Peroxide

Organic peroxides

 for the cross-linking of rubber and polyolefins

Cross-linking of rubber and polyolefins with organic peroxides

Chemical cross-linking agents such as sulfur or organic peroxides can, under suitable conditions, link polymer chains to form a three-dimensional network. The crosslinking reaction changes many material properties of the polymer. The crosslinked 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 formulation
  • 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 crosslinked products on 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 rigidity with simple process management

There are the following disadvantages compared to vulcanization with sulfur:

  • Atmospheric oxygen disrupts the crosslinking process
  • Some additives like extender oils, antioxidants and resins can use up free radicals under certain conditions
  • The tensile and tear strengths are usually 15% lower

Peroxidic 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 polyolefin 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 fluoro rubber

Peroxidic crosslinking is possible with mixtures of:

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

 

Peroxidic crosslinking only limited or not possible with

ACM polyacrylate rubber
IIR butyl rubber
CIIR chlorobutyl rubber
CO epichlorohydrin rubber
ECO epichlorohydrin copolymer
PP polypropylene
PB polybutene-1
PIB polyisobutene
PVC polyvinyl chloride

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