What is Correx®? Everything you could need to know

If your business uses any returnable packaging or even warehouse picking bins, you may have heard of Correx®.

But what is Correx®?

Correx® is a corrugated plastic material. It is durable, hardwearing, water resistant and available in various grades and colours. Its use is widespread for signage, floor protection, and reusable packaging. The term Correx® is a trademark of Corplex.

This guide provides detailed information about this material, including:

• Correx® specifications and properties.
• Applications for corrugated plastic.
• Alternative options.
• Sustainability of Correx® as a material.

In essence, Correx® is corrugated polypropylene plastic. In simple terms, it is produced by pouring melted plastic through a metal template or die.

During the manufacturing process, plastic – propylene-ethylene copolymer – is extruded through a die. Once extruded and allowed to cool, it forms into a long, continuous sheet.

Finally, the manufacturer cuts the sheets into the required size/shape or format.

The result is a two-ply fluted, durable, yet flexible plastic.

The standard sheet sizes for Correx® boards are 8′ x 4′ (2440mm x 1220mm) or 10′ x 5′ (3050 x 1550mm).

Correx® sheets are also available in varying thicknesses, including 3mm, 4mm and 5mm. Many suppliers also detail the material’s GSM (grams per square meter). For example, 3mm Correx® is 450gsm, 4mm is 700  gsm, and 5mm is 1050gsm.

These different weights and strengths make Correx® suitable for a wide range of different applications.

Correx® is available in a range of standard colours.

Options include white, black, red, blue, green, yellow and silver/grey. It is also possible to source clear/translucent Correx®.

Where larger volumes of material are required, for example, in the case of long-run printing or some industrial packaging applications, it is possible to specify bespoke colours.

There are also a few specialist grades of Correx® available.

Firstly, it is possible to source a flame retardant Correx®. Special additives added during manufacture prevent the material from igniting. Flame retardant Correx® is popular for floor protection and other construction industry applications.

Secondly, an ESD version of Correx® is also available. This material has carbon added during extrusion. This addition means that the material channels static across its surface. As a result, the material can be used to create a Faraday cage effect (making it useful as conductive packaging or for cleanroom applications).

Finally, a recycled Correx® is available. This material uses only recycled plastics. Whilst improving sustainability, it is only available in black.

Correx® uses an ethylene-propylene copolymer, which is resistant to impact. It exhibits a high level of impact resistance at normal operating temperatures, ranging from approximately 0°C to 85°C.

Above 85°C, the material starts to soften, increasing the impact performance while losing structural strength. The material continues to soften until approximately 140°C when the polymer begins to melt.

At temperatures below 0°C, Correx® becomes more rigid but at the same time becomes more brittle.

At -18°C, the impact strength is reduced by approximately 10%. While there are no measurements for impact performance below -18°C, other industries routinely use polypropylene copolymers at temperatures down to 30°C (e.g., for ice cream tubs).

Down to temperatures around -30°C, you can expect the structure of Correx® to remain intact so long as the product is not subjected to unreasonable treatment. You can expect Correx® boxes to perform well in an environment such as on shelves, single-stacked.

The detailed performance characteristics of Correx® are as follows:

• Softening temperature (BS2782: 102D ISO 1306) 85°C
• Crystalline melting point 160 – 175°C
• Flash ignition temperature c a 350°C
• Self ignition temperature ca 380°C
• Calorific value 11000 cal. kg
• Specific heat 0.46 cal/gm°C
• Limiting oxygen index (ASTM D 2863) 0.174 – 0.180
• Burn rate (FMVSS 302) 5.3 – 8.2 cm/min

As well as its beneficial properties, Correx® offers excellent versatility in terms of conversion options. In fact, it is possible to convert Correx® in many of the same ways as with corrugated cardboard.

Correx® is easy to convert by die cutting. This process involves using a sharp steel knife cutting form, similar to a cookie cutter. Specialist equipment compresses the corrugated sheets and cutting forme together under high pressure to create the required shape and dimensions.

Die cutting can also add creases to the material, allowing for easier assembly (i.e. if being folded to create a Correx® box or tray). Creasing is where the shape blades do not pierce through the materials’ surface but simply create an impression to aid folding.

However, it is essential to consider flute direction. The material bends easily along the flutes, but folding across the flutes is more difficult.

CAD cutting is another type of conversion process that works on corrugated plastic. A large machine moves a sharp knife across the material, following a computer program, to create the required shape.

There are several additional features you can choose to add to Correx® products.

Options include moulded plastic handles, stacking corners and edge profiles. These can be glued onto or screwed into the Correx® material.

Correx® provides a flat, smooth surface that enables high-quality printing. White material allows for an accurate representation of full-colour graphics, whilst the bold hues of the other colour options combine well with single-colour print designs.

Correx® is suited to digital printing. This process involves ink being added directly to the surface of the Correx® material (rather than being transferred from printing plates as per analogue methods).

Digital printing of Correx® allows for full colour, photographic quality imagery. As a result, the material is widely used for external signage (most commonly for estate agent signs).

It is also common to print Correx® using screen printing.

This process involves forcing ink through a mesh screen onto the surface. Making certain areas of the screen resistant to the printing ink effectively creates a stencil and blocks the ink from transferring to the substrate. This, in turn, creates the required design.

Screen printing is, however, only suitable for one or two colour designs. As such, this printing method is often used for returnable packaging applications.

Due to its properties and ease of conversion, corrugated plastic is the material of choice for many applications.

Correx® is widely used for, but not limited to, the following applications:

• Returnable packaging.
• Picking bins for warehouses.
• Point of sale stands (POS).
• Signage.
• Event shell scheme panelling.
• Floor protection for building sites.
• Specialist projects, including clean rooms, medical storage, etc.

Correx® allows for the manufacture of returnable transit packaging.

As well as proving performance approaching moulded plastic containers, it can also be used over multiple trips (i.e. as part of a returnable supply chain setup).

Arguably, its main benefit, however, is the size flexibility it offers. Whilst moulded containers are only available in a limited range of sizes, Correx® tote boxes or returnable packs can be manufactured to the exact size you require.

Custom-size returnable packaging improves protection (as parts cannot move within the outer container) and warehouse and transport efficiency.

Correx® can even be used to create internal fittings, such as divider sets and layer pads, to improve usability and protection further.

Corrugated plastic is an ideal material to manufacture warehouse picking bins.

Widely used by 3PL and eCommerce fulfilment, picking bins allow for logical ordering and storage of stock and the “picking” of customer orders.

Similarly to returnable packaging, using Correx® for your picking bins allows you to source containers the exact size you require. This approach can help maximise the available space in your warehouse.

Point of sale is a great marketing and sales opportunity, and choosing Correx® for this offers many benefits. Advantages include supporting the weight of heavier products, being reusable, easy to clean, and being suitable for outside areas (e.g. in DIY warehouses or garden centres).

And, of course, Correx® FSDU (free standing display units) and POS stands can include full-colour print to ensure accurate branding.

Correx® is also popular in several specialist applications.

The fact that it is easy to clean, does not shed fibres and can be sterilised (including EtO, gamma, and autoclave sterilisation) makes Correx® a popular choice for healthcare, medical and pharmaceutical applications.

Perhaps the most widespread use of the material, Correx® is incredibly popular for external signage (most notably estate agency signs).

Correx® is weatherproof and easily printed, meaning external signage is durable and long-lasting even when exposed to the elements.

Corrugated sheeting is popular for protecting finished products, such as walls or floors, on construction sites. This industry may also use Correx® for formwork and shuttering.

Correx® itself is a brand name of Corplex. However, several materials that are nearly identical go by different names.

Other brands and names for the material include Corvex, Corriflute, Corflute, Corriplast and Twinplast.

However, there are also several alternatives to Correx® for both material and application uses.

Bubble-board is a three-layer plastic material with an interlinking internal cellular structure. This construction means it exhibits equal rigidity in both dimensions.

However, where it differs from Correx® is the available (optional) laminates that the material offers. Options include a cloth-covered version to prevent scuffs and a foam-laminated version that adds a layer of cushioning and impact protection.

These properties make it particularly suited to creating divider sets and inserts for reusable packaging.

When considering returnable packaging and picking bins, an alternative option is moulded plastic.

Being slightly more durable and longer lasting, moulded bins and containers can also be surprisingly cost-effective.

However, they are only available in a limited range of sizes, which can hinder the efficiency of handling, transport and even storage.

Somewhat surprisingly, some heavier grades of corrugated cardboard are a suitable alternative to Correx®.

Heavy-duty double wall and triple wall grades (including Tri-Mite) offer strength approaching that of Correx®. They also offer the same size, printing and conversion flexibility. Crucially, corrugated is considerably easier to recycle and most perceive it as more environmentally friendly than plastics. Corrugated packaging is also not subject to the Plastic Packaging Tax (unlike Correx®).

However, corrugated is typically only used over a single trip (making it more costly over a long period). It also has little resistance to water, making it unsuitable for long periods exposed to the weather. It also sheds fibres, making it unsuitable for many clean room and precision engineering applications.