As society has developed, the pultrusion profile industry has begun to gain prominence due to the expansion of the use of pultrusion profile process products in areas such as construction and infrastructure. This article will take you through the history of the pultrusion profile process.

1. What is the pultrusion profile process?

In short, the pultrusion profile process is a manufacturing process that creates fiber-reinforced polymers with a continuous cross-section. In everyday terms, it's a way to make things like fiberglass rods that would look the same if you cut a piece anywhere along their length.

The name sounds like a combination of "pulling" and "extruding". You may know that extrusion is the process of pushing material into a die to form a consistent cross-section. In contrast, the pultrusion profile process pulls fiber bundles through a device that binds them to some type of polymer (or plastic). Its main advantage is that it creates a consistent fiber reinforced material in an efficient manner.

2. The right environment for innovation.

If you study history, you will notice that when some important innovations are developed, it is often the case that many people are working on the same problem at the same time. You might say that the time is ripe for invention. This was certainly the case when the pultrusion profile process was developed. Several recent key advances in manufacturing have paved the way.

In the 1930s, employees at Owens-Illinois in Toledo, Ohio, developed new technology to produce large quantities of fiberglass on the cheap. It was immediately realized that one of the applications for inexpensive glass fibers might be to reinforce some kind of composite material.

At about the same time, an important innovation in polymers occurred. The American Cyanamid Company made a polyester resin that could be cured at room temperature using hardener additives. During World War II, combining these two inventions, people began experimenting with glass fibers to create a composite material consisting of a glass fiber reinforced polymer matrix.

As a result, manufacturers began making pultrusion profiles. Although they were already very useful in some applications, there were some limitations that would soon spur further development.

3. Problems to be overcome.

One of the earliest uses of pultrusion profiles was to make hulls for ships. Applications such as this involved the fabrication of custom, non-continuous shapes, using a technique where the fiberglass material (usually in a mat) was placed on a mold and then coated with resin. This has worked very well for such applications and is still widely used.

But there are other uses for pultrusion profiles, and this technique has serious drawbacks. First, if you want to create small components on a large scale, the molding technique described above is too time consuming. For example, imagine making a fishing rod in this manner. Each different size rod would require its own mold, and each rod would have to be laid by hand.

Another problem has to do with the fibers embedded in the FRP. Rod fabrication requires a mold that can completely surround the assembly to harden the complete cylindrical shape. But it is difficult to get all the fibers to align in the desired way and then hold them while encapsulating in the mold. This means that the full potential of the fiber reinforcement effect cannot be realized.

Therefore, some kind of manufacturing process was needed that would allow manufacturers to mass produce pultrusion profiles of continuous shapes (such as rods) with precisely aligned fibers.

4. The birth of the pultrusion profile process.

As we have already mentioned, the development of pultrusion molding involved many different people, each of whom contributed to the creation of the process we use today.

The first important step was the idea of impregnating fiber chains with resin in a continuous process. in 1944, J.H. Watson, an Englishman, applied for a patent on this process. According to the patent, his invention was a method for "making rope or the like. It describes infusing paper twine with a thermosetting resin and then drawing it through a heated mold to cure the resin. He lists the benefits of the resulting twine as greater strength, good flexibility, and resistance to moisture, insects and mildew.

Although Watson's mind was not on FRPs such as fiberglass, the constant drawing of fibers through equipment that coats them in resin and then hardens them is the heart of pultrusion molding.

In 1950, Melvin Meek applied for a patent for a "method of making glass rods. He noted that the current method required the creation of dies specifically for each size of bar, and stated that his method allowed for the continuous manufacture of any desired size of bar. His process is very similar to Watson's, although he has also developed a method to precisely align many individual fiber bundles while maintaining them at optimum tension throughout the process.

At this point, the shape of the pultrusion profile process is cured one section at a time in a heated die. As a result, the length of the finished product is limited to the length of the mold, as material inconsistencies are introduced at the end of each cured section. Roger White partially solved this problem in 1952 by making some adjustments to the standard process.

However, in the following year, William Goldsworthy patented newer techniques that finally got us into the process we are still largely using. His most important innovation was the development of a continuous curing system that kept the material moving so that the entire process proceeded smoothly and continuously. The result is a finished pultrusion profile with a consistent cross-section and desired length.

5. Continuous innovation.

Although the basic elements of the modern pultrusion molding process are associated with Goldsworthy's contributions, innovation certainly has not stopped. New fibers, new resins and new technologies are continually being created, allowing for the manufacture of more types of FRP for specific applications.

This is the history of the development of the pultrusion profile process. If you need more detailed information, please feel free to contact us!