Plastics fillers, ozone resistance

Among the variety of synthetic rubbers, EPM and EPDM are particularly known for their excellent ozone resistance in comparison with natural rubber (cfs-l,4-polyisoprene) and its synthetic counterparts IR (isoprene rubber), SBR (styrene-butadiene rubber), and BR (butadiene rubber). Secondly, EPDM rubber can be extended with fillers and plasticizers to a very high level in comparison with the other elastomers mentioned, and still give good processability and properties in end articles. This leads to an attractive price/performance ratio for these poljmiers. 

Halobutyl rubbers with almost completely saturated backbones usually do not require extra antioxidants or antiozonants the rubber producer adds traces of stabilizers. For severe service circumstances, particularly in blends with unsaturated rubbers, the addition of some antidegradant may be necessary. In the selection of any antidegradant care should be exercized, particularly regarding amine derivatives that may interfere in the crosslinking process, but with proper technology vulcanizates with enhanced stability may be obtained [103]. Ozone resistance and weathering behavior of halobutyl rubber vulcanizates are also dependent on the curing system, on the nature and amount of fillers and plasticizers. 

Like ldpe, polybutadienes are resistant to most nonoxidizing acids, alkalis, and salts. However, because they are unsaturated, the polyalkadienes are attacked by hydrochloric, hydrobromic, and hydrofluoric acids, as well as by hydrogen and chlorine. The reaction products, which are thermoplastic, have been used as commercial nonelastomcric plastics. NR and other diene elastomers are also attacked by peroxides and ozone. In the absence of an tioxidants and carbon black filler, these unsaturated elastomers are degraded in the sunlight. 

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