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Corrugated fiberboard

Corrugated fiberboard is a paper-based material consisting of a fluted corrugated sheet and one or two flat linerboards. It is widely used in the manufacture of corrugated boxes and shipping containers.

The corrugated medium and linerboard are made of containerboard, a paper-like material usually over 0.01 inches (0.25 mm) thick. Paperboard and corrugated fiberboard are sometimes called cardboard, although cardboard might be any heavy paper-pulp based board.

History

In the mid-19th century, an ingenious concept enabled flimsy sheets of paper to be transformed into a rigid, stackable and cushioning form of packaging for delicate goods in transit

Corrugated (also called pleated) paper was patented in England in 1856, and used as a liner for tall hats, but corrugated boxboard was not patented and used as a shipping material until December 20, 1871. The patent was issued to Albert Jones of New York City for single-sided (single-face) corrugated board. Jones used the corrugated board for wrapping bottles and glass lantern chimneys. The first machine for producing large quantities of corrugated board was built in 1874 by G. Smyth, and in the same year Oliver Long improved upon Jones' design by inventing corrugated board with liner sheets on both sides. This was corrugated board as we know it today.

The Scottish-born Robert Gair invented the pre-cut paperboard box in 1890 – flat pieces manufactured in bulk that folded into boxes. Gair's invention came about as a result of an accident: he was a Brooklyn printer and paper-bag maker during the 1870s, and one day, while he was printing an order of seed bags, a metal ruler normally used to crease bags shifted in position and cut them. Gair discovered that by cutting and creasing in one operation he could make prefabricated paperboard boxes. Applying this idea to corrugated boxboard was a straightforward development when the material became available in the early twentieth century.

The corrugated box was initially used for packaging glass and pottery containers. Later, the case enabled fruit and produce to be brought from the farm to the retailer without bruising, improving the return to the producers and opening up export markets.

Manufacture of corrugated board

Corrugated board is manufactured on large high-precision machinery lines called corrugators, usually running at about 500 feet per minute (2.5 m/s) or more. These machines over time have become very complex with the objective of avoiding some common problems in corrugated board production, such as warp and washboarding.

The manufacturing process begins with pulping, the separation of wood (hardwood and sapwood) into individual fibers, as accomplished by mechanical methods or chemical treatment.

In the classical corrugator, the paper is softened with high-pressure steam. After the board is formed it is dried in the so-called dry-end. Here the newly formed corrugated board is heated from the bottom by hot plates. On the top, various pressures are applied by a load system on the belt.

The corrugated medium is often 0.026 pounds per square foot (0.13 kg/m˛) basis weight in the U.S.; in the UK, a 90 grams per square metre (0.018 lb/sq ft) fluting paper is common. At the single-facer, it is heated, moistened, and formed into a fluted pattern on geared wheels. This is joined to a flat linerboard with a starch based adhesive to form single face board. At the double-backer, a second flat linerboard is adhered to the other side of the fluted medium to form single wall corrugated board. Linerboards are test liners (recycled paper) or kraft paperboard (of various grades). The liner may be bleached white, mottled white, colored, or preprinted.

Common flute sizes are "A", "B", "C", "E" and "F" or microflute. The letter designation relates to the order that the flutes were invented, not the relative sizes. Flute size refers to the number of flutes per lineal foot, although the actual flute dimensions for different corrugator manufacuturers may vary slightly. Measuring the number of flutes per lineal foot is a more reliable method of identifying flute size than measuring board thickness, which can vary due to manufacturing conditions. The most common flute size in corrugated boxes is "C" flute.

Corrugated fiberboard can be specified by the construction (single face, singlewall, doublewall, etc), flute size, burst strength, edge crush strength, flat crush, basis weights of components (pounds per thousand square feet, grams per square meter, etc), surface treatments and coatings, etc. TAPPI and ASTM test methods for these are standardized.

The choice of corrugated medium, flute size, combining adhesive, and linerboards can be varied to engineer a corrugated board with specific properties to match a wide variety of potential uses. Double and triple-wall corrugated board is also produced for high stacking strength and puncture resista

Broadly similar to the ex North Western VDB AEC Reliances in the last two postings were PMT's XVTs from the same year (1963). This 1976 shot shows 942 on the layover park at Hanley bus station. The bus along side it is an almost visually identical Leyland Leopard, 952 XVT. The previous years deliveries had also seen the orders split similarly with ten from each manufacturer, before returning to AEC only for the 1964s... one of which's rear end with the new wrap round rear screens just creeps into shot. The AEC's were distinguishable from the Leylands by their higher driving position, kidney bean shaped instrument binnacle and engine air intake vents behind the O/S front wheel. The Leopard's air intake was invisible and sat alongside the radiator under the driver's cab. Whilst the Leylands were undoubtedly reliable plodders, they lacked the nimble abilities of the AEC, PMT drivers of the era relate their dread of being rostered one because of the heavy controls.
This scene today has changed somewhat, further departure stands now occupy this spot, the old Good Year Tyre depot, Discount Centre by this time, was demolished many years ago and a frozen food shop now occupies the site. The blocks of late '60 flats still stand though.