How FRP Is Made

FRP In The World

You can find FRP products in just about any industry and in many different applications. For example, when you visit a waterpark you will notice many of the attractions and the stairways leading to them are made from FRP. If you have ever toured a brewery, you will notice the scaffolding and catwalks typically are made of FRP as well. Fiberglass is everywhere and for good reason—it is the most versatile and durable material available for structures and many other applications such as wall coverings and flooring. To understand how FRP is made first you must understand the material itself.

What Is FRP?

FRP is a composite made up of thermosettings (resins) and fiberglass, which is very thin fibers of glass, hence the name. These glass fibers and the various resins it is combined with is what makes up the base ingredients of FRP products. 

The resins are what contribute the various environmental and chemical resistance qualities and act as the binder for the glass fibers within the structural layer. DEFI products generally are comprised of three layers also referred to as laminates.

  • Chemical Barrier Layer (CBL): This layer provides chemical resistance that gives FRP products their anti-corrosive characteristic
  • Structural Layer: For temperature resistance and structural integrity
  • Topcoat (Surface Veil): Environmental and temperature resistance

As you can see, the emphasis in the composite is on structural strength and durability in any environment. When you get to know how FRP is made, it makes a very compelling case for the widespread use in many different industries due to the advantages it offers.

What is Pultrusion?

Pultrusion is a fabrication process that produces continuous lengths of polymer structural shapes that contain consistent cross-sections for increased strength. As the name implies a machine “pulls” the raw materials through a linear process using a continual pulling mechanism. In this case, the raw materials are the resin mixture in liquid form (resin, filler, and application-specific additives) and the glass fibers which provide the reinforcement. The fiberglass is in continuous forms—rolls of fiberglass mat and spools of fiberglass filaments similar to fine strands.

The Process Basics

Step 1

Reinforcement materials are pulled through the line and saturated in a resin bath until completely saturated.

Step 2

A surfacing veil (topcoat) is added according to the specifications of the project.

Step 3

The composite is then pulled through a pre-former which prepares it for the heated steel die. 

Step 4

The hardened shape is then pulled on through the final stage which is the cut-off saw.

The Role Of The Materials

As DEFI fiberglass products are made for many different applications and environments, there are several types of materials that can be used to create the final product to meet various specifications.


Resins are what provide the environmental and chemical resistance to the finished product and are the binding agent of the glass fibers. At DEFI we apply different variations of resins depending on the environment the products will be used in, and the traits set forth by the client such as:
  • Chemical/Corrosive Resistance
  • Environmental Temperature Resistance
  • Heat Distortion Temperature (HDT)
  • Flame Retardancy

When choosing the resins to use for a particular fabrication there are three main classifications used in FRP fabrication.

Polyester Resins

Polyester Resins are the most commonly used in the FRP industry. Polyester is a viscous liquid resin combining polyester and a monomer solution, typically styrene. These resins are so popular because they are easy to use, cure fast and are tolerant of extreme temperatures and catalysts. Within the category of polyester resin, there are two different kinds, Orthophthalic, generally the most oft-used variation, and Isophthalic—the most preferred in industries such as off-shore drilling due to its superior water resistance.

Epoxy Resins

Epoxy is used most often in DEFI products fabricated with the highest level of strength. Aside from increased strength, epoxies outperform other resins in terms of stability and bonding with other materials. Epoxy is by far the most advanced resin at this time and requires the utmost accuracy in measurements and handling. One notable way it differs from polyester is that while both cure quick and easy—epoxy cures with a hardening agent instead of heat, therefore it can cure in temperatures ranging from 5°C to 150°C.

Vinyl Ester Resin

Vinyl Ester Resin characteristically, is a hybrid of sorts as it’s handling characteristics and properties falls in between polyester and epoxy resins. Also referred to as “Vinylester,” this resin is created by esterification of epoxy using a specific acid. This process created a resin that is superior to polyester and epoxy in terms of corrosion resistance and thermal stability.


Fiberglass is used to bolster the mechanical strength, impact resistance, and to maintain a fixed shape of the finished product. Fiberglass comes in a wide variety of shapes as well as types of glass. Our DEFI team selects the proper combination based on upon intended use and ISO standards the final product must meet or exceed.