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Glossary

Abrasion
The wearing away of materials by friction. Particles become detached by a combined cutting, shearing and tearing action.
Accelerated Test
A test procedure in which conditions are increased in magnitude to reduce the time required to obtain a result. To reproduce in a short time the deteriorating effect obtained under normal service conditions.
Acid Stratification
Electrolyte strength density becomes higher at the bottom of the cell versus the top. To be avoided as much as possible, this condition can occur during acid filling or during the cycling.
Additive
A component that may be added to a material to modify its properties and in general, enhance its performance. Additives include catalysts, colorants, flame retardants and other ingredients that expand and improve the capabilities of the material.
Adhesive
The method of joining two substrates using either paste, liquid or film.
Ambient
The surrounding area; encompassing on all sides. In composites, refers to environmental conditions such as temperature, humidity, and pressure.
Antistick
A coating or surface treatment that prevents the gasket material from adhering to the flanges.
Application Cure
A gasket material is cured in application due to the temperature exposure.
Aspect Ratio
Ratio of length to diameter. For a composite, it refers to the specific ratio of the fiber or filler in the composite matrix.
Aramid
Used as a high-strength, high modulus (stiffness) fiber. It is a type of highly oriented organic material derived from polyamide, but incorporating aromatic ring structure.
Aging
The effect on materials of exposure to an environment for an interval of time. The process of exposing materials to an environment for an interval of time.
Beater Addition
A manufacturing process used to make gasket material. A water based process where the elastomer is chemically deposited onto the fibers and fillers.
Binder
The elastomer or rubber used in gasket material.
CFRP
Carbon fiber reinforced plastic.
CTE
Coefficient of Thermal Expansion is the change in length (or volume) per unit length (or volume) produced by one degree Celsius rise in temperature.
Carbon Fiber
Fiber produced by the prolysis of organic precursor fibers such as rayon, polyachrylonitrile (PAN) and pitch in an inert environment.
Catalyst
A substance that initiates a chemical reaction and enables it to proceed under milder conditions than otherwise required and which does not, itself, alter or enter into the reaction.
Chopped Strand Mat
A fiberglass reinforcement that utilizes continuous rovings that are cut into short strands, arranged in a random pattern and held together with a binder.
Compressibility
The amount (%) of material thickness reduction that occurs when the proper external load is applied to a material according to ASTM F 36 test procedures.
Compression Recovery
Measured under dry or wet conditions, a measure of the separator’s ability to recover or bounce back from compressive force. During the battery cycling process, the plates expand and contract. The separator needs the ability to recover from the compression throughout the life of the battery.
Crimp
Waviness of a fiber, a measure of the difference between the length of the unstraightened and straightened fibers.
Cycling
One discharge and recharge = 1 cycle
Deep Cycle
Depth of discharge of up to 80%.
Density
A measure of the mass of a material divided by its volume. For separators, density is determined by dividing grammage by thickness and expressed as G/m2/mm – roughly amount of material weight per unit volume.
Dielectric
The average voltage gradient at which dielectric failure or breakdown occurs under prescribed conditions. The dielectric strength is expressed in volts per mil of thickness.
Dieletric Strength
The property of an insulating material that enables it to withstand electric stress. The average potential per unit thickness at which failure of the dielectric material occurs. The higher the dielectric strength, the greater insulating properties of the material.
Dimensional Stability
Ability of a part to retain the precise shape to which it was molded, cast, or otherwise fabricated.
Dry Compression
The percent thickness loss of a separator under various loads as compared to the defined load for target thickness. It can be used as an indicator of how much a separator will compress in the manufacturers assembly process while stuffing the element in the container.
Dynamometer
An instrument for measuring force exerted or power expended.
Electrical Resistance
The measure of the opposition that a circuit presents to the passage of a current when a voltage is applied. AGM separators show far lower resistance as compared to traditional separators for flooded batteries.
Elongation
The increase in length of a material. Elongation relates to elasticity and may be an indicator of a separator's ability to resist cracking or fracturing during the assembly process, particularly at the fold of a separator wrapped around a plate.
Elongation at Break
Elongation recorded at the moment of rupture of the specimen, often expressed as a percentage of the original length.
FRP
Fiber-Reinforced Plastic. A general term for a composite that is reinforced with cloth, mat, strands, or any other fiber form.
Fatigue
The lessening or failure of mechanical properties after repeated applications of stress.
Filler
An inorganic addition to a material that may impart a variety of performance improvements such as shrinkage control, surface smoothness, water or heat resistance or is added to lower cost or density. Sometimes the term is used specifically to mean particulate additives.
Finish
A mixture of materials that is applied to fibers that improve the bonding characteristics of the resin to the fiber.
Float
Low constant voltage charge applied to back-up power applications to keep the battery full charged (Telecom/UPS/Other).
Fluid Immersion
A test method for measuring a sealing material's resistance to the fluid it is being used to seal. Fluid immersions can be performed with any fluid that needs to be sealed in a mechanical assembly, but ASTM specifies standard fluids that are used as indicators for various types of applications. The standard fluids that are used on product specifications are distilled water, ASTM Fuel B and ASTM Oil #3.
Glass Fiber
Fiber drawn from an inorganic product of fusion that has cooled without crystallizing.
Glass-Transition Temperature
The midpoint of the temperature range over which an amorphous material changes from (or to) a brittle, vitreous state to (or from) a plastic state.
Hardness
Resistance to indentation. Usually measured with a Durometer. See ASTM D 2240.
Ignition Loss
The weight of material sample that is lost when the material is exposed to excessive temperature.
Isotropic
Having uniform properties in all directions.
Impregnate
In reinforced plastics, to saturate the reinforcement with a resin. A process of filling the interstices of a porous body with polymer compound.
Mil
A unit of measurement: 1 mil = 0.001 inch.
Modulus
The ratio of stress to strain. A high modulus indicates a stiff material.
Off-Gassing
Off-gassing in batteries occurs during end-of-charge cycle and in float as a result of over-charge. Some of this is by design. Excessive off-gassing results in battery dry-out. Impurities in the system such as iron can contribute to excessive gassing.
PSoC Cycling
The battery routinely operates in a Partial State of Charge (i.e. is not fully recharged between cycles). This is a challenging environment for lead-acid batteries. The new stop-start automobile platform now requires the battery to operate in a PSoC condition.
Permeability
The passage or diffusion rate of a gas, vapor, liquid or solid through a barrier without physically or chemically affecting it.
Phenolic
A thermosetting resin produced by the condensation of an aromatic alcohol particularly based on phenol (carbolic acid) and formaldehyde.
Pore Size
Typically stated in microns for battery separators, pore size has a direct relationship with fiber diameter.
Porosity
The ratio, usually expressed as a percentage of the volume of voids (empty spaces) in a material, to the total volume of a material, including the voids. Porosity for AGM Separators is expressed as a percent between 0–100%. Typical porosity range for an AGM separator is 90-95%.
Prepreg
A cloth, mat, unidirectional fiber, or paper impregnated with resin and stored for use. Also semi-hardened construction made by soaking strands or roving with resin.
Pultrusion
A continuous process for manufacturing composites that have a crosssectional shape. The process consists of pulling a fiber-reinforcing material through a resin impregnation bath and through a shaping die, where the resin is subsequently cured.
Puncture Resistance
A defined test to approximate the separator’s ability to resist penetration or puncture from plate imperfections such as sharp edges or paste imperfections.
Recovery
Expressed in %, it is a measure of the resiliency of the material. The number indicates the percentage of "spring back" of the material after it has been compressed under a given load (the standard loads for materials are the same as those used for compression). For example, a material with 60% recovery means it regains 60% of the thickness it lost after being compressed under a given load.
Separator Basis Weight
Also known as grammage, separator basis weight is expressed in grams per square meter.
Separator Thickness
Separator thickness is defined with one of several predefined tests under a stated load. BCI test protocol calls for 10 kPa, JIS protocol calls for 20 kPa.
Shallow Cycle
Depth of discharge may be as low as 2-5% for a typical automotive battery.
Specific Surface Area
Expressed as m2/gram. Smaller diameter fibers mean higher specific surface area and smaller pores. A common measurement technique is BET Surface area. This test is time-consuming and therefore not practical for production control. Air resistance can be used as a quick method for estimating surface area.
Surface Roughness
The deviation of the topography of an actual surface from an ideal atomically smooth and planar surface.
Surfacing Veil
An ultrathin material that is used to enhance the quality of the surface finish of a composite part. It can impart ultraviolet protection as well as concealing the pattern of the reinforcement.
Tensile Strength
The maximum stress that can be applied in the plane of the gasket material (not perpendicular to its surface) while stretching a specimen to rupture.
Tensile Strength
A separator's strength is typically measured in the machine direction (MD), the direction of the flow of the separator in its manufacturing process, and Cross Machine Direction (XMD). MD tensile is typically higher than that of XMD. Tensile is one indicator of how well a separator may process during battery assembly.
Thermal Conductivity
A measure of the rate at which a material conducts heat through its thickness.
Thermoplastic
A resin that is not cross linked. Thermoplastic resin generally can be remelted and recycled.
Thermoset
A resin that is formed by cross linking polymer chains. A thermoset resin cannot be melted and recycled because the polymer chains form a three dimensional network.
Torque
A measure of force applied to an object to create a rotational or twisting effect about some point.
Ultimate Load
The maximum stress a material can withstand at the point of failure.
VRLA
Valve Regulated Lead Acid battery. Hydrogen and oxygen released in recharging are held under pressure in the system allowing them to more easily recombine into H2O or H2SO4 through the separator. Valves are designed to release gas if pressure builds beyond the system design parameters.
Vibration Resistance
AGM batteries have excellent vibration resistance for use in off-road vehicles or heavy equipment as compared to more traditional flooded batteries. AGM separators can be optimized for vibration conditions.
Wet Compression
See dry compression. In this case, the test is done with a wet separator. It is an indicator of how much the separator will relax once the acid is added to the cell and can be used to estimate final cell compression.
Wicking Height
A measure of how high acid will wick up a separator, under controlled conditions, when upright, with one end dipped in acid. Generally speaking, finer fiber will create smaller pores with higher capillary attraction resulting in greater wicking height.
Wicking Speed
A measurement of the speed at which acid will wick up a separator when upright with one end dipped in acid. Generally speaking, larger pores will allow for faster wicking but will have an inverse relationship to wicking height (see wicking height above).
Young's Elastic Modulus
The ratio of tensile or compressive stress to corresponding strain below the proportional limit of the material.