Polyurethane coating is an excellent and widely used waterproof material. It is regarded as one of the high-performance waterproof coatings, especially outstanding in projects that require high elasticity, abrasion resistance, and application on complex surfaces.
Why Does Polyurethane Have Excellent Waterproof Performance?
1. Seamless Continuous Film
Polyurethane coating is applied in liquid form-by brushing, rolling, or spraying-and cures into a continuous, dense, seamless elastic membrane.
This membrane completely covers the substrate like a "raincoat," effectively preventing water penetration.
2. Exceptional Elasticity and Elongation
Polyurethane waterproof membranes have excellent elongation (over 300% or even higher).
When the substrate (such as concrete) expands, contracts, or cracks due to temperature changes or settlement, traditional rigid waterproof layers may crack as well.
However, polyurethane coatings can stretch with the movement of the crack without breaking, thus maintaining the integrity of the waterproof layer.
3. Strong Adhesion
It adheres well to various substrates such as concrete, metal, and wood, making it resistant to peeling or delamination.
4. Chemical Resistance and Abrasion Resistance
Polyurethane coating resists acids, alkalis, and salts to a certain extent.
Its surface is tough and wear-resistant, making it suitable for walkable surfaces such as roofs and balconies.
Types of Polyurethane Waterproof Coatings
1. One-Component Polyurethane Waterproof Coating
Composition: Prepolymer, used directly from the container; cures by absorbing moisture from the air.
Advantages: Ready to use, easy to apply, no need for mixing or weighing.
Disadvantages: Curing speed depends heavily on ambient temperature and humidity; deep-layer curing may be slow.
Typical Applications: Small household repairs, non-permanent immersion areas.
2. Two-Component Polyurethane Waterproof Coating
Composition: Consists of Component A (prepolymer) and Component B (curing agent), which must be mixed in a specified ratio before use.
Advantages: More stable performance, adjustable curing time, and better mechanical properties (strength and elasticity).
Disadvantages: Requires precise mixing and thorough stirring on site; limited pot life after mixing.
Typical Applications: Large-scale projects, long-term immersion environments (e.g., pools, basements), and critical waterproofing areas.
Main Application Areas
Roof Waterproofing: Especially suitable for irregularly shaped roofs.
Basement Waterproofing: Effective on walls and floors to resist underground water pressure.
Bathrooms and Kitchens: Choose eco-friendly types and ensure good ventilation.
Swimming Pools, Water Tanks, Aquariums: Performs well under long-term immersion.
Bridges, Parking Decks, and Municipal Projects.
Comparison with Other Waterproof Coatings
vs. Acrylic Coatings:
Acrylics are also elastic and more environmentally friendly (water-based), but their elasticity and durability are usually inferior to polyurethane.
Better suited for exposed roofs, not for long-term water immersion.
vs. JS Polymer Cement Coatings:
JS coatings combine flexibility and rigidity, can be applied to damp substrates, and are non-toxic and eco-friendly.
However, their elasticity is lower than polyurethane, so they are often used indoors (e.g., bathrooms).
vs. SBS/APP Modified Bitumen Membranes:
Membranes are fast to apply but have weak points at seams and limited adaptability to complex surfaces compared to liquid-applied polyurethane coatings.