Influence of three types of impurities in insulating glass desiccant on the results of moisture permeability index.

1. The preface

Insulating glass is composed of two or more pieces of glass that are evenly spaced for effective support and are bonded and sealed at the periphery. This structure forms a dry gas space between the glass layers so that the service life of glass products can reach 15 years. Because of its good safety, energy saving, thermal insulation, heat insulation, and sound insulation properties, it has been widely used in the construction industry and automobile manufacturing industries. The moisture permeability index of the desiccant is obtained after 56 high and low-temperature cycle tests and 7 weeks of constant temperature and humidity tests for insulating glass, which not only reflects the ability of the sealant to block water vapor transmission, but also intuitively reflects the adsorption capacity and the service life of the insulating glass, and the amount of ammonia in the insulating glass density control is handed over to test the durability and moisture penetration index of the insulating glass:

Among them, T_f is the final unit moisture content of the desiccant after the water vapor seal durability test; T_i is the unit moisture content of the desiccant after the insulating glass is manufactured; T_c is the maximum unit water absorption of the desiccant.

2. The experiment

2.1 Removal and measurement of desiccant

According to the requirements of the international standard, about 60 mm from the corner of the spacer frame filled with desiccant, remove the sealant by about 10 mm, expose the spacer frame, and use an electric drill to drill a hole with a diameter ≥ 6 mm on the outer wall of the spacer frame (the hole should not penetrate the spacer The inner wall of the frame), after discarding the initial 3~5 g of desiccant, take out 20~30 g of desiccant. The operation process should be completed within 5 minutes.

The desiccant taken out from the insulating glass is put into a crucible with constant weight (the mass is mo), and its total mass m is weighed within 2 minutes. Then put the pot into the resistance furnace, within 60+20 min, the A-type desiccant is heated up to 950+20 ℃, the B-type desiccant is heated up to 350+10 ℃, and kept at the corresponding temperature for 120±5 min. Cooled to room temperature in a desiccator, and then weighed its total mass m_r.

2.2 Materials and Instruments

Both chemical glass and industrial glass, silicone rubber sealing groove, aluminum double-channel sealing insulating glass, high-temperature resistance furnace, 1/10,000 electronic analytical balance, and several clean and dry crucibles.

3. The results and discussion

3.1 The influence of the mixing of broken glass on the moisture permeability index

When taking out the desiccant, the cullet is mixed into the desiccant. Assume that the total mass of the cullet mixed in is m, the mass of the constant weight crucible is mo, and the mass of the desiccant is m, that is, m; = m glass + m ++M₀

After high-temperature calcination and heat preservation, the mass of the desiccant becomes m'dry because the crucible has a constant weight, so m=m dry+m glass+M₀.

Glass has no water-absorbing group, and the weight change is negligible. The calculation formula of the initial moisture content of the desiccant is:

The initial moisture content of the desiccant without cullet is:

It can be concluded that the mixed glass cullet leads to a decrease in the T_i value. In the same way, it can be concluded that the T_f and T_c values decrease.

^{Figure 1 The influence of the mixing of broken glass on the moisture permeability index}

3.2 The influence of the mixing of sealant on the water permeability index

If the sealant is mixed into the desiccant, the total mass of the mixed sealant is m_r. After being calcined at a high temperature and taken out, it is cooled to room temperature in a desiccator, and the mass of the sealant becomes m'_r. Desiccant initial moisture content for:

^{Figure 2 Quality change of sealant after high-temperature calcination and heat preservation} 

①: The change of sealant quality after 350℃, y=0.7004x+4E-0.5, R²=0.999.

②: The change of sealant quality after 350℃, y=0.4008x+1E-0.4, R²=0.998.

without initial moisture content of desiccant mixed with sealant:

It can be seen from Figure 1 that when the sealant is calcined at a high temperature of 350 °C for heat preservation, m' glue ≈ 0.7 m glue, and after 950 ° C high-temperature calcination and heat preservation m' glue ~ 0.4 m glue, it can be concluded that the mixed sealant leads to an increase in T; value big. In the same way, T and T can be obtained after mixing the sealant. value increases.

^{Figure 3 The influence of the mixing of sealant on the water permeability index}

3.3 The influence of the mixing of aluminum chips on the water permeability index

Assuming that the aluminum scraps are mixed into the desiccant, the total mass of the mixed aluminum scraps is m aluminum, and after high-temperature calcination and heat preservation, the mass of the aluminum scraps becomes aluminum. The quality of aluminum scraps calcined at different temperatures is shown in Table 1 and Table 2.

^{Table 1 Mass m' of aluminum scraps after high-temperature calcination at 350℃}

^{Table 2 Mass m' of aluminum scraps after high-temperature calcination at 950℃}

From the above data, it can be concluded that the quality of aluminum scraps has almost no change after high-temperature calcination at 350℃ or 950℃, and m aluminum ≈ m' aluminum. 

Desiccant initial moisture content:

It can be concluded that the mixed aluminum chips cause the T_i value to become smaller. In the same way, T_f and T_c can be obtained after mixing with aluminum chips. value decreases.

^{Figure 4 The influence of the mixing of aluminum chips on the water permeability index}

3. The conclusion

(1) When three common impurities such as broken glass, sealant, and aluminum chips are mixed into the desiccant, the water penetration index I will change and the test results will be affected. 

(2) When the desiccant is mixed with broken glass and aluminum chips, T_i, T_f, and T_c are caused the results of value decreases.

(3) T_i, T_f and T_c are caused the increase, when the desiccant is mixed with the sealant.

(4) Jinan LIJIANG Glass suggested that in the production of insulating glass, to use of a fully automatic insulating glass molecular sieve filling machine and use an efficient process control level, are important indicators to test the durability and sealing life of insulating glass.

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