Fluorinated polydiorganosiloxane base composition and method for preparation

A method for making a fluorinated polydiorganosiloxane base composition and the composition prepared thereby. The base composition can be addition cured using a platinum-metal group catalyst and an organohydrogensiloxane crosslinker to form a fluorosilicone elastomer having improved resiliency and compression set properties.

BACKGROUND OF INVENTION 
The present invention is a method for making a fluorinated 
polydiorganosiloxane base composition and the composition prepared 
thereby. The base composition can be addition cured using a platinum-metal 
group catalyst and an organohydrogensiloxane crosslinker to form a 
fluorosilicone elastomer having improved resiliency and compression set 
properties. 
Toporcer et al., U.S. Pat. No. 3,776,934, teach 
methylvinyldi(N-methylacetamido)silane and its manufacture. The 
amidosilane is taught useful as a chain extender in organosiloxane 
compositions. 
Crossan et al., U.S. Pat. No 4,020,044, teach mixing a 
methylvinyldi(N-alkylacetamido) silane and hydroxyl endblocked 
polydiorganosiloxane and allowing the mixture to react at room temperature 
to provide a polydiorganosiloxane having increased molecular weight and 
methylvinylsiloxane units in the chain. Crossan et al. report the gums 
produced can be crosslinked through the use of organic peroxides. 
Chaffee et al., U.S. Pat. No. 5,171,773, teach that a fluorinated 
polydiorganosiloxane elastomer having improved physical properties can be 
obtained through the use of a method which first reacts a hydroxyl 
endblocked methyl(fluoropropyl)siloxane having a Williams plasticity 
number greater than 5.7 mm with a methylvinyldi(N-alkylacetamido)silane to 
give a chain-extended polymer having pendant vinyl groups only at the 
location of the chain extension. Chaffee et al. teach the chain extend 
polymer can be mixed with a fumed silica having a surface area of about 
400 m.sup.2 /g. The resulting composition can be peroxide cured to form a 
silicone elastomer. 
SUMMARY OF INVENTION 
The present invention is a method for making a fluorinated 
polydiorganosiloxane base composition and the composition prepared 
thereby. The base composition can be addition cured using a platinum-metal 
group catalyst and an organohydrogensiloxane crosslinker to form a 
fluorosilicone elastomer having improved resiliency and compression set 
properties.

DESCRIPTION OF INVENTION 
The present invention is a method for making a fluorinated 
polydiorganosiloxane base composition and the composition prepared 
thereby. The method comprises: 
(A) mixing (i) 100 parts by weight of a hydroxyl end-terminated 
polymethylvinyl(methylfluoroalkyl)siloxane having about 0.2 to 1.2 mole 
percent pendant vinyl substituted on silicon and a Williams plasticity 
number of about 1.3 mm to 3.8 mm at 25.degree. C. and (ii) 0.05 to two 
parts by weight of a methylvinyl(N-alkylacetamido)silane at a temperature 
within a range of about 20.degree. C. to 80.degree. C., for a period of 
time sufficient to increase the Williams plasticity number of the 
polymethylvinyl(methylfluoroalkyl)siloxane by chain extension, 
(B) mixing with the product of step (A) 
(i) 0.5 to 10 parts by weight of a hydroxyl end-terminated 
polydimethylsiloxane having about one to six mole percent pendant vinyl 
substitution on silicon and a Williams plasticity number within a range of 
about 1.2 mm to 2.5 mm at 25.degree. C., 
(ii) one to 10 parts of a hydroxyl end-terminated 
polymethylfluoroalkylsiloxane fluid where the terminal hydroxyl 
substitution comprises about three to 10 weight percent of the fluid, and 
(iii) 20 to 50 parts of a reinforcing silica having a surface area within a 
range of about 50 m.sup.2 /g to less than 200 m.sup.2 /g, and 
(C) heating the mixture of step (B) to remove volatiles. 
In a preferred process, step (B) further comprises adding 0.25 to 5 parts 
by weight of a hydroxyl end-terminated polydimethylsiloxane fluid having 
about nine to 12 weight percent vinyl substituted on silicon and a 
viscosity of about 10 mPa.multidot.s to 60 mPa.multidot.s at 25.degree. C. 
The hydroxyl end-terminated polymethylvinyl(methylfluoroalkyl)siloxane 
(component (A)(i)) comprises about 0.2 to 1.2 mole percent pendant vinyl 
substitution on silicon (i.e. 0.2 to 1.2% of the pendant substituents on 
silicon atoms are vinyl groups) and has a Williams plasticity number 
within a range of about 1.3 mm to 3.8 mm at 25.degree. C. as determined by 
ASTM 926-67. Component (A)(i) is endblocked with hydroxydimethylsiloxy 
units and comprises repeating units described by formulas --(R.sub.f 
MeSiO)-- and --(ViMeSiO)--, where R.sub.f is a perfluoroalkylethyl radical 
comprising three to 10 carbon atoms, Me is methyl, and Vi is vinyl. 
Preferred is when R.sub.f is 3,3,3-trifluoropropyl. It is preferred that 
component (A)(i) comprise about 0.5 to 0.8 mole percent pendant vinyl 
substituted on silicon and have a Williams plasticity number within a 
range of about 2.3 mm to 3.1 mm at 25.degree. C. 
In the present method, component (A) (i) is added to a high-shear mixer 
capable of being heated and maintained under an inert environment. Such a 
mixer is described in the examples herein. In the preferred process, 
component (A) (i) is added to the mixer and heated to a temperature less 
than about 80.degree. C. under a dry nitrogen purge for a period of time 
sufficient to remove moisture present in component (A) (i). 
Component (A) (i) is mixed with about 0.5 to two parts by weight of a 
methylvinyldi (N-alkylacetamido) silane (component (A) (ii)) per 100 parts 
by weight of component (A) (i). Examples of useful components (A) (ii) are 
described in Crossan et al., U.S. Pat. No. 4,020,044 which is hereby 
incorporated by reference. In component (A) (ii) the alkyl substituent 
bonded to nitrogen can comprise one to about four carbon atoms. The 
preferred component (A) (ii) is methylvinyldi(N-methylacetamido)silane. In 
the preferred process, Component (A) (i) and component (A) (ii) are mixed 
under a nitrogen purge at a temperature within a range of about 20.degree. 
C. to 80.degree. C. for a period of time sufficient to provide a product 
having a Williams plasticity number greater than that of component (A) 
(i). In the preferred method, component (A) (i) and component (A) (ii) are 
mixed until the mixture has reached an essentially stable viscosity. 
The preferred method of this invention first dries component (A) (i) to 
remove any free water which would interfere with the reaction with 
component(A) (ii). Component (A) (ii) functions as a chain extender by 
reacting with the terminal hydroxyls of component (A) (i) first giving a 
N-alkylacetamidosilyl endblock on the polymer, then when that endblock 
reacts with another hydroxyl endblock on another polymer chain, the chains 
are joined together, giving a vinyl pendant group at the point where the 
two chains are joined by the silane. The minimum useful amount of 
component (A) (ii) is about 0.05 part by weight per 100 parts by weight of 
component (A) (i), in order to obtain any significant chain extension of 
component (A) (i). Preferably there is about 0.1 to 1.5 parts by weight of 
component (A) (ii) added per 100 parts by weight of component (A) (i). 
Higher than two parts by weight of component (A) (ii) can be added but may 
negatively impact the physical properties, such as tensile strength, of 
cured elastomer formed from the resulting fluorinated polydiorganosiloxane 
base composition. 
In step (A) of the present method, component (A) (ii) may be initially 
mixed with a portion of component (A) (i) and then cut back with one or 
more portion of the remainder of component (A) (i) during the mixing 
process of step (A). 
In step (B) of the present method, the product of step (A) is mixed with 
components (B) (i) through (B) (iii) and optionally with component (B) 
(iv). This mixing is preferably performed in the mixer in which step (A) 
was conducted. In the preferred process components (B) (i) and (B) (ii) 
and optionally (B) (iv) are mixed with the product of step (A) at a 
temperature within a range of about 20.degree. C. to 80.degree. C. for an 
amount of time sufficient to ensure good dispersion of these components in 
the product of step (A). After the mixing is completed, the reinforcing 
silica (component (B) (iii)) is added to the mixer in one or more portion 
and massing of the mixer content effected after each addition. 
In step (B), 0.5 to 10 parts by weight of a hydroxyl end-terminated 
polydimethylsiloxane having about one to six mole percent pendant vinyl 
substituted on silicon and a Williams plasticity number within a range of 
about 1.2 mm to 2.5 mm at 25.degree. C. (component (B) (i) ) is added to 
the method per each 100 parts by weight of component (A) (i). Preferred is 
when about one to two parts by weight of component (B) (i) is added to the 
method per 100 parts by weight of component (A) (i). 
In step (B), one to 10 parts by weight of a hydroxyl end-terminated 
polymethylfluoroalkylsiloxane fluid where the terminal hydroxyl 
substitution comprises about three to 10 weight percent of the fluid 
(component (B) (ii)) is added to the method per 100 parts by weight of the 
component (A) (i). Component (B) (ii) is described by formula HO(MeR.sub.f 
SiO).sub.n H, where Me is methyl, R.sub.f is a perfluoroalkylethyl radical 
comprising three to 10 carbon atoms and n has a value of from three to 12. 
Preferred is when R.sub.f is 3,3,3-trifluoropropyl and n is a value within 
a range of about three to six. In the present method, component (B) (ii) 
serves to in situ surface treat the reinforcing silica to aid dispersion 
of the reinforcing silica and to prevent the phenomena typically referred 
to as "crepe" which can occur during storage of the compositions prepared 
by the present method. Creping is characterized by an increase in 
viscosity or plasticity of a composition to the extent that it becomes 
difficult or impossible to process using conventional techniques and 
equipment. The amount of component (B) (ii) added in the present method is 
related to the amount of reinforcing silica added to the method as well as 
the surface area of the reinforcing silica filler. In general one to 10 
parts by weight of component (B) (ii) is considered useful for the 
possible range of reinforcing silica filler specified in the present 
method. A preferred range for component (B) (ii) is about three to six 
parts by weight per 100 parts by weight of component (A) (i), where the 
reinforcing silica filler (component (B) (iii)) comprises about 25 to 35 
parts by weight of component (A) (i). 
In step (B), 20 to 50 parts by weight of a reinforcing silica having a 
surface area within a range of about 50 m.sup.2 /g to less than 200 
m.sup.2 /g (component (B) (iii)) is added to the method per 100 parts by 
weight of component (A) (i). Preferred is when about 25 to 35 parts by 
weight of component (B) (iii) is added to the method per 100 parts by 
weight of component (A) (i). The present inventors have unexpectedly found 
that platinum group metal catalyzed addition cured fluorosilicone rubbers 
prepared from the base composition of the present method have 
significantly lower compression set values and higher resiliency values 
when the reinforcing silica has a surface area less than about 200 m.sup.2 
/g. Preferred is when the reinforcing silica has a surface area within a 
range of about 50 m.sup.2 /g to 150 m.sup.2 /g. Even more preferred is 
when the reinforcing silica has a surface area with a range of about 50 
m.sup.2 /g to 100 m.sup.2 /g. The reinforcing silica can be fumed or 
precipitated silica, however fumed silica is preferred. 
In step (B), optionally 0.25 to 5 parts by weight of hydroxyl 
end-terminated polydimethylsiloxane fluid having about nine to 12 weight 
percent pendant vinyl substituted on silicon and a viscosity of about 20 
mPa.multidot.s to 60 mPa.multidot.s at 25.degree. C. (component (B) (iv)) 
can be added to the method per 100 parts by weight of component (A) (i). 
Preferred is when about 0.5 to 2 parts by weight of component (B) (iv) is 
added to the method per 100 parts by weight of component (A) (i). 
In step (C) of the present method, the mixture formed in step (B) is heated 
to remove volatile components of the mixture. The apparatus in which step 
(C) is conducted, preferably the mixer in which step (A) and step (B) was 
conducted, may be held under a reduced pressure and/or purged with a 
stream of inert gas such as nitrogen to facilitate removal of volatiles. 
In a preferred method, step (C) is conducted at a temperature within a 
range of about 100.degree. C. to 200.degree. C. Preferred is when step (C) 
is conducted at a temperature within a range of about 150.degree. C. to 
170.degree. C. 
The present method provides a fluorinated polydiorganosiloxane base 
composition which can be compounded with an addition-type cure system 
using a platinum group metal-containing catalyst to form cured 
fluorosilicone elastomers having improved compression set and resiliency 
properties. 
Addition cure systems suitable for curing the fluorinated 
polydiorganosiloxane base composition require the presence of a platinum 
group metal or compound thereof catalyst and a siloxane crosslinker having 
silicon-bonded hydrogen. To improve shelf life of such catalyzed 
compositions, the curing system can also include the presence of an 
inhibitor of the platinum group metal catalyst, the inhibitor being 
removed from the composition or deactivated at elevated temperatures. 
Platinum group metal-containing catalysts useful to catalyze curing of the 
present base composition can be any of those known to catalyze the 
reaction of silicon-bonded hydrogen atoms with silicon-bonded vinyl 
groups. By "platinum group metal" it is meant ruthenium, rhodium, 
palladium, osmium, iridium, and platinum. Examples of useful platinum 
group metal-containing catalyst can be found in Lee et al., U.S. Pat. No. 
3,989,668; Chang et al., U.S. Pat. No. 5,036,117; Ashby, U.S. Pat. No. 
3,159,601; Lamoreaux, U.S. Pat. No. 3,220,972; Chalk et al., U.S. Pat. No. 
3,296,291; Modic, U.S. Pat. No. 3,516,946; Karstedt, U.S. Pat. No. 
3,814,730; and Chandra et al., U.S. Pat. No. 3,928,629 all of which are 
hereby incorporated by reference to show useful platinum group 
metal-containing catalyst and methods for their preparation. 
A group of platinum group metal-containing catalysts particularly useful in 
the present composition are the complexes prepared from chloroplatinic 
acid as described by Willing, U.S. Pat. No. 3,419,593, which is hereby 
incorporated by reference to show such complexes and their preparation. A 
preferred catalyst is a platinum-containing complex which is the reaction 
product of chloroplatinic acid and sym-divinyltetramethyldisiloxane. An 
even more preferred catalyst is a platinum-containing complex which is the 
reaction product of chloroplatinic acid with dimethylvinylsiloxy 
endblocked poly(methyl-3,3,3-trifluoropropyl)siloxane. 
Other platinum group metal-containing catalyst useful for the cure of the 
base composition of the present method are those microencapsulated 
catalysts as described, for example, in Lee et al., U.S. Pat. No. 
4,766,176, which is hereby incorporated by reference. 
The amount of platinum group metal-containing catalyst that can be used to 
effect curing of the base composition is not narrowly limited as long as 
there is a sufficient amount to accelerate a reaction between silicon-bond 
hydrogen atoms of an organohydrogensiloxane crosslinker and the vinyl 
radicals of the chain extended polymethylvinyl(methylfluoroalkyl)siloxane 
product of step (A) of the method. The appropriate amount of the platinum 
group metal-containing catalyst will depend upon the particular catalyst 
used. In general as little as about 0.001 part by weight of platinum group 
metal for every one million parts (ppm) total weight of the composition to 
be cured may be useful. Preferably the amount of platinum group metal is 
at least one ppm, on the same basis. More preferred is about one to 10,000 
ppm of platinum group metal, on the same basis. Most preferred is about 
five to 50 ppm of the platinum group metal, on the same basis. 
Organohydrogensiloxanes useful as crosslinkers in curing the present base 
compositions are well known in the art and are described, for example, by 
Polmanteer et al., U.S. Pat. No. 3,697,473 and Lee et al., U.S. Pat. No. 
3,989,668, which are hereby incorporated by reference to show examples of 
organohydrogensiloxane known in the art. The organohydrogensiloxane useful 
in the present compositions can be any of those having an average of at 
least three silicon-bonded hydrogen atoms per molecule and an average of 
no more than one silicon-bonded hydrogen atom per silicon atom. The 
remaining valences of the silicon atoms are satisfied by divalent oxygen 
atoms. The organohydrogensiloxane can be homopolymers, copolymers, and 
mixtures thereof which contain diorganosiloxane units, 
organohydrogensiloxane units, diorganohydrogensiloxy units triorganosiloxy 
units and SiO.sub.2 units. Preferably the organohydrogensiloxane 
crosslinker is readily miscible with the base composition of the present 
method. A preferred organohydrogensiloxane crosslinker is described by the 
following formula 
##STR1## 
where Me is methyl and m is a value within a range of one to three. 
The base composition comprising the platinum group metal-containing 
catalyst and the organohydrogensiloxane crosslinker may cure rapidly at 
room temperature. To hinder this curing process an inhibitor may be added 
to the composition. The inhibitor can be any of those materials known to 
inhibit the catalytic activity of platinum group metal-containing 
catalyst. By the term "inhibitor" it is meant a material that retards the 
room temperature curing of the composition when incorporated in the 
composition at less than about 10 weight percent of the composition, 
without preventing the elevated temperature curing of the composition. 
A preferred class of inhibitors useful in the present composition are 
acetylenic alcohols as described in Kookootsedes et al., U.S. Pat. No. 
3,445,420, which is incorporated herein by reference. Such acetylenic 
alcohols are exemplified by 1-ethynylcyclohexan-3-ol and 
2-methyl-3-butyn-2-ol. Other examples of classes of inhibitors which may 
be useful as inhibitors in the present compositions include those 
described in Chung et al., U.S. Pat. No. 5,036,117, Janik, U.S. Pat. No. 
4,584,361, and cyclic alkylvinylsiloxanes. 
The amount of platinum group metal-containing catalyst inhibitor required 
is the amount needed to produce the desired shelf-life and/or pot-life and 
yet not extend the cure time of the curable composition to an impractical 
level. The amount will vary widely and will depend upon the particular 
inhibitor that is used, the nature and concentration of the platinum group 
metal-containing catalyst, and the nature of the organohydrogensiloxane 
crosslinker. Inhibitor added in amounts as small as one mole of inhibitor 
per mole of platinum group metal will in some instance cause a 
satisfactory inhibition of the catalyst. In other cases as much as 500 
moles of inhibitor for every mole of platinum group metal may be needed to 
achieve the desired combination of pot life and cure time. 
In addition to the above described cure components, catalyzed base 
compositions prepared by the present method can have added to them 
optional ingredients such as heat stabilizers, pigments, flame-retardants, 
electrically conductive materials, and thermally conductive materials. 
To provide for improved shelf stability of curable compositions prepared 
using the base composition of the present method, the curable composition 
may be packaged in two parts with the platinum metal containing catalyst 
in one part and the organohydrogensiloxane crosslinker in the other part. 
The following Examples are provided to illustrate the present invention. 
These examples are not intended to limits the scope of the claims herein. 
Example 1. (Not within scope of invention) A fluorosilicone base 
composition similar to that described in Chaffee et al., U.S. Pat. No. 
5,171,773 was cured to form a fluorosilicone etastomer using both a 
peroxide cure system and a platinum catalyst addition-type cure system. 
The peroxide cured fluorosilicone rubber was formed by adding to 100 
weight parts base, 1 part by weight of cerium hydrate and 1 part by weight 
varox powder (2,5-bis(tert-butyl peroxy)-2,5-dimethyl hexane) as catalyst. 
Samples of the resulting mixture were press molded for 10 minutes at 
171.degree. C. and then post-cured for 4 hours at 200.degree. C. in a hot 
air oven. Physicals properties of the resulting fluorosilicone elastomer 
were determined by standard test methods. The test methods and physical 
property data are reported in Table 1. The platinum cured fluorosilicone 
elastomer was formed by adding to 100 weight parts base, 1.6 parts by 
weight of an organohydrogensiloxane described by formula 
##STR2## 
where Me is methyl, and m has a value of 1 to 3 with a distribution such 
that the organohydrogensiloxane had a viscosity of about 5 mPa.multidot.s, 
methyl butynol, and a complex formed by reacting hexachloroplatinic acid 
with dimthylvinylsiloxy terminated 
poly(methyl-3,3,3-trifluoropropyl)siloxane. Samples of the resulting 
mixture were press molded for 10 minutes at 171.degree. C. and then 
post-cured for four hours at 200.degree. C. in a hot air oven. Physical 
properties of the resulting fluorosilicone elastomer were determined and 
are reported in Table 1. The data provided in Table 1 demonstrate the low 
resiliency typically obtained with platinum curing of a fluorosilicone 
elastomer composition, in comparison with peroxide curing of the same 
composition. 
TABLE 1 
______________________________________ 
Cure System 
Physical Property 
Test Method Peroxide Platinum 
______________________________________ 
Durometer (Shore A) 
ASTM D2240 38 37 
Tensile, MPa ASTM 412 8.5 3.0 
Tear (Die B), kN/m 
ASTM D625 16.5 15.4 
Elongation, % 
ASTM 412 358 509 
Resiliency (BS), % 
ASTM D2632 34 25 
______________________________________ 
Example 2. The effect of reinforcing silica particle size on a fluorinated 
polydiorganosiloxane base composition within the scope of the present 
invention was evaluated. A fluorinated polydiorganosiloxane base 
composition as described in Table 2 was prepared. 
TABLE 2 
______________________________________ 
No. Parts (Wt.) 
Component 
______________________________________ 
(1) 100 Hydroxyl end-terminated polymethylvinyl- 
(methyl-3,3,3-trifluoropropyl)siloxane having 
about 0.2 to 1.2 mole percent pendant vinyl 
substituted on silicon and a Williams plasticity 
number within a range of about 2.3 mm to 
3.1 mm at 25.degree. C. 
(2) 0.3 Methylvinyldi(N-methylacetamido)silane. 
(3) 2.0 Hydroxyl end-terminated polydimethylsiloxane 
having about one to six mole percent pendant 
vinyl substituted on silicon and a Williams 
plasticity number within a range of about 
1.2 mm to 2.5 mm at 25.degree. C. 
(4) 5.1 Hydroxyl end-terminated polymethyl(3,3,3- 
trifluoropropyl)siloxane fluid where the 
terminal hydroxyl substitution comprises about 
3 to 10 weight percent of the fluid. 
(5) 1.0 Hydroxyl end-terminated polydimethylsiloxane 
having about 9 to 12 weight percent pendant 
vinyl substituted on silicon and a viscosity of 
about 20 mPa .multidot. s to 60 mPa .multidot. s at 
25.degree. C. 
(6) 28.6 Reinforcing Silica. 
______________________________________ 
The base composition was prepared by placing about 80 weight percent of 
component (1) in a Baker Perkins sigma-blade mixer and heating to 
52.degree. C. with a nitrogen purge for 10 minutes. Component (2) was 
slowly added to the mixer with constant mixing. After completion of the 
addition of component (2), the mixing was continued for an additional 30 
minutes at 52.degree. C. under nitrogen purge. The remainder of component 
(1) and all of components (3), (4), and (5) were added to the mixer and 
mixing continued for an additional five minutes. Component (6) 
(Reinforcing Silica) was then added to the mixer in several increments and 
the mixer content massed between each addition. After completion of the 
addition of the reinforcing silica to the mixer, the mixer was heated at a 
temperature of 150.degree. C. to 170.degree. C. under vacuum with a slow 
nitrogen purge and mixing continued for 90 minutes. The mixture was cooled 
to about room temperature and mixed for 30 minutes as a final step in 
forming the base composition. The silicas tested in the base compositions 
were Cab-O-Sil.RTM. L-90 (surface area 90 m.sup.2 /g), Cab-O-Sil MS-70 
(surface area 100 m.sup.2 /g) and Cab-O-Sil MS-75 (surface area 250 
m.sup.2 /g) all products of Cabot Corporation, Tuscola, Ill. 
A curable fluorosilicone elastomer composition was made by adding per 100 
weight parts of the base composition, 1.4 parts by weight of a 5 
mPa.multidot.s organohydrogensiloxane crosslinker as described in Example 
1, 3 parts by weight of a resin encapsulated platinum catalyst providing 
15 ppm platinum (based on the weight of the base composition), 0.50 part 
by weight of cerium hydrate, and 0.05 part by weight of 
1-ethynylcyclohexan-3-ol. 
Samples of the fluorosilicone elastomer compositions were molded in a press 
for 10 minutes at 171.degree. C. to cure and then post cured for four 
hours in a hot air oven at 200.degree. C. Physical properties of the cured 
elastomer compositions were tested by methods referenced in Table 3 and 
the results of this testing are described in Table 3. 
TABLE 3 
______________________________________ 
Silica Surface Area (m.sup.2 /g) 
Physical Property 
Test Method 
90 200 250 
______________________________________ 
Durometer (Shore A) 
ASTM D2240 37 43 42 
Tensile, MPa ASTM 412 9.0 6.9 11.9 
Tear (Die B), kN/m 
ASTM 625 15.9 22.2 27.3 
Elongation, % 
ASTM 412 368 360 389 
Modulus (100%), MPa 
ASTM 412 1.3 1.3 1.5 
Compression Set, % 
ASTM D395 13 23 20 
Resiliency (BS), % 
ASTM D2632 34 28 29 
______________________________________ 
Example 3. The effects of varying catalyst concentration and crosslinker 
concentration as well as the effects of post curing on cured 
fluorosilicone elastomers prepared from the base composition described in 
Table 2 and prepared as described in Example 2 were evaluated. The cure 
systems used are described in Table 4 as No. 1, 2, and 3. The values for 
each of the components is expressed as weight parts per 100 weight parts 
of the base composition. 
TABLE 4 
______________________________________ 
Description of Cure System Components 
Weight Parts 
No. 1 No. 2 No. 3 Component Description 
______________________________________ 
1.4 2.0 1.0 5 mPa .multidot. s Polymethylhydrogen(methyl- 
3,3,3-trifluoropropyl)siloxane. 
0.0 0.0 0.4 5 mPa .multidot. s Trimethylsiloxy endblocked 
polydimethylsiloxane fluid having 0.5 
weight percent hydrogen substituted on 
silicon. 
2.0 3.0 3.0 Resin encapsulated platinum containing 
catalyst (0.15 weight percent platinum). 
0.05 0.05 0.05 i-Ethynylcyclohexan-3-ol. 
0.5 0.5 0.5 Cerium hydrate. 
______________________________________ 
Cured samples of the fluorosilicone rubber compositions using cured systems 
No. 1, 2, and 3 as described in Table 4 were prepared by molding in a 
press for 10 minutes at 171.degree. C. The physical properties of these 
samples were measured by the methods described in Table 3 and the results 
are described in Table 5 under the heading "AM". Additional samples of the 
cured silicone elastomer molded as described above were post-cured for 
four hours in a hot air oven at 200.degree. C. The physical properties of 
these samples are reported in Table 5 under the heading "PC". 
TABLE 5 
______________________________________ 
Effects of Varying Cure System Components and of Post-Curing 
Cure System 
No. 1 No. 2 No. 3 
Physical Property 
AM PC AM PC AM PC 
______________________________________ 
Durometer (Shore A) 
34 38 34 39 35 41 
Tensile, MPa 9.1 8.9 8.3 8.9 9.3 7.4 
Tear (Die B), kN/m 
18.4 17.5 14.9 14.4 17.5 16.5 
Elongation, % 431 347 349 320 399 284 
Modulus (100%), MPa 
1.0 1.4 1.3 1.6 1.2 1.5 
Compression Set, % 
28 12 20 11 31 12 
Resiliency (BS), % 
40 35 41 35 40 34 
______________________________________