General Fiberglass Reinforced Polymer Composition

In this excerpt from our newest eBook Chemical Processing eBook: FRP Applications, Opportunities, and Solutions we share some basic information on the composition of Fiberglass Reinforced Polymers (FRP).

There are four main ingredients that FRP are comprised of: resins, reinforcements, fillers, and additives/modifiers. Each ingredient is equally important and all ingredients play an important role in determining the properties of the finished FRP products. To simplify, think of the resin (polymer) as the glue or the binding agent. The mechanical strength is provided by the reinforcements.


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 are divided into two major groups known as thermoset and thermoplastic. Thermoplastic resins become soft when heated, and may be shaped or molded while in a heated semi-fluid state and become rigid when cooled. Thermoset resins, on the other hand, are usually liquids or low melting point solids in their initial form.

Reinforcements: Fibers and Forms

Generally speaking there are four common types of fibers broadly used in the FRP industry: glass, carbon, natural, and arimid. Each has their advantages and applications. Similarly, reinforcements are available in forms to serve a wide range of processes, service and end product requirements. 10

Common materials used as reinforcement include woven roving, milled fiber, chopped strands, continuous chopped, and thermo-formable mat. Reinforcement materials can be designed with unique fiber architectures and be preformed (shaped) depending on the product requirements and manufacturing process.


Fillers are used as process or performance aids to impart special properties to the end product. Some examples of inorganic fillers include calcium carbonate, hydrous aluminum silicate, alumina trihydrate, and calcium sulfate. In some circumstances fillers and additives can play a critical role in lowering the cost of compounds by diluting expensive resins and reducing the amount of reinforcements. Furthermore, fillers and additives improve compound rheology, fiber-loading uniformity, enhances mechanical and chemical performance, and reduces shrinkage.

Additives and Modifiers

Additives and modifiers perform critical functions despite their relative low quantity by weight when compared to the other ingredients such as resins, reinforcements and fillers. Some additives used in thermoset and thermoplastic composites include: low shrink/low profile (when smooth surfaces are required), fire resistance, air release, emission control, viscosity control, and electrical conductivity.

An important note is that FRP products can be custom made for their intended use. Understanding the intended function and services of the FRP, will aid the design and manufacturing processes to allow for an optimal finished product (i.e. corrosion resistance). Modifiers can include catalyst, promoters, inhibitors, colorants, release agents and thixotropic agents (i.e. fumed silica and certain clays).

Download our free ebook Chemical Processing eBook: FRP Applications, Opportunities, and Solutions to learn more about FRP.

FRP Material Properties Put to Use

Viable solutions to complex problems—that’s what we all want in the end, right? For decades civil engineers have been seeking out alternatives to traditional materials of construction such as steel alloys. FRP, a relatively new class of composite material have proven to be economical and efficient with respect to the repair of buildings and structures in a broad range of industries. Fiber Reinforced Polymer composites are defined as a polymer (plastic) matrix, either thermoset or thermoplastic, that is reinforced (combined) with a fiber or other reinforcing material with a sufficient aspect ratio (length to thickness) to provide a discernable reinforcing function in one or more directions.

The high strength-to-weight ratio, also known as the specific strength, is an important material characteristic, this number allows you to compare materials of different mass or applications where resistance against breaking has priority. Typically, when comparing strength of materials of equivalent thicknesses and sizes, FRP will weigh one seventh as much as steel and half as much as aluminum.  Civil engineers have also come to appreciate the responsiveness of FRP materials; that is FRP responds linear-elastically to axial stress and can be custom designed and fabricated to meet engineering and end-user specifications with respect to axial compression, transverse tensile stress, and shear stress—among other things.

FRP material’s portfolio of benefits is diverse and includes important benefits to end-users such as excellent corrosion and abrasion resistance as well as overall durability—where other materials succumb to stringent and environments, FRP thrives.  Corrosion resistance of FRP is a function both of resin content and the specific resin used in the laminate.  Generally speaking, the higher the resin content, the more corrosion resistant the laminate.

FRP has been successfully employed in a multitude of harsh industrial and demanding structural construction scenarios including pulp and paper, oil and gas, desalination, chemical processing, waste water purification, mining and minerals, power generation, structural bridges, defense, aerospace, and marine —the list could go on and on.  Regarding the industrial/commercial side of things, here are a few common corrosion resistant FRP applications; hydrochloric acid, acetic acid, wet chlorine gas, ferric chloride, hydrogen sulfide, sulfur dioxide fume, and sodium hypochlorite—this list is not all-inclusive. For a complete list you’ll want to connect with a resin-manufacture or check out a manufacture’s resin guide.

The short of it is this—FRP when designed properly is a cost-effective material that has demonstrated its durability and ability to withstand industrial conditions, but also, importantly long-term environmental exposure—a key distinction that has interested many civil engineers involved in the rehabilitation, retrofitting and complete rebuilding of bridges, other load bearing structures and or architectural elements, such as, pre-stressing tendons, reinforcing bars, and grid-reinforcements and structural columns.  Regardless of what type of project type or project environment you are planning for there are likely supporting case studies available that demonstrate the opportunity, solutions and benefits realized when integrating FRP into project design.

More Fiberglass Terminology!

We recently shared some of the most common fiberglass terms and the explanations that could be found in our newest eBook Chemical Processing eBook: FRP Applications, Opportunities, and Solutions.

The Chemical Processing eBook is intended to be a supplemental tool to help you interact with the fiberglass industry. As part of the eBook we included a section on common fiberglass terminology, and  a few weeks ago we shared the four most common and useful fiberglass terms to know.

This week we thought we’d share four more common fiberglass terms to help increase your fiberglass literacy.

E-CR Glass- This type of reinforcement glass is similar in nature to E-Glass but does not contain boron or fluorine. Known for performing well in chemically hostile environments, specifically acidic and corrosive applications. E-CR glass is known to have higher temperature resistance, better mechanical properties, higher surface resistance, and better dielectric strength when compared to its predecessor E-glass.

Filament Winding-Filament winding is the process of winding resin-impregnated fiber or tape on a mandrel surface in a precise geometric pattern. This is accomplished by rotating the mandrel while a delivery head precisely positions fibers on the mandrel surface.

Hand Lay-up- One of the basic fiberglass fabricating techniques. The hand lay-up process uses a combination chopped –glass mat and woven continuous glass filament layered together with resin.

Spray-up- This process is similar in nature to hand lay-up and is also included in the general category of contact molding. Simply put, the spray-up process is an automated way of depositing chopped glass onto a structure. The spray-up process is particularly useful when filling a cavity or when glass mat or weave are too stiff for the design specifications.

Download our free ebook Chemical Processing eBook: FRP Applications, Opportunities, and Solutions. to learn more about FRP, fiberglass terminology, and corrosion.