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What Is GRP?

Here at Evergrip, we have specialised in GRP composite products since the company’s formation in 2001. We think it is important that our customers understand not only what GRP material is, but also how it works and why. Therefore, we have compiled this in-depth guide in order to help you get to grips what GRP material is composed of, how it is manufactured and the vast array of applications that this extremely versatile product has.

What is GRP Material?

GRP is an acronym for Glass Reinforced Plastic or Glass Reinforced Polymer. It is also often referred to as fibreglass (fiberglass in the US) or glass fibre composite and belongs to a family of products known as FRP or Fibre Reinforced Plastics.

GRP has many desirable properties which include:


These properties and many more, make for a highly versatile material with multifaceted applications, which can offer significant advantages over other materials like concrete, steel, other metals and non-reinforced thermoplastics e.g. nylon, polypropylene, ABS.

So what does FRP mean?

FRP is short for Fibre Reinforced Plastic or Fibre Reinforced Polymer. These are a group of what are known as ‘composite’ products.  Composites are formed from a combination of a minimum of two different material types, chosen for their complementary physical and chemical properties.  You could think of them as the ‘organic equivalents’ of metal alloys.

Fibre strands are embedded in a polymer resin matrix resulting in both high compressive and tensile strengths in the finished products.  A common form of fibre used is glass fibre (forming GRP), but other fibres and resin types may also be used in combination.  These give the resultant materials differing properties and hence, suitability for given applications.  Here’s an overview.

Fibres used in composites:

Resins used in composites:

Other chemicals are also added to composites to change the appearance and further enhance certain characteristics of the final product.

Additives:


Therefore, we can see that ‘FRP’ is an umbrella term used to describe an array of composite materials rather than any single type.  The finished products can possess highly diverse properties and hence uses, within engineering and manufacturing industries, with a plethora of practical applications.

What is GRP composite made from and why do we use it?

GRP products are made from Glass fibre reinforced polymers, typically with a polyester or vinylester thermoset resin matrix. Thermoset polymers are formed by a chemical reaction, initiated by adding a catalyst, which causes an irreversible hardening of the resin.  This is coupled with reinforcement,  achieved by the incorporation of glass fibres during the production process. The fibres may be in the form of fine long strands, chopped stands or woven mats. The production techniques by which this is achieved are varied and can range from a simple manual process to one which is highly automated, utilising robotic machinery.  See below for further information on these processes.

GRP has many useful properties which make the products very well suited to building & construction environments, be they internal or external.

Here is more, to add to those listed above:

How are GRP Products manufactured?

There are various production methods for the manufacture GRP products, depending on the desired shapes, properties and intended uses for finished articles.

Just for an example, an Evergrip GRP Industrial Moulded Mesh Walkway Grating Panel is produced by what is largely a manual process, using an open mould for curing.  These panels can measure anything up to around 4.0 x 1.5m and may also range between 12 – 60mm in thickness. Here, using a comb-like tool the glass fibre strands are woven back and forth across the length and width of the steel mould which has a cellular structure, to form the ‘skeleton’ of the finished of the panel.

The catalysed resin of the desired grade and colour is then poured into the heated mould until the product has cured and hardened.  The gratings then have a coat of Aluminium Oxide grit adhered to the top surface.  The photos below show a typical example of the mould used.

Structural profiled sections, including GRP Handrail profiles, are manufactured through an automated machine process known as Pultrusion.  The photos below show a machine-process schematic, factory layout (courtesy of Fiberline Composites a/s) and typical product sections that can be made using this technique.

 

Hand Lay-up / Spray Lay-up Moulding

The Hand Lay-up process requires little in the way of tooling and is primarily used in low-volume production and bespoke made products.  Manual skills present in the operatives will determine the quality of the achieved laminate.

The glass fibre reinforcement used is a woven or chopped strand mat and may also incorporate an inner coremat sandwiched between the layers of glass for added strength.  The materials are cut to size/shape before being laid into (or onto) the surface of a waxed (the release agent) open mould.  Resin is then applied with a roller or brush to fully ‘wet’ out the glass/core laminate. This is then left to fully cure in a suitably ventilated, warm drying area for several hours or overnight.  The part can then be removed, trimmed, top-coated/painted and polished as required.

Improved surface finishes may be achieved with an initial gelcoat layer applied to the mould before the reinforcement is placed into it. The top or presented surface of the finished part is the side which is in contact with the mould.  Here’s a short video outlining the process:

The Spray Lay-up technique is a semi-automated one, requiring a different manual skill set.  It utilises more expensive equipment and can often provide a computer-controlled resin/catalyst dosing system.  A pressurised spray gun incorporating a glass fibre ‘chopper’ head unit is utilised to apply the laminate to the mould in one continuous process.  The fibre is fed from a bobbin and rapidly chopped into rovings by the tool, directly into the stream of resin being applied to the mould.  Typical applications would include manufacturing baths, storage tanks & boat hulls. The process can be seen here:


Resin Transfer Moulding

Resin transfer moulding is the process of injecting a mixed resin under pressure into a mould. This process can produce smaller parts of consistently high quality and in production volumes. There is a longer video demonstration here which explains the process in full detail:


Compression Moulding

This process consists of a preheated polymer being placed into an open mould cavity, before then being closed in by a top plug, in order for the material to contact all areas of the mould.  The process widely used in the production of parts for the automotive and transportation sectors and can incorporate epoxy resin systems. A long-established manufacturer in the United States explains the system here:


Long Fibre Injection Moulding

An advanced, highly automated process for larger precision-made parts which require all the attributes of high strength and stiffness but with light weight.  Here the system uses a polyurethane matrix and long glass fibres applied by robot into a mould, where it is compressed, cures and hardens to the desired shape.


Pultrusion

Pultrusion is also a highly mechanised industrial process used to create continuous lengths of GRP composite profiles.  These sections are often associated with structural, load-bearing applications, for example, channels or beam sections.  By means of this process, profiles have highly accurate and consistent cross-sectional dimensions and therefore predictable mechanical properties, allowing for the engineered design of structures.  Originally developed in the USA, this process has been in use for more than fifty years and the technology employed ensures high quality is reproduced in every production run.

Densely packed continuous glass fibre rovings are fed from multiple bobbins and along with reinforcements and matting, are pulled by process machinery through a bath of resin and then on through a high temperature and high-pressure mould, forming and curing the finished section shape.  Finally, the sections are automatically cut to the specified lengths.

The type and shape of these finished products are determined by the design of the mould.

Typical profiles include: Angles, Square Tube, I Beam, Channel, Round Rod, Round Tube

The finished products are light in weight yet very strong, maintenance-free and are suitable for a huge range of applications replacing traditionally used metals and woods.  They have a smooth surface and are resistant to corrosion, providing a maintenance-free, long term and cost-effective solution.

We work closely with two established manufacturers of glass fibre pultruded products. Through these relationships, Evergrip can offer the first (and so far, only) complete range of CE marked and certified fibreglass structural profiles with full European Technical Assessment (ETA) for use in construction in the United Kingdom and EEA market.  The products are manufactured by Fiberline Composites A/S of Denmark and represent the culmination of many years of research, development and investment.  Take a look at this brief video which shows pultrusion in action inside their ‘state of the art’ factory:



We hold stock in the UK of commonly used structural profiles in various sizes and thicknesses, the majority of which have enhanced fire-retardant properties to meet EN 13501 / BS 476 standards. We also welcome enquiries for new profiles to be made, where there would be a significant volume usage.  We also offer design and engineering verification services along with fabrication and on-site installation.

What can GRP be used for?

GRP products have an almost limitless array of potential applications. With engineering verification and creative design, there are uses in most markets for products made partially, or entirely from GRP materials.  Here are some uses, arranged by sector:

Construction

- Fixed and portable work platforms

- Lamp posts

- Stair towers

- Bridges

- Roof trim and roof lights

- Gutters

- Glazing systems

- Cooling tower structures

- Green house structures

- Building panel sections

- Reinforcing rods (rebar)

- Sign posts

- Signs

WHY EVERGRIP ?

Since 2001, Evergrip have been focused on applications for GRP composite materials in the fields of safe access and structural support.  With many long-serving staff, we have accrued valuable experience and knowledge in assisting clients in overcoming their problems in workplaces and public spaces, across almost all market sectors.

The wearing surfaces of all Evergrip GRP Anti-slip walkway and Grating products incorporate a coating of refined aluminium oxide aggregate, giving a near diamond-hard finish. This provides outstanding resistance to long term wear and most importantly, high levels of slip resistance, in both wet and dry conditions.

Buyer’s Tip: inferior quartz type grits available on some manufacturers’ products should be avoided, as these achieve only poor wear characteristics and hence, reduced product life and value.

We hope you have found the content of this article to be interesting and informative and we look forward to an opportunity of being of service to you.  Please feel free to browse our Products and Projects sections for more ideas and applications.

Evergrip Limited

Flaxley Road, Selby, North Yorkshire
YO8 4BG United Kingdom

PHONE: 01757 212744
EMAIL: [email protected]
FAX: 01757 212 749
Company Registered Number: 04186772
Registered for VAT Number: GB 773 5346 10

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