Peroxide

Organic peroxides

 for crosslinking rubber and polyolefins

Crosslinking of rubber and polyolefins with organic peroxides

Chemical crosslinking agents such as sulfur or organic peroxides can link polymer chains into a three-dimensional network under suitable conditions. The crosslinking reaction changes many material properties of the polymer. The cross-linked polymers often show properties that are superior to the corresponding properties of the sulfur-vulcanized ones.

Advantages of peroxidic crosslinking of elastomers compared to vulcanization with sulfur:

• Simple wording
• Long storage time of the peroxide-containing mixture without scorching
• High process temperature
• Fast networking without reversion
• High temperature resistance of the finished part
• No discoloration of the cross-linked products when in contact with metals or PVC
• Most peroxides do not cause blooming
• Co-crosslinking of saturated and unsaturated rubber
• Co-crosslinking of rubber with polyethylene or other polyolefins
• Co-polymerization with polymerizable plasticizers or other co-agents for controlled hardness and stiffness with simple process control

Compared to vulcanization with sulfur, the following disadvantages arise:

• Atmospheric oxygen disrupts the crosslinking process
• Some additives such as extender oils, antioxidants and resins can deplete free radicals under certain conditions
• Tensile and tear strength are typically 15% lower

Peroxide crosslinking is possible with:

NR natural rubber
IR polyisoprene rubber
BR polybutadiene rubber
CR polychloroprene rubber
SBR styrene butadiene rubber
NBR butadiene acrylonitrile rubber
HNBR hydrogenated butadiene acrylonitrile rubber
Q silicone rubber
AO/EO polyurethane rubber
EPM ethylene-propylene copolymer
EPDM ethylene propylene terpolymer
POE polyolefi n elastomer
T Polysulphite rubber
PE polyethylene
CM Chlorinated polyethylene
CSM Chlorosulphonyl Polyethylene
EVA ethylene vinyl acetate copolymer
ABS acrylonitrile-butadiene-styrene copolymer
EBA ethylene-butyl acrylate copolymer
FPM fluorine rubber

Peroxidic crosslinking is possible with mixtures of:

NBR/EPDM
SBR/EPDM
PE/EPDM
PE/EVA
NBR/EVA
EPDM/PP
POE/EP(D)M

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