What precautions should be taken when applying acrylic sealant?

What precautions should be taken when applying acrylic sealant?
The quality of acrylic sealant application directly impacts its sealing, bonding, and service life. During application, four key aspects require careful attention: preliminary preparation, operating procedures, environmental control, and safety precautions. Specific precautions are as follows:
1. Before Application: Thoroughly Prepare the Foundation to Avoid “Inherent Defects”
Pre-application pretreatment is crucial for ensuring the sealant’s performance. Focus on checking the substrate condition and material preparation to avoid cracking or peeling due to foundation problems.

Substrate (Joint/Surface) Preparation: Ensure it’s “clean, dry, and free of impurities.”
Remove dust, oil, rust, and old adhesive residue from the substrate surface (sandpaper the metal substrate and wipe with alcohol/acetone to remove oil stains). If the surface is wet, wipe it dry with a dry cloth or allow it to air dry (moisture content should be ≤6%, refer to the product instructions for details). Otherwise, the adhesive’s adhesion will be affected and it may even cause blistering after curing. Check joint dimensions: Acrylic sealant is suitable for joints 5-20mm wide and 3-10mm deep. (Joints too narrow are prone to cracking due to thermal expansion and contraction, while joints too deep can waste material and incompletely cure.) If the joint is too wide, prefill it with a “foam stick” (made of polyethylene to prevent chemical reactions with the adhesive) to ensure uniform adhesive thickness (a recommended adhesive thickness of 1/2-2/3 the joint width).
Porous substrates (such as concrete and masonry) require a pre-priming treatment: Some acrylic adhesive can be absorbed by the porous material, resulting in uneven curing. Apply a thin layer of a similar sealant as a primer and wait until the surface is slightly dry before applying the sealant.
Material Preparation: Verify product characteristics to avoid misuse.
Confirm sealant type: Acrylic sealants are divided into solvent-based and water-based. Solvent-based sealants have strong adhesion but require ventilation, while water-based sealants are environmentally friendly but less water-resistant. Choose the appropriate product based on the application (e.g., a water-resistant sealant is needed for outdoor use/bathrooms, while a water-based sealant is needed for environmentally friendly indoor use). Do not mix different brands or types of sealants. Check the product’s condition before opening: Observe the adhesive for any separation or clumping (water-based adhesives with slight separation can be stirred evenly, while solvent-based adhesives with lumps indicate deterioration). After opening, use within the “pot life” specified in the product instructions (for solvent-based adhesives, it is recommended to use within 24 hours after opening to prevent solvent evaporation and thickening).

Prepare auxiliary tools: Glue gun (adaptable to the hose specification; manual guns are suitable for small areas, pneumatic guns are suitable for large areas), scraper (made of silicone to avoid scratching the substrate), and masking tape (applied to both sides of the joint to prevent contamination of the substrate; removed within 1 hour after application).

II. During application: Follow operating procedures to ensure adhesive layer quality.

During the application process, control the application speed, adhesive layer shape, and pre-curing treatment to avoid improper operation that may affect the sealing effect.

Gluing: Ensure “continuous, uniform, and bubble-free” application.
Gluing and venting: After installing the glue hose into the glue gun, gently press the gun handle to expel air from the hose (until glue flows continuously without bubbles). This prevents bubbles from entering the glue layer during application, which could lead to rainwater seepage later.
Gluing angle and speed: Hold the glue gun at a 45° angle to the substrate and apply the gun handle at a steady speed, ensuring that the glue fills the entire joint (no gaps) and that the glue layer is smooth. (If the surface is uneven after application, use a scraper dipped in a small amount of clean water to gently smooth it, being careful to apply evenly to avoid scraping off the glue layer.)
Avoiding “glue breaks”: When applying glue, try to complete one joint at a time. If you need to pause, mark the break point and start applying glue 5mm before the break point the next time to ensure a seamless joint. Pre-curing protection: Avoid contact with water.
For 24 hours after application (refer to product instructions for details), do not touch or squeeze the adhesive layer. Avoid contact with rain or dew (especially water-emulsion adhesives, which will dissolve in water if uncured). If outdoor application is subject to sudden rainfall, temporarily cover with plastic sheeting.
When to remove masking tape: Remove 10-30 minutes after application (when the adhesive surface is slightly dry but not fully cured). Removing it after curing may remove the adhesive layer or leave residual marks, making it difficult to clean.

III. Environmental Control: Avoid “harsh environments” to ensure stable curing. The curing of acrylic sealant is significantly affected by temperature, humidity, and ventilation. Application must be performed in a suitable environment. Failure to do so will prolong the curing time or lead to performance failure.

Temperature requirements: 5°C-35°C is optimal.

Below 5°C, the adhesive cures significantly slower (a normal 24-hour cure time may take over 48 hours at temperatures below 5°C). Furthermore, the adhesive loses elasticity after curing and is prone to cracking. Above 35°C, the solvent in solvent-based adhesive evaporates too quickly, causing a “skin” to form on the surface while the interior remains uncured, resulting in hollowing of the adhesive layer.

During winter application, if the temperature is too low, allow the adhesive to sit indoors for two hours beforehand (to return to room temperature). For outdoor application, apply the adhesive at noon when the temperature is higher. During high summer temperatures, avoid direct sunlight on the substrate. Cool the substrate before applying the adhesive (e.g., spray it with water and allow it to dry).

Humidity requirements: 40%-70% relative humidity is ideal.

When humidity is above 80%, the cure rate of water-based adhesive slows down, and the adhesive layer is susceptible to moisture absorption and mold. When humidity is below 30%, the solvent in solvent-based adhesive evaporates too quickly, causing surface cracking. Outdoor construction is prohibited on rainy or foggy days. When working in humid environments such as bathrooms, turn on exhaust fans in advance to reduce humidity and wait until the substrate is dry before applying glue.

Ventilation Requirements: Solvent-based adhesives require forced ventilation.

Solvent-based acrylic adhesives contain volatile organic solvents (such as toluene and ethyl acetate). Volatile gases can easily accumulate in a closed environment, affecting the health of workers and potentially causing uneven curing of the adhesive layer. During application, maintain air circulation by opening doors and windows or using fans. (Water-based adhesives can be ventilated normally and do not require forced ventilation.)

IV. Safety Precautions: Avoid Health Risks and Operate in a Standardized Manner

Acrylic sealants (especially solvent-based ones) contain irritants. Personal protection measures must be taken during application to avoid direct contact or inhalation.

Personal Protection: Wear gloves and a mask to avoid contact with skin and mucous membranes.

Wear nitrile gloves when applying glue (rubber gloves are easily corroded by solvents, and latex gloves may cause allergies). If the adhesive accidentally comes into contact with skin, rinse immediately with soap and water (do not use alcohol directly, as this will worsen the irritation). In case of contact with eyes, rinse immediately with plenty of water and seek medical attention. When applying solvent-based adhesive, wear an activated carbon mask to avoid inhaling volatile fumes. Avoid prolonged periods indoors and ventilate the room outdoors for 10 minutes every hour.

Environmental Safety: Keep away from sources of fire and out of reach of children.

Solvent-based acrylic adhesive is flammable. Open flames (such as lighters and welding tools) must be kept away from the application site, and smoking is prohibited. Unopened adhesive should be stored in a cool, well-ventilated area (temperature ≤ 30°C), away from heat sources and children.

After application, waste materials such as hoses and masking tape must be sorted and disposed of separately (solvent-based adhesive waste is considered hazardous waste and should not be discarded). 5. Post-Cure Inspection: Acceptance and Prompt Remediation
After the adhesive has fully cured (usually 7 days, refer to the product instructions for details), a “sealing performance acceptance” is required:

Visual inspection: Check whether the adhesive layer is smooth, free of cracks and bubbles, and whether there are gaps at the interface with the substrate.

Manual inspection: Gently pull the adhesive layer. If there is no peeling or noticeable deformation, the adhesion is satisfactory.

Waterproofing test: For outdoor or bathroom applications, spray water on the joints for 10 minutes. After 24 hours, check the inside of the substrate for water stains. If there are leaks, remove the old adhesive and reapply according to specifications.

In short, acrylic sealant application should adhere to the principles of “adequate pretreatment, standardized operation, suitable environment, and safety first.” Each step should be based on the product instructions (which may vary slightly between brands) to maximize the sealing and bonding performance and extend the service life.