Perlast G75B
Perfluoroelastomer (FFKM) and High Temperature Steam
Perfluoroelastomers (FFKMs) are elastomer
materials known for their ability to resist
aggressive fluids and high temperatures. In most
cases FFKMs will survive environments that will
destroy other elastomers making FFKMs nearly
universal sealing materials for parts such as
O-rings, T-seals, and specialized custom sealing
components.
Figure 2: Below is a micrograph at 15X magnification of the
surface of a Perlast G75B O-ring that was exposed to
saturated steam at 275°C for 168 hours. The surface is
smooth and unchanged from the unexposed specimen
showing no signs of incompatibility.
However, not all FFKMs perform the same. FFKM
by definition is a generic term for a polymer type
that can deliver a range of performance. In
particular, not all FFKMs will resist high
temperature hot water or steam. This
incompatibility can be very costly to the
equipment owner if a seal fails causing leaks and
downtime.
Below are images of FFKM O-rings with a 3.53 mm
Figure 1: Below is a micrograph at 15X magnification of the
cross
section that have been exposed to 275°C
surface of a competitive grade FFKM O-ring that has been
saturated
forsteam
168 hours.
exposed
to steam
saturated
at 275°C for 168 hours. The
surface shows bubbles and blisters that are characteristic of
fluid incompatibly or chemical attack.
Figure 3: Below is a photograph which shows a Perlast G75B
O-ring (left) and a piece of a competitive FFKM O-ring (right)
that has been exposed to saturated steam at 315°C for 24
hours. Perlast G75B FFKM has remained flexible while the
FFKM on the right is severely cracked.
 Copyright Precision Polymer Engineering Ltd | 2052A
Perlast G75B
Perfluoroelastomer (FFKM) and High Temperature Steam
Steam: 24hrs@250oC
Hardness IRHD initial
Hardness IRHD Final
Hardness Change, points
Volume Change %
Competitive FFKM
Perlast® G75B
72
65
-7
+4.4
84
74
-10
+5.2
Steam: 72hrs@250oC
Hardness IRHD initial
Hardness IRHD Final
Hardness Change, points
Volume Change %
Visual
72
65
-7
+8
Blisters
84
75
-9
+10.5
No Change
Steam: 168hrs@250oC
Hardness IRHD initial
Hardness IRHD Final
Hardness Change, points
Volume Change %
Visual
72
61
-11
+13.3
Blisters
84
74
-10
+15.7
No Change
Steam: 24hrs@275oC
Hardness IRHD initial
Hardness IRHD Final
Hardness Change, points
Volume Change %
Visual
72
68
-4
+8.0
Blisters
84
77
-7
+1.8
No Change
Steam: 72hrs@275oC
Hardness IRHD initial
Hardness IRHD Final
Hardness Change, points
Volume Change %
Visual
72
64
-8
+14.2
Blisters
84
77
-7
+10.9
OK
Steam: 168hrs@275oC
Hardness IRHD initial
Hardness IRHD Final
Hardness Change, points
Volume Change %
Visual
72
54
-18
+21.1
Cracked
84
73
-11
+19.6
No Change
Table 1: A summary of high temperature steam
resistance tests comparing two FFKM materials.
The competitive grade FFKM blisters and cracks
and is clearly incompatible with the test
environment.
Perlast G75B exhibits good
stability with no visual changes and small changes
in hardness and volume swell.
Perlast G75B is a specially formulated
FFKM that resists high temperature
saturated steam unlike other FFKMs. As
the laboratory tests indicate, various
FFKM materials can perform differently in
the same aggressive environments. This
highlights the importance of specifying
FFKMs that have been developed for
specific environments. Matching the
correct material to the application can
avoid seal failure and costly downtime.
 Copyright Precision Polymer Engineering Ltd | 2052A