▶ I. Core Classification (Based on the Needs of Building Joints)

The core classification of single-component polyurethane building sealants is to match the displacement of building joints, application locations, and working conditions. The national standard classifies them primarily into low-modulus and high-modulus types based on modulus/displacement capacity, supplemented by scenario-specific models. Different types lack universal compatibility and require precise selection. The core classifications and characteristics are shown in the table below:

Core Selection Principles：

For building joint displacement ≥20%, prioritize low-modulus adhesives to prevent cracking of the adhesive layer due to tension/compression; for rigid structural joints and joints requiring slight adhesive stress, select high-modulus adhesives.

Core Performance Advantages (Suitable for Specific Building Construction Conditions)

Compared to silicone sealants, polysulfide sealants, and other building sealing materials, single-component polyurethane sealants precisely match the diverse substrates, complex working conditions, and ease of application required in building construction. This is the core reason why it has become a mainstream type of building sealant:

1. Wide adhesion to various building substrates, no primer required: It can directly and firmly bond to commonly used building substrates such as concrete, cement mortar, marble/granite, steel/aluminum, tempered glass, and PVC/ABS plastics. Only low surface energy polyolefins (PP/PE) require a primer. It is suitable for sealing joints of different substrates in various parts of buildings, with no obvious "adhesion blind spots."

2. Strong resistance to structural displacement: After curing, it becomes a highly elastic elastomer. The low modulus type can adapt to joint expansion/settlement displacement of ±25%, matching the deformation of concrete caused by temperature, settlement, and load. It can still return to its original shape after repeated deformation, avoiding cracking and leakage of the adhesive layer, and providing a long-lasting sealing effect.

Core Application Scenarios (Covering All Buildings + Municipal Supporting Buildings)

The application of single-component polyurethane building sealant covers five core areas: main building structure, doors and windows, curtain walls, roofs, kitchens and bathrooms, flooring, and municipal water conservancy buildings. Different sealant types are precisely matched to different parts. Core scenarios and selection recommendations are as follows:

1. Main Building Structure (Core Sealing, Prevention of Settlement/Expansion Cracking)

Expansion joints, settlement joints, and construction joints of concrete walls, floors, beams, and columns: Select low-modulus weather-resistant materials to absorb structural deformation and prevent rainwater from seeping into the interior and causing steel corrosion;

Splicing joints of prefabricated building components: Select high-modulus weather-resistant materials to balance bonding strength and sealing performance, ensuring the sealing and stability of prefabricated component connections.

3. Construction Process and On-site Precautions (Specific Operating Requirements for Construction Sites)

The quality of application of single-component polyurethane building sealant directly determines the sealing and waterproofing effect of building joints. Substrate treatment, joint filling, and adhesive layer control are the three core key points. Application must be adapted to the construction site environment (e.g., open-air conditions, diverse substrates, high dust levels). The core construction steps and precautions are as follows:

1. Standard Construction Steps (Manual Application of Adhesive, General Construction Type)

Step 1: Pre-construction Preparation – Joint Cleaning + Substrate Treatment (Most critical, accounting for 70% of the sealing effect)

Cleaning joints: Use a scraper, wire brush, and blower to remove laitance, dust, sand, and oil stains from the joints, ensuring the joints are clean, dry, and free of loose debris.

Substrate treatment: For concrete substrates with protrusions or hollow areas, remove and level them; for stone substrates, apply an anti-efflorescence treatment beforehand; for metal substrates with rust, polish to the original color and apply anti-rust paint.

Drying requirements: The surface moisture content of the substrate should be ≤8%. Damp surfaces must be dried with a heat gun to prevent moisture from causing bubbles and pinholes in the moisture-curing adhesive.

Step 2: Seam Filling – Add foam sticks + apply masking tape

Foaming rod filling: Select polyethylene foam rods with a diameter 10%-20% wider than the joint, depending on the joint width. Insert them into the bottom of the joint as a backing for the adhesive layer, controlling the adhesive layer thickness to avoid slow curing and cracking due to excessive thickness.

Maskting tape application: Apply masking tape to the substrate surface on both sides of the joint to prevent adhesive from contaminating the substrate during application, facilitating subsequent repairs and improving the aesthetics of the finished product.

Step 3: Applying Adhesive – Continuous application of adhesive + smoothing and finishing

Applying the sealant: Load the sealant into a dedicated caulking gun. Cut the nozzle at a 45° angle, with a diameter slightly larger than the joint width. Insert the nozzle deep into the bottom of the joint and apply the sealant continuously and evenly from one end to the other, ensuring the sealant layer fills the entire joint without gaps or air bubbles.

Smoothing and Finishing: Immediately after applying the sealant, use a dedicated scraper to smooth the sealant layer into a triangular (dovetail) shape, ensuring a tight adhesion between the sealant and the substrate. Remove the masking tape immediately after smoothing to prevent the sealant from sticking off and damaging the substrate after curing.

Step 4: Curing and Maintenance – Environmental Control + Avoiding Stress

Curing Environment: Optimal curing temperature 15-25℃, relative humidity 50%-70%; outdoor application should avoid rain, strong winds, and direct sunlight. In high temperatures, apply the adhesive in the early morning or evening; in low temperatures (<5℃), take insulation measures to prevent slow curing.

Curing Time: Initial curing at room temperature is 1-4 hours (adhesive surface is not sticky to the touch), complete curing is 24-48 hours. Before complete curing, avoid contact with water, rain, external pressure, and vibration. Do not perform subsequent construction at joints.

Post-Cure Protection: After complete curing, if there are minor stains on the adhesive surface, wipe with a damp cloth. For outdoor applications, apply a layer of UV-resistant varnish to the adhesive surface to extend its service life.

2. On-site precautions specific to construction sites

1. Joint Size Control: Adhesive layer width:thickness = 2:1~3:1, minimum thickness ≥3mm, maximum thickness ≤10mm, width ≥6mm. Too thin a layer is prone to cracking, too thick a layer is prone to incomplete curing and bubbling.

2. Foam Rod Selection: Do not use waste paper, cloth strips, etc., as substitutes for foam rods. Foam rods must be closed-cell type to prevent water absorption and subsequent adhesive layer detachment.

3. Outdoor Adhesive Application Protection: Do not apply adhesive in rainy, snowy, or windy weather (wind speed ≥5). When exposed to high temperatures and direct sunlight, a sunshade can be erected above the joint to prevent rapid skin formation on the adhesive surface and incomplete internal curing.

4. Substrate Moisture Content: Apply adhesive after the concrete substrate has cured for ≥28 days to ensure the substrate is dry and shrinkage is stable, avoiding later shrinkage leading to adhesive layer cracking.

5. Storage Requirements: Unopened sealant should be stored in a cool, dry, and ventilated place on the construction site, away from direct sunlight, high temperatures, and rain. The temperature should be controlled between 5-25℃. Shelf life is 9-12 months. 6. Use within 24 hours of opening: Use the glue cartridge within 24 hours of opening. After use, immediately seal the nozzle with the sealing cap to prevent the glue from contacting air, forming a skin, and hardening. If the nozzle forms a skin, cut off the skin and continue use.

7. Safety precautions: Wear gloves, a mask, and goggles during construction to avoid contact with skin and eyes. If contact occurs, immediately rinse with clean water and seek medical attention if necessary. Keep the construction area well-ventilated to prevent the accumulation of volatile adhesives.

8. Local repairs: If cracks or detachment occur at building joints later, first remove the old glue layer, clean the joint, let it dry, and then reapply the glue. Do not apply glue directly to the surface of the old glue layer.

Implementation Standards

Factory overview