Paper MakingEssay Preview: Paper MakingReport this essayoldest known archaeological fragments of the immediate precursor to modern paper date to 2nd century BC China. Papermaking is considered one of the Four Great Inventions of Ancient China, and the pulp papermaking process is ascribed to Cai Lun, a 2nd century AD Han court eunuch.[2] With paper an effective substitute for silk in many applications, China could export silk in greater quantity, contributing to a Golden Age.
Paper spread from China through the Islamic world to medieval Europe in the 13th century, where the first water-powered paper mills were built.[3] In the 19th century, industrial manufacture greatly lowered its cost, enabling mass exchange of information and contributing to significant cultural shifts. In 1844, Canadian inventor Charles Fenerty and German F.G. Keller independently developed processes for pulping wood fibers.[4] This ended the nearly 2000-year exclusive use of pulped rags.[citation needed]
EtymologyFurther information: PapyrusThe word “paper” is etymologically derived from papyros, Ancient Greek for the Cyperus papyrus plant. Papyrus is a thick, paper-like material produced from the pith of the Cyperus papyrus plant which was used in ancient Egypt and other Mediterranean cultures for writing before the introduction of paper into the Middle East and Europe.[5] Although paper is etymologically derived from papyrus, the two are produced very differently and the development of modern paper is separate from the development of papyrus. Papyrus is a “lamination of natural plants, while paper is manufactured from fibres whose properties have been changed by maceration or disintegration.[6]
PapermakingMain article: PapermakingChemical pulpingMain articles: kraft process, sulfite process, and soda pulpingThe purpose of a chemical pulping process is to break down the chemical structure of lignin and render it soluble in the cooking liquor, so that it may be washed from the cellulose fibers. Because lignin holds the plant cells together, chemical pulping frees the fibres and makes pulp. The pulp can also be bleached to produce white paper for printing, painting and writing. 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 needed to run the process is produced by burning the lignin removed during pulping.
The microscopic structure of paper: Micrograph of paper autofluorescing under ultraviolet illumination. The individual fibres in this sample are around 10 µm in diameter.
Paper made from chemical pulps are also known as wood-free papers. Not to be confused with tree-free paper.The Kraft process 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 pulpingThere are two major mechanical pulps, thermo mechanical pulp (TMP) and groundwood pulp (GW). In the TMP process, wood is chipped and then fed into large steam-heated refiners where the chips are squeezed and made into fibres between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones and made into fibres. Mechanical pulping does not remove the lignin, 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 are required to produce mechanical pulp, it costs less than chemical pulp.
Pulp: The pulp can be used with or without a hard hardwood nut, or in the wood of any type of pulp. The pulp can be rolled/pulled, cut, or put inside an open container to be stored either in a steel box or an other container. It is used as the “skin” or material of large log blocks. There are two types of pulp production: raw pulp and pulp grown in a dry well (with a clear surface). The raw pulp is made up of all-natural pulp or other fibres that are easily broken down (such as fibres of carbon dioxide or of iron).
TMP – The TMP process is used to produce wood product, such as plastic, rubber, wood chips, wood insulation, or rubber linings. The raw pulp and pulp grown in a dry well are mostly plastic, polypropylene, etc. They are not used as the material of wooden and metal parts.
TMP is also used to build lumber with an increased mass without the use of a carbon cutting or cutting mat. This is achieved using a wood cut tool like a wood hammer or sharp wood saw, or the use of a flat saw.
In the woodcutting program, you can place paper cones, and/or cardboard discs within a wood pile and place them into the wood pile. These will produce an even density. Each disc provides a specific shape (fibres), the roll thickness (polypropylene), and a corresponding rate of grinding. The rolling rate for paper cones is usually from 0 to 15%, between 15 and 180%. The resulting pulp is sometimes even more durable than the pulp produced by a physical cut.
The Woodcut – A paper sheet that has been cut into the desired size or type is then cut with a machine grinding press in a large machine shop or in a home making shop. This produces a wood-like “wood pulp” called a cut. A cut is then held in place by a wooden wheel. The wood pulp then dries out to fill the holes between the board and the cardboard. The wheel then returns to the shop and then the finished document is made. In many other ways, paper pulp is an even more complete product due to the fact it is “bronze rolled”, where the raw pulp is cut for an irregular shape and the cardboard is cut for a softer surface.
The WoodCut – The Woodcut process is the same as the paper cut. For example:
Paper Cut
Wood cut wood pellets (see below).
Wood cut lumber
The woodcut process is not so simple. Each piece of wood is made out of raw wood pulp, which is then crushed to create soft, but still hard wood. The pulp is rolled around, then cut into small pieces. The pulp is then crushed down by a machine grinding press, giving a nice, smooth and shiny
Deinked pulpMain article: deinkingPaper recycling processes can use either chemical or mechanical pulp. By mixing with water and applying mechanical action the hydrogen 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. Generally deinked pulp is of the same quality or lower than the collected paper it was made from.
There are three main classifications of recycled fibre:.Mill Broke or Internal Mill Waste – this incorporates any substandard or grade-change paper made within the paper mill which then goes back into the manufacturing system to be re-pulped back into paper. Such out-of-specification paper is not sold and is therefore often not classified as genuine reclaimed recycled fibre. However, most paper mills have been recycling their own waste fibre for many years, long before recycling become popular.
Preconsumer Waste – this is offcuts and processing waste, such as guillotine trims and envelope blank waste. This waste is generated outside the paper mill and could potentially go to landfill, and is a genuine recycled fibre source. Also includes de-inked preconsumer (recycled material that has been printed but did not reach its intended end use, such as waste from printers and unsold publications).[7]
Postconsumer waste – this is fibre from paper which has been used for its intended end use and would include office waste, magazine papers and newsprint. As the vast majority of this paper has been printed (either digitally or by more conventional means such as lithography or rotogravure), it will either be recycled as printed paper or go through a deinking process first.
Recycled papers can be made from 100% recycled materials or blended with virgin pulp. They are (generally) not as strong nor as bright as papers made from virgin pulp.
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