Composite modification of heavy calcium carbonate and its effect on the properties of epoxy resin
Heavy calcium carbonate has the characteristics of wide source of raw materials, good thermal stability, non-toxicity and low price, etc. Heavy calcium carbonate with small particle size has the absolute advantage in toughening, but the surface energy of the refined particles is large, and it is easy to be agglomerated in dispersing medium. In addition, the hydrophilic property of the surface of heavy calcium carbonate is not compatible with hydrophobic resins, thus affecting its filling effect in polymers.
Therefore, in order to improve the use and functional value of calcium bicarbonate in the industrial field, so that it can be uniformly dispersed in the dispersing medium, its surface modification is necessary.
The addition of modified calcium bicarbonate can reduce the production cost of epoxy resin structural adhesive, and at the same time can improve its mechanical properties. Among them, dry modification is widely used because of less consumables, low cost and simple process.
There are many studies on the modification of calcium bicarbonate, in addition to the attempts of a single modifier, in these years, researchers have turned to the compounding of a variety of modifiers, and the functionalization of modified calcium bicarbonate has become more and more targeted.
R & D personnel using stearic acid and titanate coupling agent as a compound modifier, heavy calcium carbonate dry modification, and explored the effect of modified calcium carbonate on the mechanical properties of epoxy resin composites, with a view to providing practical data for the development of high value-added products of heavy calcium carbonate.
1、Composite modification of heavy calcium carbonate
Weigh the quantitative drying of heavy calcium carbonate to the mixing tank, put the mixing tank into the corresponding temperature of the water bath, add a certain amount of stearic acid, the use of high-speed disperser for calcium carbonate dispersion; and then add bis (dioctyloxy pyrophosphate ester-based) ethylenic titanate coupling agent, high-speed dispersion to get modified heavy calcium carbonate. The modified calcium carbonate/epoxy resin composite was prepared by compounding it with epoxy resin.
2.Test results
(1) When the dosage of stearic acid is 1.5% of the mass of calcium bicarbonate, the modification time of stearic acid is 20 min, the dosage of titanate is 2.0% of the mass of calcium bicarbonate, and the modification time of titanate is 10 min, 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) After stearic acid, titanate modification and composite with epoxy resin did not change the crystal shape of calcium bicarbonate, the composite modifier successfully grafted on the surface of calcium bicarbonate. The inter-particle dispersion of modified calcium bicarbonate was good, and the combination with epoxy resin was strong.
