Liquid gypsum set accelerator
a technology of liquid gypsum and accelerator, which is applied in the field of compositions of gypsum boards, can solve the problems of reduced potency before, partial calcination, and easy degradation of gypsum based accelerators
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example 1
[0033]Liquid gypsum set accelerator was prepared in a planetary ball mill (Retsch—Newtown, Pa.) by grinding a mixture of 30 g land plaster and 60 ml isopropyl alcohol (isopropanol) for 1 hour at 500 rpm in a 125 ml stainless steel vessel equipped with thirty 5 mm stainless steel bearings. The resulting slurry comprised about 35 wt % land plaster. A conventional ball mill accelerator was used as a control.
[0034]The particle size distribution of the liquid gypsum set accelerator and control were measured using laser diffraction analysis (Microtrac—York, Pa.), and are shown in Table 1. The liquid gypsum set accelerator had a particle size distribution that was substantially smaller than the control. Approximately 50% of the mass of the liquid gypsum set accelerator particles had a diameter (D50) of about 5.52 μm, and about 45.74% of the particles had a diameter less than 5.5 μm (50 of about 39.79 μm. The dry accelerator comprised of a ground mixture of land plaster and starch (1:1, lan...
example 2
[0035]The gypsum set time was measured for gypsum boards prepared using either the liquid gypsum set accelerator or a control accelerator as described in Example 1. Experimental ½ inch, 1250 lb / msf gypsum boards were prepared in a laboratory, having a gypsum slurry composition as set forth in Table 2, comprising about 1% accelerator on stucco (equivalent land plaster basis). The control accelerator was added to the gypsum board composition before liquid reagents, as in conventional manufacturing processes. The liquid gypsum set accelerator was added to the gypsum board composition with liquid reagents, as in at the boot or canister.
TABLE 2Gypsum Board CompositionComponentWeight (g)Stucco783Dispersant2.5Accelerator9.25Retarder0.04Starch16.4Paper Pulp0.54Soap Solution14Total Water744.44Dextrose1.0Coalescing Agent0.14Total1571.31
[0036]The rate of the hydration reaction was measured as the temperature of the gypsum slurry over time, and is shown in FIG. 1. The gypsum board prepared with...
example 3
[0037]The crystal morphology of gypsum board samples prepared using conventional and liquid gypsum set accelerators was compared. Samples of set gypsum board compositions were prepared using the liquid gypsum set accelerator and control conventional dry ball-milled accelerator of Example 1. The crystal morphology of the samples was analyzed by scanning electron micrograph (SEM), and crystal habit and numbers were tabulated by analyzing a known area of the SEM micrograph. The control sample was found to have a gypsum crystal count of 91 over an area of 112.5μ2, with an average length of 2.18 μm, an average width of 0.49 μm, and an average aspect ratio of 6.44, as shown in FIG. 2. The sample prepared using the liquid gypsum set accelerator was found to have a significantly higher gypsum crystal count of 137, with smaller gypsum crystals having an average length of 1.65 μm, an average width of 0.42 μm, and an average aspect ratio of 4.56, as shown in FIG. 3.
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