Glass reinforced formative ( GRP ) /glass roughage reinforced fictile ( GFRP ) products are composite materials consisting of a polymer matrix reinforced with glass fibers and can be used as a jacket or an isolate substantial on pipe, tanks, and vessels. GRP falls underneath the broader class of Fiber Reinforced Plastic and this article will discuss the virtual
benefits and challenges during installation of pre-cured GRP and wet-applied, ultraviolet ( UV ) -cured GRP .


Uncured GRP was first used in the industry for 2 independent reasons. The chemical bail at the lap created a water-tight seal ; and the fabric, when installed correctly onto a pipe, created a water-tight joint. This is highly significant in cryogenic applications. additionally, the uncured material was easy and easy to manipulate, compared to stainless steel .
While uncured GRP continues to be used for many applications—for model, in areas requiring insulating material to fit a singular shape—customers such as major vegetable oil companies are listing pre-cured GRP in their insulation specifications. The benefits of on-site customizability that make uncured GRP perfect for some applications can render it less attractive for those requiring absolute uniformity and quicker initiation. Pre-cured GRP besides may be selected for ease of removal for system inspection, scavenge, and repairs ; and because it does not present the like challenges as using wet-applied, ultraviolet ( UV ) -cured GRP in certain geographic areas, particularly in boastfully scale applications.

As a manufacturer of both products, I know each product offers its own benefits and challenges, and most jobs require the use of pre-cured material for the majority of the job and uncured rolls for the areas that have a unique form, so it is crucial to have a solid understanding of both .

The Curing Process

As noted in the name, wet-applied, UV-cured GRP needs to be cured post-application, ideally, with natural sunlight. If an area does not receive sufficient sunlight for curing—for example, the undersides of pipes or tanks—lamps need to be used. If the stick out is on an operate implant, supernumerary precautions must be taken. Each lamp can cure a maximum area of 1m² necessitate, a minimum of 30 minutes. Accounting for time required to set up and move the lamp, the actual production rate for curing equates to 0.5m² per hour per lamp. cure time is critical to understand and factor into project plan to ensure all wet-applied, UV-GRP is 100 % cured .
With pre-cured GRP, pieces are bonded in concert using the specific manufacturer ’ south adhesives. The lone areas requiring on-site bring around are end point areas, where wet-applied, UV-GRP can be used to flash onto the protrusions, or at collide points where insulation from unlike pipes may be in touch with each other .

Protection during Application

The application area for wet-applied, UV-cured GRP needs to be in full enclosed to protect against sunlight and precipitation. The nature of wet-applied, UV-cured GRP requires that it be kept out of natural sunlight until completely installed to avoid having it bring around prematurely. During application, the UV-GRP material is besides susceptible to water damage. Installers need to take care that uncured material not get moisture, as that affects the cure march, possibly resulting in the merchandise not ultimately curing or curing with decreased physical properties .
Pre-cured GRP systems do not require sheltering during application beyond that required by traditional jacketing systems or beyond what is required to protect the insulation when it is applied .

Installation Training

As with all insulation products, proper train and understand of manufacturer instructions is overriding. A manufacturer ’ randomness certificate aim program for wet-applied, UV-GRP takes at least 3 days to ensure the installer understands the critical aspects of treat, shaping, curing, and painting the product. failure to in full understand any of these points can result in a poor and potentially failed jacket application .
trail besides is recommended when using a pre-cured GRP arrangement, although the system is, by design, easier to install, as all parts are pre-fabricated. A coach seance of 4 to 6 hours will show the installer how the arrangement fits together. Using professional, trade-qualified insulation installers, along with insulation inspectors, are hush recommended to ensure the initiation is completed by rights .
As with all insulating material products and applications, any GRP facility requires diligence on the part of everyone involved, from the contractor installing it to inspectors and the general contractor who has final approval .

UV-Resistant Coating

An built-in weakness of any GRP facing arrangement is UV degradation, the procedure by which UV rays from the sun causal agent the polymer social organization of the GRP material to break down. Because the substantial is UV cured, UV inhibitors can not be used in the formulation. pigmentation can be used to help retard UV degradation, but in order to meet ISO 20340 or ASTM G154 standards, the material will need to be painted. It is authoritative that systems installed outdoors be protected from UV degradation using the manufacturer-recommended, UV-resistant coat .
The manufacturer can supply the pre-cured GRP material pre-coated with the recommended UV‑resistant coat. Some manufacturers do this as an option, while other manufacturers coat all their products as standard commit .
The UV-resistant coating will need to be applied to a wet-applied arrangement after the broad bring around phase is complete. In project plan, is significant to factor in the expense and time to accomplish this footfall, specially if scaffold is involved.


Characteristics of the different types of GRP should be considered when specifying which material to use at joints. Wet-applied, UV-GRP systems are installed using overlap joints that become polymerically bonded together once cured with UV light. In impression, they become one piece of thermosetting plastic. This ensures a fully sealed, rigid jacket organization without any tractability in the joints .
Pre-cured GRP systems have adhesive in the joints between neighboring pieces of jacket. The joints overlap by 2 ” ( 50mm ), and the adhesive fills the joint to create the waterproof seal. These elastomeric adhesives have between 300 to 500 % elongation to break. While the joints are impregnable, they are besides compromising and able to absorb child movement of the insulation system .

System Removal

When installed correctly, a wet-applied UV-GRP system can be unmanageable to open or remove. A muggy inner surface means it frequently bonds to the surface underneath prior to cure, which can cause insulation and vapor retarder damage. once removed, the GRP materials can not be reused and must be discarded .
If a pre-cured GRP organization is used, it is possible to cut the elastomeric adhesive material used in the joints. The pre-cured GRP can then be removed the same direction it was applied. Following a exhaustive cleaning to remove adhesive residue, petroleum, and dust, the fittings can be re-applied. Pre-cured GRP facing can be removed in this manner for inspection, or to repair leaks, and then re-installed without excessive extra materials costs ; although there is added parturiency cost in the careful removal and clean of the pre-cured GRP pieces .


The shape and size of wet-applied, UV-GRP parts is up to the installer, allowing for complete customization to courtship arrangement needs. While customizability is an asset for some applications, it can present aesthetic challenges for jobs where 2 or more crews are working with the material, as it is unmanageable to cut pieces on locate with 100 % consistency.
The material will however achieve the want cachet, but sizing parts slenderly differently can present a telescope effect that is visually less appealing .
When a pre-cured GRP system is utilize, the sizes are pre-determined by the manufacturer and created or cut in a factory setting, where greater accuracy is accomplishable. Sizing is done in reference with the client or using an industry-accepted insulation sizing standard such as ASTM C450-18 : Standard Practice for Fabrication of Thermal Insulating Fitting Covers for NPS Piping, and Vessel Lagging, ensuring the GRP facing will fit the insulation minimum and maximal size tolerances .


A wet-applied, UV-cured GRP system needs to be rigorously inspected from the moment it arrives on site to the final hardening. If ill installed, little action can be taken to repair it. once installed it is not possible to check that the UV-GRP has cured all the way through without doing a destructive test. The system broadly employed by manufacturers is to apply trial cure sample distribution patches across the unharmed application, which is difficult and time devour .
A manufacturer can control all aspects of fabrication, including size and cure, with pre-cured GRP, which is sold with physical lastingness and open fire performance characteristics integral. Pieces can be installed by the contractile organ and then a full system inspection can be carried out, as with a traditional metal system .

Shelf Life

Uncured UV-GRP material has a finite shelf life of about 12 months from the date of fabricate. This time period can be extended after an inspection of the corporeal by the manufacturer ; but significant amounts of UV-GRP materials have been written off by the manufacturer after the 12-month stigmatize. In contrast, pre-cured GRP materials have no ledge life limitations. They can be stored indefinitely .

Additional Considerations

Both wet-applied and pre-cured GRP systems can be applied over any type of insulation. Wet-applied UV‑cured GRP is a delicate, gluey, compromising material that will conform to the shape of the surface to which it is applied and over certain insulating material types, it can damage the insulation underneath during the cure serve, or become cracked, if proper steps are not followed. For model, when putting uncured GRP over cellular glass, one must build a skeleton social organization made with pre-cured GRP pieces to which the uncured GRP can adhere in regulate to protect the cellular glass from damage. Applying uncured GRP to fibrous insulation besides requires attention to detail. If the contractor lays on a part incorrectly and tries to remove and reposition it, a layer of hempen fabric will be removed from the insulation, frankincense affecting thickness and performance .
environmental considerations besides must be taken into account. With wet-applied UV-GRP, failure to understand how to manage the environment can result in previous cure, leading to high risk of failure ascribable to unbonded joints. It is well to have uncured material bind to uncured corporeal. hardness testers can be used to assist in this. failure to ensure the substrate is suitable, deoxyadenosine monophosphate well as cope the furrow of the fabric, can result in a less pleasing appearance of the exterior surface .
machine-made GRP uses 2 barrier films on both sides of the resin matrix, so the fabric can be manufactured in coil class. The products are made on a Sheet Molding Compound machine. Without the barrier films, there would be no means to package the material, as the resins would meld together when packaged. Understanding how to manage the barrier films is another critical component. If they are removed anterior to broad cure, even for a abruptly time, it will result in grating, whitened areas that may not be acceptable to the inspector. Often, an installer will attempt to rectify these areas using a manufacturer-supplied mousse. If the mousse is not applied and cured cursorily, dust from the job web site can adhesiveness to the wet gel and cause the sphere to look unsightly.

In terms of aesthetics, even when a wet-applied, UV-GRP system is installed by an experience insulating material contractor, there will be wrinkles where the material overlaps or as the material steps down from an overlap to the insulation surface, due to different thicknesses. With a pre-cured GRP system, a smooth complete is achieved in the manufacturer ’ randomness factory. The pre-cured GRP then provides a degree, bland finish when applied over flexible insulating material materials such as fiber- or aerogel blanket. Of course, as with all insulating material systems, the appearance of GRP jacketing systems is subject on the skill level of the installer. It is always recommended to use amply trained insulating material installers who have experience with the products and ideally have completed a manufacturer ’ s training course .
Copyright Statement
This article was published in the October 2019 exit of Insulation Outlook magazine. Copyright © 2019 National Insulation Association. All rights reserved. The contents of this web site and Insulation Outlook cartridge holder may not be reproduced in any means, in whole or in part, without the prior written permission of the publisher and NIA. Any unauthorized duplicate is strictly prohibited and would violate NIA ’ s copyright and may violate early copyright agreements that NIA has with authors and partners. Contact publisher @ to reprint or reproduce this capacity .

Leave a Reply

Your email address will not be published.