Accelerator Activators
Inorganic compounds – mainly metal oxides-zinc oxide, hydrated lime
Organic Acids – Normally in combination with metal oxides
Stearic, oleic
Alkaline substances – will increase ph of rubber
Usually increases cure rate
Age Resistors (Antidegredants) – All rubbers are affected by aging
Prevent or slow polymer breakdown caused by
Ozone, oxygen, heat, light, weather
Chemical Protectants – 3 types
Amines – tend to discolor, “staining”
Phenolics – nonstaining
Phosphites – used as stabilizers for SBR
Physical Protectants – waxy materials that bloom to surface forming a protective coat
Shields the part from ozone, oxygen etc.
Effects of oxygen on elastomers
Softens (or usually softens) – NR, IR, IIr
Hardens ( or usually hardens)- CR, SBR, NBR, BR, EPDM, CSM, FKM
PHR – usually 2-3 phr
Amines are about 65% of the age resistors