2.3 Dispersion of calcium carbonate (particle size 17Î¼m) in organic media
(Fig. 1) In a certain amount of liquid paraffin, add unmodified heavy CaCO3 and modified heavy CaCO3 (coupling agent: 0.75% of heavy CaCO3 mass) in proportion, and determine the system. Viscosity and draw Figure 1.
The surface properties of the heavy CaCO3 before modification are oleophobic, so it is not easy to disperse in the organic medium liquid paraffin. It can be seen from Fig. 1 that the unactivated heavy calcium carbonate has a viscosity in the organic paraffin mixed system. Its content in the system increases and increases (curve 1). When m(CaCO3)/m (liquid paraffin) reaches 0.2, the viscosity in the system increases sharply, but the heavy CaCO3 after modification is due to its surface. The performance becomes lipophilic, so it is easy to disperse in liquid paraffin. From the curve 2, it can be seen that the viscosity of the mixed system greatly decreases with the increase of its content in the system. Only when m(CaCO3)/m (liquid paraffin) reaches 0.9, the viscosity in the system increases sharply. This further demonstrates that the activated heavy CaCO3 has good dispersibility in the organic medium, indicating that it is filled with organic high polymer. When the material can increase its filling amount, its performance is not influenced by too much to reduce the cost, and because of its compatibility with the polyolefin, its fluidity is improved, thereby greatly improving the processing conditions.
2.4 The amount of aluminate
The effect on the viscosity of the CaCO3/liquid paraffin system (Fig. 2) was surface treated with an aluminate coupling agent at 0 to 1.5% of the mass of CaCO3 (particle size 17 Î¼m), respectively. The resulting product was m(CaCO3)/m (liquid paraffin). =1:2 mix and shake, and the viscosity of the system is plotted as FIG. 2 . It can be seen from Figure 2 that the aluminate coupling agent has a significant viscosity-reducing effect on the viscosity of the system, and the effect is very prominent. At the beginning, the viscosity of the mixed system dropped rapidly with the increase of the amount of the aluminate coupling agent. After that, the viscosity of the system tends to be gentle after passing through an inflection point. This is because as the amount of aluminate coupling agent increases, the surface of the CaCO3 particle is continuously covered by the aluminate coupling agent molecule, and its surface properties have also undergone significant changes, from the original hydrophilicity to the lipophilicity, so that The viscosity in the system drops rapidly. When the amount of aluminate coupling agent reaches a certain point (in this case, the inflection point), the surface of the CaCO3 particle is almost completely covered by the aluminate coupling agent molecule, and thereafter the aluminate is added. The coupling agent has little effect on the viscosity reduction of the system, but it will increase the cost. Therefore, the optimum amount of aluminate coupling agent should be near the inflection point, which is about 0.8%. The reduction in viscosity plays an important role in improving the rheology of the process, which will reduce energy consumption and reduce wear on mechanical equipment.
The results in Fig. 1 and Fig. 2 indicate that the heavy calcium carbonate treated with the composite coupling agent will have a good dispersibility and a lower viscosity in the resin matrix, which will facilitate the processing performance of the polymer matrix composite material. Improvements and improvements in certain mechanical properties .
The heavy calcium carbonate activated by the composite coupling agent is changed from hydrophilicity to lipophilicity, and the oil absorption rate is significantly reduced. The treatment of heavy calcium carbonate by the composite coupling agent can significantly reduce the paraffin oil/calcium carbonate mixture. The viscosity of the system, when the amount of the coupling agent reaches 0.75%, the viscosity-reducing effect is close to the optimum value.
Source: China Plastics Additives Network
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