Manufacturing Fibreglass

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Fibreglass is a strong, durable and surprisingly flexible material, making it suitable for a wide variety of applications, including ponds and swimming pools. But how, exactly, is it made?

It turns out that there are several different ways of making fibreglass, but they all work by incorporating glass fibres and resin into an plastic base. The combination of materials adds strength and durability, but at a much lower price point than similarly performing materials, such as carbon fibre.

Heating And Extruding

The first step in the manufacture of fibreglass is to create the glass and silica filaments that will eventually be incorporated into the resin and plastic base. The strands are heated so that they become pliable, and then extruded – or stretched out – until they become fine strands.

The strands are then collected, usually by a specialist machine, into rovings – the name for a reel of strands. The rovings can then be used for a range of applications, either being woven directly into products, or used to create a mesh-like material for other applications.


The pultrusion process combines the filaments with a resin. The term pultrusion is a portmanteau, the combination of two words, “pull” and “extrusion.” Whereas extrusion refers to materials being pushed through apparatus, pultrusion means that materials are being pulled.

The pultrusion process works by feeding the strands of material through an apparatus where they are bathed in resin and then heated using a heat source to provide the curing. The strands of glass (or other material) become impregnated with resin, enhancing their ductile and tensile properties.

Fibreglass made using pultrusion can be cut in a variety of shapes and sizes, depending on the end use. Pultrusion is, therefore, a highly flexible method for creating composite materials.

Chopped Strand Mat

Chopped strand mat is a particular way of laying up the fibres in fibreglass material. In this type of reinforcement, fibres are laid randomly on top of each other until they make a sheet, after which, a binder is applied. Chopped strand mats are often used for one-off fibreglass moulds. The material is pliable when wetted out, allowing it to be fitted to a particular shape, but soon dries and hardens.

Coating The Roving

Rovings need to be coated in a special primer to protect them during the manufacturing process. Failing to safeguard rovings can lead to local failures in the material during the manufacturing process. Each strand needs to be able to rely on the shear strength of the surrounding plastic to maintain its integrity: when there is a misalignment in the fibre matrix, breakages can occur. Manufacturers, therefore, need to be careful when laying up fibres.

GEE-GRP know how to make their own fibreglass for a range of applications across different industries. Customers can order one off fibreglass moulds or prototypes, or have a particular design mass-produced. GEE-GRP can also laminate and finish fibreglass products for a wide variety of applications, including use in hostile climates. Making high quality fibreglass required the correct expertise and specialist equipment.

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