DISCOVERING RUBBERS

All crosslinkable macromolecular materials are defined Rubbers. At environmental temperature they are predominantly amorphous and the glass transition temperature is low. With increasing temperature the rubber become more flexible and the elasticity decreases. By vulcanization with sulfur or other macromolecules similar chemical / physical process are cross-linked to form a large structure elastomers (rubber hose) or tight structure (hard rubber). Thanks to their special characteristics, the rubbers are used in many sectors.

The criterion for the use of rubbers is their resistance to heat. Very important in rubber technology is the reinforcement of the mixtures by active fillers (carbon black for black products and silica for light products). The traditional synthetic rubbers show good processing characteristics; It should not forget that many rubber mixtures also contain plasticizers. There are different types of rubber, which are described below.

RUBBER R – Polymers containing unsaturated carbon

The NR (natural rubber) has a high resistance and elasticity, in addition to a thermal application area continued from -50 ° C to 70 ° C, while in the short period may be up to 120 ° C; also has a low mechanical damping, is not oil-resistant and must be stabilized to ozone. The IR (isoprene rubber) is an imitation of NR and has an elasticity slightly higher. The BR (butadiene rubber) is almost never used in its pure state, but cut with other rubbers, thus forming wear-resistant mixtures and cold. The CR (chloroprene rubber) has a good stability to aging and a reduced permeability to gases, is poorly flammable and quite resistant to oils and greases, can be used up to 130 ° C and has a prolonged heat application range from – 40 ° C to 110 ° C. The SBR (styrene butadiene rubber) is often used in place of NR as rubber suitable for all purposes, is not resistant to mineral oils, can be used up to 120 ° C and has a prolonged heat application range from -40 ° C to 100 ° C. The NBR (nitrile-butadiene rubber) can be used up to 130 ° C, it has a prolonged heat application range from -30 ° C to 100 ° C and is resistant to ozone; increasing the percentage of ACN increases the resistance to oils, fuels and greases, although in compensation there is less flexibility in the cold. NCR (nitrile-chloroprene rubber) has a slightly higher resistance to oil than the CR. The IIR (butyl rubber) has good chemical and aging resistance, reduced gas permeability and good vulcanizzabilità, in addition to a prolonged heat application range from -40 ° C to 130 ° C; There are also versions that contain chlorine (CIIR) and bromine (BIIR), characterized by good processability and aging stability with minimal air permeability. The PNR (polynorbornene rubber) has a heat deformation resistance and a tendency to creep lower than the NR. The TOR (trans-poliottenamero rubber) is mainly used as a polymer filler component for other rubbers; in this way the charge is absorbed more easily and better distributed, it also reduces the viscosity of the compound at processing temperatures and it has a better fluidization during processing. The HNBR (hydrogenated NBR) rubber is more resistant to oils, oxidation and corrosion compared to NBR, up to 150 ° C.

The NR is used for the construction of springs and tires for vehicles, while the BR for the construction of the tread. The CR is particularly suitable for bellows, tubes, profiles for gaskets, conveyor belts and coatings for cables. The SBR is generally used for the realization of blends for tires, technical rubber articles and hoses, while the NBR is the most important insulating material for the construction of vehicles, machinery, pipes and linings for brakes. The IIR is used for the creation of air chambers, cores of tires, gas-tight membranes and caps for pharmaceutical use, whereas the PNR is suitable for the soft coating rollers. The HNBR is used for the construction of vehicles and transport systems for oil.

RUBBER M – Polymers that contain polymer chains of polyethylene saturated

EPM and EPDM (ethylene propylene-diene rubber) are atactic copolymers of ethylene and propylene and exhibit good chemical resistance, weathering, ozone and aging; the interval of prolonged use temperature is from -40 ° C to 130 ° C. The AECM (ethylene-acrylic ester rubber) is an elastomer with excellent heat resistance and medium resistance to oils; It has a prolonged heat application range from -25 ° C to 170 ° C and can reach up to 200 ° C. The EAM (ethylene-vinyl acetate rubber) combines high thermal resistance at a good oil resistance and has a prolonged heat application range from -10 ° C to 150 ° C. The CSM (EP rubber clorosolfonata) is a special clear rubber with good resistance to atmospheric and chemical agents and presents a prolonged heat the application range from -20 ° C to 120 ° C. The CM (chlorinated rubber PE) has a resistance to hot oil and boiling slightly better than that of the CSM, in addition to a lower temperature embrittlement. The ACM (acrylic ester rubber) has a higher heat resistance of NBR and a prolonged heat application range from -25 ° C to 150 ° C, can be used up to 170 ° C and is resistant to UV rays, oil and ozone. The FKM (fluororubber) and the FFKM (perfluoro rubber) have a high resistance to the attack of chemical agents, oxidants and ultraviolet rays; in particular the FKM has a prolonged heat application range from -20 ° C to 200 ° C and can reach up to 250 ° C. The FPM (tetrafluoroethylene-propylene rubber) has a very high chemical resistance.

EPM and EPDM are used for the production of external parts of motor vehicles, sealing rings, o-rings, and gaskets. The AECM is used for the realization of special gaskets for vehicles while the CM is shown for technical articles, coatings for cables and hoses for engines. The ACM is indicated for seals intended for motor shafts, while the FKM and FFKM for special gaskets in the chemical industry and oil industry.

RUBBER O – Polymers that contain oxygen atoms

The CO, ECO and ETER (epichlorohydrin rubber homopolymer, copolymer and thermopolymer) have the same resistance to oils NBR, but have thermal resistance, cold resilience and significantly higher elasticity; also they have a prolonged heat application range from -40 ° C to 120 ° C. The PO (propylene rubber) has good resistance to heat and cold, but reduced resistance to oils.

The CO, ECO and the ETER are mainly used for the realization of flexible tubes and special seals for the automotive industry.

RUBBER Q – Polymers that contain oxygen and silicon atoms

The MQ, the MPQ, the MVQ, the PVMQ and the MFQ (rubber poly-dimethyl-siloxane, rubber methyl-phenyl-siloxane, methyl vinyl siloxane rubber, rubber methyl-phenyl-vinyl-siloxane and methyl-fluor- rubber siloxane) are silicone rubbers that have high electrical characteristics and are physiologically harmless; have extended the field of thermal use from -60 ° C to 180 ° C, they can reach 300 ° C and can be attacked by the steam above 100 ° C. The MVFQ (fluorinated silicone rubber) has a prolonged heat application range from -60 ° C to 175 ° C, less bulging of MVQ and is more resistant to cold than the FKM.

The silicone rubbers are particularly suitable for the manufacture of fixed seals, furniture, destined to elastic long-lasting joints for the building, suitable for contact with fuels and oils, and used in the aeronautical and space sectors, without forgetting the hoses, electrical insulation and conveyor belts.

RUBBER T – Polymers that contain sulfur atoms

The TM and TE (polysulfide rubber) are highly resistant to solvents and to aging and have low thermal and mechanical resistance. They are mainly used for the realization of interiors of containers coatings.

RUBBER E – Polymers that contain carbon, oxygen and nitrogen

The AU and the EU (rubber urethane polyether and polyester urethane rubber) have endurance, flexibility and very high elasticity, have relatively high mechanical damping and are resistant to wear, oils, fuels and ozone.

They are suitable for the realization of hydraulic seals, pinions for chains, pulleys, bellows, transmission belts, fenders and bumpers.

RUBBERS: TYPES

Shown below are the most common RUBBER trade names available at LIMA.

CODICE VARIANT
LM950 NEOPRENE
LM951 NBR
LM953 SILICONE
LM954 EPDM
LM958 VITON
LM959 SBR 70 SH

RUBBERS: TRADE NAMES

Shown below are the most common trade names for the RUBBERS.

Please remember that LIMA can provide both generic materials and materials covered by trademark (ie that show the TM or ® endorsements), based on the requirements of the customer. If the customer wishes to details made of plastic material covered by trademark, LIMA will stock up directly by the holding company of the said trademark.

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