Coroplast and Corrugated Plastic Sheets

Corrugated plastic sheets, also known as Twinwall plastic sheets, are being explored by innovative boat builders, and ultralight odd project makers everywhere. The material offers some attractive characteristics.

I started building a Coroplast folding boat. first step is a model, then I start laying out the boat on a large sheet of HiCore.

What are Corrugated Plastic Sheets?

These are polypropylene or polypropylene copolymer plastics sheets extruded to resemble corrugated cardboard. Instead of the zig-zag pattern of the cardboard most plastic corrugated sheets have square channels. These are referred to as flutes and can run either with the length of the sheet or across the width.

Coroplast is a trade name for Corrugated plastic sheet made in many colours and thicknesses. Coroplast is a US company. In other parts of the world other trade names might be better known. Examples are Plaskolite, Corplast, Coroboard, Corruboard, Polyflute, Intepro, Correx, Twinplast, Impraboard, Alylux, Akylux, vikuprop are other tradenames. If you are looking for a local supplier Googling these alternatives might be helpful.

Corrugated plastic boards are manufactured worldwide. Coroplast is an American company, while Corflute is made in Australia and Correx is made in the UK. There are also several Asian Suppliers.

Characteristics of corrugated plastic sheets

Polypropylene is a chemically inert thermoplastic which is highly resistant to oil, solvents and corrosive chemicals. It also resists staining.

Polypropylene is sensitive to UV degradation and special additives are sometimes added to improve performance in sunlight.

The plastic sheets can be melted, heat bonded, and will burn.

Polypropylene is a light material and usually floats (some copolymers are slightly heavier.) In addition to the light weight of the actual material, Coroplast has channels which trap air allowing the panels to float. Some boat designers have suggested that by closing the ends of the channels with hot melt glue, or tape, boats made from coroplast do not require extra flotation.

Coroplast is not affected by wetting and can be used outside.

It is quite impact resistant and not subject to cracking at normal temperatures. It does become brittle at low temperatures and softens and eventually melts at high temperatures.

Because polypropylene is tough and flexible and resistant to fatigue, it can resist multiple flexing. Because of this it is often used in live hinges.

This ability to flex without breaking makes it useful for reusable applications. Experimental boat builders have also exploited this characteristic since it allows them to build a boat that can be folded up numerous times.

Polypropylene is not one material but a range of plastics with a range of characteristics depending on the crystal form and the exact composition.

My page on polypropylene rope has more information.

Because it is so resistant to wetting, and to chemical interaction, it is quite difficult to paint and glue most plastics corrugated panels. Many suppliers will subject their sheets to a Corona process which makes the surface easier to paint or glue. The same effect can be attained by quickly (and carefully) passing a torch over the surface.

Finishes, tapes and glues must be carefully tested before use. Some success has been reported using hot melt glues, construction adhesives and CA (crazy glues, Locktite, cyano acrylyde).

What are Corrugated Plastic Sheets uses?

Coroplast and other sheets have wide use as graphic signs and point of purchase display. The sheets are available in many colours and thicknesses. They can be cut, die cut, folded, heatbound and printed if suitable inks and paints are chosen. Premium extra smooth surfaces have been developed for sign making.

Many boxes and shipping containers are made from this material. Asparagus boxes are an example. Glasses are sometimes rented in corrugated plastic boxes which resist dirt and water better than cardboard.

Because the material can be repeatedly flexed, designers have use it for re-closable boxes and trendy briefcases.

Model airplane enthusiasts have used it because it resists the fuel and is quite impact resistant.

It has been used in the construction industry and has replaced Luan plywood in some applications. In hurricane country, corrugated plastic sheets help protect windows while still allowing light through. Since it does not splinter or shatter it is quite a safe material.

Guinea pig enthusiasts have embraced corrugated plastics as inner liners for cages! Coroplast is waterproof and not toxic. Here is one example of a Nice Guinea pig run.

Because it can be folded and fastened using specialized tape, boatbuilders have been exploring its use.I have a page with some fun folding boats made from coroplast

What is Available?

Corrugated plastic is available is a great number of colours and transparency. It is also available in a wide range of thicknesses from 2 to 25 mm. Composition can be modified to improve UV resistance, fire resistance, and can be produced so that it is wholly recyclable.

Most sheets used for boat building will be 48x96 sheets. It is available (rarely) larger or in smaller sheets. The direction of the flutes can be widthwise or lengthwise.

Corrugated plastic can easily be cut with an utility knife or with sheers but it is highly resistant to tearing. Although stiff enough to support a sign it is not as stiff as equivalent thickness plywood. Stiffness is a factor of the thickness of the sheet as well, some of the thicker boards are quite stiff..

Corrugated plastic is widely available from plastic goods suppliers, sign makers and many large box stores such as Home Depot sell it. Doing a Search for the various trade names will usually produce a supplier. The Coroplast website also have a dealer finding page.

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Small Print

This information is for general knowledge. Using non tested materials can be dangerous. If you build a coroplast boat (or any other project) be careful and make sure you test and use your boat in safe waters with appropriate personal flotation devices and backup help.