What Are the Advantages of Fiberglass Reinforced Plastic?

fiberglass reinforced plasticNow that we have covered what fiberglass reinforced plastic is and how fiberglass reinforced plastic is fabricated, we’ve come to one of the questions we most often get asked, “What are the advantages of Fiberglass Reinforced Plastic?”

Corrosion Resistance

Perhaps the prime reason for using fiber-glass-reinforced plastics (FRP) is because of their inherent corrosion resistance. In many cases, they are the only materials that will handle a given service environment; and in other cases, their corrosion resistance is combined with their economy to make them the most economical acceptable solution. Corrosion resistance of FRP is a function of both the resin content and the specific resin used in the laminate. Generally speaking, the higher the resin content, the more corrosion resistant the laminate.

Weight Advantages

Another very distinct advantage of FRP is its low weight-to-strength ratio. As a rule of thumb, for the same strength, FRP will weigh approximately one seventh as much as steel, and half as much as aluminum.

Lightweight properties are important when considering the cost and ease of installation, especially for pipe and tanks. FRP’s inherent lightweight is an advantage when equipment must be mounted on existing structures, such as scrubbers on mezzanines or rooftops, and for specialty applications such as FRP tank trailers.

High Strength

While not as important for corrosion-resistant equipment, high strength does play a major role in the design of FRP equipment for such applications as missiles, pultruded shapes, etc. For filament wound pipe and duct, the high strength gives the lightweight features discussed earlier.


Often, a major advantage of FRP is its lower cost. When comparing materials for corrosion service, rubber lining, titanium, Monel, Hastelloy, Carpenter 20, and the exotic stainless materials are very frequently alternatives to FRP. In these cases, FRP may offer both a satisfactory solution to corrosion problems and the lowest cost. There is no rule of thumb for comparing costs of FRP with other materials. These costs depend upon the application, the design considerations, the pressures (or vacuums) involved, the product configurations, and raw material cost and availability.


Too many people overlook the versatility of FRP. It is best for many applications because you can do things with it that cannot be done economically with other materials. You can mold almost any configuration, or piece of equipment, for which you can build a temporary or permanent mold. For ductwork, for example, you can make all types of elbows, rectangular to circular transitions, Tee inlets, and flanges all in a wide proliferation of round and rectangular sizes and shapes at minimal tooling cost. It is also possible to use FRP to line existing structures

What Should I Know About Designing or Purchasing FRP Products/Equipment?

To learn more about designing for fiberglass reinforced plastic or buying FRP, please download our free whitepaper, “Fiberglass Reinforced Plastics for Corrosion Resistance.”


How is Fiberglass Reinforced Plastic Fabricated?

fiberglass reinforced plasticsIn this post, the second of our FRP blog post series, we’re going to cover three of the most common fabrication methods for fiberglass reinforced plastic. The first of which is the most basic:

Hand Lay-Up

This is the most basic of fabrication techniques for fiber-glass-reinforced plastics. Sometimes, it is also referred to as “contact molding.” A simple mold, whether male or female, is used. It is first coated with an appropriate release agent and the layup fabrication is started. The first material applied is normally a 10-mil layer of resin and special corrosion resistant glass called “C-glass”. This reinforcing glass is in the form of a very thin veil or surfacing mat, similar in appearance to the “angel hair” used for Christmas decorations. This first 10-mil layer gives a high-resin, low glass content corrosion barrier.

In the hand-lay-up process, this 10 mil layer is followed by a minimum of two layers of fiberglass in a mat form. This mat consists of chopped glass fibers, randomly oriented, with a binder that holds them into a coarse cloth like form that can be cut, handled and applied. Resin, catalyzed to cure at a predetermined rate, is applied by means of brush or spray gun. The resin is worked into the chopped-glass mat by means of rollers, similar to paint rollers.

When the wall thicknesses are ¼ inch or more, (typically, when past the first two layers of chopped mat), a stronger glass reinforcement is used. This reinforcement is known in the trade as “woven roven,” and consists of continuous glass filament woven in a pattern similar to a coarse cloth. The woven roving reinforcement and chopped mat are put in alternate layers, with the final layer being chopped mat.

Spray Up

This is very similar to hand lay-up, and is also included in the general category of “contact molded” fabrication. Spray up is simply an automated way of depositing the chopped glass. Fabrication still starts with the 10 mils of surfacing vein glass in a continuous fiber form, similar to a thin rope. It is pulled through a gun head that chops it into short lengths and sprays it toward the mold. At the same time, catalyst and resin are sprayed through the gun head. Thus, the catalyst, resin and glass are all deposited at one time. The resulting spray lay-up is rolled to obtain good wet-out of the glass and to remove any entrained or entrapped air. Savings come from a reduction of labor and the use of a lower cost form of glass reinforcement. For heavier laminates, woven roving is still used between alternate layers of chopped glass laminate.

Filament Winding

In this fabrication method, which is primarily applicable to round or cylindrical parts continuous glass fiber, again in the form of a very thin rope, are pulled through a bath of catalyzed resin. In the bath, the glass fibers are thoroughly wetted and the excess resin removed. The resin-impregnated fibers are then wrapped around a rotating mandrel. Typically, this is mounted in a winding machine resembling a lathe. The glass fibers traverse the length of the rotating mandrel, laying the fibers in a predetermined pattern. Typical products that are produced by filament winding include frp pipe of various sizes and large diameter tanks. Depending upon the application, fabrication of the part will start with a number of layers of high-resin-content “C-glass” surfacing mat (usually 20 to 60 mils total), followed by approximately 100 mils of the randomly dispersed chopped fibers, and then followed by the filament winding.

Are There Other Fabrication Options?

Yes, in addition to hand lay-up, spray up, and filament winding there are three other fabrication options; pultrusion, press molding, and centrifugal casting. To learn more about these fiberglass reinforced plastic fabrication techniques, please download our free brochure, “Fiberglass Reinforced Plastics for Corrosion Resistance.”

Smoke Resistance? Fiberglass Reinforced Plastic is Smokin’

fiberglass reinforced plasticsBut seriously, during a fire fiberglass reinforced plastic does create smoke.  As we mentioned in a previous blog post, new regulations and code requirements regulating smoke toxicity have made smoke an important consideration, for some.

Why Is Smoke A Concern?

Personnel safety is the main reason why smoke is a concern in service environments. Smoke can present a personnel safety hazard for two reasons:

1. Heavy dense smoke cannot only make breathing difficult, but can obscure the escape paths when people are trying to escape from a building during a fire.

2. Smoke toxicity, especially from organic materials, is also a critical safety consideration. Even if the smoke is very light, but is highly toxic, personal injuries can occur.

Smoke toxicity is one of the reasons the New York City and New York State Fire Marshals have now added to their code requirement consideration for low smoke toxicity.

Is Smoke An Important Building Factor?

Whether smoke is an important factor in your construction is really dependent on your unique requirements. However, rather than deciding to spend a lot of time and energy trying to develop low smoke alternative, you really should try to determine if low smoke is really important in your service environment. If your tank, piping, or duct application is mostly outdoors in an industrial location, then perhaps smoke is of only minor importance. In cases where this is the case, if you are going to have a major plant fire, the smoke generated probably is the least of anyone’s worries. Likewise, in many service installations where there is low “people occupancy”, such as water and waste treatment facilities, composting facilities, warehousing buildings, etc., then again, low smoke is perhaps only of secondary importance.

Deciding whether fire retardancy (low flame spread), smoke generation, or smoke toxicity are even important or necessary for your application should be your first step in determining if smoke is an important building factor. These features are going to cost you extra money. If they are not required, do not specify them. Well over 90% of all FRP composite pipe and duct installed to date is not fire retardant and does not provide low smoke generation and low smoke toxicity properties.

When choosing and specifying the materials for your system, consider the cost of the materials, installation and, most importantly, long-term operating costs. Installation of a Factory Mutual approved system may provide lower insurance rates. However, such a system may also cost more in materials and labor, and may require replacement or repairs in half the time when compared to a properly constructed dual laminate system.

If smoke generation, smoke toxicity and smoke resistance are important to your project, then we recommend that you select the internal barrier/liner of your duct or pipe based upon the best resin matrix for your service environment.

What is FRP?

fiberglass reinforced plasticFiberglass reinforced plastic is not only versatile, but also offers a wide range of practical and environmental benefits. The ins and outs of FRP have given rise to a lot of questions over the years, so we’ve put together a short series of blog posts to cover some of the basics of FRP. Starting with…

What is FRP?

The term FRP, which is common throughout the industry, refers to plastic that has been reinforced with glass fibers. Fiberglass reinforced plastics (FRP) are used for many varied applications; from boats and bathtubs to missiles. However, examples of equipment currently fabricated out of fiberglass-reinforced plastics include FRP tanks and vesselsFRP pipe, FRP ductwork hoods, fans, scrubbers, stacks, grating, and specialty fabrications. One of the fastest growing areas is the use of FRP for pollution-control equipment.

What Can Be Used to Reinforce the Plastic?

Many reinforcements can be used for plastic materials-including polyester fibers, carbon fibers and, of course, glass fibers. For corrosion-resistant equipment, approximately 95% of the applications normally involve the use of glass fibers (with some polyester fibers being used on certain specific occasions.).

What Resins Are Typically Used?

Glass fibers can be added to virtually all of the thermosplastic and thermoset resins, For corrosion resistant equipment, the resins used are primarily those of the thermosetting type. These are resins that, once they have “hardened,” remain in their cured configuration when subjected to heat-up to their distortion temperature or the temperature at which they will degrade. Examples of thermoset resins include the epoxies, polyesters, vinyl-esters, and furan. There are other thermo- setting materials, but these four are used in the vast majority of applications for fiber-glass reinforced plastics. The term “polyester” is a generic one that refers to a wide range of materials. It can include everything from a general-purpose resin used in boats and bathtubs to the most exotic, high-temperature corrosion resins. For corrosion-resistant equipment, specialized corrosion-resistant-grade resins are available.

A number of companies manufacture isophthalic polyester resins, which have a distinct place in the hierarchy of corrosion-resistant materials. Very frequently, to reduce costs, a customer will have equipment built with one of the premium-grade resins used for the corrosion inner liner, the balance of the structural laminate being built with an isophthalic polyester resin.

One type of corrosion-resistant resin in use is the vinylester resin. The vinyl-esters are similar in corrosion resistance to the bisphenol A polyester resins, but for many applications, possess improved physical properties, especially impact and toughness.

The original vinyl-ester resin from Dow was known as Derakane 411. This is a very good resin up to 180°F, but the physical properties fall off very rapidly past that point.

Several years ago, Dow introduced Derakane 470 resin, with improved high-temperature properties and improved solvent resistance. Another addition from Dow has been Derakane 510, a fire-retardant vinyl-ester resin. This resin achieves its fire-retardancy without use of such materials as antimony trioxide.

FRP Fire Resistance: Fiberglass Reinforced Plastic and Fires

No one wants to have a fire in their building or business, but what if you do? How will materials made from fiberglass reinforced plastic react? What about FRP fire resistance? With new regulations and code requirements regulating smoke toxicity, like those in New York City, the amount of smoke created in a fire is also something a lot of builders are keeping in mind these days. So,

What Do You Need to Know About FRP and Fires?

While the fiberglass reinforcements used in corrosion resistant laminates will not burn, most thermoset resins used as the matrix for “FRP” laminates will support combustion. Even the “fire retardant” resins will burn vigorously when fire is supported by an outside source. The rate of flame spread is somewhat lower for these fire retardant resins. Fire retardant thermoset resins typically contain halogens or bromine molecules. When combustion occurs, these additives suppress or smother the flame and the laminate becomes self-extinguishing.

What About Smoke?                                                                               

When the more common thermoset resins (polyesters, epoxies, vinyl esters, etc.) used for fiberglass reinforced plastic composites burn, large amounts of heavy, black, dense smoke can be generated. The carbon chains in these resins contribute to that smoke. There is no difference in the density of the smoke generated between a non-fire retardant resin and a fire retardant resin. The only difference is that the amount of smoke may be less when fire retardant resins are used, and the fire is not supported by an external source.

Although some facilities can experience more damage from the smoke rather than the actual fire, such as in electronics plants, for most facilities the fire itself, and the damage it can cause, is of far greater concern than smoke. As one plant engineer of a major chemical plant told us one time, “When we have a fire in a chemical plant, we are allowed to have smoke.” In those cases of typically wide-open spaces, or facilities with low occupancy, the smoke generated is the least of the problems when a chemical plant or refinery catches on fire.

How Much Smoke Will Be Generated?

ASTM E-84 test results for polyesters, vinyl esters, and epoxies typically yield smoke generation values in excess of “750”. It can be said unequivocally that if FRP composite pipe and FRP ductwork is exposed to a “raging fire”, there will be a lot of smoke generated. The ASTM test can only provide a hint of how much smoke.

Inquiries to all of the major manufacturers of resin systems used for corrosion resistant applications have solicited written responses that they have no, and know of no, polyester and vinyl ester thermoset resin systems that will generate, by themselves, smoke generation values under 350. If you are going to be specifying flame spread and smoke generation levels, we recommend that you consult with either a knowledgeable fabricator, or one of the resin manufacturers.

If you want to learn more about fiberglass reinforced plastic and smoke, please download our “Smoke and Fiberglass Reinforced Plastic Components.”