Epichlorohydrin (CO, ECO, ETER)
Common chemical composition:
There are three types of epichlorohydrin: homopolymers (CO), copolymers (ECO) and terpolymers (ETER).
Homopolymers result in mixtures that are not easy to process in terms of finding a good balance between green strength and tackiness of cylinders. However, they produce vulcanizates with excellent oil resistance at up to 135°C, with good fuel resistance, good heat resistance (135/150°C), quite good resistance to low temperatures (-18/-20°C), excellent ozone resistance and very low gas permeability.
The copolymers exhibit properties and performance similar to those of homopolymers but weakened. They differ from them in that:
- they have lower fuel and oil resistance;
- they perform better at low temperatures: their vulcanizates are not prone to crystallization;
- they exhibit less permanent deformation at low temperatures;
- they have higher gas permeability.
In contrast to the previous two, terpolymers have double bonds outside the main chain of the polymer: thus they are can cross-link with sulfur, retaining stability at oxidation of the epoxy epichlorohydrin chain. However, if cross-linked with sulfur, these terpolymers cannot be used with other polyepichlorohydrins, as the presence of carbon-sulfur bonds would lower heat resistance.
Fields of Application:
These types of rubber were introduced as elastomers for automotive articles intended to function at higher temperatures than normal, especially in the context of exhaust gas recovery. So far epichlorohydrin has been used in:
- carburetor pipes;
- fuel filler sleeves;
- membranes and sleeves for exhaust gas recovery;
- rubberized fabrics for heat resistant articles;
Epichlorohydrin is mainly converted to bisphenol A diglycidyl ether, used as a constituent in the manufacture of epoxy resins. It is also a precursor to monomers for other resins and polymers.
Another use involves conversion to synthetic glycerol. However, the rapid increase in biodiesel production, in which glycerol is a waste product, has led to an excess of this product on the market, making this process uneconomic.