Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1376 2022-05-11 14:28:14

Registered: 2005-06-28
Posts: 36,971

Re: Miscellany

1350) Polycarbonate


Polycarbonate (PC) is a tough, transparent synthetic resin employed in safety glass, eyeglass lenses, and compact discs, among other applications. PC is a special type of polyester used as an engineering plastic owing to its exceptional impact resistance, tensile strength, ductility, dimensional stability, and optical clarity. It is marketed under trademarks such as Lexan and Makrolon.

PC was introduced in 1958 by Bayer AG of Germany and in 1960 by the General Electric Company of the United States. As developed by these companies, PC is produced by a polymerization reaction between bisphenol A, a volatile liquid derived from benzene, and phosgene, a highly reactive and toxic gas made by reacting carbon monoxide with chlorine. The resultant polymers (long, multiple-unit molecules) are made up of repeating units containing two aromatic (benzene) rings and connected by ester (CO-O) groups.

Mainly by virtue of the aromatic rings incorporated into the polymer chain, PC has exceptional stiffness. It is also highly transparent, transmitting approximately 90 percent of visible light. Since the mid-1980s this property, in combination with the excellent flowing properties of the polymer when molten, has found growing application in the injection-molding of compact discs. Because PC has an impact strength considerably higher than most plastics, it is also fabricated into large carboys for water, shatterproof windows, safety shields, and safety helmets.


Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. They are easily worked, molded, and thermoformed. Because of these properties, polycarbonates find many applications. Polycarbonates do not have a unique resin identification code (RIC) and are identified as "Other", 7 on the RIC list. Products made from polycarbonate can contain the precursor monomer bisphenol A (BPA).


Structure of dicarbonate (PhOC(O)OC6H4 )2CMe2 derived from bis(phenol-A) and two equivalents of phenol. This molecule reflects a subunit of a typical polycarbonate derived from bis(phenol-A).

Carbonate esters have planar OC(OC)2 cores, which confers rigidity. The unique O=C bond is short (1.173 Å in the depicted example), while the C-O bonds are more ether-like (the bond distances of 1.326 Å for the example depicted). Polycarbonates received their name because they are polymers containing carbonate groups (−O−(C=O)−O−). A balance of useful features, including temperature resistance, impact resistance and optical properties, positions polycarbonates between commodity plastics and engineering plastics.

Properties and processing

Polycarbonate is a durable material. Although it has high impact-resistance, it has low scratch-resistance. Therefore, a hard coating is applied to polycarbonate eyewear lenses and polycarbonate exterior automotive components. The characteristics of polycarbonate compare to those of polymethyl methacrylate (PMMA, acrylic), but polycarbonate is stronger and will hold up longer to extreme temperature. Thermally processed material is usually totally amorphous, and as a result is highly transparent to visible light, with better light transmission than many kinds of glass.

Polycarbonate has a glass transition temperature of about 147 °C (297 °F), so it softens gradually above this point and flows above about 155 °C (311 °F). Tools must be held at high temperatures, generally above 80 °C (176 °F) to make strain-free and stress-free products. Low molecular mass grades are easier to mold than higher grades, but their strength is lower as a result. The toughest grades have the highest molecular mass, but are more difficult to process.

Unlike most thermoplastics, polycarbonate can undergo large plastic deformations without cracking or breaking. As a result, it can be processed and formed at room temperature using sheet metal techniques, such as bending on a brake. Even for sharp angle bends with a tight radius, heating may not be necessary. This makes it valuable in prototyping applications where transparent or electrically non-conductive parts are needed, which cannot be made from sheet metal. PMMA/Acrylic, which is similar in appearance to polycarbonate, is brittle and cannot be bent at room temperature.

Main transformation techniques for polycarbonate resins:

* extrusion into tubes, rods and other profiles including multiwall
* extrusion with cylinders (calenders) into sheets (0.5–20 mm (0.020–0.787 in)) and films (below 1 mm (0.039 in)), which can be used directly or manufactured into other shapes using thermoforming or secondary fabrication techniques, such as bending, drilling, or routing. Due to its chemical properties it is not conducive to laser-cutting.
* injection molding into ready articles

Polycarbonate may become brittle when exposed to ionizing radiation above 25 kGy (J/kg).


Electronic components

Polycarbonate is mainly used for electronic applications that capitalize on its collective safety features. Being a good electrical insulator and having heat-resistant and flame-retardant properties, it is used in various products associated with electrical and telecommunications hardware. It can also serve as a dielectric in high-stability capacitors. However, commercial manufacture of polycarbonate capacitors mostly stopped after sole manufacturer Bayer AG stopped making capacitor-grade polycarbonate film at the end of 2000.

Construction materials

The second largest consumer of polycarbonates is the construction industry, e.g. for domelights, flat or curved glazing, roofing sheets and sound walls. Polycarbonates are used to create materials used in buildings that need to be durable but light.

3D Printing

Polycarbonates are used extensively in 3D FDM printing, producing durable strong plastic products with a high melting point. Polycarbonate is relatively difficult for casual hobbyists to print compared to thermoplastics such as Polylactic acid (PLA) or Acrylonitrile butadiene styrene (ABS) because of the high melting point, difficulty with print bed adhesion, tendency to warp during printing, and tendency to absorb moisture in humid environments. Despite these issues, 3D printing using polycarbonates is common in the professional community.

Data storage

A major polycarbonate market is the production of compact discs, DVDs, and Blu-ray discs. These discs are produced by injection-molding polycarbonate into a mold cavity that has on one side a metal stamper containing a negative image of the disc data, while the other mold side is a mirrored surface. Typical products of sheet/film production include applications in advertisement (signs, displays, poster protection).

Automotive, aircraft, and security components

In the automotive industry, injection-molded polycarbonate can produce very smooth surfaces that make it well-suited for sputter deposition or evaporation deposition of aluminium without the need for a base-coat. Decorative bezels and optical reflectors are commonly made of polycarbonate. Its low weight and high impact resistance have made polycarbonate the dominant material for automotive headlamp lenses. However, automotive headlamps require outer surface coatings because of its low scratch resistance and susceptibility to ultraviolet degradation (yellowing). The use of polycarbonate in automotive applications is limited to low stress applications. Stress from fasteners, plastic welding and molding render polycarbonate susceptible to stress corrosion cracking when it comes in contact with certain accelerants such as salt water and plastisol. It can be laminated to make bullet-proof "glass", although "bullet-resistant" is more accurate for the thinner windows, such as are used in bullet-resistant windows in automobiles. The thicker barriers of transparent plastic used in teller's windows and barriers in banks are also polycarbonate.

So-called "theft-proof" large plastic packaging for smaller items, which cannot be opened by hand, is typically made from polycarbonate.

The canopy of the Lockheed Martin F-22 Raptor jet fighter is made from a piece of high optical quality polycarbonate, and is the largest piece of its type formed in the world.

Niche applications

Polycarbonate, being a versatile material with attractive processing and physical properties, has attracted myriad smaller applications. The use of injection molded drinking bottles, glasses and food containers is common, but the use of BPA in the manufacture of polycarbonate has stirred concerns (see Potential hazards in food contact applications), leading to development and use of "BPA-free" plastics in various formulations.

Laboratory safety goggles

Polycarbonate is commonly used in eye protection, as well as in other projectile-resistant viewing and lighting applications that would normally indicate the use of glass, but require much higher impact-resistance. Polycarbonate lenses also protect the eye from UV light. Many kinds of lenses are manufactured from polycarbonate, including automotive headlamp lenses, lighting lenses, sunglass/eyeglass lenses, swimming goggles and SCUBA masks, and safety glasses/goggles/visors including visors in sporting helmets/masks and police riot gear (helmet visors, riot shields, etc.). Windscreens in small motorized vehicles are commonly made of polycarbonate, such as for motorcycles, ATVs, golf carts, and small airplanes and helicopters.

The light weight of polycarbonate as opposed to glass has led to development of electronic display screens that replace glass with polycarbonate, for use in mobile and portable devices. Such displays include newer e-ink and some LCD screens, though CRT, plasma screen and other LCD technologies generally still require glass for its higher melting temperature and its ability to be etched in finer detail.

As more and more governments are restricting the use of glass in pubs and clubs due to the increased incidence of glassings, polycarbonate glasses are becoming popular for serving alcohol because of their strength, durability, and glass-like feel.

Other miscellaneous items include durable, lightweight luggage, MP3/digital audio player cases, ocarinas, computer cases, riot shields, instrument panels, tealight candle containers and food blender jars. Many toys and hobby items are made from polycarbonate parts, like fins, gyro mounts, and flybar locks in radio-controlled helicopters, and transparent LEGO (ABS is used for opaque pieces).

Standard polycarbonate resins are not suitable for long term exposure to UV radiation. To overcome this, the primary resin can have UV stabilisers added. These grades are sold as UV stabilized polycarbonate to injection moulding and extrusion companies. Other applications, including polycarbonate sheets, may have the anti-UV layer added as a special coating or a coextrusion for enhanced weathering resistance.

Polycarbonate is also used as a printing substrate for nameplate and other forms of industrial grade under printed products. The polycarbonate provides a barrier to wear, the elements, and fading.

Medical applications

Many polycarbonate grades are used in medical applications and comply with both ISO 10993-1 and USP Class VI standards (occasionally referred to as PC-ISO). Class VI is the most stringent of the six USP ratings. These grades can be sterilized using steam at 120 °C, gamma radiation, or by the ethylene oxide (EtO) method. Dow Chemical strictly limits all its plastics with regard to medical applications. Aliphatic polycarbonates have been developed with improved biocompatibility and degradability for nanomedicine applications.

Mobile phones

Some major smartphone manufacturers use polycarbonate. Nokia used polycarbonate in their phones starting with the N9's unibody case in 2011. This practice continued with various phones in the Lumia series. Samsung has started using polycarbonate with Galaxy S III's hyperglaze-branded removable battery cover in 2012. This practice continues with various phones in the Galaxy series. Apple started using polycarbonate with the iPhone 5C's unibody case in 2013.

Benefits over glass and metal back covers include durability against shattering (weakness of glass), bending and scratching (weakness of metal), shock absorption, low manufacturing costs, and no interference with radio signals and wireless charging (weakness of metal).  Polycarbonate back covers are available in glossy or matte surface textures.


Polycarbonates were first discovered in 1898 by Alfred Einhorn, a German scientist working at the University of Munich. However, after 30 years' laboratory research, this class of materials was abandoned without commercialization. Research resumed in 1953, when Hermann Schnell at Bayer in Uerdingen, Germany patented the first linear polycarbonate. The brand name "Makrolon" was registered in 1955.

Also in 1953, and one week after the invention at Bayer, Daniel Fox at General Electric in Schenectady, New York, independently synthesized a branched polycarbonate. Both companies filed for U.S. patents in 1955, and agreed that the company lacking priority would be granted a license to the technology.

Patent priority was resolved in Bayer's favor, and Bayer began commercial production under the trade name Makrolon in 1958. GE began production under the name Lexan in 1960, creating the GE Plastics division in 1973.

After 1970, the original brownish polycarbonate tint was improved to "glass-clear."


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.


#1377 2022-05-12 13:53:52

Registered: 2005-06-28
Posts: 36,971

Re: Miscellany

1351) Jute


Jute is a long, soft, shiny bast fiber that can be spun into coarse, strong threads. It is produced from flowering plants in the genus Corchorus, which is in the mallow family Malvaceae. The primary source of the fiber is Corchorus olitorius, but such fiber is considered inferior to that derived from Corchorus capsularis. "Jute" is the name of the plant or fiber used to make burlap, hessian or gunny cloth.

Jute is one of the most affordable natural fibers, and second only to cotton in the amount produced and variety of uses. Jute fibers are composed primarily of the plant materials cellulose and lignin. Jute fiber falls into the bast fiber category (fiber collected from bast, the phloem of the plant, sometimes called the "skin") along with kenaf, industrial hemp, flax (linen), ramie, etc.. The industrial term for jute fiber is raw jute. The fibers are off-white to brown, and 1–4 metres (3–13 feet) long. Jute is also called the "golden fiber" for its color and high cash value.


Jute is a vegetable fibre. It is very cheap to produce, and its production levels are similar to that of cotton. It is a bast fibre, like hemp, and flax. Coarse fabrics made of jute are called hessian, or burlap in America. Like all natural fibres, Jute is biodegradable."Jute" is the name of the plant or fiber that is used to make burlap, Hessian or gunny cloth. It is very rough and is very difficult to cut or tear.

The jute plant is easily grown in tropical countries like Bangladesh and India. India is the largest producer of jute in the world. Jute is less expensive than cotton, but cotton is better for quality clothes. Jute is used to make various products: packaging materials, jute bags, sacks, expensive carpets, espadrilles, sweaters etc. It is obtained from the bark of the jute plant. Jute plants are easy to grow, have a high yield per acre and, unlike cotton, have little need for pesticides and fertilizers.

In Iran, archaeologists have found jute existing since the Bronze Age.


Jute, Hindi pat, also called allyott, is either of two species of Corchorus plants—C. capsularis, or white jute, and C. olitorius, including both tossa and daisee varieties—belonging to the hibiscus, or mallow, family (Malvaceae), and their fibre. The latter is a bast fibre; i.e., it is obtained from the inner bast tissue of the bark of the plant’s stem. Jute fibre’s primary use is in fabrics for packaging a wide range of agricultural and industrial commodities that require bags, sacks, packs, and wrappings. Wherever bulky, strong fabrics and twines resistant to stretching are required, jute is widely used because of its low cost. Burlap is made from jute.

Jute has been grown in the Bengal area of India (and of present-day Bangladesh) from ancient times. The export of raw jute from the Indian subcontinent to the Western Hemisphere began in the 1790s. The fibre was used primarily for cordage manufacture until 1822, when commercial yarn manufacture began at Dundee, Scot., which soon became a centre for the industry. India’s own jute-processing industry began in 1855, Calcutta becoming the major centre. After India was partitioned (1947), much of the jute-producing land remained in East Pakistan (now Bangladesh), where new processing facilities were built. Besides the Indian subcontinent, jute is also grown in China and in Brazil. The largest importers of raw jute fibre are Japan, Germany, the United Kingdom, Belgium, and France.

The jute plant, which probably originated on the Indian subcontinent, is an herbaceous annual that grows to an average of 10 to 12 feet (3 to 3.6 metres) in height, with a cylindrical stalk about as thick as a finger. The two species grown for jute fibre are similar and differ only in the shape of their seed pods, growth habit, and fibre characteristics. Most varieties grow best in well-drained, sandy loam and require warm, humid climates with an average monthly rainfall of at least 3 to 4 inches (7.5 to 10 cm) during the growing season. The plant’s light green leaves are 4 to 6 inches (10 to 15 cm) long, about 2 inches (5 cm) wide, have serrated edges, and taper to a point. The plant bears small yellow flowers.

The jute plant’s fibres lie beneath the bark and surround the woody central part of the stem. The fibre strands nearest the bark generally run the full length of the stem. A jute crop is usually harvested when the flowers have been shed but before the plants’ seedpods are fully mature. If jute is cut before then, the fibre is weak; if left until the seed is ripe, the fibre is strong but is coarser and lacks the characteristic lustre.

The fibres are held together by gummy materials; these must be softened, dissolved, and washed away to allow extraction of the fibres from the stem, a process accomplished by steeping the stems in water, or retting. After harvesting, the bundles of stems are placed in the water of pools or streams and are weighted down with stones or earth. They are kept submerged for 10–30 days, during which time bacterial action breaks down the gummy tissues surrounding the fibres. After retting is complete, the fibres are separated from the stalk by beating the root ends with a paddle to loosen them; the stems are then broken off near the root, and the fibre strands are jerked off the stem. The fibres are then washed, dried, sorted, graded, and baled in preparation for shipment to jute mills. In the latter, the fibres are softened by the addition of oil, water, and emulsifiers, after which they are converted into yarn. The latter process involves carding, drawing, roving, and spinning to separate the individual fibre filaments; arrange them in parallel order; blend them for uniformity of colour, strength, and quality; and twist them into strong yarns. Once the yarn has been spun, it can be woven, knitted, twisted, corded, sewn, or braided into finished products.

Jute is used in a wide variety of goods. Jute mats and prayer rugs are common in the East, as are jute-backed carpets worldwide. Jute’s single largest use, however, is in sacks and bags, those of finer quality being called burlap, or hessian. Burlap bags are used to ship and store grain, fruits and vegetables, flour, sugar, animal feeds, and other agricultural commodities. High-quality jute cloths are the principal fabrics used to provide backing for tufted carpets, as well as for hooked rugs (i.e., Oriental rugs). Jute fibres are also made into twines and rough cordage.


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.


#1378 2022-05-13 14:25:35

Registered: 2005-06-28
Posts: 36,971

Re: Miscellany

1352) Unsaturated polyester

Unsaturated polyester is any of a group of thermosetting resins produced by dissolving a low-molecular-weight unsaturated polyester in a vinyl monomer and then copolymerizing the two to form a hard, durable plastic material. Unsaturated polyesters, usually strengthened by fibreglass or ground mineral, are made into structural parts such as boat hulls, pipes, and countertops.

Unsaturated polyesters are copolyesters—that is, polyesters prepared from a saturated dicarboxylic acid or its anhydride (usually phthalic anhydride) as well as an unsaturated dicarboxylic acid or anhydride (usually maleic anhydride). These two acid constituents are reacted with one or more dialcohols, such as ethylene glycol or propylene glycol, to produce the characteristic ester groups that link the precursor molecules together into long, chainlike, multiple-unit polyester molecules. The maleic anhydride units of this copolyester are unsaturated because they contain carbon-carbon double bonds that are capable of undergoing further polymerization under the proper conditions. These conditions are created when the copolyester is dissolved in a monomer such as styrene and the two are subjected to the action of free-radical initiators. The mixture, at this point usually poured into a mold, then copolymerizes rapidly to form a three-dimensional network structure that bonds well with fibres or other reinforcing materials. The principal products are boat hulls, appliances, business machines, automobile parts, automobile-body patching compounds, tubs and shower stalls, flooring, translucent paneling, storage tanks, corrosion-resistant ducting, and building components. Unsaturated polyesters filled with ground limestone or other minerals are cast into kitchen countertops and bathroom vanities. Bowling balls are made from unsaturated polyesters cast into molds with no reinforcement.


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.


#1379 2022-05-14 14:24:29

Registered: 2005-06-28
Posts: 36,971

Re: Miscellany

1353) Carding


Carding, in textile production, is a process of separating individual fibres, using a series of dividing and redividing steps, that causes many of the fibres to lie parallel to one another while also removing most of the remaining impurities. Carding may be done by hand, using hand carders (pinned wooden paddles that are not unlike steel dog brushes) or drum carders (in which washed wool, fleece, or other materials are fed through one or more pinned rollers) to prepare the fibres for spinning, felting, or other fabric- or cloth-making activities.

Cotton, wool, waste silk, other fibrous plant materials and animal fur and hair, and artificial staple are subjected to carding. Carding produces a thin sheet of uniform thickness that is then condensed to form a thick continuous untwisted strand called sliver. When very fine yarns are desired, carding is followed by combing, a process that removes short fibres, leaving a sliver composed entirely of long fibres, all laid parallel and smoother and more lustrous than uncombed types. Carded and combed sliver is then spun.


Carding is a mechanical process that disentangles, cleans and intermixes fibres to produce a continuous web or sliver suitable for subsequent processing. This is achieved by passing the fibres between differentially moving surfaces covered with "card clothing", a firm flexible material embedded with metal pins. It breaks up locks and unorganised clumps of fibre and then aligns the individual fibres to be parallel with each other. In preparing wool fibre for spinning, carding is the step that comes after teasing.

The word is derived from the Latin Carduus meaning thistle or teasel, as dried vegetable teasels were first used to comb the raw wool before technological advances led to the use of machines.


These ordered fibres can then be passed on to other processes that are specific to the desired end use of the fibre: Cotton, batting, felt, woollen or worsted yarn, etc. Carding can also be used to create blends of different fibres or different colours. When blending, the carding process combines the different fibres into a homogeneous mix. Commercial cards also have rollers and systems designed to remove some vegetable matter contaminants from the wool.

Common to all carders is card clothing. Card clothing is made from a sturdy flexible backing in which closely spaced wire pins are embedded. The shape, length, diameter, and spacing of these wire pins are dictated by the card designer and the particular requirements of the application where the card cloth will be used. A later version of the card clothing product developed during the latter half of the 19th century and was found only on commercial carding machines, whereby a single piece of serrated wire was wrapped around a roller, became known as metallic card clothing.

Carding machines are known as cards. Fibre may be carded by hand for hand spinning.


Science historian Joseph Needham ascribes the invention of bow-instruments used in textile technology to India. The earliest evidence for using bow-instruments for carding comes from India (2nd century CE). These carding devices, called kaman (bow) and dhunaki, would loosen the texture of the fibre by the means of a vibrating string.

At the turn of the eighteenth century, wool in England was being carded using pairs of hand cards, in a two-stage process: 'working' with the cards opposed and 'stripping' where they are in parallel.

In 1748 Lewis Paul of Birmingham, England, invented two hand driven carding machines. The first used a coat of wires on a flat table moved by foot pedals. This failed. On the second, a coat of wire slips was placed around a card which was then wrapped around a cylinder. Daniel Bourn obtained a similar patent in the same year, and probably used it in his spinning mill at Leominster, but this burnt down in 1754. The invention was later developed and improved by Richard Arkwright and Samuel Crompton. Arkwright's second patent (of 1775) for his carding machine was subsequently declared invalid (1785) because it lacked originality.

From the 1780s, the carding machines were set up in mills in the north of England and mid-Wales. Priority was given to cotton but woollen fibres were being carded in Yorkshire in 1780. With woollen, two carding machines were used: the first or the scribbler opened and mixed the fibres, the second or the condenser mixed and formed the web. The first in Wales was in a factory at Dolobran near Meifod in 1789. These carding mills produced yarn particularly for the Welsh flannel industry.

In 1834 James Walton invented the first practical machines to use a wire card. He patented this machine and also a new form of card with layers of cloth and rubber. The combination of these two inventions became the standard for the carding industry, using machines first built by Parr, Curtis and Walton in Ancoats, and from 1857 by Jams Walton & Sons at Haughton Dale.

By 1838, the Spen Valley, centred on Cleckheaton had at least 11 card clothing factories and by 1893, it was generally accepted as the card cloth capital of the world, though by 2008 only two manufacturers of metallic and flexible card clothing remained in England, Garnett Wire Ltd. dating back to 1851 and Joseph Sellers & Son Ltd established in 1840.

Baird from Scotland took carding to Leicester, Massachusetts in the 1780s. In the 1890s, the town produced one-third of all hand and machine cards in North America. John and Arthur Slater, from Saddleworth went over to work with Slater in 1793.

A 1780s scribbling mill would be driven by a water wheel. There were 170 scribbling mills around Leeds at that time. Each scribbler would require 15–45 horsepower (11–34 kW) to operate. Modern machines are driven by belting from an electric motor or an overhead shaft via two pulleys.


Predating mechanised weaving, hand loom weaving was a cottage industry that used the same processes but on a smaller scale. These skills have survived as an artisan craft in less developed societies- and as art form and hobby in advanced societies.

Hand carders

Hand cards are typically square or rectangular paddles manufactured in a variety of sizes from 2 by 2 inches (5.1 cm × 5.1 cm) to 4 by 8 inches (10 cm × 20 cm). The working face of each paddle can be flat or cylindrically curved and wears the card cloth. Small cards, called flick cards, are used to flick the ends of a lock of fibre, or to tease out some strands for spinning off.

A pair of cards is used to brush the wool between them until the fibres are more or less aligned in the same direction. The aligned fibre is then peeled from the card as a rolag. Carding is an activity normally done outside or over a drop cloth, depending on the wool's cleanliness. Rolag is peeled from the card.

Carding of wool can either be done "in the grease" or not, depending on the type of machine and on the spinner's preference. "In the grease" means that the lanolin that naturally comes with the wool has not been washed out, leaving the wool with a slightly greasy feel. The large drum carders do not tend to get along well with lanolin, so most commercial worsted and woollen mills wash the wool before carding. Hand carders (and small drum carders too, though the directions may not recommend it) can be used to card lanolin rich wool.

Drum carders

The simplest machine carder is the drum carder. Most drum carders are hand-cranked but some are powered by an electric motor. These machines generally have two rollers, or drums, covered with card clothing. The licker-in, or smaller roller meters fibre from the infeed tray onto the larger storage drum. The two rollers are connected to each other by a belt- or chain-drive so that their relative speeds cause the storage drum to gently pull fibres from the licker-in. This pulling straightens the fibres and lays them between the wire pins of the storage drum's card cloth. Fibre is added until the storage drum's card cloth is full. A gap in the card cloth facilitates removal of the batt when the card cloth is full.

Some drum carders have a soft-bristled brush attachment that presses the fibre into the storage drum. This attachment serves to condense the fibres already in the card cloth and adds a small amount of additional straightening to the condensed fibre.

Cottage carders

Cottage carding machines differ significantly from the simple drum card. These carders do not store fibre in the card cloth as the drum carder does but, rather, fibre passes through the workings of the carder for storage or for additional processing by other machines.

A typical cottage carder has a single large drum (the swift) accompanied by a pair of in-feed rollers (nippers), one or more pairs of worker and stripper rollers, a fancy, and a doffer. In-feed to the carder is usually accomplished by hand or by conveyor belt and often the output of the cottage carder is stored as a batt or further processed into roving and wound into bumps with an accessory bump winder.

Raw fibre, placed on the in-feed table or conveyor is moved to the nippers which restrain and meter the fiber onto the swift. As they are transferred to the swift, many of the fibres are straightened and laid into the swift's card cloth. These fibres will be carried past the worker / stripper rollers to the fancy.

As the swift carries the fibres forward, from the nippers, those fibres that are not yet straightened are picked up by a worker and carried over the top to its paired stripper. Relative to the surface speed of the swift, the worker turns quite slowly. This has the effect of reversing the fibre. The stripper, which turns at a higher speed than the worker, pulls fibres from the worker and passes them to the swift. The stripper's relative surface speed is slower than the swift's so the swift pulls the fibres from the stripper for additional straightening.

Straightened fibres are carried by the swift to the fancy. The fancy's card cloth is designed to engage with the swift's card cloth so that the fibres are lifted to the tips of the swift's card cloth and carried by the swift to the doffer. The fancy and the swift are the only rollers in the carding process that actually touch.

The slowly turning doffer removes the fibres from the swift and carries them to the fly comb where they are stripped from the doffer. A fine web of more or less parallel fibre, a few fibres thick and as wide as the carder's rollers, exits the carder at the fly comb by gravity or other mechanical means for storage or further processing.


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.


#1380 Yesterday 14:08:49

Registered: 2005-06-28
Posts: 36,971

Re: Miscellany

1354) Cardboard

Cardboard is a generic term for heavy paper-based products. The construction can range from a thick paper known as paperboard to corrugated fiberboard which is made of multiple plies of material. Natural cardboards can range from grey to light brown in color, depending of the specific product; dyes, pigments, printing, and coatings are available.

The term "cardboard" has general use in English and French, but the term cardboard is deprecated in commerce and industry as not adequately defining a specific product. Material producers, container manufacturers, packaging engineers, and standards organizations, use more specific terminology.


In 2020, the United States hit a record high in its yearly use of one of the most ubiquitous manufactured materials on earth, cardboard.  With around 80 per cent of all the products sold in the United States being packaged in cardboard, over 120 billion pieces were used that year. In the same year, over 13,000 separate pieces of consumer cardboard packaging was thrown away by American households, combined with all paper products and this constitutes almost 42 per cent of all solid waste generated by the United States annually.

However, despite the sheer magnitude of paper waste, the vast majority of it is composed of one of the most successful and sustainable packaging materials of modern times - corrugated cardboard, known industrially as corrugated fiberboard.


Various card stocks:

Various types of cards are available, which may be called "cardboard". Included are: thick paper (of various types) or pasteboard used for business cards, aperture cards, postcards, playing cards, catalog covers, binder's board for bookbinding, scrapbooking, and other uses which require higher durability than regular paper.


Paperboard is a paper-based material, usually more than about ten mils (0.010 inches (0.25 mm)) thick. It is often used for folding cartons, set-up boxes, carded packaging, etc. Configurations of paperboard include:

* Containerboard, used in the production of corrugated fiberboard.
* Folding boxboard, comprising multiple layers of chemical and mechanical pulp.
* Solid bleached board, made purely from bleached chemical pulp and usually has a mineral or synthetic pigment.
* Solid unbleached board, typically made of unbleached chemical pulp.
* White lined chipboard, typically made from layers of waste paper or recycled fibers, most often with two to three layers of coating on the top and one layer on the reverse side. Because of its recycled content it will be grey from the inside.
* Binder's board, a paperboard used in bookbinding for making hardcovers.

Currently, materials falling under these names may be made without using any actual paper.

Corrugated fiberboard

Corrugated fiberboard is a combination of paperboards, usually two flat liners and one inner fluted corrugated medium. It is often used for making corrugated boxes for shipping or storing products. This type of cardboard is also used by artists as original material for sculpting.


Most types of cardboard are recyclable. Boards that are laminates, wax coated, or treated for wet-strength are often more difficult to recycle. Clean cardboard (i.e., cardboard that has not been subject to chemical coatings) "is usually worth recovering, although often the difference between the value it realizes and the cost of recovery is marginal". Cardboard can be recycled for industrial or domestic use. For example, cardboard may be composted or shredded for animal bedding.


The material had been first made in France, in 1751, by a pupil of Réaumur, and was used to reinforce playing cards. The term cardboard has been used since at least 1848, when Anne Brontë mentioned it in her novel, The Tenant of Wildfell Hall. The Kellogg brothers first used paperboard cartons to hold their flaked corn cereal, and later, when they began marketing it to the general public, a heat-sealed bag of wax paper was wrapped around the outside of the box and printed with their brand name. This development marked the origin of the cereal box, though in modern times the sealed bag is plastic and is kept inside the box. The Kieckhefer Container Company, run by John W. Kieckhefer, was another early American packaging industry pioneer. It excelled in the use of fiber shipping containers, particularly the paper milk carton.


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.


Board footer

Powered by FluxBB