Elastomers - properties & applications

What are the 2 types of elastomers?

What are their respective characteristics?

• conventional elastomers

  • chemically cross-linked (polymer chains tightly tied together by strong chemical bonds)

  • Can’t be melted (need to be produced in one single step)

  • Not really recyclable (because you can’t melt them into a new shape)

• thermoplastic elastomers

  • Combine the best properties of plastics & rubbers

  • CAN be melted

  • Physical/thermal non-permanent bonds

List all elastomers that you know

• CR chloroprene rubber

• EPDM ethylene propylene diene terpolymer rubber

• NR natural rubber

• SBR styrene-butadiene rubber

• SIR polysiloxanes (formerly silicone rubber)

• Polysulphides

Properties & applications of natural rubber NR

• made from latex

• Vulcanisation with sulfur (chemical process that turns the sticky, raw rubber into tough, elastic material)

• 70% for car tires

• 12% for latex products

• 8% for technical products

Properties & applications of styrene-butadiene rubber SBR

• copolymer of 1,3-butadiene (1 monomer) & styrene (other monomer)

• tires

• Seals

• Conveyor belts (tapis roulants)

Properties & applications of chloroprene rubber CR

• synthetic rubber

• Very resistant to ageing

• hoses = pipes

• Drive belts

• Diving suits (équipement de plongée)

• Unreinforced & steel-reinforced construction bearings (roulement)

• Joint tapes (rouleau joint)

• Joint that can “slide” in bridges to prevent them from breaking when they expand with temperature increases

Properties & applications of ethylene propylene diene terpolymer rubber EPDM

• synthetic caoutchouc

• Short-term properties similar to CR’s (behavior under a brief load)

• unreinforced bearings (roulements)

• Joint tapes

• Waterproofing membranes

• Hoses = pipes

• Pond liners (bâches de bassins)

Properties & applications of polysiloxanes (silicone rubber) SIR

• oily, paste-like or rubber-like

• Can be used from -50 to 180°C

• Hydrophobic (doesn’t absorb water)

• Good chemical resistance

• seals

• Adhesives

• Conveyor belts (tapis roulants)

• Electrical insulation

• Joint compounds

• Baking moulds

• Cosmetics

• Implants

Properties & applications of polysulphides

• sulfur-based rubber

• joint compounds

• Insulating glass

Properties & applications of thermoplastic elastomers (give examples)

• block polymers OR polyblends

• TPO → cable sheathing, conveyor belts (tapis roulants)

• TPU → car door handles, gear lever, steering wheel, sport shoes, ski boots

• SBS → transparent films, toys

What’s the difference between copolymer, block polymer and polyblends?

• copolymer = any polymer made from multiple different types of monomers bonded together in the same chain

  • block polymers = special type of copolymers where monomers alternate in a block sequence AAAABBBBAAAABBBB

• polyblends = physical mixture of multiple different polymers (physically mixed, no chemical bonds)

How do we read TPE-O or TPO?

TPE-U or TPU?

What does the last letter indicates?

TPE-O/TPO = thermoplastic elastomer based on olefin

TPE-U/TPU = thermoplastic elastomer based on urethane

→ the last letter indicates the plastic used for the hard part