Marshall Experimental Sprayable Ablator (MXSA) ingredients were compounded into a two part system which requires a minimum of handling by the user. Preweighed two part kits were developed which require that the user supply only the solvent. The kits consist of all of the powdery materials in Part A, and the epoxy resin (AA397) in Part B. Recent aging data on the kits indicates that they are useable for at least 6 months. The acronym MXSA has recently been replaced with MSA (Marshall sprayable ablator)

Mcleod, A.

English

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Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=19770024315 2020-03-22T07:29:31+00:00Z
lAerotherm Project 6596
INTERIM REPORT
(NASA-CR-1503E5)	 MSXA PACKAGING Interim
Repoct., 14 Sep. 1976 - 31 Jul. 1977
(Aercthera Ccrp.) 	 10 p HC A02/MF A01
CSCL 07L
G3/25
MXSA PACKAGING
N77-.31259
Unclas
46278
s.
r,1
For the Period Sept. 14, 1976
through July 31, 1977
Prepared for
National Aeronautics and Space Administration
George C. Marshall Space Flight Center
Marshall Space Flight Center
Alabama 35812
Contract NAS8-32210
%r
,von , r C
..yam
Prepared by:
Al McLeod
Chemist
Approved b
'
	 belano
Program Manager
i	 i	 i	 I	 l
A
OBJECTIVE
Investigate the applicability of compounding MXSA ingredients into a
two or three part system which would require a minimum of handling by the
user. The major portion of the solvent shall be excluded from the premixed
kit and only used to produce homogeneity or a dust-free kit.
SUMMARY
Preweighed two part MSA (MXSA)* kits have been developed which require
that the user supply only the solvent. The kits consist of all of the
powdery materials in Part A, and the epoxy resin (AA397) in Part B. Recent
aging data on the kits indicate that they are useable for at l east 6 months.
DISCUSSION
A.curex has developed a two-part drum-size kit based on the MSA formula-
tion supplied by MSFC. The powdery materials, including microballoons,
fiberglass, thixotropic agent and curing agent have been combined into Part A,
while Part B consists of the AA397 binder. The solvents for the formulation
are supplied by the user, thereby reducing shipping weight. The kits as
supplied by Acurex are easily handlable as Part A weighs less than 80 lbs
including the fiber drum, while Part B is supplied in a 5-gallon steel
pail. The formulation of the kits is shown in Table 1. The only formu-
lation change between the kit and the material developed by NASA is that
the liquid eutectic curing agent (Shell Z) has been replaced by its two
solid amine components (71 percent methylene dianiline and 29 percent
meta-phenylene diamine). This change was necessary because the liquid
Shell Z does not disperse well in the powdery components of the formulation.
This change causes no mixing problems as the amines are soluble in the
solvent system.
*
The acronym MXSA (Marshall experimental sprayable ablator) has recently
been replaced with MSA (Marshall sprayable ablator).
,
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Requirements for developing a kit from the formulation supplied by
MSFC include the following.
1. The components must form a homogeneous blend
2. The components must not react with each other
3. No significant changes in formulation are permitted
4. The density of cured MSA foam must be in the 16- to 18-lb/ft3
range
5. The flatwise tensile strength must be in excess of 150 psi
6. The kits must be stable for 6 or preferably 12 months
7. The kit must be easy to use
These requirements were used to evaluate the seven schemes shown in
Figure 1; of these seven schemes, Kit No. 2 was eventually selected. Kits
Nos. 1, 3, 5, and 6 were eliminated on the basis that the addition of the
liquid AA397 or Shell Z to the fillers resulted in lumps which are not
dispersible unless the mixture is heated, or solvent is added. The addition
of 25 percent of the solvent does give a uniform mixture with a consistency
of damp sand, however, the long-term stability of this mixture is question-
able due to potential solvent evaporation.
Formulations No. 7 (also Nos. 3 and 5) were eliminated because it
was found that Bentone 27 Thixotropic agent reacts with epoxy resins as
reported by Celanese (Tech. Bull. No. 0168; Long-term Stability of Thixotropic
Epoxy Resins and Curing Agents), and confirmed at Acurex.
Formulation No. 2 was then selected over formulation No. 4 on the basis
of the good results obtained and the fact that formulation No. 4 is three-
part kit while Formulation No. 2 is a two-part kit, thereby cutting down the
number of operations required by the user.
Typical flatwise tension strengths obtained are shown in Table 2.
The values of 230 and 200 psi for Samples 1 and 2 are considered to be
equivalent because of the small number of samples and the greater density
of Sample 1. The fewer value obtained with Sample 3 compared to Sample 2 is
due in part to the greater thickness and in part to insufficient drying times
3
KIT #1
Part A Part B
All
	 Fillers
+ Shell Z
AA397
KIT #3
Part A Part B
All
	
Fillers
+ AA397 Shell	 Z
KIT #2
Part A Part B
All	 Fillers
+ Dry Shell AA397
Z Components
KIT #4
Part A Part B Part C
All	 Fillers AA397 Shell	 Z
KTT 4S
Part A Part B
All	 Fillers
(Exce pt Bentone AA397
27) + Shell	 Z Bentone27
KIT #6
Part A Part B
All	 Fillers
(Except Shell
	 Z
Bentone 27) Bentone
+ AA397 27
KIT #7
Part A Part B
All	 Fillers AA397
(Except Bentone Bentone 27
27)+ Dry Shell
Z Components
Figure 1. MSA kits.
4
TABLE 2. FLATWISE TENSILE STRENGTH OF MSA FOAM 
Amine Curing Kit Storage Sample Sample Flatwise Tensile No.	 of
Aqent Time Density Thickness Strength b (psi) Specimens
1.	 Shell	 Z — 16.4 1/4 inch 230 4
2. MDA/mPDA initial 16.2 1/4	 Inch 200 4
3. MDA/mPDA 6 months 16.3 3/8 inch 151 5
a Using Type K832, 1/4-inch glass fibers
bTested after 2 weeks room temperature cure
between applying layers of MSA in the sample billet preparation. The excess
solvent carried epoxy resin to the surface of the sample during evaporation,
giving a sample with a nonuniform cross section. This was evidenced by the
failure mode of the samples which was generally near the low resin surface of
the billet. This work will be repeated with 1/4-inch thick samples and uniform
resin content samples, and the data will be presented in the next report.
The 1/4-inch chopped glass fibers used in these kits has proven to be
unsatisfactory for spray applications, as it does not break up properly
in the solvent, thereby causing spray nozzle plugging problems and nonuniform
distribution of the glass in the foam composite. Acurex and MSFC are currently
processing a contract modification to remake the MSA kits, using 1/4-inch
Owens Corning Type K847 chopped fiberglass, which is known to disperse properly
in the solvent and the foam composite.
A proposed Materials and Formulation Specification for MSA is included
in this report as Appendix A. This specification details formulation
procedures for the MSA kits along with quality control requirements for the
raw materials. It also gives mixing instructions for the use of the kit.
EXPERIMENTAL
Accelerated aging studies were conducted by mixing the filler materials
with (1) AA397 resin, (2) Shell Z curing agent and (3) a dry blend of Shell Z
components (71 percent MDA and 29 percent m-PDA). The mixtures were sealed in cans
and heated to 165°F (74°C) for 1 week. This aging cycle is equivalent
5
w
-Z
to approximately 30 weeks of natural aging at 70°F based on the approxima-
tion that reaction rates double for each 18°F (10°C) of temperature rise.
An examination of the samples showed no significant change in the
Shell Z or dry-blend of Shell Z components, with the fillers. However, the
blend of fillers and AA397 resin contained hard lumps in the mixture which
undoubtedly are due to polymerization of AA397, possibly catalyzed by
Bentone 27.
The resistance of blended MSA dry components to stratification by
vibrations was tested. This was done to simulate the settling or separation
of components during shipment.
A gallon can half-full of the dry blend was shaken 16 hours on a
sieve shaker. Then the top and bottom halves of the mixture were sieved to
determine particle size distribution and component distribution. The results
are shown in Table 3. The sieve analyses are nearly identical for both
halves of the mixture with no migration of the glass fibers. Thus it appears
that the MSA dry blend is quite stable to vibration and shippable without
self-sieving.
TABLE 3. 16-HOUR VIBRATION TESTING OF MSA COMPONENTS
Sieve Size Top Half Bottom Half
+60 (primarily 1/4-in,	 glass fibers) 3.2% 2.5%
-60 + 100 5.5% 6.3%
-100 91.3% 91.2%
Lap shear tensile testing was done as a quality control test for the
AA397 (Lot 10-4) adhesive in Part B of the MSA kit. AA397 was cured with
Shell Z at 121°C (250°F) on dichromate etched aluminum substrate. An
average of six bonds tested at room temperature gave a lap shear tensile
strength of 5120 psi which passes our 5000-psi minimum specification for
the Shell Z cured AA397.
1APPENDIX A
MATERIAL AND FORMULATION SPECIFICATION
FOR
MARSHALL SPRAYABLE ABLATOR (MSA)
A.1	 SCOPE
This specification details formulation requirements and vendor specifi-
cations for the materials necessary to produce MSA foam kits. Incoming
receiving inspection requirements for the materials have not been established.
A.2	 DESCRIPTION
The MSA kits produced by this specification consist of Part A, a dry
blend of microballoons, fillers and curing agent; and Part B, the epoxy resin.
A.3	 PROCESS DESCRIPTION
A.3.1 Raw Material Requirements
A record of lot numbers and incoming inspection results shall be kept
on each lot of raw material.
A.3.1.1 Bakelite BJO-0930 Phenolic Microballoons (Union Carbide Chemical
Company.)
The BJO-0930 phenolic microballoons shall be in accordance with the
following specifications:
a. Apparent density (untamped): 64 to 104 kg/m' (4 to 6.5 lb/ft')
(Method: Union Carbide WC-24)
b. True density (liquid displacement in 1 percent Dupanol OS in
Toluene): 210 to 250 kg/m 3 (13.1 to 16.7 lb/ft')
c. Floatation in 1 percent Dupanol OS in Toluene solution — not
less than 90 percent shall float. (Method: Union Carbide WC-245-A-2)
7
8
t
h
Y.'
J
d. Particle size, percent on 40 mesh	 0.2 maximum
(Method: Union Carbide WC-7-D-4)	
y
1
e. Moisture content, percent 	 4.0 maximum i
(Method: Union Carbide WC-6-G-1)
A.3.1.2 Eccospheres Glass Microballoons 1G-101 (Emerson & Cumming)
The 1G-101 microballoons shall be in accordance with the following
specifications:
a. True density (liquid displacement) 300 to 350 kg/m 3 (18.8 to 21.8
lb/ft')
b. Bulk density (tamped) 160 to 240 kg/m 2 (10 to 15 lb/ft')
c. Particle size, percent on 40 mesh	 0.2 maximum
A.3.1.3 1/4-Inch Chopped Glass Fibers (Owens Corning Type K 847)
A.3.1.4 1/16-Inch Milled Glass Fibers (Owens Corning Type 731 CA)
A.3.1.5 Bentone 27 (National Lead Industries)
A.3.1.6 Methylene Dianiline
The methylene dianiline shall be in accordance with the following
specification.
a. Melting point: 90°C minimum
b. Grindability — must be capable of being ground in a hammer-mill
to pass through a 35 mesh sieve at 0°C
A.3.1.7 Meta-phenylenediamine (Shell CL)
a. Melting point: 63°C minimum
b. Grindability — must be capable to be ground in a hammer-mill to
pass through a 35 mesh sieve at 0°C
A.3.1.8 AA397 Epoxy Resin
a. Infrared spectrum — the Spectrum shall not have an isocyanate
band at 2300 cm-1
_',	 _	 1'_ _,	 . i	 I	 1-	 t_
rb. Lap shear strenyth — the lap shear strength at room temperature
shall be 3.44 x 10 7
 N/mz
 (5000 psi) or greater when cured with
Shell Z (14 phr) at 250°F for 1 hour on etched* 2024-T3 clad
aluminum adherents.
A.3.2 MSA Formulation Procedures
A.3.2.1 Equipment
The equipment for MSA formulation include a 0.25 m 3 (9 ft') paddle-
type mixer, a hammer-mill and screens of 50, 40, 35, 30 and 8 mesh.
A.3.2.2 Formulation (drum size kit)
a. Add 16.1 kg (35.47 lb) BJO-0930 phenolic microballoons to mixer.
b. While stirring, screen 5.37 kg (11.8 lb) Eccospheres IG-101
through 50 mesh into the mixer.
c. Screen the 1/4-inch chopped glass -fibers through an 8 mesh sieve
two times to remove long fibers then screen 0.537 kg (1.18 lb)
1/4-inch chopped glass fibers through an 8 mesh sieve into the
rotating mixer.
d. While stirring screen 1.34 kg (2.96 lb) 1/16-inch milled glass
fibers through 8 mesh into the mixer.
e. While stirring, screen 1.47 kg (3.23 lb) Benton 27 through 30
mesh into the mixer.
f. While stirring, screen 1.56 kg (3.44 lb) methylene dianiline (MDA)
through 30 mesh into the mixer.
NOTE: MDA and Shell Z should be ground (separately) in a hammer-mill to
to pass throu gh a 35 mesh sieve.
g. While stirring, screen 0.635 kg (1.39 lb) Shell CL into the mixer.
*
H2 SO4/Na 2 Cr2 0 7/H20 (25/3/72 PBW) at 160 ±10°F for 10 to 15 minutes.
9
n;
h. Continue stirring for a minimum of 2 minutes after the mixture
appears uniform.
i. Pour into a lined 55-gallon fiber drum and record the weight,
lot and batch numbers. This comprises Part A.
j. Weigh 15.66 kg (34.49 lb) AA397 into an unlined 5-gallon steel
pail and record the lot and batch numbers.
Part By
Weight Drum Size Kit
Part A 1.725 1	 drum (27.01	 Kg)
Part B 1.000 1	 drum (15.66 Kg)
Denatured Ethyl Alcohol 0.047 739 grams (0.92 liters)
Methylene Chloride, 	 Induscrial 4.304 67.4 Kg (50.8 liters)
Perchloroethylene,	 Industrial 5.265 82.45 Kg	 (50.8 liters)
For best results, Part B is added to a stirred mixture of the alcohol
and solvents. All of Part B must be added and the material on the sides of
the can should be removed by dissolving in a little solvent. Stirring is
continued until all Part B is dissolved. Part A is then added to the
stirring solvent and mixing continued for at least 10 minutes prior to
spraying.
An alternate mixing procedure is to add Part A to approximately
three-fourths of the solvent using the other one-fourth of the solvent to
dissolve Part B.
10
i
a'
s
S
e
t
3
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