CA1152736A - Neutron-absorbing elastomeric compositions and methods for preparing the same - Google Patents
Neutron-absorbing elastomeric compositions and methods for preparing the sameInfo
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- CA1152736A CA1152736A CA000373973A CA373973A CA1152736A CA 1152736 A CA1152736 A CA 1152736A CA 000373973 A CA000373973 A CA 000373973A CA 373973 A CA373973 A CA 373973A CA 1152736 A CA1152736 A CA 1152736A
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/02—Selection of uniform shielding materials
- G21F1/10—Organic substances; Dispersions in organic carriers
- G21F1/103—Dispersions in organic carriers
- G21F1/106—Dispersions in organic carriers metallic dispersions
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
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Abstract
ABSTRACT OF THE DISCLOSURE
Neutron-absorbing elastomers are prepared by cross-linking a comosition which consists essentially of the following: firstly, dior-ganopolysiloxanes having an average of from 15 to 20 mole percent of SiC-bonded phenyl groups and an average viscosity of from 105 to 107 mPa.s at 25°C.; secondly, a neutron-absorbing filler selected from the group consisting of boron carbide, boroxide, boric acid, cadmium oxide, lithium oxide and mixtures thereof which is present in an amount of from 30 to 70 percent by volume based on the total volume of the diorganopolysiloxane containing SiC-bonded phenyl groups and the neutron-absorbing filler;
and thirdly, a cross-linking agent. These elastomers are more resistant to gamma radiation. They exhibit increased elongation at break and increased tear resistance, thereby providing elastomers which are less sensitive to stresses caused by vibration and bending. They also exhibit greater flame retardancy.
Neutron-absorbing elastomers are prepared by cross-linking a comosition which consists essentially of the following: firstly, dior-ganopolysiloxanes having an average of from 15 to 20 mole percent of SiC-bonded phenyl groups and an average viscosity of from 105 to 107 mPa.s at 25°C.; secondly, a neutron-absorbing filler selected from the group consisting of boron carbide, boroxide, boric acid, cadmium oxide, lithium oxide and mixtures thereof which is present in an amount of from 30 to 70 percent by volume based on the total volume of the diorganopolysiloxane containing SiC-bonded phenyl groups and the neutron-absorbing filler;
and thirdly, a cross-linking agent. These elastomers are more resistant to gamma radiation. They exhibit increased elongation at break and increased tear resistance, thereby providing elastomers which are less sensitive to stresses caused by vibration and bending. They also exhibit greater flame retardancy.
Description
~l~iZ736 The present invelltion relatcs to organopolysiloxanes and more particularly to organopolysiloxane compositions wllich may be cross-linked to form neutron-absorbing elastomers.
Neutron-absorbing elastomeric compositions which are obtained from compositi.ons capabl.e of being cross-linked containing d;.organopoly-siloxanes having SiC--bonded phenyl groups and neutron-absorbillg fillers are known in the art. For example, German Patent Application No.
Neutron-absorbing elastomeric compositions which are obtained from compositi.ons capabl.e of being cross-linked containing d;.organopoly-siloxanes having SiC--bonded phenyl groups and neutron-absorbillg fillers are known in the art. For example, German Patent Application No.
2,822,494, published December 7, 1978, (Brand Industrial Services, Tnc.) discloses neutron-absorbing compositions containing diorganopolysiloxanes having SiC-bonded phenyl groups; however, it does not disclose the pro-portion of SiC-bonded phenyl groups present on the diorganopolysiloxane.
Organopolysiloxane compositions which may be cured to form elastomers containing a polydiorganosiloxane gum having up to lO mole per-cent of phenyl radicals, reinforcing silica filler, an organic peroxide, a platinum-containing material and carbon black are described in United States Patent No. 3,652,488 to Harder.
It is an object of one aspect of this invention to provide a cross-linked organopolysiloxane composition which is capable of absorbing radiation.
An object of another aspect of this invention is to provide an elastomer ~hich is more resistant to gamma radiation.
An object of still another aspect of this invention is to pro-vide a cross-linkable organopolysiloxane composition which is capable of forming neutron-absorbing elastomers.
An object of still another aspect of this invention is to pro-vide neutron-absorbing elastomers having increased elongation and increased tear resistance.
An object of a further aspect of this invention is to ?rovide neutron-absorbing elastomers having improved flame retardancy.
~.
i2736 In accordance with an aspect of this invention, compositions are provided which are capable of being cross-linked to form neutron-absorbing elastomers, the composition consisting essentially o: (a) a diorganopolysiloxane having an average of from 15 to 20 mole percent of SiC-bonded phenyl groups and an average viscosity of from 105 to 107 mPa.s at 25C.; (b) a neutron-absorbing filler selected from the group con-sisting of boron carbide, boroxide, boric acid, cadmium oxide, lithium oxide and mixtures thereof which is present in an amount of from 30 to 70 percent by volume based on the total volume of the diorganopolysiloxane containing SiC-bonded phenyl groups and the neutron-absorbing filler;
and (c) a cross-linking agent.
By one variant, the SiC-bonded phenyl groups are present as diphenylsiloxane units.
By another variant, the diorganopolysiloxane is represented by the formula (HO)XSiR3 X(siR2)nsiR3_X(H)x where R is selected from the group consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, with the proviso that from 15 to 20 percent of the number of R radicals are phenyl radicals, n is an integer such that the diorganopolysiloxane has an average viscos-ity of from 105 to 10 mPa.s at 25C. and x is 0 or 1.
By another variant, the cross-linking agent is a peroxide com-pound.
By another variant, the diorganopolysiloxane contains at least 2 SiC-bonded alkenyl groups and the cross-linking agent is a methyl-hydrogenpolysiloxane and a platinum compound.
It has been found that the cross-linked compositions of aspects of this invention, when cornpared with known dimethylpolysiloxane composi-tions in the preparation of neutron-absorbing materials have certain : , .
'.
.
- \
152~36 advantages. For example, neutron-absorbing elastomers obta;ned from the compositions of aspects of this invention may conta;n greater amounts of neutron-absorbing fillers and are more resistant to gamma radiation.
Moreover, even with the same amount of neutron-absorbing fillers, the elastomers obtained from the compos;tions of aspects of th;s invention exhibit increased elongation at break and increased tear r2sistance, thereby providing elastomers l~hich are less sensitive to stresses caused by vibration and benidng. Furthermore, the elastomers obtained from the compositions of aspects of this invention exhibit greater flame retardancy than similar compositions containing dimethylpolysiloxanes.
As discussed above, the diorganopolysiloxanes present in the compositions of aspects of this invention are preferably represented by the following general formula:
(Ho)XSiR3 X(siR20)nsiR3_x)O )x where R represents the same or different monovalent hydrocarbon radicals or substituted monovalent hydrocarbon radicals, with the proviso that from 15 to 20 percent of the number of such R radicals are phenyl groups, n is an integer such that the diorganopolysiloxanes have an average vis-cosity of from 105 to 107 mPa.s at 25C. and x is 0 or 1.
Although this is not generally shown, siloxane units other than the diorganosiloxane units (SiR20~ may be present within or along the siloxane chain of the above-cited formula. Examples of other siloxane units which are generally present only as impurities, are those having the formulas RSiO3/2, R3SiOl/2 and SiO4/2, where R is the same as above.
It is preferred that such other siloxane units be present in an amount less than 1 mole percent.
Although it is preferred that the phenyl groups be present as diphenylsiloxane units, they may also be present, for example, in units of the follol~ing general formula ~here R' represents a monovalent hydrocarbon radical other than the phenyl groups or a substituted hydrocarbon radical.
It is preferred that the monovalent hydrocarbon radicals other than the phenyl group and the substituted hydrocarhon radicals each con-tain from 1 to8 carbon atoms per radical.
Exa~ples of suitable hydrocarbon radicals represented by R and R', other than the phenyl groups, are alkyl radicals, e.g , the methyl and the ethyl radicals, as well as the propyl, butyl and hexyl radicals, alkenyl radicals, e.g., the vinyl, the allyl, the ethylallyl and the buta-dienyl radical; alkaryl radicals, e.g., the tolyl radicals and the aralkyl radicals, e.g., the beta-phenylethyl radical.
Examples of substituted hydrocarbon radicals represented by R
and R' are especially halogenated hydrocarhon radicals, e.g., the 3,3,3-trifluoropropyl radical, chlorophenyl and bromotolyl radicals; and cyanoalkyl radicals, e.g., the beta-cyanoethyl radical.
Because of their availability, it is preferred that at least 80 percent of the number of the SiC-bonded organic radicals other than phenyl groups be methy radicals.
In the same or different molecules having the above formula, the values for x may be the same or different. M;xtures of molecules having various values for n may be present.
The compositions of aspects of this invention may contain any of the neutron-absorbing fillers which have been or could have been incorporated into neutron-absorbing elastomers. A preferred filler is -~ boron carbide (B4C) having a particle size of from 5 to 500 micrometers.
Additional examples of neutron-absorbing fillers are boroxide, boric acid, cadmium oxide and lithium oxide. Mixtures of various neutron-absorbing materials may also be employed.
: ~j ~5;2736 In addition to the diorganopo]ysiloxane and the neutron-absorbing fillers, the compositions of aspects of this invention may con-tain otller materials, e.g., cross-linking agents, fillers other than neutron-absorbing fillers, heat-stabilizers, anti-oxidants, flame retar-dants, processing aids and pigments.
The preferred cross-linking agents are the peroxide compounds.
Suitable examples of peroxide compounds which may be used as cross-linking agents are acylperoxides, e.g., dibenzoyl peroxide, bis-(4-chlorobenzoyl)-peroxide and bis-(2,4-dichlorobeonzoyl~-peroxide; alkyl peroxides and arylperoxides, e.g., di-tert-butyl peroxide and dicumyl peroxide;
perketals, e.g., 2,5-bis-(tert-butylperoxy)-2,5-dimethylhexane, as well as peresters, e.g., diacetyl peroxydicarbonate, tert-butyl perbenzoate, tert-butylperoxy isopropyl carbonate and tert-butylperisonanoate. Also, tert-butyl-beta-hydroxyethylperoxide may be used as a cross-linking agent.
Additional examples of cross-linking agents which may be used in the com-positions of aspects of this invention are azo compounds which form radicals, e.g., a~oisobutyric acid nitrile. However, when the composition contains diorganopolysikoxanes having at least 2 SiC-bonded alkenyl groups, particularly vinyl groups, per molecule, it is possible to use methyl-hydrogenpolysiloxane and platinum catalysts.
Tf the compositions of aspects of this invention contain per-oxide compounds as the cross-linking agent, it is preferred that they be present in an amount of from 0.5 to 5 percent by weight based on the total weight of the composition.
Examples of fillers other than neutron-absorbing fillers which may be employed in the compositions of aspects of this invention are rein-forcing fillers, e.g. pyrogenically obtained silicon dioxide having a surface area of from 100 to 300 m2/g and non-reinforcing fillers, e.g., quartz meal. It is preferred that the compositions contain ?yrogenically , ' .
-~\ l~
~Z736 obtained silicon dioxide having a surface area of from 100 to 300 m2/g in an amount which does not exceed more than 30 percent by weight, based on the total weight of the other constituents of the composition.
Examples of flame retardant agents which may be employed are graphite, alum;num oxide trihydrate which may contain organosiloxy groups on its surface, and platinum or platinum compounds, or plat;num complexes and mixtures of at least two of such substances~
If the compositions of aspects of this invention contain graph-ite, then the amount of graphite should be in the range of from 1 to 10 percent by weight, based on the total weight of the other constituents of the composition.
If the compositions of aspects of this invention contain plati-num, platinum compounds or platinum complexes, particularly in combination with graphite, then the platinum may be present in an amount of from 1 to 10 parts by weight of platinum (calculated as elemental platinum) per mil]ion parts by weight of the composition.
When the compositions of aspects of this invention contain aluminum oxide trihydrate, then the amount of aluminum oxide trihydrate present in thè composition may range from 10 to 40 percent by weight, based on the total weight of the other constituents of the composition.
~xamples of processing aids which may be incorporated in the compositions of aspects of this invention are organopolysiloxanes having an average viscosity of from 100 to 1,000 mPa.s at 25C. and from 10 to 20 mole per-cent of SiC-bonded phenyl groups. ~en the compositions of aspects of this invention contain such processing aids, they should be present in an amount of from 1 to 10 percent by weight based on the total weight of tlle other constituents of the composition.
In prepa~ing the compositions of aspects of this invention, all of the constituents may ~e mixed in any desired se~uence, in a conventional .
:a ~sz736 mixing device, e.g., for example, a kneader. Mixing may tatie place at room temperature. I-lowever, mixing may also be carried out at higher - temperatures, for example, at temperatures in the range of from 35 to 200C, However, heat-sensitive constituents such as the organic peroxide - compounds may, of course, be mixed only at temperatures at which they remain unchanged.
The compositions of aspects of this invention may be shaped by any technique known in the art for shaping cross--linl;able compositions containing diorganopolysiloxanes having a viscosity of at least lO mPa.s at 25C. Examples of suitable shaping techniques are injection molding, transfer molding or other methods involving pressure or extrusion.
The compositions of aspects of this invention may be cross-linked by any suitable means known for cross-linking compositions contain-ing the particular cross-link ng agent. For example, when a peroxide cross-linking agent is used, cross-linking may be accomplished by heating the compositions to between 120 and 180C. It is preferred that heating be continued (so-called tempering), for example, for 4 hours at 200C.
However, if the objects prepared from the compositions of aspects of this invention are thicker than 8 mm, then it is preferred that they be heated for from 4 to 6 hours at 150C. and then for 4 to 6 hours at 200C.
Neutron-absorbing elastomers prepared from the compositions of aspects of this invention are resistant to gamma radiation up to 1011 rad and can absorb at least 10 7 neutrons for each square centimer of surface.
Example A 500 liter kneader was used for mixing 180 kg of a diorgano-polysiloxane containing vinyldimethylsiloxy terminal units and consisting of 82.9 mole percent of dimethylsiloxane units, 17 mole percent of diphenylsiloxane units and 0.1 mole percent vinylmethylsiloxane units (17 mole percent SiC-bonded phenyl groups and 0.1 mole percent SiC-b-llded ~ !L5iZ736 vinyl groups) and having a viscosity of 15-106 mPa.s at 25C., with 450 kg (52 percent by volume) of boron carbide, and 20 kg of pyrogenically obtained s;licon dioxide having a surface area of 150 m2/g, and 3 kg of a diorganopolysiloxane containing vinyldimethylsiloxy terminal units which consists of 92 mo]e percent dimethylsi]oxane units and 18 mole percent diphenylsiloxane units (18 mole percent of SiC-bonded phenyl groups) and a viscosity of 100 mPa.s at 25C. at a temperature of 150C. After the mixture has cooled to room temperature, 20 kg of graphite having a surface area of 10 m /g, 1 kg of a 1 weight percent solution of H2PtC16 6H2O in ethylene glycol monomethyl ether, and 7 kg of dicumylperoxide are added to the mixture. The resultant composition is formed into 2 mm thick .
plates, then heated for 15 minutes to 165C. under a pressure of 100 bar (abs.) and then heated for 4 hours at 200C. in the absence of pressure.
; Comparison Example The process described in the preceding example is repeated, except that 180 kg of a trimethylsiloxy end-blocked diorganopolysiloxane which consists of 99.9 mole percent dimethylsiloxane units and 0.1 mole percent of vinylmethylsiloxane units having a viscosity of 10-106 mPa.s at 25C. are substituted for the diorganopolysiloxane containing 17 mole percent SiC-bonded phenyl groups used in the preceding example.
Properties of the resultant elastomer are shown in the table. The table shows the extent of flame retardancy as measured by the LOI (_imited Oxygen Index) factor, as determined in accordance with ASTM-D 28 63-70.
The higher the factor, the higher the flame retardancy.
.
'ABLE
xam~le_o~arison F. a ple Shore-A Hardness 80 82 Elongation at break, percent 160 50 Tensi.le strength, N/mm 1.9 2 Resistance to tearin~ N/~m 15 6 LOI factor, percent 60 52
Organopolysiloxane compositions which may be cured to form elastomers containing a polydiorganosiloxane gum having up to lO mole per-cent of phenyl radicals, reinforcing silica filler, an organic peroxide, a platinum-containing material and carbon black are described in United States Patent No. 3,652,488 to Harder.
It is an object of one aspect of this invention to provide a cross-linked organopolysiloxane composition which is capable of absorbing radiation.
An object of another aspect of this invention is to provide an elastomer ~hich is more resistant to gamma radiation.
An object of still another aspect of this invention is to pro-vide a cross-linkable organopolysiloxane composition which is capable of forming neutron-absorbing elastomers.
An object of still another aspect of this invention is to pro-vide neutron-absorbing elastomers having increased elongation and increased tear resistance.
An object of a further aspect of this invention is to ?rovide neutron-absorbing elastomers having improved flame retardancy.
~.
i2736 In accordance with an aspect of this invention, compositions are provided which are capable of being cross-linked to form neutron-absorbing elastomers, the composition consisting essentially o: (a) a diorganopolysiloxane having an average of from 15 to 20 mole percent of SiC-bonded phenyl groups and an average viscosity of from 105 to 107 mPa.s at 25C.; (b) a neutron-absorbing filler selected from the group con-sisting of boron carbide, boroxide, boric acid, cadmium oxide, lithium oxide and mixtures thereof which is present in an amount of from 30 to 70 percent by volume based on the total volume of the diorganopolysiloxane containing SiC-bonded phenyl groups and the neutron-absorbing filler;
and (c) a cross-linking agent.
By one variant, the SiC-bonded phenyl groups are present as diphenylsiloxane units.
By another variant, the diorganopolysiloxane is represented by the formula (HO)XSiR3 X(siR2)nsiR3_X(H)x where R is selected from the group consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, with the proviso that from 15 to 20 percent of the number of R radicals are phenyl radicals, n is an integer such that the diorganopolysiloxane has an average viscos-ity of from 105 to 10 mPa.s at 25C. and x is 0 or 1.
By another variant, the cross-linking agent is a peroxide com-pound.
By another variant, the diorganopolysiloxane contains at least 2 SiC-bonded alkenyl groups and the cross-linking agent is a methyl-hydrogenpolysiloxane and a platinum compound.
It has been found that the cross-linked compositions of aspects of this invention, when cornpared with known dimethylpolysiloxane composi-tions in the preparation of neutron-absorbing materials have certain : , .
'.
.
- \
152~36 advantages. For example, neutron-absorbing elastomers obta;ned from the compositions of aspects of this invention may conta;n greater amounts of neutron-absorbing fillers and are more resistant to gamma radiation.
Moreover, even with the same amount of neutron-absorbing fillers, the elastomers obtained from the compos;tions of aspects of th;s invention exhibit increased elongation at break and increased tear r2sistance, thereby providing elastomers l~hich are less sensitive to stresses caused by vibration and benidng. Furthermore, the elastomers obtained from the compositions of aspects of this invention exhibit greater flame retardancy than similar compositions containing dimethylpolysiloxanes.
As discussed above, the diorganopolysiloxanes present in the compositions of aspects of this invention are preferably represented by the following general formula:
(Ho)XSiR3 X(siR20)nsiR3_x)O )x where R represents the same or different monovalent hydrocarbon radicals or substituted monovalent hydrocarbon radicals, with the proviso that from 15 to 20 percent of the number of such R radicals are phenyl groups, n is an integer such that the diorganopolysiloxanes have an average vis-cosity of from 105 to 107 mPa.s at 25C. and x is 0 or 1.
Although this is not generally shown, siloxane units other than the diorganosiloxane units (SiR20~ may be present within or along the siloxane chain of the above-cited formula. Examples of other siloxane units which are generally present only as impurities, are those having the formulas RSiO3/2, R3SiOl/2 and SiO4/2, where R is the same as above.
It is preferred that such other siloxane units be present in an amount less than 1 mole percent.
Although it is preferred that the phenyl groups be present as diphenylsiloxane units, they may also be present, for example, in units of the follol~ing general formula ~here R' represents a monovalent hydrocarbon radical other than the phenyl groups or a substituted hydrocarbon radical.
It is preferred that the monovalent hydrocarbon radicals other than the phenyl group and the substituted hydrocarhon radicals each con-tain from 1 to8 carbon atoms per radical.
Exa~ples of suitable hydrocarbon radicals represented by R and R', other than the phenyl groups, are alkyl radicals, e.g , the methyl and the ethyl radicals, as well as the propyl, butyl and hexyl radicals, alkenyl radicals, e.g., the vinyl, the allyl, the ethylallyl and the buta-dienyl radical; alkaryl radicals, e.g., the tolyl radicals and the aralkyl radicals, e.g., the beta-phenylethyl radical.
Examples of substituted hydrocarbon radicals represented by R
and R' are especially halogenated hydrocarhon radicals, e.g., the 3,3,3-trifluoropropyl radical, chlorophenyl and bromotolyl radicals; and cyanoalkyl radicals, e.g., the beta-cyanoethyl radical.
Because of their availability, it is preferred that at least 80 percent of the number of the SiC-bonded organic radicals other than phenyl groups be methy radicals.
In the same or different molecules having the above formula, the values for x may be the same or different. M;xtures of molecules having various values for n may be present.
The compositions of aspects of this invention may contain any of the neutron-absorbing fillers which have been or could have been incorporated into neutron-absorbing elastomers. A preferred filler is -~ boron carbide (B4C) having a particle size of from 5 to 500 micrometers.
Additional examples of neutron-absorbing fillers are boroxide, boric acid, cadmium oxide and lithium oxide. Mixtures of various neutron-absorbing materials may also be employed.
: ~j ~5;2736 In addition to the diorganopo]ysiloxane and the neutron-absorbing fillers, the compositions of aspects of this invention may con-tain otller materials, e.g., cross-linking agents, fillers other than neutron-absorbing fillers, heat-stabilizers, anti-oxidants, flame retar-dants, processing aids and pigments.
The preferred cross-linking agents are the peroxide compounds.
Suitable examples of peroxide compounds which may be used as cross-linking agents are acylperoxides, e.g., dibenzoyl peroxide, bis-(4-chlorobenzoyl)-peroxide and bis-(2,4-dichlorobeonzoyl~-peroxide; alkyl peroxides and arylperoxides, e.g., di-tert-butyl peroxide and dicumyl peroxide;
perketals, e.g., 2,5-bis-(tert-butylperoxy)-2,5-dimethylhexane, as well as peresters, e.g., diacetyl peroxydicarbonate, tert-butyl perbenzoate, tert-butylperoxy isopropyl carbonate and tert-butylperisonanoate. Also, tert-butyl-beta-hydroxyethylperoxide may be used as a cross-linking agent.
Additional examples of cross-linking agents which may be used in the com-positions of aspects of this invention are azo compounds which form radicals, e.g., a~oisobutyric acid nitrile. However, when the composition contains diorganopolysikoxanes having at least 2 SiC-bonded alkenyl groups, particularly vinyl groups, per molecule, it is possible to use methyl-hydrogenpolysiloxane and platinum catalysts.
Tf the compositions of aspects of this invention contain per-oxide compounds as the cross-linking agent, it is preferred that they be present in an amount of from 0.5 to 5 percent by weight based on the total weight of the composition.
Examples of fillers other than neutron-absorbing fillers which may be employed in the compositions of aspects of this invention are rein-forcing fillers, e.g. pyrogenically obtained silicon dioxide having a surface area of from 100 to 300 m2/g and non-reinforcing fillers, e.g., quartz meal. It is preferred that the compositions contain ?yrogenically , ' .
-~\ l~
~Z736 obtained silicon dioxide having a surface area of from 100 to 300 m2/g in an amount which does not exceed more than 30 percent by weight, based on the total weight of the other constituents of the composition.
Examples of flame retardant agents which may be employed are graphite, alum;num oxide trihydrate which may contain organosiloxy groups on its surface, and platinum or platinum compounds, or plat;num complexes and mixtures of at least two of such substances~
If the compositions of aspects of this invention contain graph-ite, then the amount of graphite should be in the range of from 1 to 10 percent by weight, based on the total weight of the other constituents of the composition.
If the compositions of aspects of this invention contain plati-num, platinum compounds or platinum complexes, particularly in combination with graphite, then the platinum may be present in an amount of from 1 to 10 parts by weight of platinum (calculated as elemental platinum) per mil]ion parts by weight of the composition.
When the compositions of aspects of this invention contain aluminum oxide trihydrate, then the amount of aluminum oxide trihydrate present in thè composition may range from 10 to 40 percent by weight, based on the total weight of the other constituents of the composition.
~xamples of processing aids which may be incorporated in the compositions of aspects of this invention are organopolysiloxanes having an average viscosity of from 100 to 1,000 mPa.s at 25C. and from 10 to 20 mole per-cent of SiC-bonded phenyl groups. ~en the compositions of aspects of this invention contain such processing aids, they should be present in an amount of from 1 to 10 percent by weight based on the total weight of tlle other constituents of the composition.
In prepa~ing the compositions of aspects of this invention, all of the constituents may ~e mixed in any desired se~uence, in a conventional .
:a ~sz736 mixing device, e.g., for example, a kneader. Mixing may tatie place at room temperature. I-lowever, mixing may also be carried out at higher - temperatures, for example, at temperatures in the range of from 35 to 200C, However, heat-sensitive constituents such as the organic peroxide - compounds may, of course, be mixed only at temperatures at which they remain unchanged.
The compositions of aspects of this invention may be shaped by any technique known in the art for shaping cross--linl;able compositions containing diorganopolysiloxanes having a viscosity of at least lO mPa.s at 25C. Examples of suitable shaping techniques are injection molding, transfer molding or other methods involving pressure or extrusion.
The compositions of aspects of this invention may be cross-linked by any suitable means known for cross-linking compositions contain-ing the particular cross-link ng agent. For example, when a peroxide cross-linking agent is used, cross-linking may be accomplished by heating the compositions to between 120 and 180C. It is preferred that heating be continued (so-called tempering), for example, for 4 hours at 200C.
However, if the objects prepared from the compositions of aspects of this invention are thicker than 8 mm, then it is preferred that they be heated for from 4 to 6 hours at 150C. and then for 4 to 6 hours at 200C.
Neutron-absorbing elastomers prepared from the compositions of aspects of this invention are resistant to gamma radiation up to 1011 rad and can absorb at least 10 7 neutrons for each square centimer of surface.
Example A 500 liter kneader was used for mixing 180 kg of a diorgano-polysiloxane containing vinyldimethylsiloxy terminal units and consisting of 82.9 mole percent of dimethylsiloxane units, 17 mole percent of diphenylsiloxane units and 0.1 mole percent vinylmethylsiloxane units (17 mole percent SiC-bonded phenyl groups and 0.1 mole percent SiC-b-llded ~ !L5iZ736 vinyl groups) and having a viscosity of 15-106 mPa.s at 25C., with 450 kg (52 percent by volume) of boron carbide, and 20 kg of pyrogenically obtained s;licon dioxide having a surface area of 150 m2/g, and 3 kg of a diorganopolysiloxane containing vinyldimethylsiloxy terminal units which consists of 92 mo]e percent dimethylsi]oxane units and 18 mole percent diphenylsiloxane units (18 mole percent of SiC-bonded phenyl groups) and a viscosity of 100 mPa.s at 25C. at a temperature of 150C. After the mixture has cooled to room temperature, 20 kg of graphite having a surface area of 10 m /g, 1 kg of a 1 weight percent solution of H2PtC16 6H2O in ethylene glycol monomethyl ether, and 7 kg of dicumylperoxide are added to the mixture. The resultant composition is formed into 2 mm thick .
plates, then heated for 15 minutes to 165C. under a pressure of 100 bar (abs.) and then heated for 4 hours at 200C. in the absence of pressure.
; Comparison Example The process described in the preceding example is repeated, except that 180 kg of a trimethylsiloxy end-blocked diorganopolysiloxane which consists of 99.9 mole percent dimethylsiloxane units and 0.1 mole percent of vinylmethylsiloxane units having a viscosity of 10-106 mPa.s at 25C. are substituted for the diorganopolysiloxane containing 17 mole percent SiC-bonded phenyl groups used in the preceding example.
Properties of the resultant elastomer are shown in the table. The table shows the extent of flame retardancy as measured by the LOI (_imited Oxygen Index) factor, as determined in accordance with ASTM-D 28 63-70.
The higher the factor, the higher the flame retardancy.
.
'ABLE
xam~le_o~arison F. a ple Shore-A Hardness 80 82 Elongation at break, percent 160 50 Tensi.le strength, N/mm 1.9 2 Resistance to tearin~ N/~m 15 6 LOI factor, percent 60 52
Claims (5)
1. A composition which is capable of being cross-linked to form neutron-absorbing elastomers consisting essentially of: (a) a diorganopolysiloxane having an average of from 15 to 20 mole percent of Sic-bonded phenyl groups and an average viscosity of from 105 to 107 mPa.s at 25°C.; (b) a neutron-absorbing filler selected from the group con-sisting of boron carbide, boroxide, boric acid, cadmium oxide, lithium oxide and mixtures thereof which is present in an amount of from 30 to 70 percent by volume based on the total volume of the diorganopolysiloxane containing SiC-bonded phenyl groups and the neutron-absorbing filler;
and (c) a cross-linking agent.
and (c) a cross-linking agent.
2. The composition of claim 1 in which said SiC-bonded phenyl groups are present as diphenylsiloxane units.
3. The composition of claim 1 wherein said diorganopolysiloxane is represented by the formula (HO)xSiR3-x(SiR2O)nSiR3-x(OH)x where R is selected from the gorup consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, with the pro-viso that from 15 to 20 percent of the number of R radicals are phenyl radicals, n is an integer such that the diorganopolysiloxane has an average viscosity of from 105 to 107 mPa.s at 25°C. and x is 0 or 1.
4. The composition of claims 1, 2 or 3 wherein said cross-linking agent is a peroxide compound.
5. The composition of claims 1, 2 or 3 wherein said diorgano-polysiloxane contains at least 2 SiC-bonded alkenyl groups and the cross-linking agent is a methylhydrogenpolysiloxane and a platinum compound.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19803018548 DE3018548A1 (en) | 1980-05-14 | 1980-05-14 | CROSSLINKABLE MASSES TO ELASTIC RADIATION PROTECTION MATERIALS AND ELASTOMERS FROM SUCH MASSAGES |
| DEP3018548.9 | 1980-05-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1152736A true CA1152736A (en) | 1983-08-30 |
Family
ID=6102451
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000373973A Expired CA1152736A (en) | 1980-05-14 | 1981-03-26 | Neutron-absorbing elastomeric compositions and methods for preparing the same |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0041155A1 (en) |
| JP (1) | JPS5833258B2 (en) |
| BR (1) | BR8102115A (en) |
| CA (1) | CA1152736A (en) |
| DE (1) | DE3018548A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7939014B2 (en) | 2005-07-11 | 2011-05-10 | Saint-Gobain Performance Plastics Corporation | Radiation resistant silicone formulations and medical devices formed of same |
| US7943697B2 (en) | 2005-07-11 | 2011-05-17 | Saint-Gobain Performance Plastics Corporation | Radiation resistant silicone formulations and medical devices formed of same |
| US9133340B2 (en) | 2005-07-11 | 2015-09-15 | Saint-Gobain Performance Plastics Corporation | Radiation resistant silicone formulations and medical devices formed of same |
| EA035978B1 (en) * | 2017-05-25 | 2020-09-08 | Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт автоматики им. Н.Л. Духова" | Structural heat-resistant boron-bearing composition and method for preparing the same |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5196228A (en) * | 1984-02-17 | 1993-03-23 | Mcdonnell Douglas Corporation | Laser resistant elastomer composition and use in coating process |
| DE3612971C2 (en) * | 1986-04-17 | 1997-09-18 | Minnesota Mining & Mfg | Process for the preparation of an elastomeric neutron protection material |
| CA2055303A1 (en) * | 1990-12-03 | 1992-06-04 | Michael K. J. Lee | Curable random dimethylsiloxane/diphenylsiloxane copolymer compositions |
| RU2604237C1 (en) * | 2015-06-29 | 2016-12-10 | Федеральное государственное унитарное предприятие "Ордена Ленина и ордена Трудового Красного Знамени научно-исследовательский институт синтетического каучука имени академика С.В. Лебедева" (ФГУП "НИИСК") | Heat-resistant filling composition for neutron protection |
| CN109535535B (en) * | 2018-11-14 | 2022-01-11 | 北京市射线应用研究中心有限公司 | Multifunctional damping material and preparation method and application thereof |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1270724A (en) * | 1960-07-27 | 1961-09-01 | Dow Corning | Silicone rubbers with improved irradiation resistance |
| US3114721A (en) * | 1961-01-23 | 1963-12-17 | Gen Electric | Radiation shielding compositions |
| GB954594A (en) * | 1962-06-30 | 1964-04-08 | Gentex Corp | Flexible shield for ionizing radiations |
| US3457214A (en) * | 1965-12-15 | 1969-07-22 | Gen Electric | Low temperature vulcanizing composition and article made therefrom |
| DE2413850C3 (en) * | 1974-03-22 | 1979-01-11 | Bayer Ag, 5090 Leverkusen | When exposed to water or steam, the transparent elastomers can be crosslinked with a polystyrene foam cup |
| US4176093A (en) * | 1977-02-22 | 1979-11-27 | Zoch Harold L | Neutron absorbing room temperature vulcanizable silicone rubber compositions |
-
1980
- 1980-05-14 DE DE19803018548 patent/DE3018548A1/en not_active Withdrawn
-
1981
- 1981-03-26 CA CA000373973A patent/CA1152736A/en not_active Expired
- 1981-04-08 BR BR8102115A patent/BR8102115A/en unknown
- 1981-05-12 EP EP19810103608 patent/EP0041155A1/en not_active Withdrawn
- 1981-05-14 JP JP56071503A patent/JPS5833258B2/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7939014B2 (en) | 2005-07-11 | 2011-05-10 | Saint-Gobain Performance Plastics Corporation | Radiation resistant silicone formulations and medical devices formed of same |
| US7943697B2 (en) | 2005-07-11 | 2011-05-17 | Saint-Gobain Performance Plastics Corporation | Radiation resistant silicone formulations and medical devices formed of same |
| US8129468B2 (en) | 2005-07-11 | 2012-03-06 | Saint-Gobain Performance Plastics Corporation | Medical devices including a non-polar silicone matrix and a radiation resistant component |
| US9133340B2 (en) | 2005-07-11 | 2015-09-15 | Saint-Gobain Performance Plastics Corporation | Radiation resistant silicone formulations and medical devices formed of same |
| EA035978B1 (en) * | 2017-05-25 | 2020-09-08 | Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт автоматики им. Н.Л. Духова" | Structural heat-resistant boron-bearing composition and method for preparing the same |
Also Published As
| Publication number | Publication date |
|---|---|
| BR8102115A (en) | 1982-01-12 |
| EP0041155A1 (en) | 1981-12-09 |
| DE3018548A1 (en) | 1981-11-19 |
| JPS5833258B2 (en) | 1983-07-19 |
| JPS578251A (en) | 1982-01-16 |
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