of next step.