Silicone sealant is a necessity for seam sealing in construction. If we use it improperly, it will cause problems such as water leakage and air leakage, which will affect the overall quality and use of the house. This article sorts out the common problems of silicone sealants in construction for you guys, let's take a look.
1. What are the restrictions on the use of acidic silicone rubber and neutral silicone sealant?
Acid silicone sealant cannot be used on the surface of metal, coated glass (including mirror), cement surface, stone and other materials, otherwise it will cause rust, oxidation or corrosion of the material surface, resulting in silicone pollution or bonding failure;
Neutral cure silicone should not be used in high temperature environment for it will release methanol gas during curing process and hangs quickly, which is easy to cause bubbles;
Besides, neutral silicone adhesives cannot be used in long-term water immersion environments. Such as: fish tank bonding;
Neutral oxime type silicone adhesive cannot be used on metal surfaces such as copper, lead and zinc, otherwise it will cause rust, oxidation or corrosion of material surfaces, formation of contamination or colloidal bond failure.
2. Why does silicone sealant chalk, crack or shrink significantly?
Inferior silicone sealant is mixed with inferior raw materials such as white oil in the production, and it is prone to chalking, cracking or obvious shrinkage after curing.
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3. Why does the silicone sealant turn yellow or discolor?
(1) Raw materials such as EPDM (EPDM), neoprene, and asphalt paint are incompatible with silicone sealant, resulting in yellowing or discoloration;
(2) Acid and alkaline substances such as certain cleaning agents, cement slurry and other corrosive substances cause the silicone glue to discolor;
(3) The oxime-type silicone adhesive is prone to discoloration in an acidic environment.
Precaution:
Compatibility test on accessory materials before construction, and apply silicone after passing the test; avoid colloid contact with corrosive substances or exposure to corrosive environment.
4. Why does color silicone sealant fade?
Colored silicone sealant are tinted with inorganic or organic pigments. Inorganic pigments have few colors, but have good weather resistance and are not easy to fade; organic pigments are rich in color, but have poor weather resistance and are easy to fade.
Precaution:
It is recommended that customers choose inorganic pigments as much as possible when they need tinting glue, and do not pursue color similarity too much for bright colors that may be tinted with organic pigments.
5. Why does the sealant have unqualified bonding?
(1) The sealant does not stick to the substrate itself;
(2) The construction is not standardized, such as the surface of the substrate is not clean, the maintenance environment or maintenance time does not meet the requirements, the primer is not applied as required, and the proportion of the two components is not equal.
Precaution:
- No silcone sealant can guarantee good adhesion with all substrates, so the adhesion and compatibility test must be carried out on the substrate before construction, apply primer liquid if necessary;
- Before apply the slicone sealant, the dust, oil stains and other contaminants on the surface of the substrate must be cleaned according to the prescribed method;
- One-component curing for at least 7 days, two-component curing for at least 3 days, In the case of low temperature and humidity, the curing time should be extended.
6. What are the main reasons for the bulging of silicone sealant seams?
(1) The construction is not standardized, especially the backer rod used is too wide and exceeds the width of the glue joint. During construction, the backer rod is pressed into the deformation, resulting in the colloid bulging after the silicon adhesive is applied;
(2) The curtain wall plate is too big and the joint displacement is large, which causes the colloid to be compressed and bulged;
(3) When the temperature and humidity are low during construction, and the temperature difference between day and night, the curing speed of the silicone is more slowly, especially in winter and the colloid bulges due to the thermal expansion and contraction of the curtain wall panel.
7. What are the main reasons for the bubbles of silicone adhesive seams?
(1) Air is carried when the sealant is applied, for example, the continuity and uniformity of the sealant are not well mastered, or the air is carried when the glue is repeatedly trimmed;
(2) Before applying the sealant, the interface or accessory materials are not guaranteed to be dry as required. For example, if the backer rod is wet, the moisture will penetrate into the sealant strip and bubbles;
(3) The accessories release gas, eg. improper selection of the backer rod or the closed cell of the backer rod is punctured during construction, resulting in outgassing;
(4) The surface temperature of the substrate is too high, which causes the sealant to solidify quickly, and the released small molecular gas cannot be removed in time;
(5) The silicone sealant reacts with some materials, such as alkaline concrete and cement react with the silicone to release gas.
8. What are the main reasons for the cracking of silicone sealant joints?
(1) Improper selection of silicone sealant, displacement ability can not meet the design requirements;
(2) The design of the sealant seam is unreasonable, for example, the excessively wide sealant seam makes it difficult to apply silicone sealant and the sealing is not in place;
(3) The installation of the curtain wall plate is displaced, and the deviation is too large;
(4) Before the sealant is completely cured, the seam displacement is too large;
(5) The sealant has three-sided bonding, resulting in limited displacement capacity;
(6) The thickness of the silicone is too thin, resulting in damage to the sealant or bond failure.
9. What is the cause of stone pollution?
Because stone is a porous material, when using ordinary sealants, it may be invaded by substances released by the silicone sealant and cause contamination.
Precaution:
Use special silicone sealant for stone with special formula design; carry out contamination test before apply to ensure they work well.
10. What are the main reasons for the failure of insulating glass seals?
(1) The quality of the sealing butyl rubber itself may be incompatible with the silicone sealant;
(2) The secondary silicone sealant is filled with mineral oil;
(3) Contact with other silicone sealants filled with mineral oil, such as curtain wall weathering silicone or door and window sealant;
(4) Other factors such as desiccant or processing technology.
