GRP stands for "Glass-Reinforced Plastic." It is a composite material made up of a polymer matrix (usually a type of plastic resin) reinforced with glass fibers. GRP is also commonly known as "fiberglass" because the primary reinforcement used is glass fibers.
The GRP pipe composition is shown below:
For each layer different reinforcements and resins may be used.
Internal layer
The liner or the chemically resistant layer is the internal layer of the pipe; it is in direct contact with the conveyed fluid. This layer has the function of guaranteeing the maximum resistance to the chemical corrosion and securing the impermeability of the whole pipe, due to:
- higher content of resin;
- special kind of resin used;
- special kind of glass reinforcement used.
The liner is generally made of two monolithic sub-layers and the standard liner thickness is about 0.8÷1.2 mm. Of course, this thickness can be increased when needed.
Mechanically Resistant Layer
It is also called “the structural layer”. It is the layer, with a high content of reinforcing glass fiber that guarantee the mechanical resistance of the whole pipe to stresses due to internal and/or external pressure, external loads due to handling and installation, soil loads, traffic loads, thermal loads, beam loads, etc. The structural layer is obtained in different ways, depending on the manufacturing technology.
Outer Layer
The topcoat or gel coat is the outer layer of the pipe, having a minimum thickness of 0.2-0.3 mm or more depending on the design requirement. Normally, it consists of pure resin, with a UV inhibitor added in order to protect the pipe from the sun exposure.
Here's a breakdown of the main components of GRP:
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Glass Fibers: These are typically made from fine strands of glass that are woven together to form a mat or fabric. Glass fibers provide the strength and stiffness to the composite material.
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Plastic Resin: The plastic resin, often polyester or epoxy, acts as the matrix that holds the glass fibers together. It also provides protection against environmental factors and helps shape the final product.
3. Silica (SiO2) Silica (SiO2) appears in the crystalline form as quartz (virtually pure silica sand) and when it is less pure, it appears in the form of sand. The silica sand is mainly added to the structural part of the laminate to increase the thickness and stiffness of the pipes.
GRP is known for its exceptional strength-to-weight ratio, corrosion resistance, and durability. It is widely used in various industries, including construction, automotive, aerospace, marine, and the manufacturing of pipes and tanks. GRP pipes, for example, are known for their corrosion resistance and are commonly used in the transportation of various fluids, such as water and chemicals.