There are two main types of corrugated plastic. Corrugated plastic sheet usually comprises what appear to be three layers - two flat sheets with a ribbed center layer. In fact, they are really two layers, often referred to as twinwall plastic. Corrugated plastic can also mean sheets of plastic which are wave-like in profile and may be reinforced with chopped glass fiber. They are single layer and used mainly for roofing of garages and outhouses, but gardeners also use them to build sheds. Here we will focus on the twinwall version, also known as corrugated plastic board or fluted plastic board.
How Corrugated Plastic Sheets are made
The materials used include polypropylene and polyethylene, widely used and versatile thermoplastics. Polypropylene has a neutral ph and is resistant to many chemicals at normal temperatures, but can be dosed with additives to provide a variety of other resistance such as UV, anti-static and fire resistance, for example.
Polycarbonate is also used, but this is a much less versatile material, particularly in respect of its relatively poor impact resistance and brittleness, although it is stiffer. PVC and PET are also used.
In the basic manufacturing process, the sheet is extruded - that is the molten plastic is pumped (typically with a screw mechanism) through a die which provides the profile. Dies are typical 1 - 3 metres wide, delivering a product of thickness up to 25 mm. Mono- and co-extrusion techniques are used depending on the precise profile required.
Advantages and Uses
In buildings: Suppliers claim it is an ideal material for storm shutters and that it is 200 times stronger than glass, 5 times lighter than plywood. It does not require painting and maintains its color, it is translucent and does not rot.
Clear polycarbonate corrugated sheet is used for roofing sun rooms where its rigidity, light weight and insulating properties are ideal, and low impact resistance is less of an issue. It is also used for small structures such as greenhouses where its air core provides a useful insulating layer.
Humanitarian Relief: The material is ideal for temporary shelters need after flood, earthquake and other disasters. The lightweight sheets are easily transported by air. Easy to handle and fix to wooden frames their waterproof and insulating properties offer rapid shelter solutions when compared to traditional materials such as tarpaulins and corrugated steel sheets.
Packaging: Versatile, flexible and impact resistant, polypropylene board is ideal for packaging components (and agricultural produce too). It is more eco-friendly than some molded packaging which can not be recycled. It can be stapled, stitched and easily cut to shape with a hobby knife.
Signage: It is available in a wide variety of colors, is readily printed on (typically using UV printing) and can easily be fixed using a wide variety of methods - its light weight being an important factor.
Pet enclosures: It is such a versatile material that rabbit hutches and other domestic pet enclosures are built with it. Fittings such as hinges can be bolted to it; being non-absorbent and easy to clean it offers a very low maintenance finish.
Hobby Applications: Modellers are using it to build airplanes, where its light weight combined with rigidity in one dimension and flexibility at right angles provides properties ideal for wing and fuselage construction.
Medical: In emergency, a section of sheet can be rolled around a broken limb and taped into place as a splint, also providing impact protection and body heat retention.
Corrugated Plastic: the Future
The uses that this category of board are put to demonstrate its fantastic versatility. New uses are being identified almost every day. For example, a patent has recently been filed to use layered sheets (alternate layers fused at right angles) in air-to-air heat exchangers.
Demand for corrugated plastic is sure to grow, but as many of the plastics used are dependent on crude oil, the raw material costs are subject to the fluctuations (and inevitable growth) of oil prices. This may prove to be a controlling factor.