Title:
PROCESSING AIDS FOR HYDROXY-TERMINATED POLYBUTADIENE PROPELLANT(U)
United States Patent 3801385
Abstract:
This patent describes a novel solid propellant formulation containing a hydroxy-containing polybutadiene polymer, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of a compound selected from the group consisting of those having the generic formula: ##SPC1## Wherein R is hydrogen, ω-hydroxy alkyl, phenyl, cyclohexyl, ##SPC2## R' is an ω-hydroxy alkyl or hydroxyphenyl, R" is alkyl, and n is an integer from 1 to about 20; or ##SPC3## Wherein R'" is an alkyl or aryl group and m is an integer from 1 to about 20. This invention also includes the method of forming said formulation, and casting and curing the same to form a solid propellant.
US Patent References:
/3666575.html
Fisher - May 1972 - 3666575
/3677840.html
Shaw et al. - July 1972 - 3677840
POLYURETHANE PROPELLANT COMPOSITIONS PREPARED WITH HYDROXY-TERMINATED POLYESTERS
Winkler et al. - October 1970 - 3532567
Room temperature cured solid propellant
Christian et al. - August 1968 - 3399088
METHOD FOR MANUFACTURING CAST SOLID POLYURETHANE PROPELLANTS
Lippert - September 1970 - 3529042
/3666575.html
Fisher - May 1972 - 3666575
/3677840.html
Shaw et al. - July 1972 - 3677840
POLYURETHANE PROPELLANT COMPOSITIONS PREPARED WITH HYDROXY-TERMINATED POLYESTERS
Winkler et al. - October 1970 - 3532567
Room temperature cured solid propellant
Christian et al. - August 1968 - 3399088
METHOD FOR MANUFACTURING CAST SOLID POLYURETHANE PROPELLANTS
Lippert - September 1970 - 3529042
Inventors:
Mastrolia, Edmund J. (Sacramento, CA)
Michigian, Harry (Carmichael, CA)
Michigian, Harry (Carmichael, CA)
Application Number:
05/076343
Publication Date:
04/02/1974
Filing Date:
08/19/1970
View Patent Images:
Export Citation:
Assignee:
Aerojet General Corporation (El Monte, CA)
Primary Class:
Other Classes:
149/44, 149/38, 149/76, 149/20
International Classes:
C06B23/00; C06D5/06
Field of Search:
149/19,60,76,83,20,38,44
US Patent References:
| 3305523 | Modification of telechelic-type polymers | February 1967 | Burnside |
Primary Examiner:
Padgett, Benjamin R.
Assistant Examiner:
Miller E. A.
Attorney, Agent or Firm:
Jacobs, Mark C.
Claims:
We claim
1. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of di-2-ethylhexylthiodipropionate.
2. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of dilauryl thiodipropionate.
3. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of distyryl thiodipropionate.
4. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of a dithiodipropionate selected from the group consisting of ditridecyl thiodipropionate, di-2-ethylhexyl thiodipropionate, dilauryl thiodipropionate, and distyryl thiodiopropionate.
1. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of di-2-ethylhexylthiodipropionate.
2. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of dilauryl thiodipropionate.
3. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of distyryl thiodipropionate.
4. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of a dithiodipropionate selected from the group consisting of ditridecyl thiodipropionate, di-2-ethylhexyl thiodipropionate, dilauryl thiodipropionate, and distyryl thiodiopropionate.
Description:
BACKGROUND OF THE INVENTION
Most methods of improving propellant flow properties involve the use of surfactants which coat the surface of the propellant solids, do not become part of the crosslinked binder and, hence, disrupt the solids-binder bond causing a deterioration of the propellant mechanical behavior. This invention reduces the viscosity and extends the pot life of hydroxy-terminated polybutadiene composite propellants while improving the resistance of the binder towards oxidative attack. The improvements in pot life and viscosity will allow additional time for motor casting after the addition of the curing agent, thus providing greater assurance of void free castings and, hence, improved grain integrity. In a preferred embodiment, this invention reduces the viscosity and extends the pot life of high solids loading hydroxy-terminated polybutadiene propellants and simultaneously provides an enhancement of propellant mechanical behavior over a wide temperature range.
SUMMARY OF THE INVENTION
Briefly, this invention comprises a novel solid propellant formulation containing a hydroxy-containing polybutadiene polymer, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of a compound selected from the group consisting of those having the generic formula: ##SPC4##
Wherein R is hydrogen, ω-hydroxy alkyl, phenyl, cyclohexyl, ##SPC5##
R' is an ω-hydroxy alkyl or hydroxyphenyl, R" is alkyl, and n is an integer from 1 to about 20; or ##SPC6##
Wherein R'" is an alkyl or aryl group and m is an integer from 1 to about 20.
It is an object of this invention to provide a novel propellant formulation having increased pot life and reduced viscosity.
More specifically, it is an object of this invention to provide a propellant of increased pot life and reduced viscosity having a high solids loading.
It is a further object to improve the manufacture and casting of propellants based on hydroxy-terminated polybutadiene binders, and preferably based on the polyurethane polymer resulting from the reaction of a hydroxy-terminated polybutadiene and an organic di- or polyisocyanate.
In a preferred embodiment, it is an object of this invention to provide a propellant having improved mechanical properties in the cured state together with improved pot life and reduced viscosity in the uncured state.
These and other objects and advantages of this invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Compounds containing the general structure ##SPC7##
wherein R'" and m are as defined above, are effective processing aids in the preparation of high solids loading hydroxy-terminated polybutadiene propellants. Specifically, ammonium perchlorate propellants prepared with hydroxy-terminated polybutadiene prepolymers, cured with aliphatic or aromatic diisocyanates or polyisocyanates and plasticized with hydrocarbon or ester species, show a substantial improvement in viscosity characteristics in the presence of small quantities of these materials.
This invention improves the processing characteristics of high solids loading hydroxy-terminated polybutadiene propellants and simultaneously provides improvements in the uniaxial tensile properties of these propellants over the temperature range of -75 to +160°F by the use of the compounds having the formula ##SPC8##
wherein R' is as defined above. Compounds found to provide this enhancement in flow properties and mechanical behavior belong to a family of substituted alkanol and hydroxyphenyl amines. The most dramatic improvements in both propellant processing and mechanical property behavior was obtained with either diethanolamine or triethanolamine.
While not bound by any theory, it is believed that the compounds of the above formulae react with the ammonium perchlorate and/or ammonium nitrate oxidizer, liberating ammonia and tightly adhere to the surface of the oxidizer. ##SPC9##
The hydroxy species present in the amines react with the isocyanate curing agent, thus forming a firm bond between the solid oxidizer and the crosslinked binder. Compounds of this type contain at least two functional groups (e.g., OH species) which form a complete polymer network. The improvement in flow properties (wetting action) achieved with the alkanol amines occurs by providing a "bridge" between the polar solid oxidizer and the essentially non-polar binder, thus resulting in greater compatibility between the binder components and the solid oxidizer. ##SPC10##
The oxidizer-binder bond which is formed and is believed to account for the mechanical property improvements, is assured by the completion of the above reaction with hydroxyl species.
Thiodipropionate esters of the general structure ##SPC11##
where R'" is either an alkyl or aryl radical, also reduce the initial viscosity and extend the pot life (as determined by the time between curing agent addition and time when the propellant viscosity at +135°F reaches 30,000 poise) of solid rocket propellants based on hydroxy-terminated polybutadiene binders.
In general, the propellant formulations of this invention contain inorganic oxidizing agents such as ammonium perchlorate, ammonium nitrate and potassium perchlorate; organic oxidizers such as cyclotrimethylene trinitramine and cyclotetramethylene tetranitramine; metallic fuels such as powdered aluminum, beryillium, boron and magnesium; plasticizers such as hydrocarbon oils and high molecular weight esters; and curing or crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate. The solids content of these propellants may range up to 92 percent, where these solids consist of the oxidizer(s) plus the metallic fuel(s).
The effect of the compounds of the above formulae is to make the solids and the polymeric fuels more compatible, resulting in better wetting of the solids by the liquids, and hence, better flow properties of the slurries. A typical example of the improvements in the viscosity of a highly loaded hydoxy-terminated polybutadiene propellant is shown in FIG. 1 for the thiodipropionate esters di-2-ethylhexyl-thiodipropionate, dilauryl thiodipropionate, and distyryl thiodipropionate. In all cases, regardless of whether the structure contains aromatic or alkyl groups, a similar effect of reduction of propellant viscosity is achieved. As shown below, this improvement in flow characteristics is achieved without deterioration of the state of cure.
The following propellant formulations were prepared. ##SPC12## ##SPC13##
Shore A Batch Thiodipropionate ester, % Hardness No. 1 None (control) 60 2 di-2-ethylhexylthiodipropionate 44 3 dilauryl thiodipropionate 56 4 distyryl thiodipropionate 65
The improvement in propellant processing that can be achieved with the tertiary amine bonding agents is shown in FIG. 2. The best results are obtained with either diethanolamine, triethanolamine, cyclohexyl substituted diethanolamine, or combinations of the above three with other bonding agents. This can be seen by comparing the viscosity buildup of Propellant 5 which contains no bonding agent to Propellant 6, Propellant 7 and Propellant 8 which contain diethanolamine, triethanolamine and cyclohexyl substituted diethanolamine. Also, comparison of the viscosity characteristics of Propellant 6 to propellants containing any of the above three bonding agents in combination with other bonding agents also demonstrates superior processing properties for the latter systems.
The mechanical behavior of these propellants over a wide temperature range (as measured by both uniaxial tensile properties and in strain evaluation cylinders) is shown in the following table. ##SPC14##
The effect of the various bonding agents on low temperature (-40°F and -75°F) mechanical properties can be seen by comparing the results from batch Propellant 5 (no bonding agent) to the results from the other propellant batches. A dramatic improvement in the uniaxial tensile properties over the entire temperature range can be seen upon incorporating bonding agents into the propellant formulation. The best results are obtained with either diethanolamine or triethanolamine, (compare batches Propellant 7, Propellant 9 and Propellant 6 to Propellant 5).
The improvement in thermal cycling strain capability can be seen by comparing Propellant 5 (no bonding agent) to Propellant 7 (triethanolamine bonding agent). With the triethanolamine bonding agent the thermal cycling capability (160°F to -75°F), was increased from 22.5% for one cycle in the propellant containing no bonding agent to 10 cycles at 22.2% in the propellant containing triethanolamine.
Having fully described the invention, it is intended that it be limited only by the lawful scope of the appended claims.
Most methods of improving propellant flow properties involve the use of surfactants which coat the surface of the propellant solids, do not become part of the crosslinked binder and, hence, disrupt the solids-binder bond causing a deterioration of the propellant mechanical behavior. This invention reduces the viscosity and extends the pot life of hydroxy-terminated polybutadiene composite propellants while improving the resistance of the binder towards oxidative attack. The improvements in pot life and viscosity will allow additional time for motor casting after the addition of the curing agent, thus providing greater assurance of void free castings and, hence, improved grain integrity. In a preferred embodiment, this invention reduces the viscosity and extends the pot life of high solids loading hydroxy-terminated polybutadiene propellants and simultaneously provides an enhancement of propellant mechanical behavior over a wide temperature range.
SUMMARY OF THE INVENTION
Briefly, this invention comprises a novel solid propellant formulation containing a hydroxy-containing polybutadiene polymer, a solid oxidizing agent and having a high solids content; the improvement wherein the propellant has an increased pot life and reduced viscosity by the incorporation therein of a small effective amount of a compound selected from the group consisting of those having the generic formula: ##SPC4##
Wherein R is hydrogen, ω-hydroxy alkyl, phenyl, cyclohexyl, ##SPC5##
R' is an ω-hydroxy alkyl or hydroxyphenyl, R" is alkyl, and n is an integer from 1 to about 20; or ##SPC6##
Wherein R'" is an alkyl or aryl group and m is an integer from 1 to about 20.
It is an object of this invention to provide a novel propellant formulation having increased pot life and reduced viscosity.
More specifically, it is an object of this invention to provide a propellant of increased pot life and reduced viscosity having a high solids loading.
It is a further object to improve the manufacture and casting of propellants based on hydroxy-terminated polybutadiene binders, and preferably based on the polyurethane polymer resulting from the reaction of a hydroxy-terminated polybutadiene and an organic di- or polyisocyanate.
In a preferred embodiment, it is an object of this invention to provide a propellant having improved mechanical properties in the cured state together with improved pot life and reduced viscosity in the uncured state.
These and other objects and advantages of this invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Compounds containing the general structure ##SPC7##
wherein R'" and m are as defined above, are effective processing aids in the preparation of high solids loading hydroxy-terminated polybutadiene propellants. Specifically, ammonium perchlorate propellants prepared with hydroxy-terminated polybutadiene prepolymers, cured with aliphatic or aromatic diisocyanates or polyisocyanates and plasticized with hydrocarbon or ester species, show a substantial improvement in viscosity characteristics in the presence of small quantities of these materials.
This invention improves the processing characteristics of high solids loading hydroxy-terminated polybutadiene propellants and simultaneously provides improvements in the uniaxial tensile properties of these propellants over the temperature range of -75 to +160°F by the use of the compounds having the formula ##SPC8##
wherein R' is as defined above. Compounds found to provide this enhancement in flow properties and mechanical behavior belong to a family of substituted alkanol and hydroxyphenyl amines. The most dramatic improvements in both propellant processing and mechanical property behavior was obtained with either diethanolamine or triethanolamine.
While not bound by any theory, it is believed that the compounds of the above formulae react with the ammonium perchlorate and/or ammonium nitrate oxidizer, liberating ammonia and tightly adhere to the surface of the oxidizer. ##SPC9##
The hydroxy species present in the amines react with the isocyanate curing agent, thus forming a firm bond between the solid oxidizer and the crosslinked binder. Compounds of this type contain at least two functional groups (e.g., OH species) which form a complete polymer network. The improvement in flow properties (wetting action) achieved with the alkanol amines occurs by providing a "bridge" between the polar solid oxidizer and the essentially non-polar binder, thus resulting in greater compatibility between the binder components and the solid oxidizer. ##SPC10##
The oxidizer-binder bond which is formed and is believed to account for the mechanical property improvements, is assured by the completion of the above reaction with hydroxyl species.
Thiodipropionate esters of the general structure ##SPC11##
where R'" is either an alkyl or aryl radical, also reduce the initial viscosity and extend the pot life (as determined by the time between curing agent addition and time when the propellant viscosity at +135°F reaches 30,000 poise) of solid rocket propellants based on hydroxy-terminated polybutadiene binders.
In general, the propellant formulations of this invention contain inorganic oxidizing agents such as ammonium perchlorate, ammonium nitrate and potassium perchlorate; organic oxidizers such as cyclotrimethylene trinitramine and cyclotetramethylene tetranitramine; metallic fuels such as powdered aluminum, beryillium, boron and magnesium; plasticizers such as hydrocarbon oils and high molecular weight esters; and curing or crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate. The solids content of these propellants may range up to 92 percent, where these solids consist of the oxidizer(s) plus the metallic fuel(s).
The effect of the compounds of the above formulae is to make the solids and the polymeric fuels more compatible, resulting in better wetting of the solids by the liquids, and hence, better flow properties of the slurries. A typical example of the improvements in the viscosity of a highly loaded hydoxy-terminated polybutadiene propellant is shown in FIG. 1 for the thiodipropionate esters di-2-ethylhexyl-thiodipropionate, dilauryl thiodipropionate, and distyryl thiodipropionate. In all cases, regardless of whether the structure contains aromatic or alkyl groups, a similar effect of reduction of propellant viscosity is achieved. As shown below, this improvement in flow characteristics is achieved without deterioration of the state of cure.
The following propellant formulations were prepared. ##SPC12## ##SPC13##
Shore A Batch Thiodipropionate ester, % Hardness No. 1 None (control) 60 2 di-2-ethylhexylthiodipropionate 44 3 dilauryl thiodipropionate 56 4 distyryl thiodipropionate 65
The improvement in propellant processing that can be achieved with the tertiary amine bonding agents is shown in FIG. 2. The best results are obtained with either diethanolamine, triethanolamine, cyclohexyl substituted diethanolamine, or combinations of the above three with other bonding agents. This can be seen by comparing the viscosity buildup of Propellant 5 which contains no bonding agent to Propellant 6, Propellant 7 and Propellant 8 which contain diethanolamine, triethanolamine and cyclohexyl substituted diethanolamine. Also, comparison of the viscosity characteristics of Propellant 6 to propellants containing any of the above three bonding agents in combination with other bonding agents also demonstrates superior processing properties for the latter systems.
The mechanical behavior of these propellants over a wide temperature range (as measured by both uniaxial tensile properties and in strain evaluation cylinders) is shown in the following table. ##SPC14##
The effect of the various bonding agents on low temperature (-40°F and -75°F) mechanical properties can be seen by comparing the results from batch Propellant 5 (no bonding agent) to the results from the other propellant batches. A dramatic improvement in the uniaxial tensile properties over the entire temperature range can be seen upon incorporating bonding agents into the propellant formulation. The best results are obtained with either diethanolamine or triethanolamine, (compare batches Propellant 7, Propellant 9 and Propellant 6 to Propellant 5).
The improvement in thermal cycling strain capability can be seen by comparing Propellant 5 (no bonding agent) to Propellant 7 (triethanolamine bonding agent). With the triethanolamine bonding agent the thermal cycling capability (160°F to -75°F), was increased from 22.5% for one cycle in the propellant containing no bonding agent to 10 cycles at 22.2% in the propellant containing triethanolamine.
Having fully described the invention, it is intended that it be limited only by the lawful scope of the appended claims.