of rubber and polyolefines with organic peroxides
Chemical crosslinking agents such as sulphur and organic peroxides are able to link polymer chains creating a three-dimensional network. This crosslinking reaction changes several material characteristics. The material characteristics of a crosslinked polymer are superior to the equivalent characteristics of the sulphur cured polymers.
Important criteria for selecting a suitable crosslinking peroxide are processing and crosslinking temperature.
Safe processing temperature t2
The raw materials (polymer, additives, peroxide) have to be homogenized before the crosslinking reaction can take place. Although the temperature sensitive peroxide will be the last raw material which is added for homogenization, one has to take care to avoid temperatures at which the peroxide decomposes and the crosslinking reaction starts. This maximum processing temperature of the peroxides is called the scorch temperature. The safe processing temperature t2 is defined as the temperature, at which the scorch time is longer than 20 minutes.
Typical crosslinking temperature t90
The typical crosslinking temperature t90 is defined as the temperature at which 90% of the crosslinks in the compound are formed within about 12 minutes.
Peroxide crosslinking of elastomers has the following advantages over the sulphur cure:
• simple formulation
• long storage time of the peroxide containing compound without scorching
• high processing temperature
• rapid vulcanization without reversion
• high temperature resistance of final product
Peroxide crosslinking possible for:
|SBR||Styrene butadiene rubber|
|NBR||Acrylonitrile butadiene rubber|
|HNBR||Hydrogenated acrylonitrile butadiene rubber|
|EPM||Ethylene propylene copolymer|
|EPDM||Ethylene propylene terpolymer|
|CSM||Chlorosulphonyl polyethylene rubber|
|EVA||Ethylene vinylacetate copolymer|
|ABS||Acrylonitrile butadiene styrene copolymer|
|EBA||Ethylene butylacrylate copolymer|
For further information please refer to the delivery program.