|
Click
on a letter: Acceptance test, a test, or series of tests
conducted by the procuring agency, or an agent thereof, upon receipt to
determine whether an individual lot of materials conforms to the purchase
order or contract or to determine the degree of uniformity of the material
supplied by the vendor, or both. Accelerator, a material that, when mixed with a catalyst
or a resin, speeds up the chemical reaction between the catalyst and the
resin. Acrylic resins, Polymers of acrylic or methacrylic esters,
sometimes modified with nonacrylic monomers such as the ABS group. Acrylics
are widely used in lighting fixtures because they are either slow burning
or self-extinguishing, and do not produce harmful smoke or gases in the
presence of flame. Activation, The chemical process of making a surface more
receptive to bonding with a coating or an encapsulating material. Additive, A substance added to another substance, usually
to improve properties, such as plasticizers, initiators, light stabilizers,
and flame retardants. Adduct, A chemical addition product. Adhere, to cause two surfaces to be held together by adhesion Adherend, a body held to another body by an adhesive. (See
also substrate.) Adhesion, the state in which two surfaces are held together
by interfacial forces which may consist of valence forces or interlocking
action, or both. Mechanical adhesion, an adhesion between surfaces in
which the adhesive holds the parts together by inter- locking action. Adhesive, a substance capable of holding materials together
by surface attachment. Adhesive assembly, a group of materials or parts, including
adhesive, placed together for bonding or which has been bonded together. Adhesive failure, rupture of an adhesive bond, such that
the separation appears to be at the adhesive adherend interface. Adhesive strength, The strength of the bond between an adhesive
and an adherend. Air-bubble void, Air entrapment within a molded item or
between the plies of reinforcement or within a bond line or encapsulated
area; localized, non-interconnected and spherical in shape. Anhydride, A compound from which water has been extracted,
an oxide of a metal or non-metal that forms a base or an acid when united
with water. Anisotropic, Exhibiting different properties when tested
along axes in different directions. Not isotropic. Apparent viscosity, resistance to shear at a given rate
of shear, expressed as viscosity in absolute units. Aromatic, Unsaturated hydrocarbon with one or more benzene
ring structures in the molecule. Ash content, Proportion of the solid residue remaining after
a reinforcing substance has been incinerated. Assembly adhesive, an adhesive that can be used for bonding
parts together, such as in the manufacture of a boat, airplane, furniture,
and the like. Assembly time, the time interval between applying the adhesive
on the substrate ant the application of pressure, heat, or UV light, to
the assembly. Batch, the manufactured unit or a blend
of two or more units of the same formulation and processing. Block coploymer, An essentially linear copolymer consisting
of a small number of repeated sequences of polymeric segments of different
chemical structure. Bond, the union of materials by adhesives. Bond line, the layer of adhesive which attaches two adherends. Bond strength, the unit load applied to tension, compression,
flexure, peel, impact, cleavage, or shear, required to break an adhesive
assembly with failure occurring in or near the plane of the bond. Branched polymer, In the molecular structure of polymers,
a main chain with attached side chains, in contrast to a linear polymer.
Two general types are recognized, short-chain and long-chain branching. B-stage, in polymer chemistry, an intermediate stage in
a thermosetting resin reaction in which the material softens when heated,
and swells but does not dissolve in certain liquids. Burning rate, The tendency of plastic articles to burn at
given temperatures. Calorimeter, An instrument capable of making
absolute measurements of energy deposition in a material by measuring
its change in temperature and imparting the knowledge of the characteristics
of its material construction. Carbon black, A black pigment produced by the incomplete
burning of natural gas or oil. It is widely used as fillers, particularly
in the rubber industry. Because it possesses useful ultraviolet radiation
protective properties, it is also used in molding compounds intended fir
outside weathering applications. Catalyst, a substance that initiates or changes the rate
of chemical reaction, but is not consumed or changed by the reaction. Chain length, The length of the stretched linear macromolecule,
most often expressed by the number of identical links. Coefficient of elasticity, The reciprocal of Young's modulus
in a tension test Coefficient of thermal expansion (CTE), The change in unit
of length or volume accompanying a unit change of temperature. Cohesion, the state in which the constituents of a mass
of material are held together by chemical and physical forces. Cohesive failure, rupture of an adhesive bond, such that
the separation appears to be within the adhesive. Cohesive strength, Intrinsic strength of an adhesive. Compound, In reinforced plastics and composites, the intimate
admixture of a polymer with other ingredients, such as fillers, softeners,
plasticizers, reinforcements, catalysts, pigments, or dyes. A thermoset
compound usually contains all the ingredients necessary for the finished
product, while a thermoplastic compound may require the subsequent addition
of pigments, blowing agents, and so forth. Compressive strength, The ability of the material to resist
a force that tends to crush or buckle. The maximum compressive load sustained
by a specimen divided by the original cross-sectional area of the specimen. Condensation, a chemical reaction in which two or more molecules
combine with the separation of water or some other simple substance. Conditioning, Subjecting a material to prescribed environmental
and/ or stress history before testing. Conductivity, The reciprocal of volume resistivity, the
electrical or thermal conductance of a unit cube of any material (conductivity
per unit volume). Comformal coating, A coating that covers and exactly fits
the shape of the coated object. Consistency, that property of a liquid adhesive by virtue
of which it tends to resist deformation. Contaminant, An impurity or foreign substance present in
a material or environment that affects one or more properties of the material,
particularly adhesion. Coupling agent, Any chemical designed to react with both
the reinforcement and matrix phases of a composite material to form or
promote a stronger bond at the interface. Crack, An actual separation of material, visible on opposite
surfaces of the part, and extending through the thickness. A fracture. Crazing, fine cracks that may extend in a network on under
the surface of or through a layer of adhesive. Cross link, to form chemical bonds between molecules. Crystallinity, A regular arrangement of the atoms of a solid
in space. In most polymers, including cellulose, this state is usually
imperfectly achieved. The crystalline regions are submicroscopic volumes
in which there is some degree of regularity in the arrangement of the
component molecules. In these regions there is sufficient geometric order
to obtain definite x-ray diffraction patterns. C-stage, in polymer chemistry, the final stage in thermosetting
resin reaction in which the material dot not soften when heated, and is
essentially insoluble in most liquids. Cure, to change the physical properties of an adhesive b
chemical reaction, which may be condensation, polymerization, or vulcanization;
usually accomplished by the action of heat and catalyst, alone or in combination,
wit, or without pressure. Curing agent, relative to adhesives, a substance or mixture
of substances that is part of an adhesive and is used to promote curing
by taking part in the reaction. Curing temperature, the temperature to which an adhesive
or an assembly is subjected to cure the adhesive. Curing time, the period of time during which an assembly
is subjected to heat or pressure, or both, to cure the adhesive. Dark reaction, The gelling of material in
storage without light initiation. Debond, A deliberate separation of a bonded joint or interface,
usually for repair or rework purposes. Degassing, Subjecting a material to vacuum for the purpose
of removing gasses. This process is often used to remove air from a material. Degradation, A deleterious change in the chemical structure,
physical properties, or appearance of a material. Degradation temperature, Temperature at which a material
begins to degrade. Degrease, To remove oil and grease from adherend surface.
Dessicant, A substance that can be used to dry materials
due to its affinity for water. Dew point, The temperature to which water vapor pressure
must be reduced to obtain saturation vapor pressure. As air is cooled,
the amount of water that it can hold decreases. If air is cooled sufficiently,
the actual water vapor pressure comes to equilibrium with the saturation
water vapor pressure and any further cooling results in the condensation
of moisture. Dielectric, A nonconductor of electricity, the ability of
a material to resist the flow of an electrical current. Dielectric constant, The ratio of the capacitance of an
assembly of two electrodes separated by a plastic insulating material
to its capacitance when the electrodes are separated by air. Dielectric loss factor, The product of the dielectric constant
and the tangent of the dielectric loss angle for a material. Also called
the dielectric loss index. Dielectric 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. Differential scanning calorimeter, Measurement of energy
absorbed (endotherm) or produced (exotherm). May be applied to melting,
crystallization, resin curing, loss of solvents, and other processes involving
a change in energy. May also be applied to processes involving a change
in heat capacity, such as glass transition (Tg). Diffusion, The movement of a material, such as a gas or
liquid, in the body of a plastic. If the gas or liquid is absorbed on
one side of a piece of plastic and given off on the other side, the phenomenon
is called permeability. Diffusion and permeability are not due to holes
or pores in the plastic but are caused and controlled by chemical mechanism. Dilatant, A fluid that exhibits increasing viscosity with
an increase in shear rate. Diluent, an ingredient added to an adhesive, usually to
reduce the concentration of bonding materials. Dispersion, Finely divided particles of a material in suspension in another substance. Dissipation Factor: Is the measurement of the quality
of
a capacitor: how Doctor-bar or blade, A scraper mechanism that regulates the amount of adhesive on the spreader rolls or on the surface being coated. Dopant, A material
added to a polymer to change a physical property. Dry, to change the physical state of an adhesive on an adherend
by the loss of solvent constituents by evaporation or absorption, or both. Dry strength, the strength of an adhesive joint determined
immediately after drying under specified conditions or after a period
of conditioning in a standard laboratory atmosphere. Drying temperature, the temperature to which an adhe- sive
on an adherend or in an assembly or the assembly itself is subjected to
dry the adhesive. Drying time, the period of time during which an adhesive
on an adherend or an assembly is allowed to dry with or without the application
of heat or pressure, or both. Ductility, The amount of plastic strain that a material
can withstand before fracture. Also, the ability of a material to deform
plastically before fracturing. Durability, as related to adhesive joints, the endurance of joint strength relative to the required service conditions. Elastic deformation, Any portion of the
total deformation of a body that occurs immediately when load is applied
and disappears immediately and completely when the load is removed. Elasticity, A materials property by virtue of which a material
tends to recover its original size and shape after removal of a force
causing deformation. Elastic limit, The greatest stress a material is capable
of sustaining without permanent strain remaining after the complete release
of the stress. A material is said to have passed its elastic limit when
the load is sufficient to initiate plastic or nonrecoverable deformation. Elastomer, a macromolecular material which, at room temperature,
is capable of recovering substantially in size and shape after removal
of a deforming force. Elongation, Deformation caused by stretching. The fractional
increase in length of a material stressed in tension. When expressed as
a percentage of the original gage length, it is called percentage elongation. Encapsulation, The enclosure of an item in plastic, sometimes
referring specifically to the enclosure of capacitors or circuit boards. Engineering adhesive, A bonding agent intended to join metal,
plastics, wood, glass, ceramics, or rubber. The term differentiates such
bonding agents from glues used to join paper and other nondurables. Environment, The aggregate of all conditions (such as contamination,
temperature, humidity, radiation, magnetic and electric fields, shock
and vibration) that externally influence the performance of an item. Epichlorohydrin, The basic epoxidizing resin intermediate
in the production of epoxy resins. It contains an epoxy group and is highly
reactive with polyhydric phenols such as bisphenol A. Epoxide, Compound containing the oxirane structure, a three
member ring containing two carbon atoms and one oxygen atom. The most
important members are ethylene oxide and propylene oxide. Epoxy resin, A viscous liquid or the brittle, solid-containing
epoxide groups that can be linked into final form by means of a chemical
reaction with a variety of setting agents used with or without heat. Exotherm, The temperature-time curve of a chemical reaction
or a phase change giving off heat, particularly the polymerization of
casting resins. The amount of heat given off. Extender, substance, generally having some adhesive action,
added to an adhesive to reduce the amount of the primary binder required
per unit area. Fatigue, The failure or decay of mechanical
properties after repeated applications of stress. Fatigue tests give information
on the ability of a material to resist the development of cracks, which
eventually bring about failure as a result of a large number of cycles. Filler, a relatively nonadhesive substance added to an adhesive
to improve its working properties, permanence, strength, or other qualities. Fillet, that portion of an adhesive which fills the corner
or angle formed where two adherends are joined. Film, Sheeting having a nominal thickness not greater than
0.25 mm (0.010 in.). Fines, Very small particles (usually under 200 mesh) accompanying
larger grains, usually of molding powder. First order transition, A change of state associated with
crystallization, melting, or a change in the crystal structure of a polymer. Fixture, or set time, The shortest time required by an adhesive
to develop handling strength such that test specimens can be removed from
fixtures, unclamped, or handled without stressing the bond and thereby
affecting bond strength. Flame resistance, Ability of a material to extinguish flame
once the source of heat is removed. Flame retardance, Certain chemicals that are used to reduce
or eliminate the tendency of a resin to burn. Flame treating, A method of rendering inert thermoplastic
objects receptive to inks, lacquers, paints, adhesives, and so forth,
in which the object is bathed in an open flame to promote oxidation of
the surface of the article. Flexibility, That property of a material by virtue of which
it may be flexed and bowed repeatedly without undergoing rupture. Flexibilizer, An additive that makes a finished plastic
more flexible or tough. Flow, movement of an adhesive during the bonding process,
before the adhesive is set. Fourier transform, An analytical method used automatically
in advanced forms of spectroscopic analysis such as infrared and nuclear
magnetic resonance spectroscopy. Functionality, The average number of reaction sites on an
individual polymer chain. Gap-filling adhesive, an adhesive capable
of forming and maintaining a bond between surfaces that are not close
fitting. Gel, a semisolid system consisting of a network of solid
aggregates in which liquid is held. Also, the initial jellylike solid
phase that develops during the formation of a resin from a liquid. Gel time, The period of time from the initial mixing Glass transition temperature (Tg), The appropriate midpoint
of the temperature range over which the glass transition takes place.
Also, the inflection point on a plot of modulus versus temperature. The
measured value of Tg depends considerably on the rat e of temperature
change in any experiment. Glue, originally, a hard gelatin obtained from hides, tendons,
cartilage, bones, etc., of animals, and also an adhesive prepared from
this substance by heating with water. Green strength, The mechanical strength of material, that,
even though cure is not complete, allows removal from the mold and handling
without tearing or permanent distortion. Also called initial tack. Hardener, A substance or mixture of substances
added to an adhesive to promote or control the curing reaction by taking
part in it. Hardness, The resistance to surface indentation, usually
measured by the depth of penetration of a blunt point under a give load
using a particular instrument according to a prescribed procedure. Hygroscopic, Capable of attracting, absorbing, and retaining
atmospheric moisture. Hysteresis, Incomplete recovery of strain during unloading
cycle due to energy consumption. This energy is converted from mechanical
to frictional energy (heat) Immiscible, With respect to two or more
fluids, not mutually soluble; incapable of attaining homogeneity. Impact strength, The characteristic that gives a material
the ability to withstand shock loading. The work done in fracturing a
test specimen in a specified manner under shock loading. Impact test, The measure of the energy necessary to fracture
a standard design when sheared by a single blow from a test machine hammer. Infrared (IR), Pertaining to that part of the electromagnetic spectrum between the visible light range and the radar range. Radiant heat is in this range, and infrared heaters are frequently used in the thermoforming and curing of plastics and composites. Infrared analysis is used for the identification of polymer
constituents. Infrared spectroscopy or spectrometry, A technique used
to observe or plot the wavelengths in the electromagnetic spectrum lying
beyond the red from approx. 250 nm to 4500 nm. Inhibitor, a substance that slows down chemical reaction.
Inhibitors are sometimes used in certain types of adhesives to prolong
storage or working life. Initial modulus, The slope of the initial straight portion
of the stress-strain or load-elongation curve. Initial strain, The strain produced in a specimen by given
loading conditions before creep occurs. Initial stress, The stress produced by strain in the specimen
before stress relaxation occurs. Initiator, Sources of free radicals, often peroxides or
azo compounds. They are used in free-radical polymerization, for curing
thermosetting resins, and as cross-linking agents for elastomers and cross
linked polyethylene. Insulator, A material of such low electrical conductivity
that the flow of current through it can usually be neglected. Similarly,
a material of low thermal conductivity, such as that used to insulate
structural shells. Isocyanate plastics, Plastics based on resins made by the
condensation of organic isocyanates with other compounds. Generally reacted
with polyols on a polyester or polyether backbone molecule, with the reactants
being joined by the formation of a urethane linkage. Isomer, A compound, radical, ion, or nuclide that contains
the same number of atoms of the same elements but differs in structural
arrangement and properties. Isotropic, Having uniform properties in all directions.
The measured properties of an isotropic material are independent of the
axis of testing. Jig, A mechanism for holding a part and
guiding the tool during machining or assembly operation. Joint; adhesive joint, location at which two adherends are
held together with a layer of adhesive; lap joint, a joint made by placing
one adherend partly over another and bonding together the overlapped portions. Joint conditioning time, the time interval between the removal
of the joint from the conditions of heat or pressure, or both, used to
accomplish bonding and the attainment of approximately maximum bond strength. Legging, the drawing of
filaments or strings when adhesive-bonded substrates are separated. Liquid resin, An organic, polymeric liquid that becomes
a solid when converted to its final state for use. Load, The force applied to a specimen at any given time. Lot, A specific amount of material produced at one time
using one process and constant conditions of manufacture and offered for
sale as a unit quantity. Macroscopy, Interpretation using only the
naked eye or magnification no greater than 10X. Manufactured unit, a quantity of finished adhesive or finished
adhesive component, processed at one time. Matrix, The part of an adhesive which surrounds or engulfs
embedded filler or reinforcing particles and filaments. Maturing temperature, The temperature, as a function of
time and bonding condition, that produces desired characteristics in bonded
components. Mechanical adhesion, Adhesion between surfaces in which
the adhesive holds the parts together by interlocking action. Melt, A charge of molten plastic. Melting point, The first-order transition in crystalline
polymers. The fixed point between the solid and liquid phases of a material
when approached from the solid phase under 1 atm pressure. Mer, The repeating structural unit of a polymer. Modulus of elasticity, The ratio of the stress to strain
produced in a material that is elastically deformed. Also called Young's
modulus. Modifier, Any chemically inert ingredient added to an adhesive
formulation to change its properties. Moisture absorption, The pick-up of water vapor from air
by a material, in reference to vapor withdrawn from the air only, as distinguished
from water absorption, which is the gain in weight due to the absorption
of water by immersion. Moisture content, The amount of moisture in a material determined
under prescribed conditions and expressed as a percent of the mass of
the moist specimen, that is, the mass of the dry substance plus the moisture. Monomer, a relatively simple compound which can react to
form a polymer. Morphology, The overall physical form of the physical structure
of a bulk polymer. Common units are lamellae, spherulites, and domains. Newtonian behavior, a fluid with properties
such that at a given temperature, the viscosity is independent of shear
rate. Nitrogen blanket, The use of nitrogen to produce an inert
atmosphere. Normal stress, The stress component that is perpendicular
to the plane on which the forces act. Non-Newtonian behavior, a fluid with properties such that
when the shear rate is varied the shear stress doesn't vary in the same
proportion, or even in the same direction. The viscosity of such fluids
will therefore change as the shear rate is varied. Nonvolatile content, the portion of a material that re-
mains after volatile matter has been evaporated under specified ambient
or accelerated conditions. Novolak, a phenolic-aldehydic resin that, unless a source
of methylene groups is added, remains permanently thermoplastic. Oligomer, A polymer consisting of only a
few monomer units, for example, a dimmer, trimer, tetramer, and so forth,
or their mixtures. One component adhesives, An adhesive material incorporating
a latent hardener or catalyst that is activated by heat. Open assembly time, The time interval between the spreading
of the adhesive on the adherend and the completion of the assembly of
the parts for bonding. Organic, Originating in plant or animal life or composed
of chemicals of hydrocarbon origin, either natural or synthetic. Outgassing, Devolitization of plastics or applied coatings
during exposure to vacuum. Oven dry, The condition of a material that has been heated
under prescribed conditions of temperature and humidity until there is
no further significant change in it mass. Oxidation, In general, any chemical reaction in which electrons
are transferred. Paste, an adhesive composition having a
characteristic plastic-type consistency, that is, a high order of yield
value, such as that prepared by heating a mixture of starch and water
and subsequently cooling the hydrolyzed product. Peel strength, the average load per unit width of bondline
required to separate progressively a flexible member from a rigid member
or another flexible member at a separation angle of approximately 180°. Penetration, the entering of an adhesive into an adherend. Permanence, the resistance of an adhesive bond to deteriorating
influences. Permeability, The passage or diffusion of a gas, vapor,
liquid or solid through a barrier without physically or chemically affecting
it. Phase, A visibly separate but not necessarily separable,
portion of a system. Phenolic resin, A thermosetting resin produced by the condensation
of an aromatic alcohol with an aldehyde, particularly of phenol with formaldehyde..
Used in high temperature applications with various filler and reinforcement. Plastic, A material that contains as an essential ingredient
on organic polymer of large molecular weight; that is solid in its finished
state; and that, at some stage in its manufacture or when in is being
processed into finished articles, can be shaped by flow. Plastic deformation, Any portion of the total deformation
of a body that occurs immediately when load is applied but that remains
permanent when the load is removed. Plasticity, a property of adhesives that allows the material
to be deformed continuously and permanently without rupture upon the application
of a force that exceeds the yield value of the material. Plasticizer, in an adhesive, a substance added to increase
softness, flexibility, and extensibility. Poisson's ratio, The ratio of the change in lateral width
per unit width to change in axial length per unit length caused by the
axial stressing or stretching of a material. The ratio of transverse strain
to the corresponding axial strain below the proportional limit. Polyamid, A thermoplastic polymer in which the structural
units are linked by amide ot thio-amide groupings (repeated nitrogen and
hydrogen). Polymer, a compound formed by the reaction of simple molecules
having functional groups which permit their combination to proceed to
high molecular weights under suitable conditions. Polymers may be formed
by polymerization (addition polymer) or polycondensation (condensation
polymer). When two or more monomers are involved, the product is called
a copolymer. Polymerization, a chemical reaction in which the mole- cules
of a monomer are linked together to form large molecules whose molecular
weight is a multiple-of that of the original substance. When two or more
monomers are involved, the process is called co-polymerization or heteropolymerization. Polyol, An alcohol having many hydroxyl groups. Also known
as a polyhydric alcohol or polyalcohol. In cellular plastic usage, the
term includes compounds containing alcoholic hydroxyl groups, such as
polyethers, glycols, polyesters, and castor oil, which are used in urethane
foams and other polyurethanes. Polysulfide, A synthetic polymer containing sulfur and carbon
linkages, produced fom organic dihalides and sodium polysilfide. The material
is elastomeric in nature; resistant to light, oil, and solvents; and impermeable
to gases. Polyurethanes, A large family of polymers with widely varying
properties and uses. All of these polymers are based on the reaction product
of an organic isocyanate with compounds containing a hydroxyl group. The
reaction product of an isocyanate with an alcohol is called a urethane.
Polyurethanes may be thermoplastic or thermosetting, rigid or flexible,
cellular or solid. The properties of any of these types may be tailored
within wide limits to suit the desired application. Porosity, A condition of trapped pockets of air, gas, or
vacuum within a solid material. Usually expressed as a percentage of the
total nonsolid volume to the total volume (solid plus nonsolid) or a unit
quantity of material. Post-cure, a treatment (normally involving heat) applied
to an adhesive assembly following the initial cure, to modify specific
properties. Post-cure, to expose an adhesive assembly to an addi- tional
cure, following the initial cure, for the purpose of modifying specific
properties. Pot, To embed a component or assembly in liquid resin, using
a shell, can, or case that remains an integral part of the product after
the resin is cured. Pot life, The length of time that a catalyzed thermosetting
resin system retains a viscosity low enough to be used in processing.
Also called working life. Potting, Similar to encapsulating except that steps are
taken to ensure complete penetration of all voids in the object before
the resin polymerizes. Preheating, The heating of a compound before molding or
casting, to facilitate the operation or reduce the molding cycle time. Primer, a coating applied to a surface, prior to the application
of an adhesive, to improve the performance of the bond. Pseudoplastic, This type of fluid will display a decreasing
viscosity with an increasing shear rate. This type of flow behavior is
often referred to as shear thinning. Qualified products list (QPL), A list of
commercial products that have been pretested and found to meet the requirements
of a specification, especially a government specification. Qualification test, a series of tests conducted by the procuring
activity, or an agent thereof, to determine conformance of materials,
or materials system, to the requirements of a specification which normally
results in a qualified products list under the specification. Relative humidity, The ratio of the actual
pressure of existing water vapor to the maximum possible (saturation)
pressure of water vapor in the atmosphere at the same temperature, expressed
as a percentage. Release agent, A material that is applied in a thin film
to the surface of a mold to keep the resin from bonding to the mold. Rheopectic, Essentially the opposite of thixotropic, in
that a fluid's viscosity increases with time as it is sheared at a constant
rate. RTV, room temperature vulcanization. Resin, (1) a solid, semisolid, or pseudosolid organic material that has an indefinite and often high molecular weight, exhibits a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally. (2) liquid resin-an organic poly- meric liquid which, when converted to its final state for use, becomes a resin. Room temperature, A temperature in the range of 20°
to 30° C (68 to 86°F). The term room temperature is usually applied
to an atmosphere of unspecified relative humidity. Room temperature-curing adhesive, An adhesive that sets
to handling strength in the temperature range from 20 to 30° C (68
to 86° F) and later reaches full strength without heating. Sagging, Run-off or flow-off of adhesive
from an adherend surface due to application of excess or low-viscosity
material. Sealant, A material applied to a joint in paste or liquid
form that hardens or cures in place, forming a seal against gas or liquid
entry. Self extinguishing resin, A resin formulation that will
burn in the presence of a flame but will extinguish itself within a specified
time after the flame is removed. Set, to convert an adhesive into a fixed or hardened state
by chemical or physical action, such as condensation, polymerization,
oxidation, vulcanization, gelation, hydration, or evaporation of volatile
constituents. Setting temperature, the temperature to which an adhe- sive
or an assembly is subjected to set the adhesive. Setting time, the period of time during which an assembly
is subjected to heat or pressure, or both, to set the adhesive. Set-up, To harden, as in the curing of a polymer resin. Shadow cure, Shear, An action or stress resulting from applied forces
that causes or tends to cause two contiguous parts of a body to slide
relative to each other in a direction parallel to their plane of contact. Shear rate, The overall velocity over the cross section
of a channel with which molten polymer layers are gliding along each other
or along the wall in laminar flow. Shear strain, the tangent of the angular change, due to
force between two lines originally perpendicular to each other through
a point in the body. Shear strength, in an adhesive joint, the maximum average
stress when a force is applied parallel to the joint. Shear stress, The component of stress tangent to the plane
on which the forces act. The stress developing in a polymer melt when
the layers in a cross section are gliding along each other or along the
wall or a channel (in laminar flow). Shear stress is equal to force divided
by the area sheared. Shelf life, The length of time a material, substance, product,
or reagent can be stored under specified environmental conditions and
continue to meet all applicable specification requirements and / or remain
suitable for its intended function. Shore hardness, A measure of the resistance of material
to indentation by a spring loaded indicator. The higher the number, the
greater the resistance. Silicones, plastics based on resins in which the main polymer
chain consists of alternating silicon and oxygen atoms, with carbon-containing
side groups. Single-lap specimen, In adhesive testing, a specimen made
by bonding the overlapped edges of two sheets or strips of material. Solids content, the percentage by weight of the nonvolatile
matter in an adhesive. Solvent adhesive, an adhesive having a volatile organic
liquid as a vehicle. Specific gravity, The density (mass per unit volume) of
any materials divided by that of water at a standard temperature. Specific heat, The quantity of heat required to raise the
temperature of a unit mass of a substance 1( under specified conditions. Spectrometry, A method based on designation of the wavelengths
within a particular portion of a range of radiation or absorptions, for
example, ultraviolet emission, and absorption spectrometry. Spectroscopy, The study of spectra using an instrument for
dispensing radiation for the visual observation of emission or absorption. Storage life, the period of time during which a packaged
adhesive can be stored under specified temperature conditions and remain
suitable for use. Strain, the unit change due to stress, in the size or shape
of a body referred to its original size or shape. Static charge, The electric charge produced by the relative
motion of a non-conducting material. Stiffness, A measure of modulus. The relationship of load
and deformation. The ratio between the applied stress and resulting strain.
A term often used when the relationship of stress to strain does not conform
to the definition of Young's modulus. Storage life, The period of time during which a packaged
adhesive can be stored under specified temperature conditions and remain
suitable for use. Stress, force exerted per unit area at a point within a
plane. Stress crack, External or internal cracks in a plastic caused
by tensile stresses less than that of its short-time mechanical strength,
frequently accelerated by the environment to which the plastic is exposed.
The stresses that cause cracking may be present internally or externally
or may be combinations of these stresses. Stringiness, the property of an adhesive that results in
the formation of filaments or threads when adhesive transfer surfaces
are separated. Stripper, A chemical solvent or acid that can remove an
adhesive bond. Structural adhesive, a bonding agent used for transferring
required loads between adherends exposed to service environments typical
for the structure involved. Structural bond, A bond that joins basic load-bearing parts
of an assembly. The load may be either static or dynamic. Substrate, as related to adhesives, a material upon which
an adhesive is applied. Surface preparation, a mechanical or chemical method used
to make a substrate more receptive to forming an adhesive bond. Surface tension, The force existing in a liquid-vapor-phase
interface that tends to diminish the area of the interface. Surfactant, A compound that affects interfacial tensions
between two liquids. It usually reduced surface tension. Tack, the property of an adhesive that enables
it to form a bond of measurable strength immediately after adhesive and
adherend are brought into contact under low pressure. Teeth, the resultant surface irregularities or projections
formed by the breaking of filaments or strings which may form when adhesive-bonded
substrates are separated. Tensile strength, in an adhesive joint, the maximum tensile
stress that a material is capable of sustaining calculated from the maximum
load applied perpendicular to the joint divided by the original cross-sectional
area of the joint. Thermal conductivity, The quantity of heat conducted per
unit time through unit area of a slab of unit thickness having unit temperature
difference between its faces. Thermoplastic, a material that will repeatedly soften when
heated and harden when cooled. Thermoset, a crosslinked polymeric material. Thermosetting resin, n-a polymeric material capable of crosslinking
under the influence of heat, pressure, radiation, ultraviolet light, or
chemical agents to form a thermoset. Thixotropy, in a liquid, the property of thinning when subjected
to strains greater than the yield strain and of rethickening with time
upon subsequent rest. Tolerance, The guaranteed maximum deviation from the specified
nominal value of a component characteristic at standard or stated environmental
conditions. T-peel strength, The average load per unit width of bond
line required to produce progressive separation of two bonded, flexible
adherends, under conditions designated in ASTM D 1876. Toughness, A measure of the ability of a material to absorb
energy. The actual work per unit volume or unit mass of material that
is required to rupture it. Two-component adhesive, An adhesive supplied in two parts
that are mixed before application. Such adhesives usually cure at room
temperature. Ultimate elongation, The elongation at rupture. Ultraviolet (UV), Zone of invisible radiations beyond the
violet end of the spectrum of visible radiations. Because UV wavelengths
are shorter than visible wavelengths, their photons have more energy,
which initiates some chemical reactions and degrades most plastics, particularly
aramids. UV curing adhesive, An adhesive in which the chemical curing
mechanism is initiated with ultraviolet light. In most cases the UV light
alone is sufficient to completely cure the adhesive. Viscoelasticity, A property involving a
combination of elastic and viscous behavior. A material having this property
is considered to combine the features of a perfectly elastic solid and
a perfect fluid. Viscosity, of a liquid, The measure of the internal friction
of a fluid. This friction becomes apparent when a layer of fluid is made
to move in relation to another layer. The resistance to flow expressed
as the ratio of the applied shear to the resulting rate of shear strain. Void, Air or gas that has been trapped and cured . Voids
are essentially incapable of transmitting structural stresses or nonradiative
energy fields. Volatile content, The percent of volatiles that is driven
off as a vapor from a plastic or an impregnated reinforcement. Volatiles, Materials, such as water and alcohol, in a sizing
or resin formulation, that are capable of being driven off as a vapor
at room temperature or at slightly elevated temperature. Volume resistivity, Ratio of the potential gradient parallel
to the current in the material to the current density. Vulcanization, a chemical reaction in which the physical
properties of a rubber are changed in the direction of decreased plastic
flow, less surface tackiness, and increased tensile strength by reacting
it with sulfur or other suitable agents. Water absorption, The ratio of the weight
of water absorbed by a material to the weight of the dry material. Water break test, Any surface that is chemically clean can
be tested by the use of a drop of water, preferably distilled water. If
the surface is clean, the water will break and spread; a contaminated
surface will cause the water to bead. Webbing, filaments or threads that may form when adhesive
transfer surfaces are separated. Wet strength, the strength of an adhesive joint determined
immediately after removal from a liquid in which it has been immersed
under specified conditions of time, temperature, and pressure Wetting, The spreading, and sometimes absorption, of a fluid
on or into a surface. Wicking, The flow of a liquid along a surface into a narrow
space. This capillary action is caused the attraction of the liquid molecules
to each other and to the surface. Working life, the period of time during which an adhe- sive,
after mixing with catalyst, solvent, or other com- pounding ingredients,
remains suitable for use. Yield strain, the strain
below which a material acts in an elastic manner, and above which it begins
to exhibit permanent deformation or flow. Yield strength, The stress at the yield point. The stress
at which a material exhibits a specified limiting deviation from the proportionality
of stress to strain. The lowest stress at which a material undergoes plastic
deformation. Below this stress the material is elastic; above it, the
material is viscous. Often defined as the stress needed to produce a specified
amount of plastic deformation. Yield stress, the stress (either normal or shear) at which
a marked increase in deformation occurs without an increase in load. (Synonym
yield value) Yield value, The behavior of some fluids in which they act
much like a solid at zero shear rate. They will not flow until a certain
amount of force is applied. That amount of force is the Yield value. The
pourability of a material is directly related to its yield value. Young's modulus, The ratio of normal stress to corresponding strain for tensile or compressive stress less than the proportional limit of the material.
|
|
||||
Innovative
Solutions in Adhesive Applications