O-rings obtainable from vinylidenfluoride (VDF)-based ionically cured copolymers having compression set lower than 20%.

The present invention refers to cured fluoroelastomers having oustanding 
seal properties at high temperature measured as compression set on O-ring 
lower than 20% as defined hereinunder. 
More particularly the cured fluoroelastomers of the present invention, 
which find application in the preparation of O-ring, have the indicated 
compression set values without requiring LONG post-curing times usually 
utilized in the industrial practice. The results are still more surprising 
if it is considered that time necessary to obtain said compression set 
values is 30' or lower compared with the 24 hours normally employed. 
It is to be noticed moreover that already after press moulding, as defined 
hereunder, the compression set values are already sufficiently low for 
many applications. 
It is well known that one of the most important applications of 
fluoroelastomers relates to the preparation of O-rings. These are obtained 
from fluoroelastomeric copolymers based on units deriving from 
vinylidenefluoride (VDF), hexafluoropropene (HFP) and optionally 
tetrafluoroethylene (TFE). 
The commercial products utilized for this purpose have high elastomeric 
characteristics at low and at high temperatures and show good 
processability so that they can be easily injection molded with automatic 
cycles. 
VDF-based fluoroelastomers show low compression set values, even lower than 
20%. However, these require long post-curing time, generally in the range 
of 24 hours at the temperature of 250.degree. C. This is a drawback at 
nowadays VDF-based fluoroelastomers, since it is impossible the automation 
of the injection molding production cycles and post-curing, due to the 
excessively long residence times in continuous device ovens. 
It was felt the need to have available VDF-based fluoroelastomers to 
prepare O-ring requiring very short post-curing times, at least lower than 
or equal to 30', in order to make possible automatic production cycles as 
defined above. 
Fluoroelastomers having post-curing times of 1 hour obtained by peroxidic 
curing are known in the art. In particular see European patent application 
EP 661304, which describes terpolymers based on VDF, HFP and/or 
perfluoroalkylvinylethers and TFE, showing low compression sets, but never 
lower than 20. These lower compression set values are obtainable only when 
the terpolymer has a high fluorine content (higher than 68% by weight). 
The compression set obtainable by using a VDF/HFP copolymer and/or 
perfluoroalkylvinylether, in absence of the TFE termonomer, shows higher 
compression set values and at any rate higher than 20%. 
It was desirable to find a tonically curable VDF-based copolymer with good 
low temperature properties able to be processed by a less expensive 
technology without using the peroxidic curing which, as well known, shows 
remarkable difficulties during the transformation cycle. In particular the 
peroxidic curing is more laborious and requires a combination of technical 
expedients due to the peroxide unstableness besides problems of harmful 
toxic emissions during curing. 
Taking into account the prior art on the curing of ionic type, no 
indications exist on how to reduce the post-curing time to values lower 
than 30' in order to use the above mentioned continuous automatic 
production cycles of molded manufatured articles. 
For instance in U.S. Pat. No. 4,123,603 and EP 445839 in the name of the 
Applicant, are described terpolymers formed by VDF, HFP and TFE units in 
very narrow concentration ranges. They are ionically curable showing a 
satisfactory combination of properties at high and at low temperatures, 
and, at the same time, have good processability, especially as regards the 
mold releasing after curing. For this reason they are particularly 
suitable for the O-rings manufacture. 
However, such terpolymers show the drawback of requiring long post-curing 
times to obtain manufactured articles with good final properties and, in 
particular, the compression set. 
In the prior art described above it is possible to obtain sufficiently low 
compression set values at high temperatures, lower than 20%. In 
particular, such copolymers are capable to overcome commercial 
specifications such as the "Military Specification (MIL-R-83248B)", 
according to which the maximum value required for the compression set at 
200.degree. C. for 70 hours on O-ring, is 20%. It is to be noticed that 
said good compression set values are obtainable only after long post 
curing times, 250.degree. C. for 24 hours. 
It is an object of the present invention vinylidenefluoride (VDF) and 
hexafluoropropene (HFP)-based ionically cured copolymers showing a highly 
stable network giving a cured material only requiring very low or even 
zero post-curing time (at any rate lower than 30 minutes) to obtain a 
compression set value lower than 20%; the copolymer, before curing coming 
from the polymerization reactor and after latex coagulation, washing and 
drying, results highly stable to thermal degradation and the copolymer 
when submitted to thermal treatment at the temperature of 250.degree. C. 
for 1 hour does not show at the FT-IR analysis the presence of peaks 
and/or bands and/or halos of the double bonds --CH.dbd.CF-- at the 
frequency of 1720 cm.sup.-1 ; moreover the copolymer, before curing, 
subjected to gel permeation chromatography (GPC) shows an amount less than 
3% by weight, preferably lower than 2.5% by weight, of polymer fractions 
having molecular weight lower than 10,000, when the Mooney viscosity (ML 
1+10 at 121.degree. C.) is 20, and lower than 0.5% by weight when the 
Mooney viscosity is 50. 
The Mooney viscosity indicated above is determined according to ASTM D 
1646-82. 
The measurement by gel permeation chromatography (GPC) of the molecular 
weight distribution is performed according to the following: 
Utilized Equipment 
Pump: Waters-Mod. 590 
Detector: refraction index (HP 1047A) 
Columns: precolumn plus 4 10.sup.6 Angstrom (.ANG.), 10.sup.5 521 , 
10.sup.4 .ANG., 10.sup.3 .ANG., (Ultrastyragel) columns 
Injection: injector (Rheodyne 7010) 
Operating Conditions 
Eluent: tetrahydrofurane (THF) 
Eluent flow rate: 1 cm.sup.3 /min. 
Sample concentration: 0.5% by weight 
Loop injection: 200 microliters (.mu.l) 
Temperature: 30.degree. C. 
Process Acquisition System Data 
software waters Millenium 2010 (2.15) 
The calibration curve is obtained by Tecnoflon.RTM. copolymer VDF/HFP 
(80/20 by moles) fractionation in THF solution. 
The coagulation, washing and drying procedure of the polymer from the 
polymerization latex is the following: addition of an electrolyte agent 
(alluminium sulphate) in amount of 5 g/l of latex; 6 washings with 
demineralized water (each washing carried out with 1 l of water per l of 
original latex); drying in oven at 80.degree. C. for 24 hours. 
In general, the Mooney viscosity of the copolymer, before curing, and 
without the addition of the curing ingredients as defined hereinunder, 
which can be utilized in the above mentioned injection and compression 
molding applications is comprised from 15 to 150, preferably from 20 to 
100. 
The curable fluoroelastomers, object of the present invention, are prepared 
by using as radical initiator an organic peroxide, which can be selected 
in particular from: 
(a) dialkylperoxides, wherein alkyl has from 1 to 12 carbon atoms, for 
instance diterbutylperoxide (DTBP); 
(b) dialkylperoxydicarbonates, wherein the alkyl has from 1 to 12 carbon 
atoms, for instance diisopropylperoxydicarbonate: 
(c) diacylperoxides, wherein acyl has from 2 to 12 carbon atoms, for 
instance diacetylperoxide; 
(d) peroxyesters having from 3 to 20 carbon atoms, for instance 
terbutylperoxyisobutyrate. 
The process for preparing the fluoroelastomers of the invention comprises 
the copolymerization of the corresponding monomers in aqueous emulsion in 
the presence of an organic peroxide as defined above. The polymerization 
in emulsion can be carried out according to known methods such as for 
instance those described in Kirk Othmer, Encyclopaedia of Chemical 
Technology, vol. 8, pages 500 and seq., 1979. 
The process temperature is comprised between 100 and 150.degree. C., 
preferably between 105 and 130.degree. C. One can operate at pressures 
comprised between 10 and 100 bar, preferably between 20 and 50 bar. 
As known, the emulsion polymerization technique requires the presence of a 
surfactant. Particularly preferred are at least partially fluorinated 
surfactants, corresponding to the general formula: 
EQU R.sub.f --X.sup.- M.sup.+ 
wherein R.sub.f is a (per)fluoroalkylic chain C.sup.5 -C.sub.16 or a (per) 
fluoropolyoxyalkylenic chain, X.sup.- is --COO.sup.- or 
--SO.sub.3.sup.-, M.sup.+ is selected from: H.sup.+, NH.sub.4.sup.+, an 
alkaline metal ion. Among the most commonly used we can cite: ammonium 
perfluoro-octanoate, (per)fluoropolyoxyalkylenes terminated with one or 
more carboxylic groups, optionally salified with sodium, ammonium and 
alkaline metals, preferably sodium, partially fluorinated 
alkylsulphonates. See for instance U.S. Pat. No. 4,524,197. 
Chain transfer agents selected from those commonly employed in the 
fluoroelastomers synthesis can be added to the reaction mixture. We can 
cite: hydrogen, hydrocarbons having from 1 to 12 carbon atoms, for 
instance methane, ethane, methylcyclopentane; chloro(fluoro)carbons having 
from 1 to 10 carbon atoms, optionally containing hydrogen, for instance 
chloroform, trichlorofluoromethane; esters, alcohols, ethers having from 1 
to 12 carbon atoms, for instance ethylacetate, diethylmalonate, 
diethylether, isopropanol, and the like. 
Other chain transfer agents can be generally used as molecular weight 
regulators. Among them, iodinated and/or brominated chain transfer agents, 
such as for instance the compounds of general formula Rf.sub.b (I).sub.x 
(Br).sub.y (Rf.sub.b =perfluorinated hydrocarbon radical containing from 1 
to 8 carbon atoms, x, y=integers comprised between 0 and 2, with at least 
x or y=1 and x+y.ltoreq.2), are comprised. 
If desired, iodides and/or bromides of alkaline or alkaline-earth metals 
can be used, according to the European patent application No. 407,937, 
which are not chain transfer agents. 
After the polymerization in emulsion is completed, the fluoroelastomer is 
isolated from the polymeric latex with known methods, such as the 
coagulation by addition of electrolytes or by cooling. A detailed process 
has been described above. 
The preparation of fluoroelastomers, object of the present invention, can 
be advantageously carried out in the presence of microemulsions of 
perfluoropolyoxyalkylenes, according to U.S. Pat. No. 4,864,006, or also 
of microemulsions of fluoropolyoxyalkylenes having hydrogenated terminals 
and/or hydrogenated repeating units, according to European patent 625,526. 
The polymerization can be also advantageously carried out by using an 
emulsion or a dispersion of perfluoropolyoxyalkylenes and water according 
to the method described in the U.S. Pat. No. 4,789,717. 
The emulsions and dispersions of perfluorooxyalkylenes and water described 
for instance in European patent applications 196,904, 280,312 and 360,292 
can also be used. 
The fluoroelastomers, object of the present invention, comprise VDF 
copolymers with HFP. Typical fluoroelastomer copolymers compositions are 
the following: 
VDF 60-85% by moles, HFP 15-40% by moles, preferably 
VDF 75-80% by moles, HFP 20-25% by moles. 
Besides copolymers also terpolymers or tetrapolymers having the essential 
characteristics indicated above for the VDF/HFP copolymers can be 
prepared. Tetraf luoroethylene (TFE), (per) fluoroalkylvinylethers (PAVE) 
CF.sub.2 =CFOR.sub.fa, wherein R.sub.fa is a (per) fluoroalkyl C.sub.1 
-C.sub.6, for instance perfluoromethylvinylether, can be used a 
termonomers. 
Suitable compositions are the following: 
______________________________________ 
VDF 60-75 % by moles 
HFP 12-22 " 
PAVE 0-5 " 
TFE 3-20 ". 
______________________________________ 
When PAVE is present, generally it partially substitutes HFP. 
Also small amounts of units deriving from a fluorinated bis-olefin can be 
present in the polymer as described in European patent application EP 
661,304 in the name of the Applicant incorporated herein by reference; the 
amount of bisolefin is generally comprised between 0.01-1% by moles. 
The fluoroelastomers object of the present invention can also contain units 
deriving from non fluorinated ethylenically unsaturated monomers, in 
particular non fluorinated olefins (Ol) C.sub.2 -C.sub.8, in amounts 
generally comprised between 0%-10% by moles, such as for instance ethylene 
and propylene, preferably ethylene. 
The fluoroelastomers object of the present invention are ionically cured, 
as known in the art. 
For the cross-linking curing and accelerating agents well known in the art 
are used. The amount of the accelerant agent is comprised between 0.05-5 
phr, the curing agent between 0.5-15 phr, preferably 1-6 phr. For 
instance, as curing agents, aromatic or aliphatic polyhydroxyl compounds, 
or their derivatives, can be employed, as described for instance in 
EP-335,705 and U.S. Pat. No. 4,233,427. Among them in particular we can 
mention: di-, tri- and tetrahydroxy benzenes, naphthalenes or anthracenes; 
bisphenols wherein the two aromatic rings are connected each other through 
a bivalent aliphatic, cycloaliphatic or aromatic radical, or through an 
oxygen or sulphur atom, or also a carbonyl group. The aromatic rings can 
be replaced by one or more atoms of chlorine, fluorine, bromine, or by 
carbonyls, alkyls, acyls. In particular the bisphenol AF is preferred. As 
accelerating agents we can cite for instance: quaternary ammonium or 
phosphonium salts (see for instance EP-335,705 and U.S. Pat. No. 
3,876,654); amino-phosphonium salts (see for instance U.S. Pat. No. 
4,259,463); phosphoranes (see for instance U.S. Pat. No. 3,752,787); the 
imino compounds described in EP-182,299 and EP-120,462; etc. The 
quaternary ammonium or phosphonium salts and the aminophosphonium ones are 
preferred. 
Instead of using the acceleranting and the curing agents separately, an 
adduct of the two substances, in a molar ratio from 1:2 to 1:5, preferably 
from 1:3 to 1:5, can also be used in amounts from 1 to 5 phr (2 to 4.5 
preferred). The acceleranting agent being one of the onium-organic 
compounds having a positive charge, as defined above. The curing agent 
being selected among the compounds indicated above, in particular di- or 
polyhydroxylic or di- or polythiolic. The adduct being obtained by melting 
the product of the reaction between the acceleranting and the curing 
agents, in the indicated molar ratios or by melting the 1:1 adduct mixture 
with the curing agent in the indicated amounts. Optionally it can be 
present also an excess of the acceleranting agent with respect to that 
contained in the adduct, generally in amounts from 0.05 to 0.5 phr. 
For preparing the adduct, the following cations are particularly preferred: 
1,1-diphenyl-1-benzyl-N-diethylphosphoranamine and tetrabutyl phosphonium 
or ammonium; among anions, particularly preferred are, bisphenol compounds 
wherein the two aromatic rings are linked by a bivalent radical selected 
among the perfluoroalkylic groups from 3 to 7 carbon atoms and the OH in 
para position. 
The adduct can be prepared as follows. 
The cross-linking agent such as the polyhydroxylic or polythiolic compound, 
is reacted in aqueous solution or in a suitable solvent, for instance 
methanol, wherein the acceleranting agent is soluble, in a first stage, 
with a basic substance (for instance NaOH, KOH, Ca(OH).sub.2 and 
tBuO.sup.- K.sup.+) by using generally an equivalent gram of basic 
substance per mole of polyhydroxylic or polythiolic compound. The reaction 
product is then reacted in a second stage with the acceleranting agent 
salt (for instance chloride). The desired salt precipitates. After 
filtering and drying, the product is melted, and after cooling, solidifies 
in flakes or pellets giving the adduct used in the present invention. The 
so prepared adduct is particularly suitable for its handling and its 
incorporation in the cross-linkable compounds. 
The adduct preparation is described in the European patent application EP 
684 277 in the name of the Applicant herein incorporated by reference. 
The curing blend contains moreover 
i) one or more inorganic acids acceptors selected from those known in the 
ionic curing of the vinylidenefluoride copolymers, in amounts 1-40 parts 
per 100 parts fluoroelastomeric copolymer; 
ii) one or more basic compounds selected from those known in the ionic 
curing of vinylidene fluoride copolymers, in amounts from 0.5 to 10 parts 
for 100 parts of fluoroelastomeric copolymer. 
The basic compounds mentioned in point ii) are commonly selected in the 
group of Ca(OH).sub.2, Sr(OH).sub.2, Ba(OH).sub.2, metal salts of weak 
acids, such as for instance carbonates, benzoates, oxalates and phosphites 
of Ca, Sr, Ba, Na and K and mixtures of the hydroxides mentioned above 
with the above metal salts; among the compounds of type i) MgO can be 
mentioned. 
The indicated amounts of the components of the compound are referred to 100 
phr of copolymer or terpolymer of the invention. Other conventional 
additives, such as thickeners, pigments, antioxidants, stabilizers and the 
like, can be added to the curing compound. 
It has been moreover found that the cured fluoroelastomers of the present 
invention can find application also as gaskets, shaft seals, hoses. 
They are also suitable for gaskets with metal inserts utilized for pieces 
of big sizes for applications in automotive and chemical industry. It is 
well known that for pieces of remarkable sizes the post curing procedure 
is extremely difficult. 
For these applications the fluoroelastomers of the present invention after 
press curing at high temperature, generally between 170.degree. C. and 
230.degree. C., show values of final properties, such as mechanical 
properties and compression set, already reading their final stable values. 
This means that at high temperature working condition, generally between 
100.degree. C. and 200.degree. C., the values of the final properties 
remain almost unchanged. It has been found indeed that the compression 
set, after press moulding at 170.degree. C. for a few minutes, generally 
in the range of 10 minutes, reaches a value lower than 30%. This low value 
is what required for these kinds of manufactured articles. This result is 
obtained without the need of long time and high temperature post curing 
process. 
When a higher chemical resistance is required, for instance higher 
resistance to polar solvents, compositions based on VDF and the other 
above mentioned comonomers, in mixtures having a fluorine content higher 
than 68% by weight, can be used. 
The present invention will be now better illustrated by the following 
examples which have a merely indicative purpose but it is not limitative 
of the scope of the present invention.

EXAMPLES 
Preparation of the Microemulsion 
In a glass reactor equipped with stirrer, under mild agitation, the 
following components for the preparation of 1 kg of microemulsion are fed 
as follows. The correspondence by volume is equal to 782 ml. 
1) 170 ml of acid are introduced in the reactor, which have a number 
average molecular weight 600 and have the formula: 
##STR1## 
wherein n/m=10 2) 170 ml of a 30% by volume aqueous emulsion of ammonium 
hydroxide are added; 
3) 340 ml of demineralized water are added; 
4) 102 ml of Galden.RTM. D02 are added, having the formula: CF.sub.3 
O(CF.sub.2 --CF(CF.sub.3)O).sub.n (CF.sub.2 O).sub.m CF.sub.2 COOH 
wherein n/m=20 and having average molecular weight of 450. 
Example 1 
In a 21 l horizontal reactor, equipped with stirrer working at 50 rpm, 15 l 
of water and 150 g of the microemulsion prepared according to the 
procedure described are introduced. 
The reactor is heated up to 122.degree. C. and then brought to the pressure 
of 35 relative bar by feeding monomers until the following composition of 
the top reactor gas phase was obtained: 
VDF=53% moles HFP=47% moles. 
After introducing 12 g of diterbutylperoxide (DTBP) the reaction is started 
and the pressure is maintained constant for the whole polymerization by 
feeding a mixture consisting of: 
VDF=78.5% moles 
HFP=21.5% moles 
After a prefixed amount of reacted monomeric mixture corresponding to 4500 
g, the reaction is stopped. The polymerization total time results equal to 
265 minutes. 
The latex having a concentration of 271 g/l latex is then coagulated by 
using an electrolyte agent (aluminium sulphate), washed and dried at 
80.degree. C. for 24 h. 
The obtained polymer shows a mooney viscosity ML (1+10 at 121.degree. C.) 
equal to 51. 
The .sup.19 F NMR analysis shows the following composition: 79.3% by moles 
of HFP, 20.7% by moles of VDF. 
The other chemical physical properties, intrinsic viscosity and 
polydispersity indexes obtained by GPC. are shown in Tab. 1. 
The material has been formulated as in Tab. 2a. M1 is a master batch 50/50 
by weight of bisphenol AF with Tecnoflon.RTM. copolymer 80/20 by moles of 
VDF/HFP; M2 is a master batch 30/70 by weight of 
1,1-diphenyl-1-benzyl-N-diethylphosphoranamine. The rheometric, ODR, 
mechanical and compression set data with different post-curing times are 
shown in Tabs 2a, 3a, 2b and 3b. 
Example 2 
The same reactor of Example 1 is utilized. Material charges, stirring, 
temperature, pressure, initial loading and monomers continuous feeding 
conditions are equal to those of Example 1. Also in this case 12 g of DTBP 
are fed to start the reaction. 
Moreover 30 g of 1,6-diiodoperfluorohexane (C.sub.6 F.sub.12 I.sub.2), as 
chain transfer agent, in the form of a solution obtained by dissolving it 
in 18 ml of Galden.RTM. D02 are fed before the reaction is started. 
The following bis-olefin is also added: 
EQU CH.sub.2 .dbd.CH(CF.sub.2).sub.6 CH.dbd.CH.sub.2 
The initially amount added is equal to 0.23 g dissolved in 1 ml of 
Galden.RTM. D02, and other 19 solution inserts are carried out every 210 g 
of reacted monomer. Each insert is equal to the initially amount added. 
During the reaction, further 6 g of DTBP are added after 300 minutes and 
2600 g of reacted monomer. 
The reaction is stopped after a prefixed amount of reacted monomer, equal 
to 4200 g, which corresponds to a total polymerization time of about 430 
minutes. 
The resulting latex, having a concentration of 250 g/l is coagulated by 
aluminium sulphate washed and dried at 80.degree. C. for 24 h (see the 
procedure in the description). 
The obtained polymer results to have a mooney viscosity ML (1+10 at 
121.degree. C.) of 39. 
The .sup.19 F NMR analysis shows the following composition: 79.2% by moles 
of HFP, 20.8% by moles of VDF. 
The other chemical physical properties, intrinsic viscosity and 
polydispersity indexes obtained by GPC are shown in Tab. 1. 
The material has been formulated as in Tab 3a and the rheomotric, ODR, 
mechanical and compression set data with different post-curing times are 
shown in Tab. 3a and 3b. 
Example 3 Comparative 
In a 10 l vertical reactor, equipped with stirrer working at 545 RPM, 6.5 l 
of water are introduced. The reactor is then heated to the initial 
temperature of 85.degree. C. and at a pressure of 19 relative bar with VDF 
and HFP in the following monomeric composition VDF=53% moles, HFP=47% 
moles. 
Subsequently the reaction is started by the addition of 9.8 g of ammonium 
persulphate as a 150 g/l aqueous solution. 
At the start of the reaction 10 g of ethyl acetate are fed as a 5.6% by 
weight aqueous solution. 
During the polymerization reaction the pressure is kept constant by feeding 
the monomers in the following molar ratios: 
VDF=78.5% moles 
HFP=21.5% moles 
After 120 minutes and a consumption of the monomeric mixture of 2800 g, the 
reaction is stopped. 
The resulting latex having a concentration of 350 g/l, is coagulated by 
aluminium sulphate, washed and dried at 80.degree. C. for 24 h as in 
example 2. 
The obtained polymer shows a mooney viscosity ML (1+10 at 121.degree. C.) 
of 32. 
The .sup.19 F NMR analysis shows the following composition: 79.0% by moles 
of HFP, 21.0% by moles of VDF. 
The other chemical physical properties, intrinsic viscosity and 
polydispersity indexes obtained by GPC are shown in Tab. 1. 
The material has been formulated as in Tabs. 2a and 3a and the rheometric, 
ODR, mechanical and compression set data with different post-curing times 
are shown in Tabs 2b and 3b. 
TABLE 1 
______________________________________ 
EXAMPLE 1 2 3 cfr 
______________________________________ 
MOONEY VISCOSITY 51 39 32 
(1 + 10 at 121.degree. C.) 
INTRINSIC VISCOSITY 88 83 90 
(ASTM D 1416-83) (ml/g) 
GPC 3.6 5.6 5.5 
(ASTM D 3593-80) 
Mw/Mn 
FRACTION BY WEIGHT 0.4% 1.4% 1.4% 
HAVING M &lt; 10000 
FT-IR NO NO YES 
APPEARANCE PEAK OR 
BAND AT 1720 cm.sup.-1 
AFTER THERMAL TREATMENT 
250.degree. C. .times. 1 h 
______________________________________ 
TABLE 2a 
______________________________________ 
Compound 3 
Compound 1 (comp.) 
______________________________________ 
Polymer Ex. 1 
phr 100 -- 
Polymer Ex. 3 (comp.) " -- 100 
M1 " 4 4 
M2 " 1.5 1.5 
MgO-De " 3 3 
Ca(OH).sub.2 " 6 6 
Black MT " 30 30 
Rheometric properties 
Mooney raw polymer 
ML (1 + 10 at 121.degree. C.) 
51 32 
Mooney Compound 
ML 121.degree.,1 + 10' 76 57 
ODR at 177.degree. C., arc 3.degree.,12' 
ML lbf.in 14 8 
MH lbf.in 101 104 
ts2 s 129 141 
ts10 s 159 174 
t'50 s 183 196 
t'90 s 204 231 
Vmax lbf.in/s 2.54 2.56 
______________________________________ 
TABLE 2b 
______________________________________ 
Compound 3 
Compound 1 (comp.) 
______________________________________ 
After press 170.degree. C. .times. 10' 
M100% MPa 3.9 4.2 
Stress at break MPa 10.4 10.4 
Elong. at break % 272 259 
Shore hardness A points 69 70 
C.Set O-ring % 31 37 
200.degree. C. .times. 70 h 
Post-cure at 250.degree. C. .times. 30 min. 
M100% MPa 4.4 5.3 
Stress at break MPa 12.7 13.5 
Elong. at break % 239 228 
Shore A hardness points 70 71 
C.Set O-ring % 18 27 
200.degree. C. .times. 70 h 
Post-cure at 250.degree. C. .times. 8 + 16 h 
M100% MPa 5.1 5.8 
Stress at break MPa 14.3 14.1 
Elong. at break % 214 196 
Shore hardness A points 70 72 
C.Set O-ring % 18 18 
200.degree. C. .times. 70 h 
______________________________________ 
TABLE 3a 
______________________________________ 
Compound 3 
Compound 1 Compound 2 (comp.) 
______________________________________ 
Polymer Ex. 1 
phr 100 -- -- 
Polymer Ex. 2 " -- 100 -- 
Polymer Ex. 3 " -- -- 100 
(comp.) 
M1 " 5 5 5 
M2 " 1.5 1.5 1.5 
MgO-De " 3 3 3 
Ca(OH).sub.2 " 6 6 6 
Black MT " 20 20 20 
Rheometric properties 
Mooney raw polymer 
ML 121.degree.,1 + 10' 
51 39 32 
Mooney compound 
ML 121.degree.,1 + 10' 
69 56 49 
ODR at 177.degree. C., arc 3.degree.,12' 
ML lbf.in 12 10 7 
MH lbf.in 108 105 111 
ts2 s 168 186 207 
ts10 s 207 228 257 
t'50 s 237 255 288 
t'90 s 261 279 324 
Vmax lbf.in 2.39 2.34 2.2 
______________________________________ 
TABLE 3b 
______________________________________ 
Compound 3 
Compound 1 Compound 2 (comp.) 
______________________________________ 
After press 170.degree. C. .times. 10' 
M100% MPa 3.4 3.7 4.0 
Stress at break MPa 10.1 10.3 10.3 
Elong. at break % 233 227 216 
Shore A hardness points 64 64 67 
C.Set O-ring % 28 27 32 
200.degree. C. .times. 70 h 
Post-cure at 250.degree. C. .times. 30 min. 
M100% MPa 3.9 4.0 4.7 
Stress at break MPa 11.5 11.6 12.7 
Elong. at break % 206 203 199 
Shore A hardness points 64 65 66 
C.Set O-ring % 14 14 23 
200.degree. C. .times. 70 h 
Post-cure at 250.degree. C. .times. 8 + 16 h 
M100% MPa 4.6 4.5 5.3 
Stress at break MPa 14.0 11.8 14.4 
Elong. at break % 196 188 201 
Shore A hardness points 64 64 67 
C.Set O-ring % 14 14 15 
200.degree. C. .times. 70 h 
______________________________________