Composite Pipe

Glass fiber reinforced plastics (GRP) are a composite consisting of at least two different materials. The benefits of each material are united to achieve an overall effect.

A binder or matrix and reinforcing material is commonly used to combine the physically differing raw materials. Their molecules do not bond but they form a composite by joining their boundary layers. What is important is that the constituents are compatible in terms of properties and processing. This technology originated in the aviation and marine industry where particularly light high-performance materials are required.

  Resins: 

The primary functions of the resin are to transfer stress between the reinforcing fibers, act as a glue to hold the fibers together, and protect the fibers from mechanical and environmental damage. Resins used in reinforced polymer composites are either thermoplastic or thermoset. 

Thermoset resins are used to make most composites. They’re converted from a liquid to a solid through a process called polymerization, or cross-linking. When used to produce finished goods, thermosetting resins are “cured” by the use of a catalyst, heat or a combination of the two. Once cured, solid thermoset resins cannot be converted back to their original liquid form. Common thermosets are Polyester, Vinyl-ester, Epoxy, and Polyurethane. 

· Polyester: Unsaturated polyester resins (UPR) are the workhorse of the composites industry and represent approximately 75% of the total resins used. A range of raw materials and processing techniques are available to achieve the desired properties in the formulated or processed polyester resin. Polyesters are versatile because of their capacity to be modified or tailored during the building of the polymer chains. They have been found to have almost unlimited usefulness in all segments of the composites industry. The principle advantage of these resins is a balance of properties (including mechanical, chemical, and electrical) dimensional stability, cost and ease of handling or processing. Polyester producers have proved willing and capable of supplying resins with the necessary properties to meet the requirements of specific end user applications. These resins can be formulated and chemically tailored to provide properties and process compatibility.

· Epoxy: Epoxy resins have a well-established record in a wide range of composites parts, structures and concrete repair. The structure of the resin can be engineered to yield a number of different products with varying levels of performance. A major benefit of epoxy resins over unsaturated polyester resins is their lower shrinkage. Epoxy resins can also be formulated with different materials or blended with other epoxy resins to achieve specific performance features. Epoxies are used primarily for fabricating high performance composites with superior mechanical properties, resistance to corrosive liquids and environments, superior electrical properties, good performance at elevated temperatures, good adhesion to a substrate, or a combination of these benefits. Epoxy resins do not however, have particularly good UV resistance.

· Vinyl Ester: Vinyl esters were developed to combine the advantages of epoxy resins with the better handling/faster cure, which are typical for unsaturated polyester resins. These resins are produced by reacting epoxy resin with acrylic or methacrylic acid. This provides an unsaturated site, much like that produced in polyester resins when maleic anhydride is used. The resulting material is dissolved in styrene to yield a liquid that is similar to polyester resin. Vinyl esters are also cured with the conventional organic peroxides used with polyester resins. Vinyl esters offer mechanical toughness and excellent corrosion resistance. These enhanced properties are obtained without complex processing, handling or special shop fabricating practices that are typical with epoxy resins.