Possible Problems in the Construction of Silicone Window Sealants in Summer

As the summer approaches, various regions are entering barbecue mode with increasing temperatures and humidity. The curing of silicone window sealant relies on the moisture in the air, making changes in environmental temperature and humidity have a significant impact on the use of silicone sealant in construction.

Silicone window sealant needs to cure before it can function as a structural adhesive or sealant. The curing rate is influenced by the environmental temperature and air humidity. Generally, as the temperature and humidity rise, the surface drying time (for single-component products) and the break time (for two-component products) of the sealant shorten. This variation in indicators could adversely affect the application and effectiveness of the sealant, so special attention is needed during construction in the summer.

Curing Speed of Sealant at Different Temperature Conditions

Key Point 1: Rapid Surface Drying/Tensile Break Time Affects Silicone Window Sealant Trimming and Usage

For single-component silicone window sealant, the surface drying time and tensile break time of two-component products both decrease with higher temperature and humidity. Therefore, during summer construction, it's important to perform a simple test on the surface drying time before use, to understand the product's drying time in the actual usage environment. This will guide the trimming and caulking work during actual construction.

Key Point 2: Formation of Bubbles in Silicone Window Sealant After Application

After application, there may be unevenly sized bulges on the joint, and when these bulges are cut open, they reveal a hollow interior. The presence of bubbles in silicone window sealant leads to decreased adhesion and reduced sealing effectiveness.

Alcohol-based sealants release gas during the curing process due to the presence of methanol (methanol starts to evaporate around 50°C), and this effect is intensified in direct sunlight and high temperatures. Concrete and various metal window frames are not breathable, and combined with high temperatures and humidity in summer, curing happens faster. The gas released from the not fully cured layer of sealant cannot escape due to the non-porous materials, leading to uneven bubbles forming on the cured sealant strip. During high-temperature seasons, when using alcohol-based sealants, it's advisable to avoid direct sunlight during application or use appropriate shading measures.

Additionally, frequent summer thunderstorms can lead to moisture infiltration after the substrate and joints are soaked in rain. If caulking work is performed before the substrate or joints are completely dry, the moisture within the joints and substrate won't be able to dissipate into the air in a timely manner, resulting in bubble formation. In such cases, caulking work must only be carried out after the substrate or joints have thoroughly dried.

Key Point 3: Blistering in Silicone Window Sealant After Application

The curing process of single-component silicone window sealant relies on reacting with the moisture in the air to solidify. The environmental temperature and humidity have certain impacts on the curing rate. Generally, higher temperatures lead to faster curing, and higher humidity also accelerates curing. As one of the professional silicone sealant manufacturers, we recommended construction conditions are within an ambient temperature range of 4-40°C with a relative humidity above 50%RH. When the curing of the sealant is slow, it takes longer for the surface of the sealant to solidify to a sufficient depth.

During summer construction, temperature requirements are usually met. However, if the relative humidity is low (below 50%RH), the curing of the sealant slows down, extending the time required for the surface to solidify to a sufficient depth.

If the silicone window sealant's surface hasn't solidified to a sufficient depth and the width of the joint varies significantly, the joint's surface may be affected, leading to unevenness. Sometimes the joint bulges in the middle, other times there are continuous bulges, and occasionally there's twisting and distortion. These uneven joint surfaces, after final curing, are solid inside and not hollow (hollow areas are called "bubbles"), collectively referred to as "blistering".