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Abrasion resistance
Resistance of vulcanized rubber to surface abrasion.

Accelerator
Additives used to speed up a vulcanization reaction that would otherwise take hours to complete. They assure economic sustainability of the process.

Activator
Chemicals that activate the accelerator in a vulcanization reaction.

Antioxidant
Protective agent to enhance resistance of vulcanized rubber to oxidation.

Antiozonant
Protective agent to enhance resistance of vulcanized rubber to ozone attacks.

Autoclave
Boiler-like apparatus used to vulcanize rubber with high pressure and heat.

Blend
Rubbery matter state of the mixed ingredients after mastication.

Calender
A relatively simple machine consisting of cylinders rotating at opposite directions. It is mainly used to shape rubber blends into sheets.

Cavity
A term used to describe the openings on a mould that contain shapes of the product to be manufactured. A mold with nine exact cavities would fabricate nine copies of the same product in a single cycle.

CNC
Means “computer numerical control” and often used synonymously with lathes and milling machines that come with an electronic control unit and a keypad allowing either manual or electronic data entry. It is a feature shared by various machine tools today.

Compression
A primary production technique to process rubber. Material, either placed (if solid) or cast (if liquid) into the mold, is subjected to heat and pressure for a certain period of time. It is most frequently used in production of rotary shaft seals as well as hydraulic and pneumatic rubber seals.

Copolymer
A polymer composed of two types of monomers.

Cure agent
Formula component at the center of the vulcanization process that helps building cross-links between the rubber polymer chains allowing rubber to gain a stable elastomeric structure. Sulfur and peroxide are the two most preferred cure agents.

Dielectric strength
Resistance of vulcanized rubber to conduction of electricity. Rubbers used to manufacture electrical cables are desired to have high dielectric strength to act as insulator while rubbers used in tire production are preferred to act as conductor so they will not store any static load.

Elastic deformation
Deformation is defined as deviation from the initial physical form for a solid material under stress. Upon removal of the deforming force if the material returns to its original shape it is called elastic deformation.

Elasticity
Capacity of material to return to its original shape upon removal of the deforming force.

Elastomer
Elastomers are polymers with high elasticity. The word elastomer is used interchangeably with rubber. Should a distinction be needed the word elastomer is preferred to describe the vulcanized rubber.

External mixer
A basic machine comprising cylinders turning at different speeds. Resulting surface tension helps blend the ingredients with the rubber gum.

Extrusion
A primary production technique to process rubber and plastics. An extruder machine providing uninterrupted material feeding is key to the process. It is very common in manufacturing of cross-sectional shapes.

Filler
Substances that are added to the blend to reinforce the rubber or reduce the cost of the compound. Carbon black, silica, calcium carbonate, kaolinite and phenolic resins are some examples to the most frequently used fillers.

Flame resistance
Resistance of vulcanized rubber to flaming and burning.

Flash
Excess, unwanted material that overflows from the mold during production and stays attached to the product. It is either avoided through mold design or removed in a process called deflashing.

Flex resistance
Capability of vulcanized rubber to preserve its structural properties after repeated exposure to compressive forces.

Formula (recipe)
It is the formula of the desired rubber compound, shown in PHR (parts per hundred of rubber) where the amount of each ingredient is adjusted according to 100 units of the main rubber polymer. Rubber polymer(s), cure agent, accelerator, activator, filler, various process aids and protective additives are all part of this formula.

Gas impermeability
Capacity of vulcanized rubber to impede passage of gas molecules through.

Hardness
Resistance of material to plastic deformation. Different Shore scales are used to measure hardness in polymers.

Heat resistance
Capacity of vulcanized rubber to preserve its properties at high temperatures.

Hydraulic press
A common type of metalworking machinery. Its working principles are based on fluid mechanics, basically transferring the force built up in hydraulic cylinders on the mold. Hydraulic presses equipped with heaters and vacuum pumps are often used for vulcanization.

Impact resistance
Resistance of vulcanized rubber to physical shocks.

ISO 9001
A quality management system standard that became highly popular in mid-90s. The most up-to-date version, ISO 9001:2000, is still in wide use by many businesses today.

Injection
A primary production technique to process rubber and plastics. The system involves horizontal and vertical injection machines used for molding. Material is melted and mixed in a pot called barrel by an extruder screw and then injected with high pressure into the mold and allowed to cool down.

Internal batch mixer
Sealed rubber mixing machine that is isolated from the external environment and employs two tangential rotors that crush the ingredients of the blend together. It is named after its inventor, Fernley Banbury (simply “Banbury”), who developed the first prototype of the machine in 1916.

Latex
The milky organic substance obtained from the rubber tree (Hevea brasiliensis). Latex is purified by removing water from the liquid and then processed into natural rubber.

Low temperature resistance
Capacity of vulcanized rubber to maintain and adequately perform its mechanical properties at low temperatures.

Mold
A system of metal pieces and supporting components that represents the core of production molding. Invert shapes (cavities) or cross sections for the desired products are fabricated on the mold. There are various types such as compression molds, transfer molds, injection or casting molds.

Mastication
Process of turning a dry rubber mix into a dough-like rubber blend in a mixer. Main compound ingredients along with other additives and processing aids such as softeners are added at this stage.

Monomer
Molecules representing the structural building blocks of polymers that tend to come together to build long molecular chains.

Natural rubber
Rubber made of organic latex, denoted with NR.

Oil seal
Used interchangeably with rotary shaft seal. Please click to see the basic construction of an oil seal.

Plastic deformation
Deformation is defined as deviation from the initial physical form for a solid material under stress. Upon removal of the deforming force if the material fails to return to its original shape it is called plastic deformation.

Polymer
Long molecular chains with high molecular weight composed of one or more self-repeating molecular building blocks (monomers) joined together by covalent bonds.

Polymerization
The reaction where the same or different types of monomers in a suitable environment are joined together to form polymers.

Punch press
A mechanical machine press, working principles of which are based on transfer of force (torque) via a rotating flywheel. It is used with die to cut shapes out of steel sheets.

Resistance to steam
Resistance of vulcanized rubber to steam.

Resistance to acid (concentrated)
Resistance of vulcanized rubber to concentrated acid (e.g. concentrated acetic acid, concentrated sulfuric acid).

Resistance to acid (dilute)
Resistance of vulcanized rubber to diluted acid (e.g. diluted acetic acid, diluted sulfuric acid).

Resistance to alcohol
Resistance of vulcanized rubber to alcohol.

Resistance to animal fat
Resistance of vulcanized rubber to various kinds of animal fat.

Resistance to base (concentrated)
Resistance of vulcanized rubber to concentrated base (e.g. concentrated sodium hydroxide, concentrated potassium hydroxide).

Resistance to base (dilute)
Resistance of vulcanized rubber to diluted base (e.g. diluted sodium hydroxide, diluted potassium hydroxide).

Resistance to halogenated fluids
Resistance of vulcanized rubber to halogenated fluids like chlorofluorocarbon or hydrofluorocarbon.

Resistance to lubricating oil
Resistance of vulcanized rubber to lubricating oils.

Resistance to oxidation
Resistance of vulcanized rubber to oxygen attacks.

Resistance to oxygenated fluids
Resistance of vulcanized rubber to oxygenated fluids like methanol, ethanol or MTBE.

Resistance to ozone
Resistance of vulcanized rubber to ozone attacks.

Resistance to radiation
Resistance of vulcanized rubber to effects of radiation.

Resistance to water
Resistance of vulcanized rubber to water.

Resistance to weathering
Resistance of vulcanized rubber to structural degradation that results from weathering including combined effects of oxidation, ozone, light and heat.

Resistance to vegetable oils
Resistance of vulcanized rubber to vegetable oils (e.g. castor oil).

Retarder
Chemicals used to slow down the unnecessarily quick vulcanization of rubber blend to avoid scorch.

Rheometer
A widely-used lab device that measures the visco-elastic properties of materials. It is very useful to find out the optimal vulcanization time for a rubber compound.

Rubber
Polymers that exhibit high elasticity and low compression set. The term generally is used to identify unvulcanized rubber gum, ready to be added to the mix.

Rubber mix
Synonymous with rubber recipe or formula. It is used to describe the state where the primary rubber polymer is mixed up with other additives like filler, cure agent, accelerator, activator and protective chemicals ready to get masticated.

Rubber slicer
Cutting machinery used to slice the masticated blend to proper dimensions in proportion to cavities on the mold. Ability to precision processing allows minimization of waste and flash.

Shrinkage
Both plastics and rubber materials after molding (e.g. compression, injection) undergo a sudden drop in temperature, which results in reduction of material’s volume, an incident called shrinkage. Design of rubber and plastic products is always finalized taking the contraction of the material into consideration.

Service temperature
Upper limit of the temperature range a vulcanized rubber can successfully perform within.

Softener
Mostly oil-like additives included in the formula to soften the blend and improve its capacity to be processed.

Specific gravity
Density of a material relative to water (1 g/cm3). It is a dimensionless quantity.

Swelling
Increase in volume of a material left in a liquid for a certain period of time due to absorption of the liquid.

Synthetic rubber
Rubbers made of petroleum products as opposed to natural rubber made of processed organic latex. Most of the rubber varieties used today are synthetic (e.g. SBR, NBR, IR).

Tear strength
Resistance of vulcanized rubber to tearing. It is defined in standards as load or force required to induce some predefined length of rupture.

Tensile strength
Maximum tensile force the vulcanized rubber can resist before break.

Tensile strength tester
A lab device frequently used in rubber and plastics industry. It measures mechanical attributes like elasticity, elongation, deformation and tensile strength in accordance with respective methods and standards.

Thermoplastic
A term used to classify polymers that initially soften and then melt upon exposure to heat and solidify when cooled down. Ignoring the degradation of the polymer over time a thermoplastic material can be melted and solidified as many times as desired.

Thermoset
Thermosetting polymers when subjected to heat become harder and receive a stronger and more stable form. Unlike thermoplastic materials thermosetting polymers cannot be remolded because of their irreversible structure.

Tool shop
The factory unit that houses various metalworking machines such as lathes, milling machines, drillers and CNC machining centers as well as numerous measuring equipment required for mold making.

Weld line
Thin boundary line visible on molded rubber and plastic parts. Separate material flows that fail to meld together is the main reason behind this occurrence.

Viscosity
Resistance of material to flow under shear stress.

Vulcanization
The irreversible chemical reaction that creates the elastomeric structure by cross-linking the polymer chains. In practice the blend of rubber along with a proper curing agent (e.g. sulfur, peroxide) are kept in a suitable environment at a certain temperature for a certain period of time. As a result plastic properties get replaced by strong, stable elastic qualities.

Vulcanization time
Time required to complete the vulcanization process at the production station. It is of great importance to find out and apply the correct vulcanization time to assure the desired mechanical properties.

 
 
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