Rock wool board has become the core material of modern building exterior wall insulation and fireproof isolation zone by virtue of its excellent fireproof (Class A non-combustible), heat insulation and acoustic noise reduction performance. Ensure its solid bonding with the building base is the key to the quality of the project, and polyurethane adhesive is with its outstanding comprehensive performance, become the preferred solution for bonding rock wool board.
Why choose polyurethane adhesive to bond rock wool board?
Compared with traditional cement-based mortar or other adhesives, polyurethane adhesive in the application of rock wool board to show significant advantages:
Excellent bonding strength: After curing, polyurethane adhesive can form a strong elastic bonding layer, which can produce excellent mechanical occlusion and molecular adsorption on rock wool boards (porous surface) and many kinds of grass-roots level (concrete, cement mortar plaster layer, metal, etc.), and provide very high tensile and shear strength (usually up to 0.6MPa or more, which is much higher than the standard requirements).
Flexibility and anti-cracking: excellent flexibility and modulus of elasticity can effectively absorb and disperse the stress generated by temperature changes, structural deformation or external impact, greatly reducing the risk of cavitation, cracking or even falling off due to stress concentration in the rock wool panel system, and enhancing the long-term stability of the system.
Fast curing, efficiency: strong initial adhesion, fast curing speed (usually a few hours to obtain practical strength), significantly shorten the construction waiting time, accelerate the progress of the project, especially suitable for projects with a tight schedule.
Excellent weathering performance: excellent resistance to high and low temperatures (the working range is usually from -40°C to +90°C), aging resistance, water resistance and freeze-thaw resistance, which can withstand the harsh climate for a long time to ensure the durability of the system.
Easy to apply: Mostly one-component moisture curing or two-component mixing, easy to operate. Spraying, scraping or spot-framing can be used, and it is easy to control the dosage and ensure the full adhesion rate.
Reduced load: Compared with cement mortar, polyurethane adhesive has lower density, which can reduce the weight of the overall thermal insulation system.
Second, polyurethane adhesive bonding rock wool board construction core points
Grass-roots level treatment:
Ensure that the grass-roots level (concrete, plaster layer, etc.) is solid, flat, dry and clean (no oil, floating ash, mold release agent, loose material, etc.).
The deviation of flatness should be in accordance with the specification requirements (usually 2m ruler inspection, deviation ≤ 4mm), and the excessive unevenness should be leveled in advance.
If necessary, carry out interface treatment (such as brushing interface agent) to enhance the bonding force.
Material preparation:
Select the special rock wool board bonding polyurethane adhesive in line with national or industry standards (such as JG/T 438, GB 50404). Ensure that the product is within the shelf life.
The quality of rock wool board should be qualified (density, strength, hydrophobicity, dimensional stability, etc.) and the surface should be clean and dry.
Prepare tools (glue gun, mixer, scraper, serrated trowel, etc.) according to manufacturer’s instructions.
Glue application method (recommended):
Point frame method (most commonly used): Apply continuous adhesive strips (width ≥50mm) along the perimeter of the rock wool board, and evenly arrange multiple bonding points (diameter ≥100mm) in the middle of the board. The thickness of the glue point/strip is adjusted according to the flatness of the grass-roots level, usually 8-15mm, to ensure that the compaction of the bonded area ≥ 60% of the area of the rock wool board (high-level or key areas should be ≥ 70%). This method can effectively avoid drumming, and allow a small amount of moisture discharge.
Strip bonding method: Use sawtooth trowel to evenly scrape and apply parallel adhesive strips on the board surface. It is necessary to ensure the full adhesion rate.
Full adhesive method (special requirement parts): For the base of very high flatness or very high safety requirement parts (such as the bottom of high-rise buildings, corners, edges of holes, etc.), the full adhesive method can be used, and the adhesive can be evenly scraped on the back of the board with a sawtooth trowel.
Paste and compaction:
After applying the adhesive, the rock wool board should be pasted to the predetermined position as soon as possible (within the open time).
Adopt kneading and pressing method (gentle circular movement) to make the board and the grass-roots level in full contact, to ensure that the adhesive evenly covers the bonding surface and reaches the designed thickness.
At any time with a ruler to check the flatness and verticality, timely adjustment.
The joints of the boards should be closely spliced (≤2mm) to avoid through-seams. The height difference needs to be sanded and leveled.
Anchoring aid (vital):
Polyurethane adhesive is the main bonding material, but it must be matched with mechanical anchors! Especially for high-rise buildings, negative wind pressure parts or rock wool board self-weight is large.
Usually after the initial curing of the adhesive (generally 24-48 hours), special anchor bolts are installed according to the design requirements (quantity, position, depth). Anchor bolts need to penetrate the rock wool board effectively anchored into the grass-roots level, and its disk should be pressed against the rock wool board.
Curing maintenance:
During construction and curing, the ambient temperature should be between 5°C and 35°C, avoiding rain, sunshine and strong wind.
Polyurethane adhesive curing speed is greatly affected by temperature and humidity, low temperature and high humidity will significantly slow down the curing. Ensure that the adhesive is fully cured to sufficient strength (refer to the product specification, usually several days) before proceeding to subsequent processes (e.g. plastering).
Safety:
Workers need to wear protective gloves, masks, goggles, etc., to avoid the rock wool fibers and uncured adhesive contact with skin and eyes.
Keep the working environment well ventilated.
Third, the summary
Polyurethane adhesive by virtue of its high strength bonding, flexible anti-cracking, durable and efficient construction and other comprehensive advantages for the rock wool insulation system provides a reliable and efficient bonding solutions. Strictly follow the construction principle of “qualified grass-roots level, correct adhesive selection, standardized adhesive distribution, kneading compaction, anchoring in place, proper maintenance” is the key to ensure the success of polyurethane adhesive bonding of rock wool boards, and to realize the long-term safe and stable operation of the heat preservation system. In today’s building energy saving and safety requirements are increasing, the correct application of polyurethane adhesive bonding technology to improve the quality of rock wool board exterior insulation system has important practical value.
Key Tip:
Be sure to use special polyurethane adhesive for rock wool board, ordinary polyurethane adhesive may not be applicable.
Mechanical anchoring can not be omitted, and must be formed with bonding together to ensure safety.
Strict adherence to product instructions and construction specifications is the basis for success.
Before large-scale construction, carry out on-site bond strength pull-out tests to verify the reliability of the process.
For specific product recommendations, more detailed construction parameters (e.g. adhesive spacing, calculation of the number of anchor bolts) or solutions for special working conditions, further information can be provided for discussion.