Magnesium Calcium Nitrate,Calcium Magnesium Nitrate,High Purity Calcium Magnesium Nitrate,Chemical Fertilizers Magnesium Calcium Nitrate SHANXI HUAXIN FERTILIZER CORP. , https://www.sxhuaxingroup.com
1. Test contents (1) Raw materials and reagents Talc powder: particle size 0.025mm, Henan Nanyang Fangcheng talc; titanate coupling agent HY13C.
(2) Test method Weigh a certain amount of talc into a slurry with a concentration of 8.33% in a basket mill, the rotation speed of the mill is 1000r/min, and filter, wash, dry and grind after ultra-fine grinding for 3 hours; In the same manner, a 5% titanate coupling agent is added to the slurry for ultrafine pulverization-surface modification, filtration, washing, drying, and grinding.
(3) Performance test Take a certain amount of talc raw materials, talc superfine pulverized samples, ultrafine pulverization-surface modified modified samples, respectively, using laser particle size analyzer for particle size distribution measurement, activation index measurement, contact angle measurement, thermal analysis And infrared spectroscopy.
2. Discussion of test results (1) Particle size analysis 
Figure 1 Particle size distribution of talc
(2) Activation index analysis Ultrafine pulverization-modified talc after surface modification has an activation index increased from 0 to 88% compared with that before modification, and the activation index is significantly improved due to the titanate coupling agent. The hydrophobic group combines with the hydroxyl groups on the surface of the talc in a chemical bond, thereby increasing the surface tension of the talc in water.
(3) Contact angle analysis
Figure 2 Contact angle before and after talc modification
As shown in the above figure, the contact angles of talc before and after modification are 43.5° and 128.5°, respectively, and the contact angle after modification is obviously increased, and the surface activity is greatly improved. This is due to the coupling of the surface of the titanate coupling agent talc particles. To make the talc particles change from hydrophilic to hydrophobic.
(3) Thermal analysis
Figure 3 talc thermal analysis results
It can be seen from the above figure (a) and (b) that the thermal weight loss curve of the talc after the ultrafine pulverization-surface modification treatment is not the same as the thermal weight loss curve after the ultrafine pulverization, and the modified talc is at 223.5 ° C. Weight loss occurred at 556.6 °C, and a continuous exothermic peak appeared. This was due to the melting and decomposition of the titanate coupling agent, and the weight loss content was about 3.45%. In the ultrafine pulverization-surface modification test, the addition was changed. The content of the agent is 5%, and the effective utilization rate of the modifier reaches 69%. It can be seen from the above figure (c) that the talc product after the ultrafine pulverization-surface modification treatment is sufficiently washed twice with ethanol for the first time. Compared with Figure (b), the weight loss is slightly smaller, the main weight loss is about 2.64%, only 0.81% of the modifier is washed away by ethanol, and the loss is small. It can be seen that the titanate coupling agent HY13C The strength of the joint is very strong, which is mainly affected by the chemical bonding.
(4) Infrared spectroscopy
Figure 4 talc infrared spectrum talc ultrafine pulverization (a), ultrafine pulverization - surface modification integrated treatment (b), modified and washed thoroughly with ethanol twice after drying (c)
It can be seen from the b-curve and the c-curve that a characteristic peak of the coupling agent appears on the infrared spectrum of the modified talc powder, and the peak position is 2917.2 cm-1, which is a methyl asymmetric stretching vibration absorption band, 2849.9 cm. -1 is a methylene symmetric stretching vibration absorption band. The characteristic peak of the coupling agent after the modified talc powder is washed twice, which indicates that the coupling agent molecule still exists after the surface of the modified talc powder is alcohol-washed. The combination is relatively strong, because the titanate coupling agent belongs to the monoalkoxy type titanate, and the coupling is formed due to the hydrolysis reaction of the isopropoxy group with the hydroxyl group on the surface of the talc powder.
3. Conclusions (1) After superfine pulverization of talc, the d50 is 6.967μm, and the d50 decreases to 6.192μm after superfine pulverization-surface modification by titanate coupling agent HY13C.
(2) The talc activation index of the ultrafine pulverization-surface modification treatment is increased from 0 to 88%, and the compatibility with organic matter is greatly improved. The contact angle after talc modification increased from 43.5° to 128.5°, and the surface activity was significantly improved.
(3) Comprehensive analysis by TG-DTA and infrared spectroscopy, the modification of talc by titanate coupling agent HY13C is due to the hydrolysis reaction of the presence of isopropoxy group and the hydroxyl group on the surface of talc powder, forming a coupling. Strong ability to combine.
(Source: low-grade talc ultrafine grinding - Integration of surface modification, author: Li Pengju)
Talc is a common layered silicate mineral with soft and slippery characteristics. It can be widely used in paper, plastic, rubber, cable, ceramics, paint, paint, building materials and other industrial fields. The talc powder has great differences in chemical structure and physical form between the inorganic filler and the organic polymer molecular material, lacking affinity, making the mixing between the talc powder and the polymer uneven, and the adhesion is weak. Resulting in a decrease in the mechanical properties of the article. To this end, the talc must be surface modified.
Ultrafine pulverization-surface modification of minerals can greatly simplify the processes and processes of mineral processing, and is currently a hot spot in non-metallic mineral processing research.
As can be seen from the above figure, the d50 of the talc raw material is 13.56 μm, the d50 after the ultrafine pulverization treatment is 6.967 μm, and the d50 after the ultrafine pulverization-surface modification by the titanate coupling agent HY13C is 6.192 μm, which is changed. Before the sex, the particle size becomes smaller. This is because the addition of the titanate coupling agent to the system reduces the tension of the interface. According to the Gibbs adsorption theorem, adsorption occurs at the interface to form film-coated particles, thereby increasing the repellency. The particles are dispersed to improve the grinding efficiency, and at the same time, the surface energy of the modified talc particles is increased and can be used as a filler.
As shown in the above figure (a), the unmodified talc starts to lose weight at 517.3 ° C, and ends at 868.2 ° C, during which a significant endothermic peak appears, mainly due to the thermal decomposition of the dolomite component in the talc. After TG analysis, the loss on ignition was 23.72%.
The structural unit layer of the talc is a silicon-oxygen tetrahedron in which the upper and lower layers are opposed to each other, and the intermediate interlayer is a magnesium-oxygen octahedron. It can be seen from the a curve that 3673.2 cm-1 is the stretching vibration absorption band of OH, 1009.1 cm-1 is the Si-O stretching vibration absorption band, and is also the strongest absorption peak, and 667.0 cm-1 is the OH bending vibration absorption band, 447.6 cm. -1 is the deformation-bending vibration of silicon-oxygen. These wave numbers are the main characteristic groups of talc powder, while 1429.4cm-1 is the asymmetric stretching vibration frequency of carbonate in dolomite, 876.6cm-1 and 728.5cm-1. It is a characteristic absorption peak of calcium carbonate, which is the main component of dolomite.