Silicone sealant color change?

As we all know, the service life of buildings is generally at least 50 years, so the materials used must also have a long service life.

Silicone sealant has been widely used in the field of building waterproof sealing because of its excellent high and low temperature resistance, excellent weathering resistance and good bonding performance.

However, after construction for a period of time, the problem of silicone sealant discoloration emerges in endlessly, giving the outline of an abrupt "line" to the building.

Why does silicone glue change color with use?

There are many reasons for the partial or total discoloration of silicone sealant or glass glue, mainly in the following aspects:

01 Different sealant materials are incompatible

Acid sealant, neutral alcohol type sealant, neutral chamber oxime type sealant three can not be used together, they will affect each other and discoloration, acid glass glue will cause oxime type rubber yellow, neutral oxime type and neutral alcohol type glass glue both used together will turn yellow.

Oxime molecules released during curing of neutral oxime-type adhesive: -C=N-OH turns into amino after encountering acid, and amino is easily oxidized into colored substances by oxygen in the air!

02 Contact with materials such as rubber

Silicon adit sealant and most rubber (natural rubber, neoprene, three ethylene propylene rubber) direct contact when yellow, these rubber in curtain wall and doors and Windows are widely used (rubber strip, rubber pad, etc.), this kind of discoloration is characterized by non-uniformity, and rubber directly discoloration, other parts do not discoloration.

03 The sealant is overstretched causing discoloration

This phenomenon is easily mistaken for the color loss of sealant, there are three common causes of this kind of discoloration.

1) super displacement capacity with glue, joint displacement is too large, sealant is overstretched;

2) the local thickness of sealant is too thin, resulting in the discoloration of sealant concentrated in the thin part;

04 Sealant is affected by environmental factors

This type of discoloration occurs in the neutral oxime type sealant, the main cause of color change is in the air containing acid, acid in the air source, such as curing is acidic adit silicon sealant, the construction of the acrylic paint, sulfur dioxide from the atmosphere (the north winter high content), near the burning of plastic, burning asphalt, etc., These acid substances in the air can cause oxime-type sealant discoloration.

How to avoid silicone sealant discoloration?

1 before construction, do compatibility test for materials in contact with sealant to ensure compatibility between materials; Or choose more compatible accessory materials, such as silicone rubber products instead of rubber products, reduce the probability of yellowing;

2 In the construction process, neutral sealant can not contact with acid sealant. When the neutral glue encounters acid, the amines produced are oxidized and discolored by air.

3 Avoid contact or exposure of sealant to acid, alkali and other corrosive environment;

4 discoloration mainly occurs in light color, white, transparent and other products, choose dark or black sealant can reduce the risk of discoloration;

5. Choose sealant with guaranteed quality and good brand reputation.