10 Silicone Sealant Knowledge Points
You Need To Know

1.Silicone sealant has poor adhesion to some building materials .

This phenomenon is explained in two sentences “the diversity of building materials and the instability of sealant".

First of all, the diversity of building materials: there are many kinds of building materials on the market, such as sprayed aluminum and anodized aluminum. Spraying aluminum is also divided into electrophoresis, fluorocarbon and other coatings, with different surface properties. Therefore, it is necessary to know the advantages and disadvantages of adhesion through experiments. The general raw material of plastic steel profile is PVC (polyvinyl chloride), and plasticizer and filler are also added. However, there are many manufacturers and different materials, so there is also great uncertainty.

Moreover, the instability of sealant: as a chemical product, many factors affecting the quality cannot be directly observed. We will also find that sometimes there is poor adhesion from the previous test results; This also requires us to conduct compatibility test before construction.

Note: the non stick materials of customers are actually related to the diversity of building materials.

2. Neutral transparent (ketoxime type) will also turn yellow or even red after curing.

The yellowing of neutral transparent glue is due to the defects of the glue itself, which is mainly caused by the crosslinking agent and tackifier in the neutral glue. The reason is that these two raw materials contain "amino" and "vinyl". Amino and vinyl are very easy to cause yellowing. Therefore, many imported famous brand glass adhesives also turn yellow. In addition, if neutral transparent adhesive is used together with acid glass adhesive, it may 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.

Ketoxime transparent will turn yellow in varying degrees after curing for about 20 days. The yellowing trend will intensify with the increase of time

Here, the yellowing of ketoxime adhesive is not a problem in individual factories, but a problem in the whole industry of a product, including foreign manufacturers. Although yellowing is an inherent defect of current products, the curing environment also has a great impact on yellowing. First, ketoxime adhesive can not coexist peacefully with acid adhesive. It doesn't take three days to beat them together, and ketoxime adhesive will seriously turn yellow, That is, ketoxime acid intolerance; In addition, placing the cured ketoxime adhesive in a dark and humid corner will also make it turn yellow until it turns red.

3. Is there any chemical reaction when neutral glue is mixed with silica gel glue?

If the silica gel of other factories has been completely cured, generally no chemical reaction will occur again; If the silica gel of other factories has not been cured and mixed with the adhesive of our company, chemical reaction will occur. It is not recommended to mix the silicone adhesive of different manufacturers.

4. If you accidentally get the glue on the glass, what can you use to clean it?

If the glue is not cured, wipe the cloth strip quickly: if the glue is cured, you can only scrape the glue away with a knife.

5. What is the best temperature for construction?

The construction environment shall be well lit and clean. The best environmental conditions for construction are: temperature 15 ℃ ~ 27 ℃, relative humidity 40% ~ 80%. Even if the above conditions are not met, the temperature of 4C ~ 40 ℃ and the relative humidity of not less than 30% shall not be exceeded. Construction cannot be carried out when it rains or snows.

6. What are high modulus and low modulus?

High modulus - for sealant with displacement capacity of ± 20% and ± 25%, if its tensile modulus at 23 ℃ and - 20C is > 0.4MPa or > 0.6MPa respectively, the sealant is of high modulus.

Low modulus - for sealant with displacement capacity of + 20% and + 25%, its tensile modulus at 23 ℃ and - 20 ℃ is < 0.4MPa and < 0.6MPa respectively (these two conditions shall be met at the same time), then the sealant is of low modulus.

7.Heat resistance of silicone sealant

Silicone rubber is a silicone polymer with silicon oxygen bond as the main chain. It has good high and low temperature resistance, insulation and physiological properties. Among them, high temperature resistance is one of the important properties of silicone rubber. It is widely used in printing industry, electronics, electrical appliances, automobile and aerospace.

Continuous working temperature and service life of silicone rubber:

• 150 ℃ 15000 hours
• 200 ℃ 7500 hours
• 250 ℃ 2000 hours
• 316 ℃ 20-100 hours

8. Deep curing of silicone sealant is slow.

Firstly, the objective conditions of sizing have a great impact on the deep curing speed, such as construction environment, temperature and humidity.

Too low temperature and too high humidity will significantly slow down the deep curing (especially alcohol based adhesive). In addition, the ventilation at the construction site will also affect the deep curing if the air circulation is not smooth. In addition, the design of adhesive joint also has a great impact on the deep curing. When the width depth ratio of adhesive joint is inappropriate or the depth is too deep, the deep curing will be slow; In general, the deep curing is slightly slow, which will not affect the actual engineering use without quality problems (such as blistering, internal non curing, etc.). The curing period of the test piece specified in the national standard is 21 days, and the tested test piece is equivalent to the sizing thickness in the actual engineering, that is to say, the complete curing time recognized in the national standard takes 21 days, while the actual curing speed reflected by us is far less than 21 days (generally, it is reflected as slow drying if it exceeds 5-7 days): in addition, we believe that too fast curing of sealant is not good for long-term use, because too fast curing is not conducive to releasing the stress caused by temperature during curing, and there are hidden dangers. For example, the curing time of concrete is limited, and if it is too fast, it will lead to stress concentration and cracking.

9.Apply silicone glass glue to the back of a mirror. After a period of time, the mirror will show spots or traces of glue?

Mirrors on the market usually have three different back coatings: Mercury, Sterling Silver and copper. Common mirror spots appear on the mirror after sizing for a period of time. This situation should be that the user uses acid glass glue, which usually reacts with the above materials, resulting in spots on the mirror. Therefore, we emphasize that neutral glue should be selected, and neutral glue can be divided into alcohol type and ketoxime type. If ketoxime type neutral glue is selected for the mirror on the copper bottom, ketoxime will corrode the copper material. After construction for a period of time, the mirror can see traces of corrosion at the sizing position behind the mirror, one by one. If alcohol type neutral glue is used, this phenomenon will not occur. The above are due to the improper material selection caused by the diversity of substrates. Therefore, it is recommended that users should conduct a compatibility test before using the glue to see whether the glue is compatible with the material. Select appropriate glass adhesive products to avoid unnecessary losses.

10. The color of neutral silicone glue becomes lighter after construction.

This should also be the quality problem of silicone glue, which belongs to the problem of raw material selection and verification. Because some domestic adhesives are added with plasticizer (mainly white oil), they are volatile; while some adhesives are added with more CC powder. When the plasticizer volatilizes, the rubber strip is stretched due to shrinkage to show the filler color (CC powder itself is white): various color adhesives add pigments to make them become various colors. If there is a problem in pigment selection, the color of the silicone sealant will change after construction; Or the color sealant is too thin during construction, and the inherent small shrinkage of the sealant during curing will make the glue color lighter. In this case, it is recommended to maintain a certain thickness (more than 2mm) during sizing.