An APP (Atactic Polypropylene) membrane is a type of modified bituminous membrane used in the construction industry for waterproofing purposes. It is composed of bitumen (a viscous, black, and sticky material) modified with atactic polypropylene, which improves its performance characteristics.
The APP membrane you mentioned is a seven-layered membrane, meaning it consists of seven distinct layers. The layers are typically arranged as follows:
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Reinforcement Layer: This is the base layer of the membrane and provides strength and stability. In the case of the membrane you described, the reinforcement is made of polyester and HMHDPE (High Molecular High-Density Polyethylene). These materials enhance the tensile strength and dimensional stability of the membrane.
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APP Modified Bitumen Layer: The second layer is the modified bitumen layer, which contains atactic polypropylene. The addition of APP improves the flexibility, elongation, and low-temperature properties of the bitumen, making it more suitable for a wider range of weather conditions.
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Polyester Fleece Layer: A polyester fleece layer is often added to provide additional reinforcement and improve the adhesion between the layers.
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APP Modified Bitumen Layer: Another layer of the modified bitumen is applied on top of the polyester fleece layer.
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Reinforcement Layer: This layer is similar to the first layer and provides further reinforcement to the membrane.
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APP Modified Bitumen Layer: Another layer of the modified bitumen is applied.
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Protection Layer: The topmost layer is a protective coating that can be a mineral granule, a polymeric film, or a combination of both. It protects the underlying layers from UV radiation, weathering, and mechanical damage.
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