What Are The Different Types Of Fiberglass? -

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A: At DEFI structural fiberglass, we use three methods of fiberglass&#;pultrusion, open-molded, and hand layup. Pultrusion is something you would typically see in a fiberglass channel, beam, or even square tube that we use in handrails and ladders.

Open molded typically refers to the fiberglass grating&#;open molded grating.

The hand layup is when we would use a hand layup mold to make a special product or shape.

If you found us by searching Google for &#;fiberglass reinforced plastic,&#; you probably got a lot of extra results you didn&#;t expect. You might have seen several different terms that include fiberglass and the abbreviated form, &#;FRP.&#;

It can be quite confusing, especially when you learn that not all fibers in FRP are&#;glass. That&#;s right, FRP is a broad term for any plastic that is reinforced with some type of fibers. In the US you hear FRP the most and it refers to what we specialize in&#;specifically structural fiberglass. To know what structural FRP is though, you need to know what&#;s at its core&#;fiberglass.

What Is Fiberglass?

Fiberglass is created by spinning melted glass in such a way that it creates fiber strands of glass. It almost looks like the consistency of cotton candy. In and of itself these fibers can be a usable product, but more often than not, fiberglass is used in a composite like FRP.

A composite is a combination of materials that when combined, creates a new substrate.  The composite is often comprised of a matrix or base material and reinforcement material.  The matrix can be metal, plastic, or even ceramic. Fiberglass, in this case, is the reinforcement material that makes the composite stronger than the parts on their own.

What Is FRP?

FRP is an abbreviation for fiber-reinforced plastic or polymer in some circles. Not to get too scientific, a polymer is a chemical compound with a long chain-like structure of molecules.  Some polymers are natural like rubber, others are synthetic such as polypropylene.  Pliable synthetic polymers such as polypropylene are called thermoplastics while more rigid ones such as polystyrene are called thermosets. That FRP is the raw material that is manipulated to form the various profiles we create for structural building, hence it&#;s called&#;structural fiberglass.

What Is Structural Fiberglass?

Structural Fiberglass are building components manufactured using standard fiberglass profiles such as angles, tubes, I-beams, and other shapes.

Most of our products are made using three different fabrication methods depending on the end-use. As Arthur mentioned in the video, we use pultrusion, open mold process, and hand layup.

Each process has its unique applications. Most of our top-selling FRP products from DEFI are fabricated using the pultrusion method. Due to the nature of the pultrusion process, this method gives several advantages over other methods such as increased strength, higher corrosion resistance, and better impact resistance.

What Is Pultrusion?

Pultrusion is a technique for creating continuous structural fiberglass shapes but without distorting the cross-sections. This process involves pulling the three laminates mentioned before through a heated die that forms it to specs. The fiberglass reinforcement material is usually in continuous form&#;hollow spools, roving, or filament mats.

The resin liquid mix that is used to bind the fibers is cured within a catalytic reaction that is caused by the heat from the die. The resin then becomes rigid and takes on the shape of the die&#;s cavity.

The pultrusion process is used in a wide range of industries for many different applications. This is because they can duplicate the strong properties of traditional materials while correcting the weak properties.

For example, pultruded structural fiberglass grating duplicates the strength of steel grating but is corrosion-resistant, unlike steel. While there are several variations of the pultrusion method such as reciprocating pullers or caterpillar pullers&#;the concept is the same.

Hand Layup & Open Mold Process

Open molding is one of the oldest processes for creating FRP products. There are no technical skills or complex machines needed. It&#;s ideal for low-volume, labor-intensive, larger products such as vessels, tanks, car bodies, and oil pipelines.

The mold contains the structural shape that is needed therefore careful order of steps must be taken. For example, to have the final product shiny or have texture, the surface finish of the mold needs to reflect that specification.

If the external surface of the product needs to be smooth, you use a female mold to fabricate the product. In the same manner, if the inside specification is smooth, then you pour on the male mold. Either way, molds must be pristine or the finished product will reflect any defects in the mold itself.

Unlike pultrusion, since the resin is viscous and is being poured into the mold, it needs to have a releasing agent. Without a releasing agent, the product may not come free from the mold, rendering it unusable. Using a thin coating of wax, polyvinyl alcohol, or mylar film allows for a smooth release of the finished product after curing.

Hand layup is an open mold process and as the name suggests, this process is all done by hand. The quality is heavily dependent on the skill of the person crafting it. A good example of hand layup process products are safety helmets and custom shapes.

The Advantages of Pultruded Structural Fiberglass

There&#;s a reason that our number one seller is pultruded fiberglass products. The combination of the raw materials used and the pultrusion process give structural FRP benefits steel just can&#;t match:

• Extreme corrosion resistance
• Superior Strength to Weight Ratio
• Non-Slip attributes can be baked right in
• Non-Conductive
• Easy installation with basic tools
• Extreme heat resistance

In addition to those benefits, there are inherent advantages that can&#;t be duplicated with any other material other than fiberglass.

Durability

There are quite a few applications in manufacturing plants that have chemical corrosives or are exposed to harsh outdoor environments. Structures constructed from FRP easily withstand the day-to-day abuse of these environments with no damage. Steel, on the other hand, can rust, flake, and in some neglected situations&#;break, causing serious injury. You never have to worry about FRP&#;s structural integrity being compromised in these environments.

Long Term Value

Another reason why using structural FRP is such an advantage for many applications comes down to pure economics. The manufacturing process of pultrusion produces the highest output volume at the lowest conversion cost.

FRP is much lighter, cheaper to ship, and requires no maintenance. Of course, the installation of steel often needs cranes and special heavy lifting equipment. FRP can be moved with a forklift or even carried by hand.

Safety

The safety of steel can be compromised by so many different hazards. Electrical, corrosives, the elements. Safety is crucial in both the workplace infrastructure and public-use structures. At DEFI we produce FRP handrails in various designs that exceed OSHA requirements.

For more fiberglass floor gratinginformation, please contact us. We will provide professional answers.

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Special resin combinations can be used to offer traits such as heat and fire resistance in our vinyl ester and polyester handrails. We can also &#;bake in&#; any color including safety yellow and even UV barrier coatings for world-class UV resistance.

If You Can Design It&#;DEFI Can Make It

Our fiberglass products are as customized or as universal as your application requires. We have common profiles and structures in stock and also a full custom shop for your unique projects.

Contact us today and let&#;s build it better together.

Whether it&#;s pultruded or molded, fiberglass-reinforced plastic (FRP) grating offers a strong yet lightweight solution perfect for commercial and industrial applications like floor systems, walkways, work platforms, stairs, ramps, trench covers and catwalks. More durable than steel bar grating, FRP grating features include corrosion, moisture and fire resistance, nonconductive and thermal insulating properties, and dimensional stability. FRP grating is much lighter than steel grating, making it easier to install and remove when access is needed below it. And because of its exceptional durability, FRP grating is extremely low maintenance &#; keeping operational costs for ongoing upkeep minimal.

But besides all these commonalities, there are some key differences between molded and pultruded grating.

Molded FRP Grating

Molded grating typically has a square mesh pattern, but it can also be cast in a rectangular mesh configuration. Molded FRP grating panels are also cast in one piece &#; meaning that there is no mechanical joint between bearing bars. This gives the grating exceptional bi-directional strength, aiding in its ability to offer a substantial load capacity. In addition, the surface of the grating can either come with a meniscus &#; or concave &#; surface or with a quartz grit slip-resistant surface for added safety. A covered grating surface is also an option for preventing objects and substances from falling to lower levels and for creating an odor barrier.

The Molding Process

When molded grating is created, layers of liquid resin and continuous fiberglass rovings are laid one after the other in a mold until the desired thickness and panel dimensions have been achieved. Once this is done, the mold is set aside to cure. When the curing process is complete, the panel is removed from the mold.

Bedford&#;s stringent quality control processes ensure that each piece of molded grating will provide superior durability. Additionally, the high resin-to-glass ratio (approximately 65% resin to 35% glass by weight) provides excellent service life, even in the most demanding applications.

Pultruded FRP Grating

Where molded grating is a single panel of resin and fiberglass layers, pultruded grating is composed of a series of parallel bearing bars &#; with either a T- or I-shaped profile &#; kept in place by several perpendicular cross-rods. The closer the bars are placed together, the stronger the pultruded grating panel is.

Besides being unidirectional in strength, pultruded grating can support heavier loads and longer spans than comparably sized molded grating &#; making it ideal for more demanding applications. This is because the continuous glass rovings in pultruded grating helps resist tension, compression and bending while providing longitudinal strength. The continuous glass mat also increases the grating&#;s transverse strength and resistance to impact.

How Pultruded Grating Is Made

From the pultrusion process to assembly, pultruded grating goes through a series of manufacturing steps before it reaches its final form.

Step 1: Reinforcement
The pultrusion process typically starts by pulling in two forms of fiberglass reinforcement. Creels of fiberglass roving provide unidirectional strength along the length of the profile while rolls of woven fiberglass mat provide multidirectional reinforcement. All reinforcements are fed through preforming guides that will begin to shape the raw glass fibers into the final bearing bar profile for the grating.

Step 2: Impregnation and Resin Bath
The fiberglass reinforcements are pulled through a bath of thermoset resin mix &#; typically polyester or vinylester &#; blended with pigments to add color, fillers and additives to enhance properties, and catalysts to aid in curing. The resin mix will soak and permeate the glass reinforcements, which is called impregnation or &#;wet out.&#; The resin will help in holding the glass reinforcement together and transferring the load between fibers. It also plays an important role in protecting the final product from corrosion and UV rays.

Step 3: Surface Veil
Just before all the fiberglass material is pulled into the heated die, a lightweight polyester fabric &#; also called a surface veil &#; is added. The surface veil helps provide a smooth, more durable resin-rich surface in the final product &#; enhancing the product&#;s environmental and chemical resistance. The surface veil does not, however, provide additional structural strength.

Step 4: Curing and Cutting
After the surface veil is added, wet-out reinforcements are pulled through the heated pultrusion die, which begins the thermosetting process &#; causing the resin to &#;cure&#; or harden. By the time the material exits the die, a solid bearing bar with a rigid T- or I-shaped profile will have been formed with all the reinforcements laminated inside. The cured bearing bar is then pulled to the cut-off saw and cut to the appropriate length.

Step 5: Assembly
Holes are drilled every six inches along the length of the bearing bars. The cross-rods are then inserted through the holes &#; perpendicular to the bearing bars &#; and secured with epoxy. Together, the bearing bars and cross-rods make up the grating panels.

The Key Differences

The biggest differences between molded and pultruded grating stem from the differing manufacturing process. The molding process allows molded grating to be produced in single, made-to-size panels with exceptional bi-directional strength. The pultrusion process, on the other hand, reduces potential errors in production &#; creating a consistent, high-strength FRP grating product. Pultruded grating can also support heavier loads and longer spans than comparably sized molded grating &#; despite being unidirectional in strength.

Additionally, while pultruded grating is the stronger and stiffer option, molded grating provides more flexibility, corrosion resistance and impact resistance. Watch the video for a more comprehensive comparison of these two types of grating.

Regardless of their key differences, both types of FRP grating feature exceptional durability and strength as opposed to more traditional building materials like steel. And when choosing between molded and pultruded grating, the main thing to consider is the type of application.

Looking for more information about Bedford&#;s molded and pultruded grating products? Contact us or browse the available resources below.

Learn more about our FRP Grating Products

FRP Grating Resources
Download the FRP grating catalog, data sheets and other technical documents from our Resources page.

Stair Treads and Stair Tread Covers
Bedford offers a variety of molded and pultruded grating stair tread panels that are easy to cut and quick to install.

FRP Grating Clips
Bedford offers several types of stainless steel and FRP fasteners to secure our molded and pultruded grating products in place.

FRP Grating Pedestals
For applications requiring an elevated grating floor system, Bedford offers a variety of adjustable and fixed pedestals.

FAQs

What is molded grating?
Molded grating typically features a square or rectangular mesh pattern. Molded FRP grating panels are also cast in one piece without a mechanical joint between bearing bars &#; giving the grating exceptional bi-directional strength.

What is pultruded grating?
Pultruded grating is composed of a series of parallel bearing bars &#; with either a T- or I-shaped profile &#; kept in place by several perpendicular cross-rods. The closer the bars are placed together, the more unidirectional strength the pultruded grating panel provides.

What's the difference between molded and pultruded grating? 
The biggest difference between molded and pultruded grating is in the manufacturing process. The molding process allows molded grating to be produced in single, made-to-size panels with exceptional bi-directional strength. The pultrusion process creates a consistent, high-strength FRP grating product that can also support heavier loads and longer spans than comparably sized molded grating.

Contact us to discuss your requirements of heavy duty fiberglass grating. Our experienced sales team can help you identify the options that best suit your needs.