What is FRP?
FRP stands for fiberglass-reinforced plastics. The material that makes sense when protecting against corrosion. Since the introduction of other fiber reinforcement, FRP is also used to mean fiber reinforced plastics.
Other terms that are used interchangeably with FRP
All of the above mentioned terms should not be confused with reinforced thermoplastic which is entirely different. There is a wide selection of thermoset resins available for most corrosion resistant applications. Unlike thermoplastics, thermoset plastics have a highly crosslinked molecular structure. The result is a flexural, tensile strength, and temperature performance that is twice that of most thermoplastics.
Below, are tables listing the chemical resistance of polypropylene, PVC, vinyl ester FRP (Hetron-922, FR992, 980) and polyester FRP (Hetron197, 197P)
There are several ways to fabricate FRP equipment, the following explains some of the most common methods.
A process where each layer of the laminate is individually fabricated one at a time on a contact mold. Allows precise control of the glass content and ensures that the glass is thoroughly wetted out with resin. This fabrication method is the most labor intensive.
Similar to hand lay-up but glass and resin is sprayed on to the mold. Less labor intensive than hand lay-up but poor control of laminate thickness and quality due to air bubbles.
Resin Transfer Molding
Process where a closed mold is filled with glass and then injected with resin under pressure. The system is allowed to cure and then the mold is opened to remove the part.
It can actually match corrosion resistant properties of FRP, however, the industry wide data tables reflecting corrosion resistance for coatings are based on applying the product to steel without any compromise whatsoever. So much as a pin hole will cause corrosion attach and could cause eventual destruction to the coated metal products. Exhaust fans, laboratory stacks and fume hoods are very complex geometrical structures that are very difficult to coat as thoroughly as needed to guarantee against rust. We have all been to job sites and seen coated steel equipment rusting even before it is installed. Reputable manufactures may argue that they do coat every single micrometer of surface, however, once the equipment is loaded for shipping, installation is completely out of their control, and bumps and scraps will result in failure. Coating thickness can range between 1.5 – 12 mils and sometimes even thicker. Plasticair’s final FRP corrosion barrier coat is 90 mils thickness standard. Also, the important thing to note when comparing is that, the resin used in the FRP corrosion barrier is used throughout the entire composite, therefore, the integrity is far greater and more dependable than steel coated products as the FRP will not separate or fail when exposed to surface scratches.
FRP fans are coming more in line with steel coated fans as the Plastic fan industry evolves, develops, and matures. Plasticair has fans currently operating dating back to 1980 in conditions that we predict steel coated fans would not last even 2 years. Engineers and Owners should also consider that FRP may be more of an economical solution over the long term when considering equipment for mild, medium, and heavy corrosive applications as replacement parts, labor and down-time will be minimized with an FRP selection.
For heavy industrial high static applications, engineers may turn to exotic alloys which can be two, three or four times more expensive than FRP. Plasticair is well able to provide fans in solid FRP up to 60” W.G. (14,890 Pa) and up to 250F. Again, something to consider that benefits your Clients budget goals.
Brand of resin used is crucial. A simple statement that the product is FRP does not ensure that the application is correct.
There are many types of resins on the market.
For example, resin used for an FRP canoe would most likely be a general purpose / isophthalic resin and that would be suitable for that application. However, an FRP fan exposed to HF, HCl, and H2SO4 constructed of general purpose resin would not be suitable and would most likely fail.
Also, you may find in the industry that FRP is applied to thermoplastics such as PVC.
Separation can occur and PVC has half the tensile strength as most premium quality FRP resins.
How do I avoid these things?
When writing a specification, use the language “throughout” when describing the brand of resin you want. Also, some companies may subcontract fan parts outside of North America and quality control may be an issue. If not graphite lined, specifications can specify “fan wheel to be constructed of clear resin only, no pigment allowed”.
This allows an onsite check for imperfections in the glass work and also it allows a qualified FRP quality control person to assess the color of the resin and determine if the specified resin was used, if an off color is detected, a very inexpensive full lab analysis can conclude whether or not the specified resin was used