Application techniques of glass pressure dryers in polymer cement waterproof coating detection

There is a lot of discussion about GB 23445-2009 "Polymer Cement Waterproof Coatings" standard, and this paper mainly discusses the application of glass normal pressure dryers in the performance testing of polymer cement waterproof coatings (JS coatings). GB 23445-2009 standard on the use of dryers as follows: after the sample molding in standard conditions to sit 96 h, and then defilm, the defilmed sample back-up in the (40±2) c drying box processing 48 h, after removal, the sample will be placed in the dryer to cool to room temperature. There is a wide variety of dryers, and the most common glass dryers in the laboratory are both normal pressure dryers and vacuum dryers
in
. In the GB 23445-2009 standard does not require the vacuum dryer to cool the sample, so generally in the test more use of normal pressure dryer, its specifications to the seat body mouth diameter, common specifications of 100 to 400 mm, comprehensive practicality and price, the general laboratory multi-choice specifications of 240 mm and 300 mm of colorless transparent glass dryer.
GB 23445-2009 standard test sample molding size of 320mm×350 mm, according to this size, the diameter of the upper port of the dryer should be greater than 475mm to ensure the smooth placement of the sample, but at present there is no glass dryer of this specification, the condition of the sample after the dryer is shown in Figure 1, after drying the sample will be difficult to restore flat, and will affect the accuracy of the test. If the sample is split in advance and the front is stacked together (Figure 2), it will cause the following sample to bend a large amount, it is difficult to smooth after removal, and the sample is easy to stick together, cooled to room temperature after it is difficult to separate completely, also affecting the accuracy of the test. In order to ensure the accuracy of the test, it is necessary to discuss the use of dryer techniques.
1 Experimental part
1.1 instrument equipment and test preparation
multi-functional non-staged speed stirrer: D-8401, Tianjin Huaxing Scientific Instrument Factory, blade mixing rod; The test used JS coating products from 10 different domestic production enterprises and was made according to the ratio of powders and liquids required by each production enterprise (Table 1). On the basis of GB 23445-2009 standard provisions, add the following conditions: samples are coated 2 times, interval 24 h, the same period coating, the same coating size, mixing container, stirring speed, stirring time, the same molding process, each time the total quality of the emulsion powder is the same, the same person coating, using the same scraper.
1.2 Application of layered segmentation
1.2.1 JS paint samples are layered in glass dryers
In a dryer with a diameter of 240 mm, the maximum area is a square with a veragonal diameter with an edge length of about 170 mm, as shown in Figure 3, so the size of the sample can not exceed 170 mm×170 mm. Cut the molded JS paint sample (320 mm ×350 mm) into 8 pieces as shown in figure 4 dotted lines. Four 145 mm ×160mm and 4 30mm×160 mm samples were obtained, which were placed in the (40±2) drying box as required by GB 23445-2009 and processed for 48 h, and the samples were cooled to room temperature in a glass dryer using layered frame layering (Figure 5, Figure 6). The size of the layered frame is based on the size that can be put into the dryer: in a glass dryer with a size of 240 mm, the size of the layered frame can be selected with a size of 220 mm, figure 5 is 4 145 mm×160 mm samples placed on the layered frame, and four additional 30 mm×160 mm samples can be placed on the bracket. Considering the height of the dryer and the permeability between layers, it is recommended that the layered frame should not exceed 6 layers at most.
1.2.2 JS paint sample split
dry cooling to room temperature JS paint samples are then divided according to the solid line of Figure 4, you can get 32 test pieces, to meet the GB 23445-2009 standard stretching performance and low tenderness test number of requirements.
1.3 Mechanical Performance Test
the stretch strength and fracture elongation of JS coating samples were determined by reference to GB 23445-2009.2 Results and Discussion JS coating products from 10
manufacturers were placed in the dryer at room temperature exposed cooling and "split layering" respectively, and their untreated stretch strength and fracture elongation rates of 2 h and 5 h were tested, as shown in Figures 7-8.
From Figures 7 and 8, it can be known that, when other conditions are consistent, the JS coating sample uses a dryer to cool 2 h and cool 5 h, and its stretch strength and fracture elongation vary little, of which 50% of the sample extrusion strength change rate is less than 3.0%, the first sample change rate is the smallest, only 1.44%, 30% of the sample stretch strength change rate is between 3% and 5%, the stretch strength change rate is the largest number 9 sample, the change rate is only 9.94%. The largest change rate of fracture elongation was 8 sample, reaching 9.77%, the smallest change rate of fracture elongation was 9 sample, only 3.08%, and 50% of the sample fracture elongation rate was between 5% and 7%.
shows that the length of cooling time of JS coating samples in the dryer has little effect on the performance test results, and the detection data obtained by this method is stable. The stretch strength and fracture elongation of the exposed and cooled JS coating samples at room temperature vary greatly. Only 1 sample stretch strength change rate is less than 20%, 14.66%, the remaining 9 samples stretch strength change rate is more than 20%, of which 3 samples have more than 40% of the stretch strength change rate, 9 sample stretch strength change rate is 45.71%. 80% of the sample fracture elongation rate change rate between 26% to 30%, 40% of the sample fracture elongation rate change rate between 30% to 40%;
test results vary greatly during exposed cooling because the 10 JS coating products tested were all acrylic emulsions, which are thermoplastic polymers, and different temperatures and humidity can cause changes in molecular forces. The temperature and humidity vary greatly when the room temperature is bare and cool, resulting in unstable test results. Due to the different acrylic emulsion varieties used by different manufacturers, their sensitivity to temperature and humidity is also different, resulting in different product test results vary in magnitude.
3 Conclusion
the JS paint sample with a dryer can maintain the stability of the performance test results of JS coating products. The "layered segmentation method" allows the glass normal pressure dryer to be fully utilized in the test of JS coating performance, which is important for maintaining the flatness of the test to ensure the accuracy of the test results.