Page 349 - BOLA Catalogue

TECHNICAL INFORMATION
Elastomers
Their main characteristic is their elasticity: Elastomers can easily be stretched and bent and return to their original shape and size after being released. These synthetic materials are most commonly used for o-rings, flat gaskets or resilient elements.
NBR – Acrylonitrile-Butadiene-Caoutchouc
Elastomer on the base of acrylonitrile-butadiene-caoutchouc which is mainly used as budget- priced sealing material (e. g. O-rings for stop-cocks). This material has a good resistance to mineral oils and fats as well as to HFA, HFB and HFC-hydraulic fluids. It has a very good elasticity. PERBUNAN® (its well-known trade name of BAYER AG) is not resistant to brake fluids on the basis of glycol, HFD liquids, aromatic compounds(e. g. benzol), ester, ketone and amines as well as in concentrated acids and caustic solutions. Due to its restricted chemical resistance, PERBUNAN® is not the ideal material for chemistry.
FKM – Fluorocaoutchouc
Elastomer on the base of fluorocaoutchouc, more familiar as VITON®(DuPont). Many O-rings, lip seals and sleeves are made of FPM. It has a very good resistance to heat, chemicals, weather and ozone. Furthermore, it is resistant to sulphurated mineral oils and fats and to hardly inflammable HFD liquids (basis phosphor ester or chlorinated hydrocarbon). It is not resistant to anhydrous ammonia, caustic soda, potassium, ketones, ether, dioxane, as well as some amines and organic acids. For BOLA products, FPM is mainly used as sealing material, mostly protected from the medium by a PTFE sealing lip.
EPDM
...
CH2 CH C
N
CH2
C C CH2 ... H H
n
FHFFFF
...
C C X
F H F
C C Y C C F F F
F
C Z ...
F
n
EPDM 3 is an elastomer on the base of ethylene-propylene-diene-caoutchouc which is mostly used
for gaskets and O-rings. The main applications are in the area of hot water, steam and suds. It is
not resistant to hydraulic fluids on the base of mineral oil but it is weather-proof, non-ageing and ... CH2 CH2 X CH2 CH Y CH CH Z ... resistant to ozone. At BOLA, EPDM O-rings are mainly used for applications where VITON® O-rings
arenotsufficient.
CH3
CH2
CH CH3 n
FFKM – Perfluoro-Caoutchouc
An elastic sealing material with natural recovery and good accommodation to the sealing surfaces and a chemical resistance comparable with PTFE. FFKM O-rings have a very high chemical and thermal resistance. Such seals can withstand virtually all kinds of chemicals and can be used at long duration conditions with temperatures up to +260 °C. Perfluoro-caoutchouc is better known under the trade names KALREZ® by DuPont, CHEMRAZ® by Greene Tweed, respectively DyneonTM Perfluoroelastomers PFE by Dyneon.
Elastomers - Chemical Resistance
CF2
CF2 X
CF
CF2 CF ...
Br n CF3
...
CF Y O
Classes of substances at 20°C
NBR
FKM
FFKM
EPDM
Water
++
++
++
++
Acids
+
+
++
++
Lyes
+
+
o
++
Oils and fats
+
++
++
-
Fuels
+
++
++
-
Ozone
o
++
++
++
Hydrocarbon, aliphatic
++
++
++
-
Hydrocarbon, aromatic
-
++
++
-
Hydrocarbon, chlorinated
-
++
++
-
Temperature range, °C
-40 up to +130
-20 up to +200
-20 up to +250
-30 up to +140
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Definition: - o +
+++
not suitable, not recommended possible, moderate to good good
very good, best choice