Classification and Selection of Sealants

1.Classification:

(1) Silicone sealant: It is what we usually call glass glue. It is divided into acidic and neutral types. Neutral glue is further divided into: stone sealant, mildew-proof sealant, fireproof sealant, pipe sealant, etc.

(2) Polyurethane sealant: Mainly used for waterproof sealing in construction, generally more expensive than silicone glue.

(3) Polysulfide sealant: Mainly used for sealing of hollow glass.

(4) Acrylic sealant: Mainly used for sealing of building nodes, but water resistance is average.

2.Silicone sealant is generally used for home decoration, which can meet most needs:

(1) Acidic glass glue is mainly used for general bonding between glass and other building materials. Neutral glue overcomes the characteristics of acidic glue corroding metal materials and reacting with alkaline materials, so it has a wider range of applications and its market price is slightly higher than acidic glue.

(2) Acidic silicone glass glue will corrode or fail to bond copper, brass (and other copper-containing alloys), magnesium, zinc, electroplated metal (and other zinc-containing alloys). It is also recommended not to use acidic glass glue on masonry items and carbide iron substrates. Connections that move more than 25% of the joint width are also not suitable for acidic glass glue.

(3) Curing time: The curing time of glass glue increases with the increase of bonding thickness. For example, a 12mm thick acidic glass glue may take 3-4 days to solidify, but within about 24 hours, the 3mm outer layer has solidified.

3.Reasons for blackening of glass glue:

Glass glue has a certain air permeability (glass glue solidifies by absorbing moisture in the air), and the surface is a microporous structure that easily absorbs various organic matter. Therefore, it will inevitably mold and blacken in a humid environment.

4.Suggestions:

1. Use less acid glue: Acidic glue is generally transparent and easy to yellow. Especially for installing sanitary ware, it will penetrate from the inside of the gap to the outside and turn black. It is particularly obvious on light-colored walls, floors, and sanitary ware.

2. Try to use neutral anti-mildew glue: it has a certain anti-mildew effect. But it is inevitable that it will turn black, moldy, and yellow.

Everyone should pay attention to why the construction team uses glass glue during decoration. Many companies use glass glue as a universal magic weapon to cover up decoration problems.

Frequently Asked Questions

1. How to clean glass glue on hands and glass?

Answer: After the glass glue is cured, it will not stick to the hands. Rub your hands a few times; if the glass glue is not cured on the hands or glass, use a clean cloth to dip some acetone or xylene or No. 120 solvent oil (the above 3 solvents can be purchased at chemical stores, and general chemical stores have acetone for sale.) or NO.1 (Langbowan) glass glue cleaner (can be purchased from NO.1 (Langbowan) glass glue local dealers) to wipe it. (When using the above solvents, pay attention to the precautions for using the solvent) If the glass glue is cured on the glass, just scrape it with a blade.

2. What is the reason for the yellowing of neutral transparent glue?

Answer: The yellowing of neutral transparent glue is due to defects in the glue itself, mainly caused by the cross-linking agent and tackifier in the neutral glue. The reason is that these two raw materials contain "amine groups", which are very easy to cause yellowing. Many imported brand-name glass glues also turn yellow for this reason. In addition, if neutral transparent glue is used together with acid glass glue, it may cause the neutral glue to turn yellow after curing; it may also be caused by the long storage time of the glue or the reaction between the glue and the substrate.

3. What is the reason for the wrinkling of the surface after the neutral glue is cured?

Answer: There are generally several reasons: (a) The expansion coefficient of the substrate is large; (b) There is displacement or vibration; (c) Some domestic glues are too thin, with less fillers and more plasticizers (white oil) added. During the curing process, the plasticizer (white oil) evaporates to a certain extent, which makes the volume of the glue smaller, so the glue will shrink and wrinkle; (d) If the glue is applied too thinly, it is also easy to shrink and wrinkle after curing. Increasing the thickness of the glue can reduce the occurrence of this phenomenon (it is recommended to apply more than 2mm).

4. Why does acid glue fall off easily when used on cement?

Answer: This is actually one of the most basic questions in the application of glass glue. Acid glue produces acetic acid when solidifying, which will react with the surface of alkaline materials such as cement, marble, granite, etc. to form a chalky substance, which causes it to fall off.

5. After the neutral glue is dried, there is a powdery substance on the surface. What is the reason?

Answer: Generally, there are several situations: (i) The powdering phenomenon of the glue strip is due to defects in the selection of the raw materials of the glue itself; (ii) The raw materials are mixed unevenly; (iii) It may be due to the influence of the construction environment, and dust is easily adsorbed on the surface of the glue.

6. Some glass glues now react with the glue strips on the market and turn yellow. Why?

Answer: This is mainly caused by the reaction between glass glue and PVC glue strips. In order to reduce costs, some merchants now add more calcium carbonate to PVC glue strips, and calcium carbonate will react with silicone glue, which will cause yellowing. This is mainly due to the glue strips. If you choose a glass glue product with guaranteed quality, please check the quality of the glue strips. If the glass glue is of poor quality, the yellowing will naturally be greater. To avoid this problem, it is best not to use glue strips; or choose good glue strips and good glass glue. At the same time, we emphasize that before using glue in engineering, it is best to do a compatibility test to see whether the glass glue product used is compatible with other materials before deciding whether to use it.

7. Some glass glues have granules the size of salt grains when they are applied, and some granules will automatically dissolve after curing. Why?

Answer: This is a problem with the raw material formula of the glue. Because the cross-linking agent contained in some glues will crystallize in a low temperature environment, the cross-linking agent will condense in the glue bottle, and after it is applied, you will see granules the size of salt powder, but it will slowly dissolve, so the granules will automatically dissolve after curing. This situation has little effect on the quality of the glue. This situation occurs mainly due to the greater impact of low temperature.

8. Some users have applied structural glue on the edge of a steam furnace. The highest temperature is about 100℃~120℃. After applying the glue, an additional rubber ring is added to wrap it. The glue is equivalent to a seal and does not allow air to pass through. Can structural glue be used in this case?

Answer: Qualified structural glue can also be used in this case, but the strengths of structural glue are not here. It is mostly used in the structural bonding of curtain walls to give full play to its strong bonding and tensile resistance. It is a waste of money to use it here, and the effect is not as good as acid glue. If it is used for sealing gaskets on steam furnaces, it is best to use pure organic silicone glue. Good quality neutral glue can withstand high temperatures of 150℃ after curing, and good acid glue can withstand high temperatures of about 200℃. These glues have more moderate hardness and better elasticity for sealing. If there are higher high temperature resistance requirements, special high temperature resistant glass glue should be used. But I don’t know how much pressure resistance this use requires for the glue. For safety reasons, a safety test should be done.

9. Why does the mirror surface have spots or glue marks after a period of time after glass glue is applied on the back of the mirror?

Answer: There are usually three different back coatings on mirrors on the market: mercury, pure silver and copper. It is common that after a period of time, the mirror surface will have spots. This situation should be that the user has used acid glass glue, and acid glass glue usually reacts with the above materials, causing spots on the mirror surface. Therefore, we emphasize that neutral glue should be used, and neutral glue is divided into alcohol type and ketoxime type. If the copper-bottomed mirror uses ketoxime neutral glue, ketoxime will slightly corrode the copper material. After a period of construction, the mirror surface will see traces of corrosion at the back of the glue application. If the alcohol-type neutral glue is used instead, this phenomenon will not occur. The above are all improper material selection caused by the diversity of substrates. Therefore, it is recommended that users should do a compatibility test before using glue to see if the glue is compatible with the material. Only by choosing the right glass glue product can unnecessary losses be avoided.

10. What is the reason for oil seepage in the glue?

A: Generally, glue that leaks oil is not good quality glue, because it is not 100% silicone glass glue, it has added petroleum plasticizer, and plasticizer itself is an oily substance, which has swelling property, destroying the balance between plasticizer and other ingredients, and oil will leak out. In this case, it is best to choose good quality 100% silicone glass glue.