Surface Modification Of Ultrafine Ground Calcium Carbonate And Its Applied Research On PVC Products

Ground calcium carbonate (GCC) is one kind of ordinary non-metallic mineral materials. It is widely applied to many industrial areas such as rubber, plastics, coating and so on. Because it has the nature of large specific surface area and high surface energy, it is easy to become agglomerate among particles. When GCC is filled in organic basic body directly or with high quantity, it is difficult to disperse uniformly which results in descent of some properties of composites because of their poor interfacial interaction. Therefore, the surface of GCC must be modified to adjust its polarity, descend surface energy and reinforce its compatibility with organic basic body. The dispersibility of GCC into organic basic body and the properties of composites would be improved.In order to get better PVC/CaCO₃ composites, stearic acid, titanate coupling agent NDZ-311 and the two formers' compounded agent were used to modify GCC under the conditions of stirring and ultrasonic. After that, modified and unmodified GCC putting into some process additives and PVC were put together respectively to obtain PVC/CaCO₃ composites with the method of melt co-mixing.To get the optimal modification craft, activation index, volume of dispersion phase, viscosity and Infrared spectrum(IR), differential scanning calorimetry(DSC), X-ray photoelectron spectroscopy (XPS), etc. were used to evaluate and characterize successively. The results show that regardless of the type of modification craft, activation index, volume of dispersion phase and viscosity were to increase or improve after modification of GCC, chemical reaction between the surface of GCC particles and the molecular of modifiers has existed obviously. The optimal dosage of stirring modification and ultrasonic modification are 3.0% and 2.5% respectively. So, the ultrasonic craft is better than the stirring one.In order to get optimal fill percentage of GCC into PVC, many property parameters were characterized, such as tensile strength, elongation at break, notched charpy impact strength and vicat softening temperature. After the analysis of scanning electron microscope (SEM), thermogravimetry(TG), TG-DSC of PVC-based composites, results show that the optimal fill percentage of GCC in PVC is 20wt%. Meanwhile, the system of ultrasonic modified GCC/PVC composite has better impactstrength and higher vicat softening temperature than stirring one and no filled one. Moreover, the conclusion that ultrasonic craft was superior to stirring craft was proved once again.