How FRP is made, detailed background information

FRP is not the most well-known material in the world of engineers, which is unfortunate as it might be the perfect material for many industrial solutions. For more general information about FRP, visit the FRP Material Page. On this page we get more into details and answer the question ‘how FRP is made’.

Construction of an FRP laminate

FRP products normally include three types of laminates. The Chemical Barrier Layer (CBL), Structural Layer and Topcoat. The layers and the composition of resin and glass is determined by experienced engineers with specific knowledge on FRP constructions, different factors influence their selection, such as temperature, chemical properties of the medium, abrasion and more.


Resins, also called thermosettings, give the environmental and chemical resistance to the product and is the binder of the glass fiber in the structural laminate. Making a thermosetting product involves a chemical reaction in which molecules are formed and warmth is released. Once the new network of molecules exists, it creates its final shape. This network of molecules ensures fire resistance when the material is heated. Thermosetting materials are polyester, epoxy and polyurethane resins. Plasticon Composites applies different types of thermosetting depending on the medium and conditions in which the final product will be installed, naming a few:

  • Chemical properties
  • Erosion or abrasion
  • Environmental temperatures
  • Heat Distortion Temperature (HDT)
  • Possibly Fire Retardancy Class

There are three main groups of resin:

  • Polyester resins
  • Epoxy resins
  • Vinyl Ester resins

Polyester Resins

Polyester Resins are the most widely used resins in the composites industry. Sometimes, referred to as Fiberglass Resins, Polyester Resins. Most polyester resins are viscous, pale colored liquids consisting of a solution of a polyester in a monomer which is usually styrene.

The majority of all fiberglass parts are constructed using Polyester Resins because they are easy to use, fast curing, and tolerant of temperature and catalyst extremes. Unsaturated polyester resin is a thermoset, capable of being cured from a liquid or solid state when subject to the right conditions. It is usual to refer to unsaturated polyester resins as 'polyester resins', or simply as 'polyesters'. There is a wide range of polyesters made from different acids, glycols and monomers, all having varying properties

There are two main types of polyester resin used as standard laminating systems in the composites industry. Orthophthalic polyester resin is the standard economic resin used by many people. Isophthalic polyester resin is now becoming the preferred material in industries such as marine where its superior water resistance is desirable.

Epoxy resins

For composite parts that demand the ultimate strength, manufacturers depend on Epoxy Resin. In addition to increased strength properties, epoxies also generally outperform other resins like polyester and vinyl ester for dimensional stability and increased bonding with other materials.

Among resins, epoxy is considered to be the most advanced resin on the market. It often requires more accuracy in measurement and handling. The large family of epoxy resins represent some of the highest performance resins of those available at this time. The term 'epoxy' refers to a chemical group consisting of an oxygen atom bonded to two carbon atoms that are already bonded in some way.

Usually identifiable by their characteristic, amber or brown coloring, epoxy resins have a number of useful properties. Both the liquid resin and the curing agents form low viscosity easily processed systems. Epoxy resins are easily and quickly cured at any temperature from 5°C to 150°C, depending on the choice of curing agent.

Epoxies differ from polyester resins as they are cured by a 'hardener' instead of a catalyst. The hardener, often an amine, is used to cure the epoxy by an 'addition reaction' where both materials take place in the chemical reaction.

Vinyl Ester Resin

Vinyl Ester Resin is considered to be a hybrid of polyester and epoxy resins, meaning its handling characteristics, properties generally falls just between the two. Vinyl Ester, or Vinylester, is a resin produced by the esterification of an epoxy resin with an unsaturated monocarboxylic acid.

There are different Vinyl Ester Resins: Novolac based, Bromated Epoxy based and Elastomer-modified bisphenol-A based Vinyl Ester Resins. The Epoxy Vinyl Esters have several advantages over unsaturated polyesters as higher elongation and corrosion properties. They are highly resistant to acids, alkalis, solvents, hypo chlorites and peroxides.

Because of the basic structure of the Vinyl Ester molecule, it is more resistant to hydrolysis. Vinyl Ester Resin provides improved toughness in the cured polymer while maintaining good thermal stability and physical properties at elevated temperatures. These resins have improved bonding to inorganic fillers and reinforcements as a result of the internal hydroxyl group.


Fiberglass is used to improve the mechanical strength, resistance to damage from the outside and in order to maintain a fixed shape. Fiberglass comes in a wide variety of shapes; mats, roving, chopped strands, glass veil and bands. Plasticon Composites selects the correct composition of fiberglass based on the construction and is able to apply, work and laminate this material into guaranteed products with the highest mechanical strength.

Glass fibers are used to convey structural stiffness and strength to composite materials. Chemical service can influence the selection of veil material for exposed surfaces and the type of glass for gun roving’s and mats used in interior layers adjacent to the surface. Industry standards, project specifications, fabrication processes and application techniques usually dictate the design or form of the reinforcement.

The reinforcement material is made from a suitable grade of glass fiber having a surface finish compatible with the resin used to promote wetting, to control adhesion and to obtain interface stability. These shall either comply with the relevant standard as appropriate or be the subject of agreement between the purchaser and the manufacturer. The three glass types used by Plasticon Composites:

  1. E-glass
  2. C-glass
  3. ECR-glass

Knowledge is required

Experience and expertise are crucial to ensure that customers are supplied with well-designed FRP products. It is Plasticon Composites’ daily business to advise, inform and even train our customers in the art of composing FRP products.

Contact us for more information about FRP, we'll be happy to provide you more information.


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