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Topic: Vulcanization

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	Untitled Document
		The vulcanization of polyolefinic rubbers can be defined as the process by which the reaction between the polyolefin and sulphur results in greatly increased elastic properties of the polyolefin and the maintenance of these properties over a comparatively wide temperature range.
		In the early days of vulcanization, before the introduction of modern accelerators but when the advantages of adding a little organic base were appreciated, trial and error had shown that around 2.5 pphr sulphur gave a good useful vulcanized rubber product and this came to be known as a conventional vulcanizate.
		In the early 1920’s it was discovered that natural rubber latex could be vulcanized over a period of several hours by the addition of the usual ingredients – sulphur, zinc oxide and an accelerator –; to the warm latex.
	www.bouncing-balls.com /chemistry_tech_conservation/vulcanization.htm (1263 words)

	Vulcanization
		Vulcanization is a chemical process performed on rubber to strengthen it by causing polymer molecules to interlink with other polymer molecules.
		Rubber being vulcanized is usually exposed to sulfur or peroxide for curing; the sulfur atoms are released, and grow "bridges" from rubber molecule to rubber molecule, creating a tight network throughout the rubber structure.
		Vulcanized rubber was invented by the Mesoamericans, but the first commercial use was Charles Goodyear, who found a commercial means to vulcanize rubber in 1839.
	www.iscid.org /encyclopedia/Vulcanization (218 words)

	Vulcanization - Wikipedia, the free encyclopedia
		Vulcanization, or curing, of rubber, is a chemical process in which individual polymer molecules are linked to other polymer molecules by atomic bridges.
		Vulcanization is generally considered to be an irreversible process (see below), and must be contrasted strongly with thermoplastic processes (the melt-freeze cycle) which characterize the behavior of most modern polymers.
		Similar to vulcanization, in the rubber recycling process, devulcanization begins as a process by which the sulfur molecules are delinked from the rubber molecules, thereby facilitating the formation of new cross-linking structures.
	en.wikipedia.org /wiki/Vulcanization (2417 words)

	vulcanization. The Columbia Encyclopedia, Sixth Edition. 2001-05
		Vulcanization is accomplished usually by a process invented by Charles Goodyear in 1839, involving combination with sulfur and heating.
		A method of cold vulcanization (treating rubber with a bath or vapors of a sulfur compound) was developed by Alexander Parkes in 1846.
		After the sulfur and rubber (and usually an organic accelerator, e.g., an aniline compound, to shorten the time or lower the heat necessary for vulcanization) are mixed, the compound is usually placed in molds and subjected to heat and pressure.
	www.bartleby.com /65/vu/vulcaniz.html (294 words)

	MFA - CAMEO - Print Page
		Vulcanization is a process used to harden and strengthen rubber.
		In the initial process, vulcanization was done by first heating rubber till it became a viscous mass, then sulfur compounds were added and the mixture cooled.
		When vulcanized rubber is exposed to heat or light, it can degrade, forming a brownish, brittle material that may evolve sulfurous oxides.
	www.mfa.org /_cameo/frontend/material_print.asp?name=vulcanization&type=description (184 words)

	:.:.: ROmiLL.com - INDUSTRIAL MICROWAVE HEATING » RUBBER :.:.:
		In extruder the temperature is increased to 80°C-90°C while ahead of the vulcanization tunnel the MW preheating section is deployed to increase the temperature aprox.
		After passing the MW tunnel it is kept on the vulcanization temperature for the period of 60-90 seconds conventionally, i.e.
		Vulcanization and devulcanization is also often processed in batch system under high pressure – both can be very effectively speeded up and economized using the microwave preheating for suitable temperature.
	www.romill.cz /?lang=eng&show_dir=39 (886 words)

	Vulcanization process using basic zinc carbonate hydroxide - Patent 5332787
		A process is provided for vulcanizing a halogen-containing copolymer of a C.sub.4 to C.sub.7 isomonoolefin and a para-alkylstyrene utilizing a vulcanization mixture comprising a basic zinc carbonate hydroxide.
		Optionally, additional vulcanization modifiers may be present in the vulcanization zone of the vulcanization process of the present invention.
		The vulcanization mixtures used and the resulting properties are summarized in Table I. The parts shown in the Table are parts by weight per hundred parts of rubber (phr).
	www.freepatentsonline.com /5332787.html (3223 words)

	Introduction
		The time required for the vulcanization chemical process is determined by the vulcanization plateau, where the values of the most important physico-mechanical indicators (modulus, tensile strength, etc.) are optimal.
		The reason for this incomplete vulcanization is to avoid reversion and overcure that may occur due to the heat produced during the tyre use, which can lead to a continuation of the vulcanization process.
		The vulcanization time is established practically by means of a nomograme built based on the calculated thermal coefficient and on some experimental results.
	www.tut.fi /plastics/tyreschool/moduulit/moduuli_4/hypertext_2/3/3_1.html (962 words)

	Vulcanization Summary
		Vulcanization is generally considered to be an irreversible process (see below), similar to other thermosets and must be contrasted strongly with thermoplastic processes (the melt-freeze process) which characterize the behavior of most modern polymers.
		Similar to vulcanization, in the rubber recycling process, devulcanization begins as a process by which the sulfur molecules are delinked from the rubber molecules, thereby facilitating the formation of new cross-linking structures.
		The AMR Process exploits the molecular characteristics of vulcanized rubber powder in conjunction with the use of an activator, a modifier and an accelerator reacting homogeneously with particle of rubber.
	www.bookrags.com /Vulcanization (3689 words)

	Vulcanization system, rubber mixture containing said system and a process of vulcanization - Patent 4340695
		Whereas in so-called normal sulphur vulcanization the quantities of sulphur used are about 1.8 to 2.5 phr (parts by weight, based on 100 parts by weight of rubber), "semi-efficient systems" operate with medium quantities of sulphur amounting to about 1 to 1.8 phr while "efficient systems" use less than 1 phr of sulphur.
		Compared with normal sulphur vulcanization, however, the use of smaller quantities of sulphur entails disadvantages with regard to the tear resistance, tear propagation resistance, abrasion resistance and tyre cord bonding of the vulcanizates, so that the application of vulcanization with low or medium quantities of sulphur is limited.
		Vulcanization of the diene rubbers is generally carried out at temperatures in the range of from 100.degree.
	www.freepatentsonline.com /4340695.html (3101 words)

	RT/Dygert International :: Technical Info
		rubber, vulcanized compound: a crosslinked elastic material compounded from an elastomer, susceptible to large deformations by a small force and capable of rapid, forceful recovery to approximately its original dimensions and shape upon removal of the deforming force.
		vulcanization: an irreversible process during which a rubber compound, through a change in its chemical structure (for example, crosslinking), becomes less plastic and more resistant to swelling by organic liquids, while elastic properties are conferred, improved, or extended over a greater range of temperature.
		vulcanizing system: the combination of vulcanizing agent and, as required, accelerators, activators, and retarders used to produce the desired vulcanizate characteristics.
	www.rtdygert.com /technical/rubber_terms.cfm (5403 words)

	From tree to tire - News & Info Services > Customer Magazine \| Linde Gas Division
		Given the importance of vulcanization in determining the quality of the finished product, it’s not surprising that many tire manufacturers are looking at ways of optimizing this process.
		Vulcanized rubber is not only more elastic, it’s also stronger, more resistant to abrasion, much less sensitive to temperature, impermeable to gases and highly resistant to chemicals.
		Vulcanization is not the only area in the tire manufacturing process where industrial gases can offer productivity and environmental advantages.
	www.linde-gas.com /international/web/lg/com/likelgcomn.nsf/docbyalias/kh_2005_01_08 (420 words)

	[No title] (Site not responding. Last check: 2007-10-29)
		Of these substances, styrene butadiene rubber is desirable from the standpoints of vulcanization physical properties and economic factors, and chloroprene is desirable from the standpoint of increased flame-retarding properties.
		The vulcanization agent that is dispersed in the oil-extended oil used in agent B may be a sulfur vulcanization agent, with sulfur being preferred.
		The quantity of vulcanization agent should be 0.5 to 20 parts by mass per 100 parts by mass of rubber solid components.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/96710.011220&ELEMENT_SET=DECL (2528 words)

	[No title] (Site not responding. Last check: 2007-10-29)
		Dynamic vulcanization is effected by mixing the resin and chloromethylated (styrene-isobutylene) copolymer at a temperature which is at or above the curing temperature of the copolymer in equipment to provide high shear such as roll mills, Banbury Registered TM mixers, continuous mixers, kneaders or mixing extruders, e.
		For example, vulcanization can be commenced in a twin screw extruder and pellets formed of the DVA material using an underwater pelletizer thereby quenching the vulcanization before it is completed.
		The blend is then dynamically vulcanized under similar conditions with the same amount of curative based on the rubber content of the blend as was required for the rubber alone.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=01/96476.011220&ELEMENT_SET=DECL (3875 words)

	Kinetics of the vulcanization process
		The kinetics of rubber vulcanization is very important from both practically and theoretically point of view, because it allows for finding the optimum vulcanization conditions and elucidating some reaction mechanisms.
		During the vulcanization of rubber compounds, the elementary sulfur content considerably decreases due to its chemically attachment to polymer molecules.
		When large or thick objects are vulcanized, the vulcanization rate is not uniform within the product, due to the fact that temperature is not uniform.
	www.cc.tut.fi /plastics/tyreschool/moduulit/moduuli_4/hypertext_2/2/2_12.html (379 words)

	Latex Chemistry and Vulcanization
		Vulcanization is simply a process of improving the characteristics or properties of natural or synthetic rubber by heating it with sulfur.
		To produce the effect of vulcanization in latex, the various vulcanizing chemicals and other 'improvers' must be added as a liquid emulsion.
		To begin to understand vulcanization, remember that rubber molecule is a very long thread polymer made up of millions of monomer units called isoprene.
	www.gloves.com.my /vulcanization.htm (1091 words)

	FHI - Chapter 4: Recent Advances in the Research, Development and Manufacture of Latex Rubber Condoms
		Vulcanization, a chemical curing process, increases the strength and resilience of rubber by forming sulfur-sulfur crosslinks between polymeric strands of the latex.
		Vulcanization enables elastomeric materials to return to their shape more easily after being stretched and reduces the amount of change in shape.
		Shelf Vulcanization -- A decrease in strain properties, with little or no decrease in stress properties, suggests that the condoms were well protected from oxidative deterioration by good packaging but underwent shelf vulcanization, resulting in a stiffer, less elastic condom.
	www.fhi.org /en/RH/Pubs/booksReports/latexcondom/recentadvances.htm (3069 words)

	Neoprene: The First Synthetic Rubber (Site not responding. Last check: 2007-10-29)
		One of these tweaks, she said, is "vulcanization," a process named for the Roman god of fire.
		During vulcanization, another type of joining takes place--'atomic bridges' of sulfur are formed between the chains.
		Vulcanized rubbers, such as neoprene, are called "thermoset" materials because vulcanization, like baking a cake, is an irreversible process.
	www.science-education.org /classroom_activities/chlorine_compound/neoprene.html (707 words)

	Invent Now \| Hall of Fame \| Search \| Inventor Profile
		Rubber products melted in hot weather, froze and cracked in cold, and adhered to virtually everything until the day in the mid-19th century when inventor Charles Goodyear accidentally dropped some rubber mixed with sulfur on a hot stove.
		Goodyear's discovery of what came to be known as vulcanization strengthened rubber so it could be applied to a vast variety of industrial uses, including, eventually, automobile tires.
		The famous vulcanizing process, patented in 1844, was to revolutionized the rubber industry, but Goodyear was unable to profit financially from his discovery.
	www.invent.org /hall_of_fame/68.html (202 words)

	LANXESS Levapren® - Vulcanization
		Insensitive to heat, UV light and ozone due to saturated molecular structure
		All the tried and tested methods used to crosslink other polymers with a low double bond content are therefore ideal for optimal vulcanization of this polymer, e.g.
		Levapren® can be vulcanized with organic peroxides under normal conditions, i.e.
	www.levapren.com /lvp/en/about/vulcanization (158 words)

	Expert: Rubber Compounding, Polymer Bends, Vulcanization, Filler Dispersion Expert
		He has primarily studied its vulcanization and the development of properties as a function of compounding variables (selection and concentrations of additives) during his industrial career.
		He has written extensively on the vulcanization of natural rubber and on its blends with plastics and has been awarded numerous patents in these areas.
		Often, the particulate rubber was formed in situ by the dynamic vulcanization process (the vulcanization of rubber during its molten-state mixing with a thermoplastic material).
	www.intota.com /viewbio.asp?bioID=614639&perID=712809 (1607 words)

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