USEFUL INFORMATION

GLOSSARY OF THE TERMS USED IN THE RETREADING INDUSTRY

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ABRASION
The wearing away by friction

ABRASION TESTER
A machine for determining the quantity of material lost by friction-wear under specified conditions.

ADHESION
The Strength of bond between cured rubber surfaces or a cured rubber surface and non-rubber surface

ADHESION FAILURE
1] The separation of two surfaces by a force less than specified
2] The separation of two adjoining surfaces due to service conditions

ADHESIVE
A material which, when applied, will cause two surfaces in contact with each other to stick together.

ADHESIVE COATING
A surface layer applied to any product to increase its adherence to an adjoining surface.

ADHESIVE FABRIC
A fabric with a surface treatment which will bond two surfaces together when interposed between the surfaces.

AGING
Undergoing changes in physical properties over a period of time.

AIR TRAP
The surface markings or depressions due to trapping air between the material being cured and the mould or press surface.

AIR OVER AGING
A means of accelerating the change in physical properties of rubber compounds by exposing them to the action of air at an elevated temperature.

AMBIENT TEMPERATURE
The temperature of the atmosphere or medium surrounding the object under consideration.

ANTIOXIDANT
A compounding ingredient used to retard deterioration caused by oxygen.

ATMOSPHERIC CRACKING
Small fissures in the surface of rubber articles resulting from exposure to atmospheric conditions.

AUTOCLAVE
A pressure vessel used for vulcanizing rubber products by means of steam under pressure.

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BACK RIND
A distortion at the mould parting line usually in the form of a ragged or torn indentation.

BAG CURE
A method of vulcanization wherein a flexible bag is used to impart positive pressure to the article being vulcanized.

BANBURY MIXER
A specific type of internal mixer used to incorporate fillers and other ingredients into rubber

BEAD
Annular structure of rubber, with or without fabric and high-tensile steel wires built into the tyre casing to maintain a tight fit on the rim.

BEAD HEEL
That part of the bead which fills the angle formed by the junction of the rim flange and rims.

BEADING
The material used as a filler in a seam.

BEAD TOE
The innermost part of the bead opposite the heel.

BEAD REPAIR FABRIC
A calendered nylon card material used in manufacturing tyre repair patches.

BLEEDING
Surface exudation

BLISTER
A raised spot on the surface or a separation between layers usually forming a void or air-filled space in the vulcanized article.

BLOOM
A discoloration or change in appearance of the surface of a rubber product caused by the
migration of a liquid or solid to the surface. Example Sulphur bloom, Wax bloom.

BLOW UP
A blister between plies of an article

BREAKER
Strip of cord material embodies circumferentially within a pneumatic tyre immediately
above the casing and of about the same width as the tread.

BUCKLED PLY
A deformation in a ply distorting it from its normal plane.

BUFFING
The grinding of the surface producing a roughened or velvety surface.

BUFFING MARKS
The characteristic surface condition after buffing operation.

BUMPING
The application of pressure, released and reapplied, in order to vent entrapped air.

BURST
A rupture caused by internal pressure.

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CALENDER
A machine equipped with three or more heavy, internally heated or cooled rolls revolving
in opposite directions, which is used for continuously sheeting or plying up rubber
compound, and frictioning or coating fabric with rubber compound.

CALENDER STOP
A mark left on the surface of rubber sheet or sheeting due to interruption of calender
roll motion.

CARCASS
Rubber-bonded cord structure of a tyre to contain the inflation pressure.

CEMENT
A dispersion of unvulcanized raw or compounded rubber in a suitable solvent, used as an
adhesive or sealing.

CHAFER
Material in the bead area to protect against rim chafing

CHALKING
The formation of a powdery surface condition due to disintergration of surface binder or
elastomer by weathering or destructive environments.

CHURN
A vessel used for making rubber cement in which rubber compounds are stirred into
solvents.

COLD FLEXIBILITY

The relative ease of bending following exposure to specified low temperature conditioning.

COMMERCIALLY SMOOTH
A degree of smoothness of an article which is acceptable in accordance with industry
practice.

COMPOUND
The mixture of rubber and other materials which are combined to give the desired
properties when used in the manufacture of a product.

COMPRESSION SET
The deformation which remains in rubber after it has been subjected to and released from a
specific compression stress for a definite period of time at a prescribed temperature.

CORDS
Fabric, usually textile or steel, forming the body of the casing.

CORD REPAIR FABRIC
Usually a calendered nylon cord material used in manufacturing tyre repair patches.

COUNT
In fabric, the number of warp ends, or the number of filling picks, or both, in a square
inch of fabric.

CRACKING
A sharp break or fissure in the surface.

CRAZING
A surface effect on rubber articles characterised by multitudinous minute cracks.

CURE
The act of vulcanization

CROWN
Road-contacting area lying between the shoulders of a tyre.

CURE TIME
The time required to products vulcanization at a given temperature. [The cure time varies
widely, being dependent on the type of compound used and the thickness of the product.

CUSHION GUM
Used to fill in cavities in tread area as well as covering exposed tyre cord after
buffing.

CUT RESISTANT
Having the characteristic of withstanding the cutting action of sharp objects.

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DATE CODE
Any combination of numbers, letters, symbols or other methods used by a manufacture to
identify the period of manufacture of the product.

DENIER
A yarn sizing system for continuous filament synthetic fibers. The denier of filament yarn
is the weight in grams of a length of 9000 meters of that yarn.

DRIFT
1] The continued deformation under strain.
2] The change in a given durometer reading after a specified period of time.

DRY
The absence of tack, no adhering properties.

DUROMETER
An instrument for measuring the hardness of rubber. Measurs the resistanced to the
penetration [without puncturing] of the indentor into the surface of rubber.

DUROMETER HARDNESS
An arbitary numerical value which measures the resistance to indentation of the blunt
indentor point of the durometer.

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EDGE WEAR
The eroding of the edge of a tyre through abrasion.

ELASTIC LIMIT
The limiting extent to which a body may be deformed and yet return to its original shape
after removal of the deforming force.

ELASTOMER
A macro-molecular material which, in the vulcanized state, at room temperature can be
stretched repeatedly to at least twice its original length and which upon release of the
stress, will immediately return to approximately its original length.

ELONGATION
Increase in length expressed numerically as a fraction or percentage of the initial
length.

EXTRUDED
Forced through the shaping die of an extruder.

EXTRUDER
A machine with a driven screw, for continuous forming of rubber through a die.

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FABRIC COUNT
The number of warp ends per inch, and the number of filling picks per inch.

FABRIC SLAB
A thick sheet composed entirely or almost entirely, of layers of rubberised fabric.

FATIGUE
The weakening or deterioration of a material occuring when a repetition or continuous
application of stress causes strain.

FILLER
Any compounding material usually in powder form added to rubber in a substantial volume to
improve quality.

FLASH
The excess material protruding from the surface of a moulded article.

FLEX CRACKING
A surface cracking induced by repeated bending and straightening.

FLEX LIFE
The relative ability of a rubber article to withstand cyclical bending stresses.

FLEX LIFE TEST
A laboratory method used to determine the life of a rubber product when subjected to
dynamic bending stresses.

FLOW MARK
A surface imperfection similar to flow crack, but the depression is not quite as deep.

FLOW CRACK
A surface imperfection caused by improper flow and failure of stock to knit or blend with
itself during the moulding operation.

FRICTION
1] A rubber adhesive compound applied to, and impregnating afabric.
Usually by means of a calender with rolls running at different surface speeds. The process
is called frictioning.
2] The resistance to motion due to the contact of surfaces.

FRICTIONED FABRIC
A fabric impregnated with a rubber compound of friction motion.

FROSTING
A very fine surface graying or whitening usually due to a chemical breakdown of the rubber
compound by ozone thus exposing pigment particles. It is usually distinguished from bloom
in that it is not readily removable by solvents.

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GROUND FLASH
A surface produced by grinding the buffing.

GREEN RUBBER
Green rubber is an unvulcanized rubber

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HARDENING
An increase in resistance to indentation

HARDNESS
The resistance to indentation.

HAZING
A dulling of finish

HEAT RESISTANCE
The property or ability of rubber articles to resist the deteriorating effects of elevated
temperature.

HEAT HISTORY
Is the total heat to which a polymer is exposed from the time it is manufactured until the
compound is ready to be cured.

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IMPREGNATION
The act of filling the interstices of an article with a rubber compound. Generally applies
to treatment of textile fabrics and cords.

IMPRESSION
A design formed during vulcanization on the surface of any rubber article.

INDENTATION
1] The extent of deformation by the indentor point of any one of a number of standard
hardness testing instruments.
2] A recess in any surface of a rubber article.

INNER LINING
A layer of rubber, from bead toe to bead toe, on the inside of the casing.

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KNITTING
Proper flowing together of stock surface. Laminations, visible folds, cracks or lines in a
moulding are evidence of poor knitting.

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LOOSE PLY
A separation between adjacent plies.

LOW TEMPERATURE FLEXIBILITY
The ability of a rubber product to be flexed, bent or bowed at low temperatures without
loss of serviceability.

LOW TEMPERATURE FLEXING
The act of bending or bowing a rubber product under conditions of cold environment.

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MIGRATION
In a rubber compound, the movement of more or less rubber soluble materials from a point
of high concentrationto one of low or zero concentration. Migration is applied to the
movement of accelerators, antioxidants, antiozonants, Sulphur, softeners and organic
colours. It is a form of diffusion.

MILL
A machine with two horizontal rolls, used for the mastication or mixing of rubber.

MIRROR FINISH
A bright polished surface.

MODULUS
In the physical testing of rubber, the load in pounds per square inch or kilograms per
square centimeter of initial cross sectional area necessary to produce a stated percentage
of elongation, compression or shear.

MOISTURE REGAIN
The absorption of water by textile.

MOISTURE ABSORPTION
The assimilation of water by a rubber or textile product.

MOULD LUBRICANT
The material used to coat the surfaces of a mould to prevent the rubber adhering to the
metal during vulcanization.

MOULD MARK
An indentation or ridge embossed into the surface of a moulded product usually by
irregularities in the mould surface.

MOONEY SCORCH
A measure of the incipient curing characteristics of a rubber compound using the mooney
viscometer.

MOONEY VISCOCITY
A measure of the viscosity of a rubber or rubber compound determined in a mooney Shearing
disc viscometer.

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NERVE
A measure of toughness or recovery from deformation in unvulcanized rubbers or compounds.

NIP
The clearance between rolls of a mixing mill or calender.

NIPPLE
A cylinderical pipe like attachment one end of which is securely inserted and retained in
the end of the hose, serving the same purpose as a hose coupling.

NON-FILL
Improperly filled, not completed, containing voids.

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OFF GUAGE
Not conforming to specified dimensions.

OIL PROOF
Not affected by exposure to oil.

OIL SWELL
The change in volume of a rubber article resulting from contact with oil.

OPEN STEAM CURE
The state of vulcanization at which the desired combination of properties is attained.

OVERCURE
The state of cure greater than the optimum.

OXIDATION
The reaction of oxygen on a rubber product, usually evidenced by a change in the
appearance or feel of the surface or by a change in physical properties.

OXYGEN BOMB
A chamber capable of holding oxygen at an elevated pressure which can be heated to an
elevated temperature. Used for an accelerated aging test.

OZONE CRACKING
The surface cracks, checks, or crazing caused by exposure to an atmosphere containing
ozone.

OZONE RESISTANCE
The ability to withstand the deteriorating effects of ozone [generally cracking].

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PATCH PLATFORM
Is the smallest section of the patch construction and is centered over the injury in a
tyre casing. The other or remaining plies are simply reinforcement plies for the platform.

PEELING
The loosening of a Rubber layer from a base material.

PERMANENT SET
The amount by which an elastic material fails to return to its original form after
deformation.

PICK
An individual filling yarn of a fabric.

PLASTICITY
1] A measure of the resistance to shear of an unvulcanized elastomer.
2] A measurement of resistance to shear with heat history.
3] The property of vulcanized rubber of retaining a shape or form imparted to it by a
deforming force.

PLASTICIZER
A compounding ingredient which can change the hardness, flexibility, or plasticity of an
elastomer.

PLASTOMETER
1] An instrument for measuring the viscosity of raw or unvulcanized rubber
2] An instrument for measuring the hardness of vulcanized rubber

PLY
1] A layer of rubberized fabric.
2] A layer of unvulcanized rubber

PLY ADHESION
The force required to separate two adjoining reinforcing members of a rubber product.

PLY SEPAATION
A condition which occurs due to a loss of adhesion between plies.

POST CURE
An over cure supplementing the original vulcanization.

POROSITY
Air trapped or dissolved in the compound during processing.

PRESS
A machine consisting of essentially two or more heated plates which can be brought
together and separated by hydraulic pressure or mechanical action and between which rubber
articles are vulcanized under pressure.

PSI
The abbreviation for pounds per square inch

PURE GUM
A Rubber compound containing only the ingredients necessary for vulcanization.

PROTECTIVE BREAKER
An additional strip of material embodied circumferentially within a pneumatic tyre between
the tread and the breaker, and of about the same width as the tread, to minimise damage to
the breaker.

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RECOVERY
The degree to which a rubber product returns to its normal dimensions or shape after being
distorted.

RECAPPING
A process in which rubber is removed from the worn tread and over the shoulders, and new
rubber is applied.

REINFORCEMENT
1] The strength members consisting of cord, fabric and or metal of a rubber product.
2] The non-rubber elements making up a rubber product.

REINFORCING AGENT
An ingredient [not basically involved in the vulcanization process] used in the rubber
compound to increase its resistance to mechanical forces.

REMOULDING
A process in which rubber is removed as necessary and new rubber, extending from bead area
to bead area is applied.

RETREADING
A process of reconditioning a worn out tyre by top-capping, recapping or remoulding.

RETREADING CEMENT
A vulcanizable cement made out of natural rubber to provide building tack to hold the
uncured rubber in place before the built up casing is placed in the mould.

REVERSION
The softening of vulcanized rubber when it is heated too long or exposed to elevated
temperatures. It is a determination in physical properties. Extreme reversion may result
in tackiness.

ROLLING RESISTANCE
It is the measurement of energy required for a tyre to roll. Soft tyres require more
energy than tyres with high air pressure. Tyres with low rolling resistance get more
kilometers to the litre.

RUBBER
A material that is capable of recovering from large deformations quickly and forcibly and
can be, or already is modified to a state in which it is essentially insoluble [but can
swell] in boiling solvent such as benzene, M.E.K. and ethanoltoluene azeotrope. A rubber
in its modified state, free of diluents, retracts within one minute to less than 1.5 times
its original length after being stretched at room temperature [18 to 29 degree C] to twice
its length, and held for one minute before release.

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SCORCH
Scorch means premature cure and a scorched stock is wasted stock.

SCORCH TIME
That time in the heat history of a rubber compound when the effects of vulcanization can
just be detected.

SELF CURE
Vulcanization without the aid of heat.

SHELF LIFE
Shelf life of Tread Rubber and tyre repair materials is the time during which they can be
stored, preferably under controlled conditions, and remain suitable for use. The maximum
shelf life shall be determined as the longest period through which the Tread Rubber will
maintain its original curing characteristics.

SHOULDER
Transitional area between the side wall and the tread.

SIDE WALL RUBBER
Layer of rubber to protect the outsides of the tyre casing from damage.

STRESS-STRAIN
The relationship of load and deformation in a body under stress.

STRETCH
An increasing or elongation in dimension.

SUN CHECKING
The surface checks or crazing caused by exposure to direct or indirect sunlight.

SWELLING
The increase in volume or linear dimension of a specimen immersed in liquid or exposed to
a vapour.

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TACK
The ability to adhere.

TENSILE STRENGTH
Tensile strength of a rubber compound is its resistance to rupture under tension.

TOLERANCE
The upper and lower limits between which a dimension must be held.

TOP-CAPPING
A process in which the worn tread rubber only is renewed.

TRAPPED AIR
The air which is enclosed in a product or in a mould during cure. [Usually causes a loose
ply, a surface mark, depression or void].

TREAD
Outermost band of patterned rubber to provide resistance to road wear, to protect the tyre
casing and to provide road grip.

TREAD GUM
Used to fill in tread areas that Tread Rubber cannot fill. Tread Gum fill have higher
modulus than cushion Gum.

TREAD RUBBER
Shaped strip of unvulcanized rubber compound used for retreading tyres.

TYRE FITTING LINES
Circular moulded lines on the outside of the upper bead area to facilitate concentricity
when fitting.

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ULTIMATE ELONGATION UNDER CURE
The maximum elongation prior to rupture.
A state of vulcanization less than optimum. Can be evidenced by tackiness or inferior
physical properties.

UNDER TREAD
This is the thickness of rubber under a tread groove.

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VOIDS
The absence of material or an area devoid of materials where not intended.

VULCANIZATION
An irreversible process during which a rubber compound, through a change in its chemical
structure [e.g. cross linking] becomes less plastic and more resistant to swelling by
organic liquids, and elastic properties are conferred improved or extended over a great
range of temperature.

VULCANIZING CEMENT
A natural rubber solution used in retreading and repairing.

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WEATHERING
The surface deterioration of a rubber article during outdoor exposure, such as checking,
cracking, crazing or chalking.

WRINKLED PLY
A deformation in a ply distorting it from its normal plane.
[As gleaned from authoritative Reference Publications]