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The effect of desiccants on insulating glass

    Source:未知 Author:NATERGY ENERGY Release time:2016-03-22

Author: Angfeng Liu     Shandong Natergy Energy Technology Co., Ltd.

Abstract: Insulating glass desiccants with different components give quiet disparate quality performances. Based on the irrefutable experimental results, we analyze that the most popular desiccant with calcium chloride or the similarities will corrupt the IG unit obviously. It will not only cut down the life span of the IG unit, but also destroy the safety of its structure.

The standard means that all the IG unit manufactures must surely keep the lifespan of their IG units up to at least 15 years, or they will be fiercely claimed!
What is the expiration of IG Unit ?

Answer : The rapid reduction or complete loss on energy-saving function of IG unit means the end of its service life.
This means: 
1. Dew occur in the IG cavity
2. Damage of low-E membrane
3. Serious physical changing

To guarantee IG life-span need to overcome 3 points
Desiccant
Sealant
Processing control

The most important kernel: Both IG processing and sealant selection are in order to protect desiccant.
The most easy to be neglected: All performances of the desiccant will not be displayed immediately until a long time service in Insulating glass.
Deep influence on IG quality: Bad desiccant can drive sealant, spacer or glass out of service invisibly. But few people notice these points.
The most essential: In the condition of good-quality sealant service, IG lifespan depends  on desiccant.

Four kinds of bad-quality desiccants in market
4A molecular sieve                       market share 5%
Lime desiccant                             market share 3%
Calcium Chloride desiccant      market share about 50%
Pure clay desiccant                     market share about 7%
Four kinds of harmful desiccants total up a great market share 65%, the mainly harmful one  is Calcium Chloride desiccant, So it is necessary to test how the desiccant will perform in the IG unit.

The harm  from 4  bad quality desiccants for IG


Methods for distinguishing 4 bad desiccants for IG


The experiment on the effect of calcium chloride desiccant on IG unit

Execution: Shandong Natergy Energy Technology Co., Ltd. (Technical support:CBMA of China)
Target: The effect of calcium chloride desiccant  on IG unit
Test Method: observation on insulating glasses (70mm x 70 mm,variously filled with O2,air,N2 ) which are made from various adsorbed desiccants.
Test condition: Keep insulating glasses at 50℃ for 9 months, then observe the changing
Insulating glass manufacture: Zibo Shengda Glass Co., Ltd.
IG material resource:
Glass, 9A aluminum spacer, butyl and polysulfide sealant (liniz), are supplied by Zibo Shengda Glass Co., Ltd.
Molecular sieve 3A is supplied by Shandong Natergy Energy Technology Co., Ltd.
Calcium chloride desiccant, supplied by an end user.

The effect of desiccants on IG unit


Photos for the effect of different desiccants on IG after 9 months at 50 ℃
     
Photo for the effect of 30% water content CaCl2 Desiccant       Photo for the effect of 30% water content 3A molecular sieve 
on IG (air) after 9  months at 50 ℃                                         on IG (air) after 9  months at 50 ℃

   
Photo for the effect of 30% water content CaCl2 Desiccant on   Photo  for the effect of 30% water content CaCl2 Desiccant on
IG (air) after 9  months at 50 ℃                                               IG (Oxygen) after 9  months at 50 ℃

     
Corruption from holes                                                            Calcium chloride crystal
Photo for the effect of 20% water content CaCl2 Desiccant on  Photo for the effect of 30% water content CaCl2 Desiccant on
IG (argon) after 9  months at 50℃                                          IG (oxygen) after 9  months at 50 ℃

The photos of eroded aluminum bar

     

    
The eroded and cracking aluminum spacer bar

The photos of molecular sieve 3A after testing
  

                                         The desiccant has already pulverized and mixed with crystal

Rainbow phenomenon on CaCl2 filling IG Unit 
          

No rainbow on 3A IG unit                                                                 Rainbow appear on CaCl2 filling IG Unit

          
Rainbow appear on CaCl2 filling IG Unit                                               Rainbow appear on CaCl2 filling IG Unit

Analyzing photos of rainbow phenomenon
          

The rainbow do not disappear after opening the insulating              The next testing shows the glass is covered with oil vapor,
glass, It concludes that the rainbow is not water vapor.                      it can be wiped away with hand.

Conclusion: In the same case, no rainbow phenomenon occurs on the 3A molecular sieve filling IG unit, this means Calcium chloride desiccant will effect sealant heavily.

Experiment summarize
1. Molecular sieve 3A will not do any harm to IG unit at any conditions.
2. Calcium chloride desiccant has corrosiveness and the corrosiveness become stronger according with the accumulation of water adsorption. 
3. Oxygen can protect the aluminum spacer bar in a certain extent, so the IG unit filled with oxygen has the lower corrosiveness. On the contrary, the argon filled insulating glass is much worse corrupted than the oxygen one.
4. Calcium chloride desiccant can corrupt aluminum bar at a rapid speed, once it adsorbed enough water it can drive spacer stained within one week, and break spacer within several months, accompanied lots of crystal calcium chloride.
5. Calcium chloride desiccant can easily destroy butyl, the destroyed butyl vapor up onto the glass, then form the rainbow phenomenon. The rainbow can be wiped by hands, it’s the volatiles of the damaged butyl.
6. Calcium chloride desiccant is transferable and easy pulverized, the powder goes out through the bar aperture,  then fasten the corrosion and stain the glass.

In conclusion, calcium chloride desiccant destroy the insulating glasses in 4 aspects.
1. Destroy the appearance of glass:
Aluminum bar corrupted  
Crystal extruded
Rainbow occur
Desiccant powder stain glass
2.Shorten lifespan of insulating glass: Aging and destroy sealant
3.  Damage energy-saving:
Because of the acid vapor exist in the IG space, Low-e membrane tend to be corrupted.
4. Dangerous to use calcium chloride as IG desiccant:
The sealant and spacer is the backbone of IG unit, long term corruption will possibly cause serious safety problem, a large sheet glass may fall from height and it is a serious problem that can not be neglected.