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Publication numberUS3801385 A
Publication typeGrant
Publication dateApr 2, 1974
Filing dateAug 19, 1970
Priority dateAug 19, 1970
Publication numberUS 3801385 A, US 3801385A, US-A-3801385, US3801385 A, US3801385A
InventorsMastrolia E, Michigian H
Original AssigneeAerojet General Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Processing aids for hydroxy-terminated polybutadiene propellant(u)
US 3801385 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent 1191 Mastrolia et al.

[451 Apr. 2, 1974 I PROCESSING AIDS FOR HYDROXY-TERMINATED POLYBUTADIENE PROPELLANT(U) [73] Assignee: Aerojet General Corporation, El

Monte, Calif.

22 Filed: Aug. 19,1970

[2i] Appl. No.: 76,343

[52] US. Cl 149/19, 149/20, 149/38, 149/44, 149/76 [51] Int. Cl C06d 5/06 [58] Field of Search 149/19, 60, 76, 83, 20,

[56] References Cited I UNITED STATES PATENTS 3,666,575 5/1972 Fisher 149 19 3,677,840 7/l972 Shaw et al. 149/19 3,532,567 10/1970 Winkler et al. l49/19 3,399,088 8/1968 Christian et a1. 149/19 3,529,042 9/1970 Lippert l49/l9 X 3,305,523 2/1967 Burnside 149/19 X Primary Examiner-Benjamin R. Padgett Assistant ExaminerE. A. Miller Attorney, Agent, or Firm-Mark C. Jacobs [57] 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:

RNR,

wherein R is hydrogen, al-hydroxy alkyl, phenyl, cyclohexyl,

R is an w'hydroxy alkyl or hydroxyphenyl, R" is alkyl, and n is an integer from 1 to about 20; or

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.

4 Claims, 2 Drawing Figures ZATENTED APR 2 i974 'SHEU 2 BF 2 N df INVENTORS EDMUND J. MASTROLIA HARRY J. MICHIGIAN ATTORNEYS PROCESSING AIDS FOR HYDROXY-TERMINATED POLYBUTADIENE PROPELLANT(U) 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:

wherein R is hydrogen, m-hydroxy alkyl, phenyl, cyclohexyl,

R is an w-hydroxy alkyl or hydroxyphenyl, R" is alkyl, and n is an integer from 1 to about 20; or

i r l /mlz 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 dior 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 withrimproved pot life and reduced viscosity in the uncured state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Compounds containing the general structure 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 to +F by the use of the compounds having the formula 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.

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.

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 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 +135F reaches 30,000 poise) of solid rocket propellants based on hydroxy-terminated polybutadiene binders.

In general, the propellant formulations of this invention contain inorganic oxidizingagents 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 with- (C) Propellant number 1 2 3 4 5 1O Ingredient weight percent:

Nmcio. 68.00 68. as oo 68. 00 68.00 Powdered aluminum 18. 00 1& 00 18. 00 18.110 18. 00 F820: 1.00 1.00 1.00 1.00 1 0O Hydroxy-terminated poly- 4 butadiene. 7. 700 7.700 7.700 7. 812 Triethanolamine. 037 037 037 Toluene diisocyanate 453 .453 453 443 1 Dioetyl azelate 4. 410 4. 410 4. 410 4. 445

. y z rfirnap y -pphenylene diamine 0.20 0.20 0.20 0.20 0. 200 Ditridecyl thiodipropionate 0. 100 Di-2-ethy1hexylthi0dipropionate 0.20 Dilauryl thiodipropionate 0. Distyryl thiodipropionate 0. 20

20 A vflflwflw V W (C) Propellant number 6 7 8 9 Ingredient, weight percent:

NH4C10 68.00 68. 00 68.00 68. 0O Powdered aluminum 18. 00 18. 00 18. 00 18.00 F6203 1.00 1.00 1. 00 1.00 Hydroxy-temilnated polybutadiene... 7. 761 7. 761 7. 418 7. 690 Trinthannlaminn 037 Diethanolamine. 0. 037 Bis-hydroxy ethylcyclohexylamine 0.276

Bls-cyanoethyl dlhydroxy-propylamine.. 0.074 Toluene diisocyanate 0. 457 457 0. 56 0. 591 Dloctyl azelate 4. 445 4. 445 4. 445 4.445 Sym-dl-fl-naphthyl-p-phenylene dlamlne 0. 20 0. 20 0. 200 0. 200 Ditrldecyl thiodlproplonate 0.10 0.10 0.100 0. 100 a Shore A Batch Thiodipropionate ester, Hardness No 1 None (control) 2 di-Z-ethylhexylthiodipropionate 44 3 dilauryl thiodipropionate 56 4 distyryl thiodipropionate.

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.

V 'rLABLn EU) iaFfiisaxaeseswmFoam w'r PERCENT SOLIDS PROPELLANTS +160 to -75 F., thermal cycling Unlaxlal tensile properties strain, percent TDI Test level, temp., m c e E.,, Sec. 1st 5th 10th Batch number Bondlng agent eq. p.s.i. percent percent p.s.l No. cycle cycle cycle Propellant:

+77 95 3a 34 37s 1 F F F 6 Diethanolamme t. 65 40 205 41 53 1,360 2 F F F -75 366 40 52 4,925 3 22. 5 F F 4 21. 1 F F +77 132 32 32 568 1 F F E 7 Trletbanolamine A. 70 40 260 49 53 1, 436 2 F F F -75 510 45 56 5, 372 3 22. 2 22. 22. 2 4 21.9 21. 9 F +77 66 36 40 267 1 F F F s Bis-hydroxy ethyl cyclo- 70 -40 163 18 58 1,578 2 F F F hexylamme. 75 364 9 52 6, 617 3 F F F 4 21. 4 23. 0 F +77 68 29 32 320 1 F F F 9 None (control) 75 40 167 18 31 1,562 2 F F F --75 302 12 32 4,870 3 F F F 4 22, F F +77 109 37 38 390 1 F F F Bls-eyanoethyl dihydroxy- 73 -40 235 33 36 1,857 2 F F F propylamine. -75 417 31 44 4, 903 3 22. 8 22. 8 F 4 23. 0 21. 4 23. 0

The effect of the various bonding agents on low temperature (-40F and 75F) 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 (160F to -75F), 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.

We claim:

1. A novel solid propellant formulation comprising a hydroxy-containing polybutadiene, a solid oxidizing agent and having a high solids content; the improvemeit'tmieifihe propellant has H'ifiieaed 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.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3953260 *May 23, 1975Apr 27, 1976The United States Of America As Represented By The Secretary Of The NavyHydroxy terminated polybutadine
US4000024 *Oct 17, 1975Dec 28, 1976The United States Of America As Represented By The Secretary Of The Air ForceBurning rate modifiers for solid propellants
US4070213 *Jun 30, 1976Jan 24, 1978The United States Of America As Represented By The Secretary Of The ArmyDispersing aids for MT-4
US4177227 *Sep 10, 1975Dec 4, 1979The United States Of America As Represented By The Secretary Of The Air ForceDiluents can be methylene chloride, heptane, hexane, dimethylbutane/2,2-/, dichloroethane/1,1-
US4214928 *Nov 29, 1976Jul 29, 1980The United States Of America As Represented By The Secretary Of The NavyDimethyl hydantoin bonding agents in solid propellants
US4289551 *Jan 2, 1979Sep 15, 1981Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National DefenceHydroxy-terminated polybutadiene binder, diisocyanate curing agent and hydroxy-containing amide or hydantoin as surfactant
US4375522 *Jul 21, 1980Mar 1, 1983The United States Of America As Represented By The Secretary Of The NavyPolybutadienediol, toluene diisocyanate, stablizers
US4377678 *Oct 5, 1979Mar 22, 1983Nissan Motor Company, Ltd.A chain-extended, crosslinked copolymer of a diisocyanate and a hydroxylated polybutadiene; polyurethanes; pot life
US4517035 *Feb 3, 1984May 14, 1985Her Majesty The Queen In Right Of Canada, As Represented By The Minister Of National DefenceMethod of making a castable propellant
Classifications
U.S. Classification149/19.9, 149/38, 149/44, 149/76, 149/20
International ClassificationC06B23/00
Cooperative ClassificationC06B23/009
European ClassificationC06B23/00H