ASTM – ASTM American Society for Testing and Materials.
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services.
List of ASTM International standards:
ASTM is a national organization that is a part of ISO organizations. ISO is an international organization that has representations from all countries including ASTM. ISO establishes documents and updates the standards of testing materials with global consensus from the experts of the associated national organizations.
ABRASION RESISTANCE – Abrasion resistance is the ability of materials to withstand the effects of abrasion, for example: repeated wearing, rubbing, scrapping, etc.
Abrasion-resistant materials are handy in inhibiting mechanical wearing and damage. They can be used in the construction of space shuttle components. The abrasion resistance of high-performance concrete is high. This concrete containing silica-fume is useful for concrete pavement overlays where heavy or abrasive traffic occurs more.
Abrasion resistance is a property that allows a material to resist wear. The abrasion resistance of a material helps to withstand mechanical action and tends to protect the removal of materials from its surface. This allows the material to retain its integrity and hold its form. This can be important when the form of a material is critical to its function, as seen when moving parts are carefully machined for maximum efficiency. Abrasion resistance can be measured by using the abrasion scrub tester.
Abrasion resistance can be controlled through:
In rubber, there are two types of abrasion:
ABRASION RESISTANCE INDEX – The resistance to abrasion can be expressed in several ways, the most common are the weight loss (in mg) per number of cycles or the number of cycles (per unit of film thickness) needed to wear through.
ACCELERATED AGING – The Accelerate Aging test simulates real-time aging using elevated temperatures to artificially speed up the aging process. This test enables manufacturers to get their product to market faster. Accelerated aging is optional, but real-time aging is required when establishing an expiration date.
The Accelerate Aging test simulates real-time aging using elevated temperatures to artificially speed up the aging process. This test enables manufacturers to get their products to market faster. Accelerated aging is optional, but real-time aging is required when establishing an expiration date. Often, referred to as Accelerated Shelf-Life Testing – is commonly used in the medical device industry to accelerate the effects of time on a Sterile Barrier System to establish Shelf Life parameters. The Accelerated Aging process is based on the relationship of temperature and reaction rate where an increase in temperature increases the reaction rate.
ACCELERATOR – Accelerants are substances that can bond, mix or disturb another substance and cause an increase in the speed of a natural, or artificial chemical process. Chemical accelerators are used in glove manufacturing to hasten the linkage of molecules in natural rubber latex or in synthetic rubber latex-like nitrile and vinyl. The accelerants transform the liquid materials into thin, strong, and elastic glove films. Accelerator, in the rubber industry, any of numerous chemical substances that cause vulcanization (q.v.) of rubber to occur more rapidly or at lower temperatures. Many classes of compounds act as accelerators, the most important being organic materials containing sulphur and nitrogen, especially derivatives of benzothiazole.
The use of alkaline compounds of metals as vulcanization accelerators was cited in the original patent of the vulcanization process, granted to Charles Goodyear in 1844; magnesium oxide, zinc oxide, and basic lead carbonate were used until early in the 20th century, when the superiority of aniline, an organic compound, was discovered. Despite its toxicity, aniline was used as an accelerator for several years. Thiocarbanilide, less poisonous than aniline, succeeded it as the most important accelerator until it was displaced by mercaptobenzothiazole (MBT) about 1925. Compounds related to MBT have proved especially useful in vulcanizing synthetic rubbers.
During vulcanization, the accelerator apparently converts the sulphur into a compound that reacts more rapidly with rubber than does sulphur itself. An alternative possibility is that the accelerator reacts first with the rubber, changing it into a form that combines rapidly with sulphur.
ACRYLATE RUBBER – acrylate is (organic chemistry) any salt or ester of acrylic acid, Acrylates have found application in the manufacture of co-polymers for coatings and paints, sealants, adhesives, textile fibres, printing inks. It is highly superabsorbent polymers and thus used in diapers. Thermoplastic acrylate co-polymers, in biomedicine and a variety of other advanced application areas.
Acrylate polymers are a group of polymers prepared from acrylate monomers. … They are also commonly known as acrylics or polyacrylates. Acrylate polymer is commonly used in cosmetics, such as nail polish, as an adhesive.
ACRYLIC RUBBER – Acrylic rubber is a copolymer or terpolymer of ethyl acrylate and other acrylates, with a small amount of a vulcanisation-supporting monomer. It is produced by radically initiated emulsion polymerisation or by suspension polymerisation. Curing takes place by means of diamines, fatty acid soaps and peroxides, for example.
ACM is characterised by high oxygen and ozone resistance, thermal stability and good heat and chemical resistance, but it has poor hydrolysis resistance and relatively high-water absorption.
The swelling resistance in the presence of mineral oils is better than that of ethylene acrylic rubber (AEM/Vamac®).
Acrylic rubber is mostly used in the automotive industry because it is resistant to engine and transmission oil and to automatic transmission fluids (ATF). The operating temperature range is between -20°C and +150°C, while the latest generation, HT-ACM (high-temperature-resistant polyacrylate elastomers), offers long-term thermal stability up to 175°C. ACM is used to manufacture components such as engine and transmission seals, turbocharger hoses, O-rings, diaphragms and hose applications. It is also used for roller coverings.
ACRYLONITRILE – acrylonitrile toxic colourless liquid organic compound, CH=CH.CN, synthesized from propylene and ammonia; used as a monomer in the production of acrylic resins and synthetic rubber.
Acrylonitrile is manufactured by combining propylene, ammonia, and air in a process called ammoxidation. During ammoxidation, propylene, ammonia and air are fed through a catalyst at a high temperature.
Acrylonitrile is used in many industries.
It is used to make certain plastics, rubbers, and chemicals, and in the past, as a pesticide. Some examples of workers at risk of being exposed to acrylonitrile include the following: Workers involved in the manufacturing of acrylic fibers and plastics.
ACTIVATOR – Activator may refer to: Activator (genetics), a DNA-binding protein that regulates one or more genes by increasing the rate of transcription. Activator (phosphor), a type of dopant used in phosphors and scintillators. Enzyme activator, a type of effector that increases the rate of enzyme mediated reactions.
Use as an activator:
ADHESION – adhesion is the tendency of dissimilar surfaces to stick to one another. It can be measured in terms of work of adhesion in J/m2. It is the energy needed to separate 1m² of joined materials. It can also be measured as peel in N/m, which is the force required to pull off a strip of material that is 1 meter wide.
Thus, the two measures are identical: 1 J/m2 equals 1 N/m.
It is believed that surface energy is important for adhesion. However, an increase in surface energy does not necessarily improve adhesion, that is, the energy that is required to separate a (viscoelastic) polymer from a surface (often called work of adhesion) is not directly proportional to the surface tension. This can be easily shown: The typical surface energy of a polymer is in the range of 20 to 40 dyne/cm or 40 mN/m, whereas typical peel values are in the range of a 20 to 1000 N/m. Therefore, adhesion forces are at least 100 times and typically 10,000 times stronger. Thus, surface tension plays only a minor role for adhesion contrary to what is often believed. However, surface tension and wetting is still important when it comes to initiating adhesion.
So, what is the root cause of adhesion?
In fact, there are many types of forces that can occur when surfaces come in close contact:
ADHESION FAILURE – When separating adhering materials, two types of failure can occur. In the case of adhesive failure, the bonds between the adhesive and adherend break, i.e., no contaminations from the adhesive and adherend remain on the separated surfaces. This is the preferred failure mode for pressure sensitive adhesive tapes. In the case of cohesive failure, the fracture appears within either the adhesive or adherend. This is the preferred failure mode for structural adhesives.
Adhesion failure refers to the state when the adhesive loses adhesion from one of the bonding surfaces. It is characterized by the absence of an adhesive on one of the material surfaces. Surface treatment is required to fix this failure.
Understanding this state requires a careful analysis of adhesive failures. The failure may be located at the bonding interface with a very thin layer. This interface may be contaminated during surface preparation of the adherend surface and while applying an adhesive.
Adhesion failure happens at the interface between the adhesive layer and the adherends. This failure results from the hydration of the chemical bonds, which form the connection between the adhesive and the bonding surface. An adhesive bond fails when either the adhesive loosens from the substrate or when the adhesive breaks apart.
Adhesion failure is mainly substrate adhesion failure and inter coat adhesion failure. Substrate adhesion failure occurs when the whole coating system that has been used for bonding can be easily detached from the substrate. It shows the absence of adhesion of the whole coating system that has been applied. Causes of this failure are linked to three things:
Inter coat adhesion failure happens when the top coat and primer do not bond. The two primary causes of this failure are:
A common form of adhesion failure is seen when taping the substrate, which has any one of the following characteristics:
ADHESIVE – Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation.
In glues and adhesives, the mechanical adhesion through the pores of the surfaces occurs thanks to the drying or curing process. When the glue goes on, it’s in a thin, liquid adhesive form, which still allows either surface to move freely. This liquid form also allows the adhesive to soak into the pores of the surface.
An adhesive is a substance that sticks to the surface of an object such that two surfaces become bonded. A typical home improvement store carries many different adhesives for many different applications. Why are there so many adhesives? The answer is found in examining how an adhesive works and, in particular, what happens at the molecular level. The interaction of molecules is known as intermolecular bonding, or secondary bonding. Primary bonding, also known as intramolecular bonding, is the interaction of atoms within a molecule and includes covalent and polar covalent bonding. Secondary bonding includes dipole–dipole bonding (the interaction of molecules that have a permanent net dipole moment) and hydrogen bonding (an interaction that occurs when a hydrogen atom is bonded to an N, O, or F atom in a molecule).
Adhesives cure when the small resin molecules (mers) join together to form extremely large molecules known as polymers.
For example, one of the simplest polymers is polyethylene.
The mer (basic building block of the polymer) is ethylene, H 2 C=CH 2 . The addition of an initiator (R·) causes the formation of the radical RCH 2 CH 2 ·. A radical is a species that has an unpaired electron and is very reactive because it seeks the source of electrons. This radical will attach the ethylene mer (the double bond in ethylene is rich in electrons) to start a chain reaction that continues until very large polymer molecules form. This and other forms of polymerization processes are the basis for the formulation of polymers. This process is known as curing when dealing with adhesives.
Two criteria must be met in order for a molecule to possess a permanent net dipole moment: (1) an unequal sharing of electrons within the molecule such that one or more intramolecular bonds has a partial positive end and a partial negative end, and (2) a geometry such that the vector sum of the individual dipole moments does not equal zero. The ability of an atom within a molecule to attract electrons is known as electronegativity, a concept proposed by Linus Pauling who established a table of relative electronegativities. In Pauling’s table, fluorine is the most electronegative element and is given the value of 4.0. The greater the difference in electronegativity between two atoms within a molecule, the larger is the dipole moment in that bond. Because the bond between two atoms having unequal electronegativities has a partial positive end and a partial negative end, it is said to be a polar bond. If the geometry of the molecule is such that the vector sum of all of the dipole moments does not equal zero, then the molecule is polar. The electronegativities for carbon and oxygen are 2.5 and 3.5, respectively; therefore, the carbon–oxygen bond is a polar bond. A carbon dioxide molecule has two carbon–oxygen bonds; however, its geometry is such that the vector sum of the two dipole moments equals zero, and thus carbon dioxide is a nonpolar molecule. The electronegativity of hydrogen is 2.1, thus a hydrogen–oxygen bond would be polar. A water molecule has two hydrogen–oxygen bonds. The geometry of a water molecule (the H–O–H bond angle is 104.5°) is non-symmetrical, hence the vector sum of the dipole moments is not equal to zero and water is a polar molecule.
Polar molecules will attract other polar molecules because of their net dipole moments. Water molecules, however, have an additional attraction for one another, based on hydrogen bonding. This attraction is so strong that, although water is a small molecule and small molecules tend to be gases, water is a liquid at room temperature. This aspect of the chemistry of water demonstrates that hydrogen bonding is a relatively strong force that can hold molecules together.
In order for an adhesive to bond (hold together) two surfaces (substrates), there must be several types of interaction between the adhesive and both substrates.
The first type of interaction is that the adhesive must wet the substrate, meaning that the adhesive must spread itself out into a film that covers the substrate surface. In order for this to happen, the adhesive must have a low enough viscosity so that it will flow. Viscosity is the resistance of a liquid to flow. Water has a low viscosity whereas honey has a high viscosity. Because viscosity is temperature dependent, the application of a cold adhesive to a substrate, or the application of an adhesive to a cold substrate, may result in poor wetting. Another factor that affects wetting is the relative strengths of cohesive forces (between like molecules, such as two adhesive molecules) and those of adhesive forces (between unlike molecules, such as an adhesive molecule and a substrate molecule). If the cohesive forces among adhesive molecules are weaker than the adhesive forces between the adhesive molecules and the substrate surface, then the adhesive molecules will spread out over the substrate and wet its surface. An adhesive that has a relatively low viscosity and is able to wet the substrate surface will flow into any tiny cracks or pores on the substrate surface, thus promoting what is known as mechanical bonding. Mechanical bonding increases the strength of an adhesive bond and, as a result, a forced separation of the two substrate surfaces is more apt to tear the substrate surfaces.
Mechanical bonding is one of several ways that an adhesive, will bond to a substrate.
All surfaces, except those that are highly polished, have pores. If the adhesive flows into these pores and then polymerizes, a mechanical bond is formed. It is similar to placing a wick into liquid candle wax. Once the wax solidifies the wick can not be easily removed. A mechanical bond has formed.
Because the interactions of adhesive molecules with substrates are so critical, it makes sense that some adhesives would be more appropriate for a specific substrate than others. Adhesives are designed for specific applications. For example, adhesives known as “super glues” (cyanoacrylates) are useful around the home in the bonding of common substrates (e.g., dishes, toys, etc.), which can take place in a matter of seconds. Yet their usefulness is limited when bonding wood because the cure time (the time it takes for an adhesive to undergo polymerization and become capable of holding the two substrates together) in this instance is much longer.
Doyle, Daryl J. (1989). “A Review of Ultraviolet (UV) Radiation as an Adhesive Curing Agent.” Society of Manufacturing Engineers Technical Paper AD89–534, Adhesives ’89, September 12–14, 1989, Atlanta, Georgia.
Doyle, Daryl J. (1990). “Criteria for Proper Adhesive Selection: From Application to Viscosity.” Society of Manufacturing Engineers Technical Paper AD90–450, Adhesives ’90, October 1–4, 1990, Schaumburg, Illinois.
Doyle, Daryl J. (1990). “Viscosity and Its Importance to Adhesive Dispensing.” Society of Manufacturing Engineers Technical Paper AD90–710, Adhesive Technology for Automotive Engineering Applications, November 1–2, 1990, Dearborn, Michigan.
Fry, Arthur L. (1989). “The Choir Singer’s Bookmark.” Guideposts.
Plummer, Christine (1993). “The Story of Post-it™ Notes.” Chem Matters.
Adhesive Wear – Adhesive wear is a phenomenon which occurs when two metals rub together with sufficient force to cause the removal of material from the less wear-resistant surface. This wear is dependent on physical and chemical factors such as material properties, presence of corrosive atmosphere or chemicals, as well as the dynamics such as the velocity and applied load.
This phenomenon is considered corrosion by means of mechanical action rather than chemical reaction.
ASTM G77 provides specifications and testing procedures for adhesive wear testing.
Adhesive wear is also known as sliding wear or scuffing wear.
When two metal surfaces come into contact with each other, they initially touch only at a few rough points. Friction and wear originate at these points. When a compressive load is applied, these rough points are plastically deformed and finally welded together because of the high pressure that is created. As sliding continues, these bonds are broken, producing cavities on one surface and depressions on the second surface. Abrasive particles detach and rub against the surface, contributing to wear.
There are several types of adhesive wear:
Adhesive wear can cause problems such as:
The following measures can be taken to prevent adhesive wear:
Adhesive Strength – Adhesive strength refers to the ability of an adhesive to stick to a surface and bond two surfaces together. It is measured by assessing the maximum tensile stress needed to detach or unstick the adhesive perpendicular to the substrate.
The adhesive strength is the maximum tensile stress possible at the interface. It is affected by the coating thickness and the solvent retention, when solvent-containing coatings are used.
When an adhesive is bonded to an item or surface, numerous physical, mechanical and chemical forces come into play, which may affect each other.
Adhesive strength is the measurement of adhesion, or the attachment between adhesive and substrate. This may occur either by mechanical means, in which the adhesive works its way into small pores of the substrate, or by one of several chemical mechanisms.
The strength of adhesion depends on many factors, including the means by which it occurs. Methods of adhesion include:
For example, pressure-sensitive adhesives (PSA) form a bond by the application of light pressure to seal the adhesive with the adherend. The bond forms because the adhesive is soft enough to flow to the adherend. The bond has strength because the adhesive is hard enough to resist flow when stress is applied to the bond. Once the adhesive and the adherend are in close proximity, molecular interactions, such as van der Waals forces, become involved in the bond, contributing significantly to its ultimate strength.
Some high-performance permanent PSAs exhibit high adhesion values and can support kilograms of weight per square centimetre of contact area, even at elevated temperatures. Removable adhesives have low adhesion and generally cannot support much weight.
Determination of the failure point can be critical for the final use of the material and the adhesive. There are a large number of different adhesive products, which require different testing methods to characterize the properties of the material.
Testing may be performed for quality control purposes, but is more typically undertaken to adhere to industry standards and customer specifications. Even in established coating application processes, many factors can influence the adhesive strength of a coating. Seemingly minor variations in process parameters may have significant impacts on the resulting adhesion strength between the coating and the substrate.
ADHESIVE – CONTACT –
ADHESIVE – HEAT ACTIVATED – A heat activated adhesive is a type of adhesive, usually applied to a tape backing, that will not bond at normal temperatures. Instead, it becomes sticky in certain temperatures, wherein the adhesive chemicals are activated and can form a bond.
These tapes are extremely versatile and can be used for bonding in a huge variety of projects. Join us, today, as we dive deep into heat activated adhesive, its uses, benefits, alternatives, and how it all works.
ADHESIVE – SOLVENT ACTIVATED– Solvent activation consists of permitting the adhesive coating to dry completely, dampening the surface of the coating with a fast-drying solvent (e.g., methyl ethyl ketone), quickly aligning the parts, and promptly applying pressure until the adhesive sets and a self-sustaining bond develops.
Most adhesive residue can be removed from glass using acetone, found in most nail polish removers. Apply it to the area with a bit of friction, and the residue should rub away easily. If acetone doesn’t work, apply a small amount of spray lubricant, which can break down the adhesive’s hold on the glass surface.
Different Adhesive Types & How to Use Them
AGE RESISTANCE – As defined by DIN 50035, ageing refers to all the chemical and physical processes that irreversibly occur to a material over time. Polymeric materials can age for a variety of reasons, such as heat, UV radiation and media, and ageing is highly dependent on operating and environmental conditions, e.g. the service temperature.
AGING – is an essential step that ensures that the materials in the alloy do not revert to their original configuration after a time period. Aging is performed under controlled conditions so that the resultant grain structure will create a greater tensile strength in the metal than in its former state. – The selection of polymers and polymer blends for use as specific materials requires the consideration of how these will withstand the environmental conditions to which these will be subjected. The long-term stability of a polymer will depend on its aging characteristics both physical and chemical.
Physical aging is the term used to describe the observed changes in properties of glassy materials as a function of storage time, at a temperature below the glass transition, T g . This phenomenon is important mainly when the materials have a substantial amorphous content. For these materials, a quench from above T g into the glassy state introduces a no equilibrium structure which, on annealing at constant temperature, approaches an equilibrium state via small-scale relaxation processes in the glassy state. The aging process can be detected through the time evolution of thermodynamic properties such as the specific volume or enthalpy or mechanical methods such as creep, stress-relaxation, and dynamic mechanical measurements. Here, the fundamental principles of physical aging will be described, and models that quantitatively describe the aging process are briefly described.
Physical aging effects have practical implications and need to be considered when assessing the long-term stability of polymers and polymer-polymer mixtures. This chapter focuses on a discussion of the effect of blending on physical aging and gives a review of the different experimental methods that can be used to compare aging rates in blends to those of the individual components.
[5:42 AM, 5/17/2021] Stewart Fernandez Australia Upwork: Hot air oven is a widely used testing instrument that is used for analyzing the aging effect on the products and materials. … This gives the difference in the properties due to the aging process Oven ageing is a technique used to simulate the ageing process, artificially speeding it up by generating specific temperature conditions
AGING, AIR OVEN –Hot air oven is a widely used testing instrument that is used for analyzing the aging effect on the products and materials. It is used by different industries and product manufacturers to heat the products for conducting the dry tests in the laboratory.
AIR CHECKS – The quality of air in and around the building which directly affects human health is called Indoor Air Quality (IAQ). According to the research, a healthy and clean office air boosts productivity as much as by 20%, improves cognitive function by approximately 101%, and minimizes absenteeism. Equinox Labs helps in IAQ Monitoring for the corporates and offers solutions to improve and maintain the indoor air quality.
Since indoor air quality affects health and productivity air testing is important, especially during current times when it is crucial to monitor and manage air quality to minimize the spread of COVID-19 through the air.
We have a team of highly skilled professionals and use the latest equipment to manage the IAQ testing services. Our experts meticulously test a range of parameters, assessing the issues causing discomfort at the workplace. We are the trusted laboratory partner to our clients and respond to their needs with dependable testing results.
AIR-CURING – the process of becoming hard or solid by cooling or drying or crystallization. synonyms: hardening, set, solidification, solidifying.
Air curing is accomplished mainly by mechanical ventilation inside buildings. Coke, charcoal, or petroleum gas may be burned to provide heat when conditions warrant.
AMBIENT TEMPERATURE – Ambient is an adjective used to describe an aspect of the environment that completely surrounds you, but in a mellow way, like ambient music played softly throughout a restaurant, or the ambient orange glow during a setting sun.
The only way to really measure the temperature of a room in degrees is with a thermometer. However, if you download an app on your smartphone, you should be able to use the sensors on your phone to calculate the temperature of the room. Another test is using your body and how the room feels.
ANILINE POINT – The aniline point (AP) is an important physical property of a petroleum fraction. The AP gives an indication of the aromatic hydrocarbon content in a hydrocarbon mixture and can also be an indicator of the ignition point of a diesel fraction.
We can improvement aniline point by extraction with furfuraldehyde to decrease aromaticcontent in petroleum products.
Aniline appears as a yellowish to brownish oily liquid with a musty fishy odour. Melting point -6°C; boiling point 184°C; flash point 158°F. Denser than water (8.5 lb / gal) and slightly soluble in water.
ANTIOXIDANT – antioxidants include vitamins C and E, selenium, and carotenoids, such as beta-carotene, lycopene, lutein, and zeaxanthin. This fact sheet provides basic information about antioxidants, summarizes what the science says about antioxidants and health, and suggests sources for additional information.
Antioxidants are substances that can prevent or slow damage to cells caused by free radicals, unstable molecules that the body produces as a reaction to environmental and other pressures. They are sometimes called “free-radical scavengers.” The sources of antioxidants can be natural or artificial.
ANTIOZONANT – An antiozonant, also known as anti-ozonant, is an organic compound that prevents or retards damage caused by ozone. The most important antiozonants are those which prevent degradation of elastomers like rubber. A number of research projects study the application of another type of antiozonats to protect plants.
ANTISTATIC AGENTS – Static effect in plastics applications Insulating materials including most types of plastics tend to build up static charge by separation of positively and negatively charged particles. This static charge can lead to several problems, especially if it discharges spontaneously.
ASH – Ash or ashes are the solid remnants of fires. Specifically, ash refers to all non-aqueous, non-gaseous residues that remain after something burns. … Ashes as the end product of incomplete combustion are mostly mineral, but usually still contain an amount of combustible organic or other oxidizable residues.
AUTOCLAVE – Autoclaves operate at high temperature and pressure in order to kill microorganisms and spores. They are used to decontaminate certain biological waste and sterilize media, instruments and lab ware.
An autoclave is a device that works on the principle of moist heat sterilisation, wherein saturated steam is generated under pressure in order to kill microorganisms such as bacteria, viruses, and even heat-resistant endospores from various types of instruments.
Abutment – In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway; and (2) the weight of the rocks over a longwall face is transferred to the front abutment, that is, the solid coal ahead of the face and the back abutment, that is, the settled packs behind the face.
Acid deposition or acid rain – Refers loosely to a mixture of wet and dry “deposition” (deposited material) from the atmosphere containing higher than “normal” amount of nitric and sulfuric acids. The precursors or chemical forerunners of acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur and nitrogen -oxides resulting from fossil fuel combustion.
Acid mine water – Mine water that contains free sulfuric acid, mainly due to the weathering of iron pyrites.
Active workings – Any place in a mine where miners are normally required to work or travel and which are ventilated and inspected regularly.
Adit – A nearly horizontal passage from the surface by which a mine is entered and dewatered. A blind horizontal opening into a mountain, with only one entrance.
Advance – Mining in the same direction, or order of sequence; first mining as distinguished from retreat.
After Damp – Gasses resulting from underground combustion, normally carbon monoxide. This is a loose term implying any fatal gas in a mine after an explosion or fire.
Air Shaft – A vertical opening into a mine for the passage of air.
Air split – The division of a current of air into two or more parts.
Airway – Any passage through which air is carried. Also known as an air course. Airway – Any passage in a mine along which an air current moves. Some passages are driven solely for air. Other passages, such as a main level, are all purpose, to move air, men, coal, and materials.
Anemometer – Instrument for measuring air velocity.
Angle of dip – The angle at which strata or mineral deposits are inclined to the horizontal plane.
Angle of draw – In coal mine subsidence, this angle is assumed to bisect the angle between the vertical and the angle of repose of the material and is 20° for flat seams. For dipping seams, the angle of break increases, being 35.8° from the vertical for a 40° dip. The main break occurs over the seam at an angle from the vertical equal to half the dip.
Angle of repose – The maximum angle from horizontal at which a given material will rest on a given surface without sliding or rolling.
Anthracite – Coal of the highest metamorphic rank, in which the fixed carbon content is between 92 percent and 98 percent. It is hard, black, and has a semi-metallic lustre and semi-conchoidal fracture. It ignites with difficulty and burns with a short blue flame without smoke.
Anticline – An upward fold or arch of rock strata.
Aquifer – A water-bearing bed of porous rock, often sandstone.
Arching – Fracture processes around a mine opening, leading to stabilization by an arching effect.
Area (of an airway) – Average width multiplied by average height of airway, expressed in square feet.
Auger – A rotary drill that uses a screw device to penetrate, break, and then transport the drilled material (coal).
Auxiliary operations – All activities supportive of but not contributing directly to mining.
Auxiliary ventilation – Portion of main ventilating current directed to face of dead end entry by means of an auxiliary fan and tubing.
Azimuth – A surveying term that references the angle measured clockwise from any meridian (the established line of reference). The bearing is used to designate direction. The bearing of a line is the acute horizontal angle between the meridian and the line.