Heavy calcium carbonate has the characteristics of wide source of raw materials, good thermal stability, non-toxicity and low price. Heavy calcium carbonate with small particle size has an absolute advantage in toughening, but the surface energy of the refined particles is larger, and the Easy to agglomerate in dispersion medium. In addition, the hydrophilic characteristics of the surface of heavy calcium carbonate are not compatible with hydrophobic resins, thus affecting its filling effect in polymers.
Therefore, in order to improve the use value and functional value of heavy calcium carbonate in the industrial field and enable it to be evenly dispersed in the dispersion medium, it is necessary to modify its surface.
The addition of modified heavy calcium carbonate can reduce the production cost of epoxy resin structural adhesive while improving its mechanical properties. Among them, dry modification is widely used due to its characteristics of less consumables, low cost, and simple process.
There are many studies on the modification of heavy calcium carbonate. In addition to the attempts of a single modifier, researchers have turned to the combination of multiple modifiers in recent years. The functionalization of modified heavy calcium carbonate is becoming more and more targeted.
Stearic acid and titanate coupling agents were used as compound modifiers to dry-modify heavy calcium carbonate, and the effect of modified calcium carbonate on the mechanical properties of epoxy resin composites was discussed, with a view to providing important Provide actual data for the development of high value-added products of high-quality calcium carbonate.
1. Composite modification of heavy calcium carbonate
Weigh the quantitatively dried heavy calcium carbonate into the mixing tank, put the mixing tank into a water bath at the corresponding temperature, add a certain amount of stearic acid, and use a high-speed disperser to disperse the calcium carbonate; then add double ( Dioctyloxypyrophosphate (dioctyloxypyrophosphate) ethylene titanate coupling agent is used to obtain modified heavy calcium carbonate after high-speed dispersion. It was compounded with epoxy resin to prepare modified heavy calcium carbonate/epoxy resin composite material.
2. Test results
(1) When the dosage of stearic acid is 1.5% of the mass of heavy calcium carbonate, the stearic acid modification time is 20 minutes, the dosage of titanate is 2.0% of the mass of heavy calcium carbonate, and the modification time of titanate is 10 minutes. , the tensile property of the composite material is the best, which is 10.2MPa, and the oil absorption value is the lowest at this time.
(2) The crystal form of heavy calcium carbonate was not changed after modification with stearic acid, titanate, and compounding with epoxy resin. The composite modifier was successfully grafted on the surface of heavy calcium carbonate. Modified heavy calcium carbonate particles have good dispersion and strong binding with epoxy resin.