The compounds of the class of aromatic polyamides useful as matrix resins in the manufacture of composites or laminate fabrication were developed. The process for preparing this thermoplastic-thermoset polyamide system involves incorporating a latent crosslinking moiety along the backbone of the polyamide to improve the temperature range of fabrication thereof wherein the resin softens at a relatively low temperature (approx. 154 C) and subsequently sets-up or undergoes crosslinking when subjected to higher temperature (approx. 280 C)

Greenwood, T. D.

St.clair, T. L.

Wolfe, J. F.

English

NASA Technical Reports Server

st. Clair et al. 
TNERMOSET-TWERMQPIA~TI~ 
N-PRBPARGUL GROUPS 
AROMATIC POLYAMIDE CONTAINING 
Inventors: Terry L. St. Clair, Poquoson; James 
F. Wolfe, Blacksburg, both of Va.; 
Thomas D. Greenwood, Bristol, Tenn. 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Assignee: 
Appl. NO.: 447,371 
Filed: Dec. 7, 1982 
Related US. Application Data 
Division of Ser. No. 199,768, Ocl. 23, 1980, Pat. No. 
4,395,540. 
Int. c1 .3  .............................................. e086 69/32 
U.S. Cl. .................................... 528/183; 525/426; 
528/220; 528/345; 528/348 
Field of Search ................ 528/345, 183, 220, 348 
~1 References Cited 
U.S. PATENT DOCUMENTS 
4,097,456 6/1978 Barie ................................. ;. 525/426 
Primary Examiner-Harold D. Anderson 
Attorney, Agent, or Firm-Howard J. Qsborn; John R. 
Manning; Wallace J. Nelson 
The compounds are of the class of aromatic polyamides 
useful as matrix resins in the manufacture of composites 
or laminate fabrication. The process for preparing this 
thermoplastic-thermoset polyamide system involves 
incorporating a latent crosslinking moiety along the 
backbone of the polyamide to improve the temperature 
range of fabrication thereof wherein the resin softens at 
a relatively low temperature (~154"  C.) and subse- 
quently "sets-up" or undergoes crosslinking when sub- 
jected to higher temperature ( ~ 2 8 0 "  C.). 
4 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19840014678 2020-03-22T08:39:02+00:00Z
4,43 1,792 
BSET-THERMOPLASTIC AROMATIC 
POLYAMIDE COFPJTAINING N-PRQPARGYL 
GROUPS 
ORIGIN OF THE INVENTION 
The invention described herein was made jointly by 
an employee of the U.S. Government and under a 
NASA contract and is subject to the provisions of Sec- 
tion 305 of the National Aeronautics and Space Act of 
1958, Public Law 85-568 (72 Stat. 435; USC 2457). 
This is a division of application Ser. No. 199,768 filed 
Oct. 23, 1980, now U.S. Pat. No. 4,395,540. 
BACKGROUND OF THE INVENTION 
The use of thermoplastics such as polyamides as ma- 
trix resins for use in composite or laminate fabrication 
has one major drawback, they must be processed at and 
have a heat distortion temperature (HDT) of at least 50" 
C. above the temperature at which they are to be used 
so that their modulus of stiffness properties will be ac- 
ceptable. This problem becomes compounded when an 
organic fiber is to be used as the reinforcing agent with 
such a polymer because the fiber also has a characteris- 
tic temperature at which it begins to irreversibly lost its 
stiffness properties. This is generally due to a relaxation 
phenomenon occurring in a highly oriented fiber. 
The case in Doint is where the fiber to be utilized (of 
5 
10 
15 
20 
25 
rl 
L 
as thermoset-thermoplastics due to a latent chemical 
conversion. 
Another object of the present invention is a novel 
process of preparing a thermoset-thermoplastic mold- 
ing material. 
Another object of the present invention is a novel 
process for fabricating a structural composite which is a 
solvent resistant. 
Another object of the present invention is a novel 
process for fabricating structure composites. 
Another object of the present invention is a novel 
polymer which is soluble before thermal processing, but 
solvent resistant after this processing. 
SUMMARY OF THE INVENTION 
According to the present invention, the foregoing 
and other objects are attained by incorporating a latent 
crosslinking moiety at various levels along the back- 
bone of an aromatic polyamide in order to produce a 
polymer of high molecular weight which will soften to 
allow processing at a relatively llow temperature (154" 
C.) and subsequently "set-up" when treated at a higher 
temperature (280" C.). This type system may be referred 
to as a thermoplastic-thermoset resin since it initially 
behaves like a conventional thermoplastic and subse- 
quently set-up through latent crosslinking sites. 
These sites of latent crosslinking form the basis for 
the Dresent invention. These sites were necessitated by 
the aromatic polyamide class) in a structural composite 30 prodessing restrictions not to enter into any chemici 
application has a relaxation that Occurs Slightly below reactions during the fabrication of the thermoplastic 
300" C. In order to fabricate a structural laminate with component, and then, on heating to a elevated 
this fiber reinforcement a temperature of 280" c. should temperature to form crosslinks which in turn in 
not be exceeded in order to assure maximum fiber mod- a polymer system with an increased HDT and also 
ulus. This thermal restriction must now in turn be im- 35 increased resistance to solvents. 
posed in the resin or polymer meaning it should be 
processable at a temperature lower than 280" C. DETAILED DESCRIPTION OF THE 
Attempts to develop a polymer which would be ther- INVENTION 
mally and chemically compatible with the fiber led to The structure of the novel system of the present in- 
the development of an aromatic secondary polyamide 40 vention is: 
of the following recurring structure: 
0 CH3 CH3 0 O R  . =!-!I 
CH2 This polymer had the necessary property of a low HDT 
(154" C.), but the problem still existed of not being able 
to utilize the full thermal potential of the fiber (300" C.) 50 n=several hundred repeat units 
because the polymer would soften at the lower tempera- 
ture. The heating of this polymer to temperatures ap- 
proaching the relaxation temperature of the fiber had no 
effect on the polymer's HDT. 
@!-A-@CHz-@I!'-!!k 45 
where in a given unit is -cH3 and -CH~-C=CH 
in varying ratios from where -CH3 is 99% and 
-CH2C=CH is % to where -cH3 is 0% and 
-CH2C=CH is 100%. 
In the above structure it is the -cH2C-,CH or pro- 
increases the polymers HDT and solvent resistance. 
Table I illustrates the polymers HDT change as the 
propargyl group is increased for the following polymer 
There is thus a definite need in the art for an aromatic 55 
Or polyamide resin that can be cured in the pargyl group that is the latent crosslinking agent which 
region Of 300" " and have a HDT no more than 50"-70" 
C. below this temperature. 
Accordingly, an object of the present invention is to 
develop a polyamide which can be processed at or 60 
below 300" C. due to a low HDT and then subsequently 
attain a higher HDT due to a chemical conversion 
Another object of the present invention is a novel 
polyamide which can be utilized for fabricating struc- 65 
tural composites. 
Another object of the present invention is a novel 
polyamide or series of polyamides which can be utilized 
which occurs during the thermal treatment. R O  
4,463 1,792 
3 4 
and R is selected from -CN3 and --CHzGI=CH in a 
solvent such as sym tetrachloroethane. TABLE I 
HDT, after treatment to Thus, when Ar is R 280" C. for 15 min., 'CC. 
(1) 100% -CH3, (Control Composition) 165 5 
(2) 99% -CH3, 171 
(3) 95% -CH3, 193 QCH2D 0% -CHz-C=CH 1% --CH;?-CzCH 5% -CH2-C=CH 
the resulting polyamide in the above process would be 
represented by repeating units of the formula: 
(4) 90% -CH3, 200 10 
(5) 67% -CH3, 
10% -CH2-C-CH 
33% --CH?-C-CH 
206 
The improvement in solvent resistance was proven 
by immersing the polyamide (1) which contained no 
psopargyl and (4) which contained 10% propargyl into 
various solvents after treating to 280" C. for 15 minutes. 
The results were as follows: 
TABLE 11 20 
Percent Propargyl in Polymer 
Solvent 0% 10% 
Chloroform Soluble Swelling of polymer 
only 
Cresol Mixture Soluble Swelling of polymer 
only 
25 
The reaction of the propargyl group was monitored 
by infrared spectroscopy by following the disappear- 3o 
ance of the d 2 - H  absorption at 3.1 microns (wave- 
1ength)or 3025 cm-1 (frequency). The exotherms for 
the reaction of the propargyl were also monitored by 
differential scanning calorimetry @SC). The exotherm 
in the DSC spectrum for propargyl occurred between 35 
200"-350" C. generally centering at approximately 300" 
C. (maximum rate of reaction). 
The polyamides were all prepared by a conventional 
method where an aromatic diacid chloride of the gen- 
era1 formula 40 
45 where As is selected from 
is allowed to react with a bis-secondary aromatic di- 
amine of the general formula 55 
where X .is selected from 
0 
II 
-CHz-, -0-, ,C,, nil 
65 
Similarly, when Ar is 
the resulting polyamide would be represented by re- 
peating units of tke formula: 
The propargyl containing aromatic diamines were 
prepared by the N,N-dialkylation of primary aromatic 
diamines. 
EXPERIMENTAL DETAILS 
Preparation of 
p,p'-Bis(trifluoroacetamid0)diphen ylmethane 
Trifluoroacetic anyhydride (105.0 g, 0.50 mol) was 
slowly added to 40.0 g (0.20 mol) of p,p'-dizminodi- 
phenylmethane in 300 ml of tetrahydrofuran. The reac- 
tion mixture was refluxed 1.5 hours, then the solvent 
was stripped by rotary evaporation. The crude tan solid 
was recrystallized from chloroform/methanol to yield 
77.32 g (99% yield) of the desired product, mp 
229"-230" C. 
preparation of 
N,N'-Bispropargyl-p,p'-bis(trifluoroacetamido)di- 
phenylmethane 
To 3.7 g (0.34 mol) of sodium hydride in 20 ml of 
N,N'-dimethylformamide was added 20.0 g (0.051 3 
mol) of the trifluoroacetomide from the previous reac- 
tion. The resulting yellow dianion solution was filtered 
through a glass frit and 24.42 g (0.205 mol) of propargyl 
bromide was added. The reaction mixture was allowed 
to stir at room temperature for eight hours. The reac- 
tion mixture was poured into 1 N HCl and the resulting 
oil was extracted with ethyl acetate, dried with MgS04, 
and concentrated. Flash chromatography gave 20.08 g 
(84% yield) of the desired product, mp 153"-155" C. 
5 6 
Preparation of 
N,N-Bispropargyl-p,p'-diaminodiphen ylmet hane 
Powdered potassium hydroxide (0.93 g, 0.0166 mol) 
was added to a slurry of 1.94 g (0.004 mol) of N,N-bis- 5 
propargyl-p,p'-bis(frifluoroacetamido)diphenylmethane 
in 100 ml of 95% ethanol. This solution was stirred at 
room temperature for one hour, then poured into cold 
water causing the crude product to precipitate. This 
material was recrystallized from 95% ethanol to give lo 
1.05 g (92% yield) of the bispropargyl compound, mp 
107"-108" c. 
Typical Procedure for Polymerizing a 
Bisproparyldiamine with a Diacid Chloride 
Appropriate molar portions (0.02 mol total) of di- 
amines were weighed into a 50 ml resin kettle and dis- 
solved in 20-25 ml of dry CHC13 (distilled from CaH2 
after initial washing with H20 to remove EtOH3 stabi- 20 
lizer). Dry, powdered Ca (0.08 mol) was then added, 
and the reaction mixture stirred to achieve a homogene- 
ous slurry. To the vigorously stirred suspension was 
added dropwise a solution of 0.02 mol of isophthaloyl 
chloride (ICL) in 10 ml of CHCl3. The reaction mixture 25 
was cooled with an ice bath to maintain the temperature 
at 25" C. When addition of the ICL was complete, the 
addition funnel was rinsed with 5 ml of CHC13, which 
was then added to the reaction flask. At this point the 
reaction mixture normally had appreciable viscosity, 30 
and was allowed to stir at room temperature for 0.5 
hour, heating briefly at reflux (15 min.), and then either 
stirred overnight or worked up immediately if the solu- 
tion was very viscous. In some instances the extended 
reaction period seemed to increase the viscosity of the 35 
solution. 
The polymer was diluted to a volume of 125 ml with 
CHCl3 and filtered through a coarse-fritted funnel to 
remove most of the CaO. The slightly cloudy filtrate 
was transferred to a separatory funnel and extracted 
with dilute HCl, washed with water, dried (MgSO4) 
and concentrated to 100 ml. At this point the CHC13 
solution was quite viscous and colorless. White, fibrous 
polymer was then obtained by precipitation when the 45 
solution was poured slowly into either petroleum ether 
or hexane in a blender. The polymer was filtered, 
washed with petroleum ether, air dried, and then dried 
in vacuo at 100" C. overnight. 
tive of the invention and there may be modifications and 
variations therein that will be apparent to those skilled 
in the art without departing from the spirit and scope of 
the invention as set forth herein. 
What is claimed as new and desired to be secured by 55 
Letters Patent of the United States is: 
1. A solvent stable thermosetting thermoplastic poly- 
amide having improved heat distortion temperature 
characteristics and comprising repeating units of the 
formula: 60 
15 
40 
The above specific examples are considered illustra- 50 
0 .  
Ill 
-0- or -C- 
and wherein R represents a mixture of -CH3 and 
-CH2-C=CH in varying percentages. 
2. A process for preparing the polyamide of claim 1 
comprising: reacting (1) a diacid chloride of the for- 
mula: 
0 0 
Cl-C- Ar-C-CI 
II II 
where Ar is: 
with (2) a bis-secondary diamine of the general formula: 
wherein X represents a covalent bond or X represents 
10 
II 
-0- or -C- 
and wherein R represents a mixture of -CH3 and 
-CH2-C=CH in varying percentages. 
3. A solvent stable thermosetting thermoplastic poly- 
amide having improved heat distortion temperature 
characteristics and comparing repeating units of the 
formula: 
wherein X represents a covalent bond or X represents 
10 
II 
-0- or -C- 
and wherein R represents a mixture of -@H3 and 
-CHz-C=CH in varying percentages. 
4. A process for preparing the polyamide of claim 3 
comprising: reacting (1) a diaci'd chloride of the for- 
mula: 
0 0 
Cl-C- Ar-C-CI 
II II 
wherein X represents a covalent bond or X represents where Ar is: 
7 
4,43 1,792 
8 
5 
wherein X represents a covalent bond or X represents 
0 
II 10 
-0- or -C- 
with (2) a bis-secondary diamine of the general formula: 
and wherein R represents a mixture of -CH3 and. 
--CH2--C=CH in varying percentages. 
15 * * * + *  
20 
25 
30 
35 
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50 
55 
60 
65 


Thermoset-thermoplastic aromatic polyamide containing N-propargyl groups

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