HALOGEN – A halogen is a chemical element that forms a salt when it reacts with metal. Halogen lamps are illuminated by bulbs that contain a halogen and an inert gas. There are five halogens in the periodic table of chemical elements: fluorine, chlorine, bromine, iodine, and astatine.
Elements: Fluorine; Iodine; Bromine; Chlorine…
Halogens are used in the chemical, water and sanitation, plastics, pharmaceutical, pulp and paper, textile, military and oil industries. Bromine, chlorine, fluorine and iodine are chemical intermediates, bleaching agents and disinfectants.
These fire elements release substances that are toxic to humans in the form of toxic fumes but also cause corrosion of metals. Halogen-free plastics are safer, and products from them are particularly convenient to collection and escape routes (public spaces, railway stations, theaters, cinemas, shopping centers, etc.)
HALOGENATION – Halogenation is a reaction that occurs when one or more halogens are added to a substance. Halogens comprise the seventh column in the periodic table and include fluorine, chlorine, bromine, iodine, and astatine. The resulting product of a halogenation reaction is known as a halogenated compound.
A Halogenation reaction occurs when one or more fluorine, chlorine, bromine or iodine atoms replace hydrogen atoms in organic compound. The order of reactivity is fluorine > chlorine > bromine > iodine. Fluorine is especially aggressive and can react violently with organic materials.
A halogenated compound is one onto which a halogen (e.g., fluorine, chlorine, bromine, or iodine) has been attached. … In addition, the more halogenated the compound (i.e., the more halogens attached to it), the more resistant it is to biodegradation.
HARD RUBBER – Ebonite is a brand name for a material generically known as hard rubber, and is obtained by vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil. Its name comes from its intended use as an artificial substitute for ebony wood.
It is a resinous material mixed with a polymerizing or curing agent and fillers, and can be formed under heat and pressure to practically any desired shape. The bulk of today’s hard rubber is made with SBR synthetic rubber.
Ebonite is a brand name for a material generically known as hard rubber, and is obtained by vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil.
HARDNESS– Hardness is the ability of a material to resist deformation, which is determined by a standard test where the surface resistance to indentation is measured. The most commonly used hardness tests are defined by the shape or type of indent, the size, and the amount of load applied.
Hardness is the resistance of a material to localised plastic deformation. Hardness is just one mechanical measurement and properties such as toughness and strength need to be considered, as hard materials tend to have low toughness and can easily fracture.
Hardness is a measure of how much a material resists changes in shape. Hard things resist pressure. Some examples of hard materials are diamond, boron carbide, quartz, tempered steel, ice, granite, concrete. Ability of material to resist wear, tear, scratching, abrasion cutting is called hardness.
Palladium microalloys have the highest combined strength and toughness of any known material.
HEAT AGING – Heat Aging, Oven Aging exposure is performed in calibrated ovens on engineering polymers that may experience elevated temperature exposure in applications ranging from automotive to industrial.
The samples are placed in an aging oven. The temperature and duration are specified by the customer. The specimens are removed and tested after oven aging is complete.
Sample size is dependent on the tests to be performed after the aging process.
HEAT BUILD UP – Heat buildup testing (also referred to as blow out) is generally conducted by exposing a rubber sample of a specified size and shape to oscillating compressive stresses in a controlled environment. During this process, heat will be generated by the stress.
HEAT EMBRITTLEMENT – The thermal oxidation of polyethylene provides a quality example of chain scission embrittlement. … When silicone rubber is exposed to air at temperatures above 250 °C (482 °F) oxidative cross-linking reactions occur at methyl side groups along the main chain. These cross-links make the rubber significantly less ductile.
Lack of use, exposure to extremely high or low temperatures, or prolonged exposure to UV radiation can all cause rubber’s molecular chains to break down over time — and time itself is a factor, too. Rubber is one polymer that just doesn’t last forever, and its descent into decay begins the moment it’s manufactured.
HEAT HISTORY – The accumulated amount of heat a stock has been subjected to during processing operations, usually after incorporation of the vulcanizing agents. Since vulcanization takes place at elevated temperatures, incipient cure or scorch can take place if heat history has been excessive.
HERTZ, Hz – Frequency is the rate at which current changes direction per second. It is measured in hertz (Hz), an international unit of measure where 1 hertz is equal to 1 cycle per second. Hertz (Hz) = One hertz is equal to one cycle per second. Cycle = One complete wave of alternating current or voltage.
The most dangerous frequency is at the median alpha-rhythm frequencies of the brain: 7 hz. This is also the resonant frequency of the body’s organs.
HOMOPOLYMER – If a polymer consists of only one kind of monomers then it is called a homopolymer, while a polymer which consists of more than one kind of monomers is called a copolymer.
Propylene homopolymer is the most widely utilized general-purpose grade. It contains only propylene monomer in a semi-crystalline solid form. Main applications include packaging, textiles, healthcare, pipes, automotive, and electrical applications.
Neoprene is the homopolymer.
DNA homopolymer tracts, poly(dA). poly(dT) and poly(dG). poly(dC), are the simplest of simple sequence repeats. Homopolymer tracts have been systematically examined in the coding, intron and flanking regions of a limited number of eukaryotes.
HOT MELT ADHESIVE– Hot melt adhesive (HMA), also known as hot glue, is a form of thermoplastic adhesive that is commonly sold as solid cylindrical sticks of various diameters designed to be applied using a hot glue gun.
Hot melt industrial glue can be used in all types of product assembly, such as small joint assembly, large surface lamination, mounting and trip attachment. Product assembly that involves hot melt application can include appliances, mattresses, HVAC and many others.
How do hot-melts work? Hot-melts are applied to a material in the liquid (molten) state. The time between applying the adhesive and then bringing the second material in contact is called open time. When the second material is brought into contact, the adhesive cools down and solidifies very quickly.
HYDROCARBON– A hydrocarbon is an organic chemical compound composed exclusively of hydrogen and carbon atoms. Hydrocarbons are naturally-occurring compounds and form the basis of crude oil, natural gas, coal, and other important energy sources.
If someone accidentally drinks a hydrocarbon product and it enters the lungs, breathing problems can develop. Serious injury or even death may result. Hydrocarbons are oily liquids. Many are not harmful unless the oily liquid gets into the lungs.
In general, hydrocarbon molecules are structured with one or more carbon atoms forming a central structure that is surrounded by hydrogen atoms. There are four main types of hydrocarbons: Alkanes, Alkenes, Alkynes, and Aromatic hydrocarbons. In general, hydrocarbon molecules are structured with one or more carbon atoms forming a central structure that is surrounded by hydrogen atoms. There are four main types of hydrocarbons: Alkanes, Alkenes, Alkynes, and Aromatic hydrocarbons. In general, hydrocarbon molecules are structured with one or more carbon atoms forming a central structure that is surrounded by hydrogen atoms. There are four main types of hydrocarbons: Alkanes, Alkenes, Alkynes, and Aromatic hydrocarbons.
HYSTERESIS– Hysteresis occurs in a system that involves a magnetic field. Hysteresis is the common property of ferromagnetic substances. Generally, when the magnetization of ferromagnetic materials lags behind the magnetic field this effect can be described as the hysteresis effect.
Hysteresis, lagging of the magnetization of a ferromagnetic material, such as iron, behind variations of the magnetizing field.
Haulage – The horizontal transport of ore, coal, supplies, and waste. The vertical transport of the same is called hoisting.
Haulage way – Any underground entry or passageway that is designed for transport of mined material, personnel, or equipment, usually by the installation of track or belt conveyor.
Head – A passage connecting other passages.
Headframe – The structure surmounting the shaft which supports the hoist rope pulley, and often the hoist itself.
Heading – A vein above a drift. An interior level or airway driven in a mine. In longwall workings, a narrow passage driven upward from a gangway in starting a working in order to give a loose end.
Head section – A term used in both belt and chain conveyor work to designate that portion of the conveyor used for discharging material.
Heaving – Applied to the rising of the bottom after removal of the coal; a sharp rise in the floor is called a “hogsback”.
High-Volatile “A” Bituminous Coal – A non-binding bituminous coal with less than 69% fixed carbon, more than 31% volatile matter and 14,000 or more B.T.U.
High-Volatile “B” Bituminous Coal – A non-binding bituminous coal having between 13,000 and 14,000 B.T.U.
High-Volatile “C” Bituminous Coal – A binding or non-weathering coal having between 11,000 and 13,000 B.T.U.
High-Volatile Coals – Coals containing over 32 percent volatile matter.
Highwall – The unexcavated face of exposed overburden and coal in a surface mine or in a face or bank on the uphill side of a contour mine excavation.
Highwall miner – A highwall mining system consists of a remotely controlled continuous miner which extracts coal and conveys it via augers, belt or chain conveyors to the outside. The cut is typically a rectangular, horizontal cut from a highwall bench, reaching depths of several hundred feet or deeper.
Hogsback – A sharp rise in the floor of a seam.
Hoist – A drum on which hoisting rope is wound in the engine house, as the cage or skip is raised in the hoisting shaft.
Hoisting – The vertical transport coal or material.
Horizon – In geology, any given definite position or interval in the stratigraphic column or the scheme of stratigraphic classification; generally used in a relative sense.
Horseback – A mass of material with a slippery surface in the roof; shaped like a horse’s back.
Hydrocarbons – A large class of organic compounds containing only carbon and hydrogen, and occurring in coal, petroleum and natural gas.
Hydraulic – Of or pertaining to fluids in motion. Hydraulic cement has a composition which permits it to set quickly under water. Hydraulic jacks lift through the force transmitted to the movable part of the jack by a liquid. Hydraulic control refers to the mechanical control of various parts of machines, such as coal cutters, loaders, etc., through the operation or action of hydraulic cylinders.
Hydrocarbon – A family of chemical compounds containing carbon and hydrogen atoms in various combinations, found especially in fossil fuels.