Paper is thin material mainly used for writing upon, printing upon or for packaging.[citation needed] It is produced by pressing together moist fibers Fiber, also spelled fibre, is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. They are very important in the biology of both plants and animals, for holding tissues together. Human uses for fibers are diverse. They can be spun into filaments, string or rope, used as a component, typically cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units pulp derived from wood Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of trees . In a living tree it transfers water and nutrients to the leaves and other growing tissues, and has a support function, enabling woody plants to reach large sizes or to stand up for themselves. However, wood may also refer to other plant, rags or grasses Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges (Cyperaceae) and the rushes (Juncaceae). The true grasses include cereals, bamboo and the grasses of lawns (turf). True grasses,, and drying them into flexible sheets.[citation needed]

Paper is a versatile material with many uses. Whilst the most common is for writing Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and the recording of language via a non-textual medium such as magnetic tape audio and printing Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing upon, it is also widely used as a packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of design, evaluation, and production of packages. Packaging can be described as a coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging material, in many cleaning Cleanliness is the absence of dirt, including dust, stains, bad smells and garbage. Purposes of cleanliness include health, beauty, absence of offensive odor, avoidance of shame, and to avoid the spreading of dirt and contaminants to oneself and others. In the case of glass objects such as windows or windshields, the purpose can also be products, in a number of industrial and construction processes, and occasionally as a food ingredient Edible paper, as the name implies, is a paper that may be consumed without harsh effects on a normal human digestive system. Usually, the paper has no flavor and very little texture, particularly in Asian cultures.

Contents

History

Main article: History of paper The history of paper began with the papermaking process, developed in China during the Han Dynasty Further information: Science and technology of the Han Dynasty The Han Dynasty of ancient China, divided between the eras of Western Han (206 BCE – 9 CE, when the capital was at Chang'an), Xin Dynasty of Wang Mang (r. 9–23 CE), and Eastern Han (25–220 CE, when the capital was at Luoyang, and after 196 CE at Xuchang), witnessed some of the most significant advancements in premodern Chinese science and and List of Chinese inventions China has been the source of many significant inventions, including the Four Great Inventions of ancient China: paper, the compass, gunpowder, and printing . The list below contains these and other inventions

The word paper derives from the Greek term for the ancient Egyptian Ancient Egypt was an ancient civilization of eastern North Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. The civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh, and it developed over the next three millennia. Its history writing material called papyrus Papyrus is a thick paper-like material produced from the pith of the papyrus plant, Cyperus papyrus, a wetland sedge that was once abundant in the Nile Delta of Egypt, which was formed from beaten strips of papyrus plants Cyperus papyrus is a monocot belonging to the sedge family Cyperaceae. It is a herbaceous perennial native to Africa, and forms tall stands of reed-like swamp vegetation in shallow water. The immediate predecessor to modern paper is believed to have originated in China in approximately the 2nd century CE, although there is some evidence for it being used before this date. Papermaking In papermaking a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down. Water is removed from this mat of fibers by pressing and drying to make paper. Most paper is made from wood pulp, but other fiber sources such as cotton and textiles may be used is considered to be one of the Four Great Inventions of Ancient China The Four Great Inventions of ancient China are four inventions that are celebrated in Chinese culture for their historical significance and as signs of ancient China's advanced science and technology, since the first papermaking process was developed in China China (simplified Chinese: 中国; traditional Chinese: 中國; Hanyu Pinyin: Zhōngguó ; Tongyong Pinyin: Jhongguó; Wade-Giles: Chung¹kuo²) is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia during the early 2nd century CE by the Han The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty (221–206 BCE) and succeeded by the Three Kingdoms (220–265 CE). It was founded by the peasant rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty (9–23 CE) of the former regent Wang Mang. This court eunuch Cai Lun. China used paper as an effective and cheap alternative to silk, letting them sell more silk, leading to a Golden Age The term Golden Age comes from Greek mythology and legend, but can also be found in other ancient cultures . It refers either to the earliest and best age in a sequence of ages, such as the Greek range of Golden, Silver, Bronze, and Iron Ages, or to a time in the beginnings of humanity that was conceived as far better than the present. A ". The use of paper spread from China through the Islamic world The term Muslim world has several meanings. In a cultural sense it refers to the worldwide community of Muslims, adherents of Islam. This community numbers about 1.3-1.5 billion people, roughly one-fifth of the world population. This community is spread across many different nations and ethnic groups connected by religion and a shared sense of, where the first paper mills A paper mill is a factory devoted to making paper from wood pulp and other ingredients using a Fourdrinier Machine or similar apparatus. It is a common misconception that paper mills are sources of odors. Pulp mills, not paper mills can be a source of malodorous air emissions were built, and entered production in Europe in the early 12th century. Mechanized production of paper in the early 19th century caused significant cultural changes worldwide, allowing for relatively cheap exchange of information in the form of letters, newspapers and books for the first time. In 1844, both Canadian inventor Charles Fenerty Charles Fenerty , is a Canadian inventor who invented the wood pulp process for papermaking, which was first adapted into the production of newsprint. Fenerty was also a poet (writing over 32 known poems). He also did extensive traveling throughout Australia between the years 1858 to 1865 (living in the heart of the Australian gold rushes) and German inventor F.G. Keller had invented the machine and process for pulping wood for the use in paper making.[1] This would end the nearly 2000-year use of pulped rags and start a new era for the production of newsprint and eventually all paper out of pulped wood.

Papermaking

The microscopic structure of paper: Micrograph A micrograph, microphotograph or photomicrograph is a photograph or similar image taken through a microscope or similar device to show a magnified image of an item. Canadian inventor Reginald Aubrey Fessenden is credited with inventing photomicrography of paper autofluorescing Autofluorescence is the fluorescence of other substances than the fluorophore of interest. It increases the background signal under ultraviolet Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet illumination. The individual fibres in this sample are around 10uM A micrometre or micron is one millionth of a metre, or equivalently one thousandth of a millimetre or one thousand nanometres. It can also be written in scientific notation as 1×10−6 m, meaning 1⁄1000000 m in diameter. Main article: Papermaking In papermaking a dilute suspension of fibers in water is drained through a screen, so that a mat of randomly interwoven fibers is laid down. Water is removed from this mat of fibers by pressing and drying to make paper. Most paper is made from wood pulp, but other fiber sources such as cotton and textiles may be used

Chemical pulping

Main articles: kraft process The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. The process entails treatment of wood chips with a mixture of sodium hydroxide and sodium sulfide that break the bonds that link lignin to the cellulose. The process name is derived from German kraft, meaning strength/power;, sulfite process The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters. The salts used in the pulping process are either sulfites , or bisulfites (HSO3−), depending on the pH. The counter ion can be sodium (Na+),, and soda pulping Soda pulping is a chemical process for making wood pulp with sodium hydroxide as cooking chemical. In the Soda-AQ process anthraquinone may be used as a pulping additive to decrease the carbohydrate degradation. The soda process has still limited use for easy pulped materials like straws and some hardwoods. It gives pulp with lower tear strength

The purpose of a chemical pulping process is to break down the chemical structure of lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose, and render it soluble in the cooking liquor, so that it may be washed from the cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units fibers. Because lignin holds the plant cells together, chemical pulping frees the fibres and makes pulp. The pulp can also be bleached Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp, so that it becomes whiter. The main use of wood pulp is to make paper where whiteness is an important characteristic. The processes and chemistry described in this article are also applicable to the bleaching of non-wood to produce white paper for printing Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing, painting Painting is the practice of applying paint, pigment, color or other medium to a surface . In art, the term describes both the act and the result, which is called a painting. Paintings may have for their support such surfaces as walls, paper, canvas, wood, glass, lacquer, clay or concrete. Paintings may be decorated with gold leaf, and some modern and writing Writing is the representation of language in a textual medium through the use of a set of signs or symbols . It is distinguished from illustration, such as cave drawing and painting, and the recording of language via a non-textual medium such as magnetic tape audio. Chemical pulps tend to cost more than mechanical pulps, largely due to the low yield, 40–50% of the original wood. Since the process preserves fibre length, however, chemical pulps tend to make stronger paper. Another advantage of chemical pulping is that the majority of the heat and electricity Electricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction needed to run the process is produced by burning the lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose, removed during pulping.

Papers made from chemical wood-based pulps are also known as woodfree papers.

The Kraft process The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. The process entails treatment of wood chips with a mixture of sodium hydroxide and sodium sulfide that break the bonds that link lignin to the cellulose. The process name is derived from German kraft, meaning strength/power; is the most commonly practiced strategy for pulp manufacturing and produces especially strong, unbleached papers that can be used directly for bags and boxes but are often processed further, e.g. to make corrugated cardboard.

Mechanical pulping

There are two major mechanical pulps, thermomechanical pulp (TMP) and mechanical pulp. The latter is known in the USA as groundwood pulp. In the TMP process, wood is chipped and then fed into large steam-heated refiners where the chips are squeezed and fibreized between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones and fibreized. Mechanical pulping does not remove the lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose,, so the yield is very high, >95%, but also causes paper made from this pulp to yellow and become brittle over time. Mechanical pulps have rather short fibre lengths and produce weak paper. Although large amounts of electrical energy Electric potential energy is a potential energy associated with the conservative Coulomb forces within a defined system of point charges. The term "electrostatic potential energy" is preferred here because it seems less likely to be misunderstood. The reference zero is usually taken to be a state in which the individual point charges are are required to produce mechanical pulp, it costs less than chemical pulp.

Recycled paper

Paper recycling Paper recycling is the process of recovering waste paper and remaking it into new paper products. There are three categories of paper that can be used as feedstocks for making recycled paper: mill broke, pre-consumer waste, and post-consumer waste. Mill broke is paper trimmings and other paper scrap from the manufacture of paper, and is recycled processes can use either chemical or mechanical pulp. By mixing with water and applying mechanical action the hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an atomic weight of 1.00794 u, hydrogen is the lightest element bonds in the paper can be broken and fibres separated again. Most recycled paper contains a proportion of virgin fibre in the interests of quality.

There are three main classifications of recycled fibre:.

Recycled papers can be made from 100% recycled materials or blended with virgin pulp. Recycled papers are (generally) not as strong nor as bright as papers made from virgin pulp.

Additives

Besides the fibres, pulps may contain fillers such as chalk or china clay, which improve the characteristics of the paper for printing or writing. Additives for sizing Sizing or size is a substance that is applied to materials as a protecting glaze, filler, or lubricant. It is used to change surface properties in papermaking, gilding, and the manufacture of textiles and fiberglass purposes may be mixed into the pulp and/or applied to the paper web later in the manufacturing process. The purpose of sizing is to establish the correct level of surface absorbency to suit the ink or paint.

Drying

Main article: Papermachine The Fourdrinier Machine is the basis for most modern papermaking, and it has been used in some variation since its conception. The Fourdrinier accomplishes all the steps needed to transform a source of wood pulp into a final paper product

After the paper web is produced, the water must be removed from it by pressing and drying.

Pressing the sheet removes the water by force. Once the water is forced from the sheet, felt (not to be confused with the traditional felt Felt is a non-woven cloth that is produced by matting, condensing and pressing fibers. While some types of felt are very soft, some are tough enough to form construction materials. Felt can be of any color, and made into any shape or size) is used to collect the water. When making paper by hand, a blotter sheet is used.

Drying involves using air and or heat to remove water from the paper sheet. In the earliest days of papermaking this was done by hanging the paper sheets like laundry. In more modern times, various forms of heated drying mechanisms are used. On the paper machine, the most common is the steam-heated can dryer. These dryers can heat to temperatures above 200°F (93°C) and are used in long sequences of more than 40 cans. The heat produced by these can easily dry the paper to less than 6% moisture.

Finishing

The paper may then undergo sizing Sizing or size is a substance that is applied to materials as a protecting glaze, filler, or lubricant. It is used to change surface properties in papermaking, gilding, and the manufacture of textiles and fiberglass to alter its physical properties for use in various applications.

Paper at this point is uncoated. Coated paper Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight and surface gloss, smoothness or ink absorbency. Kaolinite and calcium carbonate are most often used for coating papers used in commercial printing. Other process can be poly olefin extrusion coating or silicone coating to make has a thin layer of material such as calcium carbonate Calcium carbonate is a chemical compound with the chemical formula Ca or china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone screens. (Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by calendering. Coated papers are divided into matte, semi-matte or silk, and gloss. Gloss papers give the highest optical density in the printed image.

The paper is then fed onto reels if it is to be used on web printing presses, or cut into sheets for other printing processes or other purposes. The fibres in the paper basically run in the machine direction. Sheets are usually cut "long-grain", i.e. with the grain parallel to the longer dimension of the sheet.

All paper produced by paper machines as the Fourdrinier machine are wove paper, i.e. the wire mesh that transports the web leaves a pattern that has the same density along the paper grain and across the grain. Textured finishes, watermarks and wire patterns imitating hand-made laid paper can be created by the use of appropriate rollers in the later stages of the machine.

Wove paper does not exhibit "laidlines", which are small regular lines left behind on paper when it was handmade in a mould made from rows of metal wires or bamboo. Laidlines are very close together. They run perpendicular to the "chainlines", which are further apart. Handmade paper similarly exhibits "deckle edges", or rough and feathery borders.[3]

Applications

A Paper cutter

Paper can be produced with a wide variety of properties, depending on its intended use.[4]

Types, thickness and weight

Card and paper stock for craft use comes in a wide variety of textures and colors.

The thickness of paper is often measured by caliper, which is typically given in thousandths of an inch.[5] Paper may be between 0.07 millimetres (0.0028 in) and 0.18 millimetres (0.0071 in) thick.[6]

Paper is often characterized by weight. In the United States, the weight assigned to a paper is the weight of a ream, 500 sheets, of varying "basic sizes", before the paper is cut into the size it is sold to end customers. For example, a ream of 20 lb, 8½ x 11" paper weighs 5 pounds, because it has been cut from a larger sheet into four pieces.[7] In the United States, printing paper is generally 20 lb, 24 lb, or 32 lb at most. Cover stock is generally 68 lb, and 110 lb or more is considered card stock.

The 8.5" x 11" size stems from the original size of a vat that was used to make paper.[citation needed] At the time, paper was made from passing a fiber and water slurry through a screen at the bottom of a box. The box was 17" deep and 44" wide. That sheet, folded in half in the long direction, then twice in the opposite direction, made a sheet of paper that was exactly 8.5" x 11".

In Europe, and other regions using the ISO 216 paper sizing system, the weight is expressed in grammes per square metre (g/m2 or usually just g) of the paper. Printing paper is generally between 60 g and 120 g. Anything heavier than 160 g is considered card. The weight of a ream therefore depends on the dimensions of the paper and its thickness.

The sizing system in Europe is based on common width to height ratios for different paper sizes. The largest standard size paper is A0 (A zero). Two sheets of A1, placed upright side by side fit exactly into one sheet of A0 laid on its side. Similarly, two sheets of A2 fit into one sheet of A1 and so forth. Common sizes used in the office and the home are A4 and A3 (A3 is the size of two A4 sheets).

The density of paper ranges from 250 kg/m3 (16 lb/ft3) for tissue paper to 1500 kg/m3 (94 lb/ft3) for some speciality paper. Printing paper is about 800 kg/m3 (50 lb/ft3).[8]

Some paper types include:

The future of paper

Some manufacturers have started using a new, significantly more environmentally friendly alternative to expanded plastic packaging made out of paper, known commercially as paperfoam. The packaging has very similar mechanical properties to some expanded plastic packaging, but is biodegradable and can also be recycled with ordinary paper. [9]

With increasing environmental concerns about synthetic coatings (such as PFOA) and the higher prices of hydrocarbon based petrochemicals, there is a focus on zein (corn protein) as a coating for paper in high grease applications such as popcorn bags. [10]

Also, synthetics such as Tyvek and Teslin have been introduced as printing media as a more durable material than paper.

See also

References and notes

  1. ^ Burger, Peter. Charles Fenerty and his Paper Invention. Toronto: Peter Burger, 2007. ISBN 978-0-9783318-1-8 pp.25-30
  2. ^ Natural Resource Defense Council
  3. ^ "Document Doubles" in Detecting the Truth: Fakes, Forgeries and Trickery, a virtual museum exhibition at Library and Archives Canada
  4. ^ "Grades and uses of paper". http://www.paperonweb.com/grade11.htm. Retrieved 2007-10-12.
  5. ^ "Paper Thickness Chart", Case Paper Company Inc.
  6. ^ "Thickness of a Piece of Paper", HyperTextbook.com
  7. ^ McKenzie, Bruce G., The Hammermill Guide to Desktop Publishing in Business, p. 144, Hammermill Papers, 1989.
  8. ^ "Density of paper and paperboard". PaperOnWeb. http://www.paperonweb.com/density.htm. Retrieved 2007-10-31.
  9. ^ PaperFoam Carbon Friendly Packaging
  10. ^ Barrier compositions and articles produced with the compositions cross-reference to related application
also referred to as:

External links

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