GR-S– any of a class of general-purpose synthetic rubbers that are made by copolymerizing emulsions of butadiene and styrene commonly at a temperature of either 122° F or 41° F and that are used especially in tires.
The rubber designated GRS (Government Rubber Styrene), a copolymer of butadiene and styrene, was the basis for U.S. synthetic rubber production during World War II.
Natural rubber is obtained from latex, a milky liquid present in either the latex vessels (ducts) or in the cells of rubber-producing plants. Around 20,000 species of plants produce latex, but only 2,500 species have been found to contain rubber in their latex.
The definition of a gage is a deposit or something given as a challenge to start a fight. An example of a gage is money left for a layaway item. An example of a gage is a hat thrown down to indicate a person wants to fight. Some common synonyms of gauge are criterion, standard, touchstone, and yardstick.
GARVEY DIE EXTRUSION TEST – A procedure for rating the extrusion characteristics of a rubber compound by extruding under prescribed conditions through a die of prescribed contour and dimensions. Named after its inventor, Benjamin Garvey.
GEHMAN FREEZE TEST – An apparatus for measuring the relative stiffening of rubber specimens at low temperatures by measuring the resistance to twisting at specified temperatures.
GLASS TRANSITION POINT– Glass Transition Temperature (referred herein as Tg) is the point at which a material goes from a hard brittle state to a soft rubbery state. Amorphous polymers only have a Tg. … Tg is typically calculated by using a half-height technique in the transition region.
The glass transition is not considered a first-order phase transition, but a kinetic phenomenon or a second-order transition. The glass transition is a temperature range over which the amorphous regions change from a brittle glassy state to a flexible rubbery state as they are heated.
GRAIN – The unidirectional orientation of rubber or filler particles occurring during processing (extrusion, milling, calendaring) resulting in anisotropy of a rubber vulcanizate.
GREEN STOCK – Raw, unvulcanized compound.
GREEN STRENGTH – Green strength, or handling strength, can be defined as the strength of a material as it is processed to form its final ultimate tensile strength. This strength is usually considerably lower than the final ultimate strength of a material.
Typically, a green strength of 4000 psi is needed for green machining. High green strength is also required to eliminate green cracks due to handling and excessive ejection stresses. Table V tabulates the green and sintered properties of FN-0208 mixes as a function of die temperature during compaction.
Green strength is a term used to describe a molded or cast products ability to withstand handling, mold ejection, and machining before it is completely cured or hardened. … This process must not, of course, damage or alter the finished product so a high green strength rating in any product is a desirable characteristic.
GUAYULE RUBBER – Guayule (Parthenium argentatum) is a relatively new commercial crop and the only species other than the Brazilian rubber tree (Hevea brasiliensis) that has been used for latex pro- duction on a commercial scale. Guayule is the only source of natural rubber latex free of tropical proteins.
Guayule, a new source of natural rubber
Guayule is an evergreen shrub that originated in the arid zone from the southwestern part of the USA to northern Mexico and therefore can be grown in environments totally different from those suited for para rubber trees.
Guayule is a shrub native to Chihuahuan Desert of Texas. The low-protein latex of Guayule, harvested from the roots of the plant, is safe for protein allergy users. … Its roots contain 4–5% of high-quality rubber, as resilient as Hevea-based rubber but better than the Guayule’s rubber for tire production.
GUM STOCK OR COMPOUND – Rubber compounding involves the science and engineering of rubbers and rubber additives, such as processing aids, fillers, and curing agents, in definite proportions to obtain a uniform mixture that will have desirable physical and chemical properties to meet processing at low cost and end use performance.
The two most common elements found in natural rubber are carbon and hydrogen. … Styrene-butadiene rubber is the most common synthetic rubber because of how cheap it is to produce. Styrene and butadiene are combined and react to form a compound, which is 25 percent styrene and the rest that is comprised of butadiene.
The main chemical constituents of rubber are elastomers, or “elastic polymers,” large chainlike molecules that can be stretched to great lengths and yet recover their original shape. The first common elastomer was polyisoprene, from which natural rubber is made.
GUTTA-PERCHA– Gutta-percha is a material used to fill a tooth after a root canal procedure. Gutta-percha, a plastic substance from a Malaysian tree called a percha tree, is used as a permanent filling in root canals.
Gutta-percha (GP) has been the most widely used root canal filling material because of its well-known low toxicity.
Gallery – A horizontal or a nearly horizontal underground passage, either natural or artificial.
Gasification – Any of various processes by which coal is turned into low, medium, or high Btu gases.
Gathering conveyor; gathering belt – Any conveyor which is used to gather coal from other conveyors and deliver it either into mine cars or onto another conveyor. The term is frequently used with belt conveyors placed in entries where a number of room conveyors deliver coal onto the belt.
Geologist – One who studies the constitution, structure, and history of the earth’s crust, conducting research into the formation and dissolution of rock layers, analysing fossil and mineral content of layers, and endeavouring to fix historical sequence of development by relating characteristics to known geological influences (historical geology).
Gob – The term applied to that part of the mine from which the coal has been removed and the space more or less filled up with waste. Also, the loose waste in a mine. Also called goaf.
Global climate change – This term usually refers to the gradual warming of the earth caused by the greenhouse effect. Many scientists believe this is the result of man-made emissions of greenhouse gases such as carbon dioxide, chlorofluorocarbons (CFC) and methane, although there is no agreement among the scientific community on this controversial issue.
Grain – In petrology, that factor of the texture of a rock composed of distinct particles or crystals which depends upon their absolute size.
Grizzly – Course screening or scalping device that prevents oversized bulk material form entering a material transfer system; constructed of rails, bars, beams, etc.
Ground control – The regulation and final arresting of the closure of the walls of a mined area. The term generally refers to measures taken to prevent roof falls or coal bursts.
Ground pressure – The pressure to which a rock formation is subjected by the weight of the superimposed rock and rock material or by diastrophic forces created by movements in the rocks forming the earth’s crust. Such pressures may be great enough to cause rocks having a low compressional strength to deform and be squeezed into and close a borehole or other underground opening not adequately strengthened by an artificial support, such as casing or timber.
Gob – The void resulting from excavation of coal and also meaning the area from where coal has been extracted and the roof has been allowed to fall in.
Gunite – A cement applied by spraying to the roof and sides of a mine passage.