1. How to identify the quality of sealant?

There are many types of sealants:
Silicone sealant, polyurethane sealant, polysulfide sealant, acrylic sealant, anaerobic sealant, epoxy sealant, butyl sealant, neoprene sealant, PVC sealant, and asphalt sealant.

The sealant mainly looks at several properties:
First, the breaking strength (stretching force / cross-sectional area)
Second, the bonding strength (pull force / bonding area, except for substrate damage)
Third, the elongation at break (length at the time of breaking / original length)
Fourth, anti-aging ability
V. Appearance (matiness, particles, bubbles)
Sixth, shape retention (not drawing, the facade does not sag)
Seven, shelf life
Eight, curing time
There is no good or bad, performance corresponds to the price, suitable for the best.

2. What is the cause of cracking after silicone sealant curing?
There are three forms of silicone sealant cracking:
First, cohesive failure, the performance of the crack in the middle of the crack.
Second, the bond damage, the performance of the crack on both sides of the crack.
Third, mixed damage, the performance of the crack in the middle of the crack and cracking on both sides exist at the same time. The reasons for the cohesive failure and bond failure of the sealant are explained below:

Cause Analysis:
(1) Sealant quality problem
1. With the continuous precipitation of white oil for a long time, it causes the excessive shrinkage, rigidity and loss of displacement of the joint colloid, and it can not adapt to the displacement of the thermal expansion and contraction of the substrate to cause cracking.
2, the characteristics of the 肟 type of glue: resistance to seam displacement cracking ability.
3. The content of cross-linking agent in the formula is small, which is not enough to make the sealant react to form a perfect cross-linked network structure and structural defects, which easily lead to colloid cracking.
4. The sealant is not used within the validity period.
(2) Reasons for application
1. The joint design is unreasonable, and the joint width is less than 6mm, which is easy to cause cracking.
2. The formation of a large number of bubbles during the sizing process easily leads to colloid cracking.
3.  type glue is too thin to crack easily.
4. The uneven thickness of the sizing is easy to cause the colloid to crack in a thin place.
5. When the surface temperature of the substrate is too high or too low, the glue will be easily cracked after the glue is cured.
6. The sealant is subjected to external force during the curing process, which easily leads to cracking of the colloid after curing.
7. The large external force or large deformation of the substrate, for example, earthquakes, typhoons, etc., the colloid may crack.
8. When the three-sided bonding phenomenon occurs, the displacement that the sealant can withstand will be limited to within ±15% of the original design displacement, which will easily lead to colloid cracking.


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