NATURAL RUBBER (NR)
– Excellent mechanical properties : excellent resistance to fatigue and crack propagation;
– Excellent electrical properties;
– High resilience ( ability of a material build up energy when subjected to stress without rupture occur . After ceasing the stress it may or may not be a residual strain caused by the hysteresis of the material);
– Low hysteresis (the tendency of a material or system to retain its properties in the absence of the stimulus generated);
– Adhesion to metals effectively .
STYRENE-BUTADIENE RUBBER (SBR)
SBR it’s a low cost alternative to the NR and its main features :
– Good water resistance and compression;
– Tolerates moderate chemicals and organic acids;
– Better abrasion resistance than natural rubber;
– Improved resistance to high temperatures (100 °C);
– Less flexibility and elasticity at low temperatures (to about -50 ° C). Unlike NR , in the case of high temperature, SBR has a non-hardening and softening;
– Improved resistance to aging factors;
– The gas permeability is high but smaller than the NR;
– Chemical resistance is similar to that of natural rubber.
– Not recommended for contact with ozone, strong acids, oils, greases, fats and hydrocarbons.
NITRILE BUTADIENE RUBBER (NBR)
NBR is often used in the presence of oils, solvents, hydraulic fluid. It should not be used in highly polar solvents such as acetone and MEK, ozone, chlorinated hydrocarbons and aromatic hydrocarbons. It also presents the main features :
– Good sealing to gases;
– Compressive strength, abrasion and tension;
– Increased resistance to abrasion comparably with NR and SBR;
– Reduced electrical resistance. Considered a semi-conductor and therefore can be adaptable to be used when electrical insulation is required .
ETHYLENE PROPYLENE DIENE MONOMER (EPDM)
The rapid growth in consumption of EPDM rubber is based on its excellent properties:
– Resistance to ozone and weathering;
– Very good resistance to heat and oxidation;
– Good resistance to chemical agents;
– Good low temperature flexibility (*depending on the ethylene content);
– Very good electrical insulating properties ;
– Not resistant to oils and solvents
– Resists most inorganic chemicals. Good performance compared to mineral acids , alcohols, ketones and detergents.
ISOBUTYLENE ISOPRENE RUBBER (IIR)
Main features :
– High damping ( high values of tan δ );
– Good flexibility at low temperatures;
– Limited elasticity at normal temperature;
– Good resistance to compression;
– Impermeable dimetilformamide (DMF ) which is a common electrolyte solvent .
– Very low permeability to gas and air;
– Good resistance to ozone and weathering;
– Very good resistance to steam and dry heat;
– Good resistance to oils and fats of animal or vegetable origin;
– Good electrical insulating properties.
CHLOROPRENE RUBBER (CR) – common known as NEOPRENE RUBBER
Polychloroprene Rubber has good resistance to weathering, ozone, aging and chemical agents. It also has the main features :
– Good mechanical characteristics and abrasion resistance;
– Good elasticity at low temperatures of around -40 °C and good resistance to temperatures around 100 °C ( or for short periods 120 °C);
– The gas permeability is much less than that of NR, SBR and IIR approaching the permeability of the NBR;
– Good chemical resistance to paraffin oils, an average chemical resistance to aliphatic hydrocarbons and naphthenic oils;
– Poor resistance to aromatic hydrocarbons, chlorinated hydrocarbons and polar solvents;
– No fire propagation.
Commonly called VITON (trademark of DuPont Performance Elastomers LLC) It presentes as general characteristics :
– Excellent resistance to chemicals and oils;
– Resistant to high temperatures;
– Good mechanical characteristics;
– Low chemical resistance to alkali and ketones.
POLYURETHANE RUBBER (PUR)
Polyurethane is widely used whenever it is required a high wear resistance in combination eventually with mineral oil resistance and ozone .
Products made from PUR are particularly used in the automotive industry and transport , the textile industry, food industry and mechanical engineering . Typical applications include sealants, shock absorbing and damping members, transmission elements , joints flexible and elastic, suspensions and supports with high wear resistance, diaphragms and roll covers. In these applications, the chemical and physical characteristics are combined, a good weather resistance and resistance to solvent swelling, good abrasion resistance , elasticity even at high hardness and good properties at low temperature. However in all applications, we have to consider the hydrolysis potential, limited heat resistance, and the high price of rubber.
– High resistance to breakage;
– Possibility to obtain high hardness;
– High resistance to abrasion;
– High degree of resilience;
– Resistance to heat (Temperature 75-90 °C)
– Good resistance to aging;
– Flexibility at low temperature;
– Low gas permeability , air or nitrogen;
Silicone rubber have several important applications in the pharmaceutical, food, aerospace, marine and automotive. The following main characteristics :
– Excellent resistance to high temperatures;
– Resistant to ozone, weathering and ultraviolet radiation;
– Good electrical insulation;
– Good behavior towards fire.