Rubber Sheeting Compounds

Elastomers

NR – Natural Rubber

Natural Rubber is obtained from the rubber tree. Of the many existing species, only ‘Hevea Brasiliensis’, which originated in the Amazon region, is commercially exploited. Because of its natural origin, it is not a homogenous product, but even so it is classified in different grades according to visual and analytical evaluation criteria.

Properties

  • Excellent mechanical properties, such as tensile strength, elasticity and tear resistance
  • Wide range of hardnesses, from 35 to 90 shore A
  • High resilience, excellent dynamic properties and low compression set
  • Excellent electrical properties
  • Sensitive to ozone. Weather resistance can be improved adding antiozonants combined with waxes
  • Temperature range -50 to 90 Celsius

SBR – Styrene-Butadiene Rubber

More than half of the synthetic rubber produced in the world is SBR. It is synthesised from raw materials derived from oil. SBR contains approximately 23% of styrene. Any increase in this content leads to the deterioration of its properties of elasticity and resistance to low temperatures while at the same time increasing hardness.

Properties

  • It requires reinforcing fillers to attain good mechanical properties and can achieve higher abrasion resistance than natural rubber
  • Similar to natural rubber, but with better ageing and temperature resistance
  • Lower resilience compared to natural rubber
  • Moderate tearing, ozone and weather resistance
  • Temperature range -50 to 110 Celsius

CR – Chloroprene Rubber

It offers the most balanced set of desirable properties. The chlorine atom increases the level of resistance to oils, placing it between natural rubber and nitrile rubber.

Properties

  • Excellent abrasion resistance and superior mechanical properties
  • Inferior resilience than natural rubber in low hardnesses, but higher from hardnesses of 60 shore A upwards
  • It presents good temperature and ozone resistance
  • Flame retardant
  • Good adhesion to metal
  • Temperature range -25 to 125 Celsius

NBR – Nitrile Rubber

Depending on the acrylonitrile content (ACN), they can be classified as low ACN (18-24%), medium ACN (34%) and High ACN (50%) content. By increasing the ACN content, resistance to oils, fuel increases, tensile strength, resistance to abrasion, hardness, temperature resistance and permeability are improved, resilience and flexibility at low temperatures are reduced.

Properties

  • Resistant to oils and can be formulated for applications at relatively high temperatures
  • Good mechanical properties such as traction, compression and flexion
  • Impermeable to gases
  • Ageing is moderate
  • Good adhesion to metal
  • Moderate resistance to low temperature, allowing it to reach temperatures as low as -40 Celsius, thanks to the use of adequate plastifiers
  • Temperature range -30 to 120 Celsius

EPDM – Ethylene Rubber

The copolymers of Ethylene and Propylene (EPM) can only be vulcanized by peroxides or radiation, whereas by adding Diene (EPDM) it is possible to achieve conventional vulcanization with sulphur, thereby increasing their resistance to tearing.

Properties

  • Excellent resistance to ageing, ozone, ultraviolet light and practically unalterable by weather
  • Excellent electrical properties and radiation stability
  • Moderate adhesion to metal
  • Temperature range -45 to 120 Celsius. May be formulated for continuous services at 140 Celsius

CSM – Chlorosulphonated Polyethylene Rubber

Properties

  • Excellent oxidation, weather and ozone resistance
  • Excellent resistance to hydro carbonated solvents
  • Flame resistance
  • Moderate adhesion to metal
  • Temperature range -35 to 140 Celsius

VMQ – Silicone Rubber

Unlike the rest of synthetic rubbers, its molecular chain does not contain carbon and consists of silicon and oxygen atoms.

Properties

  • Excellent temperature resistance (200-220 Celsius) in dry environments. In contact with high pressurised steam (130-140 Celsius) or in case of ageing in closed systems without the presence of oxygen, degradation by hydrolysis may occur
  • Absolutely unalterable by ozone, weather and ultraviolet radiation
  • Good electrical insulator
  • Self-extinguishable. In case of complete combustion by prolonger contact with a flame, the residue (silica) is an excellent electrical insulator
  • Physiologically inert, suitable for medical applications
  • Temperature range -70 to 220 Celsius

Viton – Fluorocarbonated Rubber

It is known as fluoroelastomer rubber. Its chemical resistance and its resistance to low and high temperatures are directly proportional to its fluorine content.

Properties

  • Extraordinary high temperature resistance. Continuously up to 250 Celsius and intermittently up to 300 Celsius
  • Extraordinary chemical resistance
  • Self-extinguishable
  • Excellent ozone and weather resistance
  • Low deformation on compression at high temperatures
  • Satisfactory resistance to low temperatures between -30 and -50 Celsius

CO/ECO – Epichlorohydrin Rubber

Properties

  • Excellent ozone and weather resistance as saturated polymers
  • Cos withstand continuous service temperatures of up to 150 Celsius and are fragile from -23 Celsius
  • ECOs and ETHERS can support continuous service temperatures of up to 135 Celsius and maintain their flexibility above -40 Celsius
  • Fire resistant
  • Excellent elastic properties