Effect of heavy calcium carbonate on the performance of acrylic emulsion modified emulsified asphalt waterproof coating.

the effect of heavy calcium carbonate on the performance of acrylic emulsion modified emulsified asphalt waterproof coating . Ma Yuran, Changying, Li Wenzhi, Liu Jinjing, Duan Wenfeng, Li Shanfa (Beijing Oriental Rain Rainbow Waterproofing Technology Co., Ltd., Beijing 101309)China's asphalt-based waterproof coatings according to the construction temperature can be divided into two categories: hot melt construction type and cold construction type, of which, cold construction waterproof coating is divided into solvent-based asphalt waterproof coating and water-milk asphalt waterproof coating two kinds. At present, the domestic water-milk asphalt waterproof coating is prepared by neoclode latex, butyl benzene latex, recycled latex and acrylate emulsion, etc. , with non-polluting, easy construction (can be built on wet grass) and other advantages. However, the water-milk-type asphalt waterproof coating itself also has some shortcomings, restricting its rapid development, such as the water-milk-type asphalt waterproof coating solid content is low, low viscosity, easy to flow, need to be constructed many times, brush drying material soft, low strength, higher raw material prices. This study modified acrylic calcium carbonate with heavy calcium carbonate in acrylic emulsion modified emulsified asphalt waterproof coating (the following acrylic asphalt coating), and discussed the effect of heavy calcium carbonate content on coating performance.1 Experimental part 1.1 Raw materials and instruments Emulsified asphalt: homemade, solid content 60%; acrylic emulsion: homemade, solid content 58%; heavy calcium carbonate: 800.Pull Tester: CMT6104, Mattes Industrial Systems (China) Co., Ltd.;1.2 Experimental steps Mix emulsified asphalt with acrylic emulsion in accordance with the prescribed proportion and stir 10 min at high speed; add additives to continue stirring 10 min at high speed; in order to prevent lumps, add heavy calcium carbonate in batches, and stir 20min at high speed; filter the prepared acrylic asphalt coating and pour it into a sealed container for preservation.Apply the film in the mold frame, the thickness of the coating is 1.5 mm (three coatings, interval of 8 h), the membrane frame in the standard test conditions to maintain 5 d, and then release and the film will be turned over, after 40 degrees C blow drying box maintenance 2 d, performance testing.2 Results and Discussion 2.1 Effect of heavy calcium carbonate content on coating stretch strength Figure 1 is the effect of heavy calcium carbonate content on the extrusion strength of acrylic asphalt coatings. As can be seen from Figure 1, with the increase of heavy calcium carbonate content, the extrusion strength of the coating shows a tendency to increase and then decrease: when the calcium carbonate content of heavy carbonate is less than 30%, the extrusion strength of the coating increases slowly with the increase of the calcium carbonate content of the heavy carbonate; Thus, the inflection point is between 30% and 35%, this point is the critical filler volume concentration (CPVC) of heavy calcium carbonate in this system, when the content of heavy calcium carbonate does not exceed this critical value, it is in a state of dispersion and humidification by emulsion, and fill the emulsion particles The small gap between the coating, so that the coating's stretch strength increases, when the content of heavy calcium carbonate exceeds this threshold, the emulsion becomes a non-continuous phase, can not completely wet the heavy calcium carbonate, will make it loosely distributed in the coating film, the properties of the coating will drop sharply, the stretch strength will also plummet.2.2 Effect of heavy calcium carbonate content on coating fracture elongation
Figure 2 is the effect of heavy calcium carbonate content on the fracture elongation rate of acrylic asphalt coatings. As can be seen from Figure 2, with the increase of heavy calcium carbonate content, the fracture elongation rate of the coating also shows a trend of increasing and then decreasing, the principle is the same as 2.1.2.3 Effect of heavy calcium carbonate content on the low temperature performance of coatingsFigure 3 shows the effect of heavy calcium carbonate content on the low tenderness of acrylic asphalt coatings.3, it can be seen that when the calcium heavy carbonate content is low, the effect on the low temperature performance of the coating is not large, and the low gentleness shows a slow decay trend. Because at this time the emulsion substrate is continuously uniform, low temperature performance or the low temperature performance of the emulsion substrate itself, but the addition of heavy calcium carbonate increases the tightness of the system, resulting in very slow decay of low temperature performance. After the content of heavy calcium carbonate exceeds 30%, that is, after exceeding the CPVC of this system, the emulsion substrate is not continuous, and the local location base material is unevenly distributed, resulting in rapid attenuation of low temperature performance.
2.4 heavy calcium carbonate content on the viscosity of the coating . Figure 4 shows the effect of heavy calcium carbonate content on the viscosity of acrylic asphalt coatings. As can be seen from Figure 4, with the increase of heavy calcium carbonate content, the viscosity of the system increases, and the rate of rise is slow and then fast. This is due to the addition of heavy calcium carbonate, the particle gap in the coating is getting smaller and smaller, the friction is getting bigger and bigger, the resistance of particle movement is also getting bigger and bigger, resulting in the system viscosity increases. In the heavy calcium carbonate content is small, emulsion can wet its particles, friction increase is small, viscosity rise is slower, when the heavy calcium carbonate content is larger, more than CPVC, emulsion substrate is no longer continuous, filler particles friction collision, resulting in a substantial increase in viscosity.2.5 Comprehensive performance of coatings with the best content of heavy calcium carbonate According to the effect of heavy calcium carbonate content on coating stretch strength, fracture elongation and low gentleness, the critical filler volume concentration of heavy calcium carbonate in this system is 30%, in order to prepare acrylic asphalt coatings for the best amount of added, in accordance with JC/T 408-2005 "water-milk asphalt waterproof coating" standards for testing, the comprehensive performance of the coating in line with the requirements of the standard, see Table 1.3 Conclusionthe effect of heavy calcium carbonate content on the stretch strength, fracture elongation, low gentleness and viscosity of acrylic asphalt coatings were studied. When the content of heavy calcium carbonate does not exceed CPVC, its addition can improve the extrusion strength and fracture elongation of the coating, but will cause a small attenuation of low temperature performance; To sum up, controlling the content of heavy calcium carbonate is one of the better means to improve the technical performance, construction performance and cost reduction of acrylic asphalt coatings..