In general, rubber is a compound (or polymer) that has rubber-like properties. The main properties are viscosity - that is, the ability to flow - and elasticity - that is, the ability to recover its original shape after being compressed or stretched. Examples of rubber are silicone surgical tubing, natural rubber automobile tires, and neoprene windshield wiper blades.
A compound that has little or no elasticity - think of silly putty - is said to be plastic. Examples of plastics are PVC window frames, polypropylene pool noodles, and polyethylene milk bottles.
A rubber compound, once cured, cannot be uncured. Therefore, rubber tires can't be melted. To be re-purposed, they must be reground and perhaps used as playground surfacing. The term for these compounds is thermosets. Plastics, on the other hand, can usually be melted and re-used, and are therefore called thermoplastic. That's good news for the environment, although it may limit the usefulness of the material itself, because it loses its performance properties above a certain temperature.
So we have thermosets, and thermoplastics. But I would like to acquaint you with a material that is almost a contradiction of terms: a thermoplastic rubber. These compounds process like a plastic but have performance properties like rubber.
Thermoplastic rubber comes in various forms, but the one that we at Reed Rubber specialize in is also one of the most popular: thermoplastic vulcanizate (TPV). Originally developed my Monsanto Corporation in 1981 under the trade name Santoprene, TPV quickly replaced EPDM in many applications, especially in automotive seals. Other brand names exist, such as Teknor-Apex's Sarlink.
The rubber phase of TPV is a fully cured EPDM rubber that is embedded in the plastic phase, which is polypropylene (PP). The PP gives TPV its recyclability, tight tolerances, light weight, and colorability. The EPDM that gives it excellent compression recovery, elasticity, long-term weatherability, and other properties.
This combination of properties makes TPV an excellent choice for gaskets and seals. It is also non-marking and has a pleasant surface texture, making it a good choice for hand grips and bumpers. It has outstanding flex fatigue resistance, which is good for hinges. It is worth noting that maintains its flexibility even down to 76°F below zero.
TPV is not a good choice when there is exposure to temperatures continuously above 250°F (or 275°F intermittently). It will not hold up well when immersed in some petroleum products. And, if a very high tensile strength is important, there are some thermoset rubbers that will do better.
We have been extruding TPV profiles for seals, grips, bumpers, and other applications since 1985. Give us a call!
