Thermosetting fluoropolymer foams are made by mixing fluid form thermosetting fluoropolymer components having a substantial fluorine content, placing the mixture in a pressure tight chamber, filling the chamber with a gas, at relatively low pressure, that is unreactive with the fluoropolymer components, allowing the mixture to gel, removing the gelled fluoropolymer from the chamber and thereafter heating the fluoropolymer at a relatively low temperature to simultaneously sure and foam the fluoropolymer. The resulting fluoropolymer product is closed celled with the cells storing the gas employed for foaming. The fluoropolymer resins employed may be any thermosetting fluoropolymer including fluoroepoxies, fluoropolyurethanes and fluoroacrylates

Lee, Sheng Y.

English

NASA Technical Reports Server

United States Patent [ill Patent Number: 4,843,123 
Lee [45] Date of Patent: Jun. 27, 1989 
CELLULAR THERMOSETTING 
FLUORODIEPOXIDE POLYMERS 
Inventor: Sheng Y. Lee, Silver Spring, Md. 
Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Appl. No.: 163,928 
Filed: Mar. 4, 1988 
Related U.S. Application Data 
Division of Ser. No. 867,987, May 29, 1986, Pat. No. 
4,731,211. 
Int. Cl.4 .............................................. C08G 59/00 
U.S. Cl. ...................................... 521/178; 521/82; 
521/97; 521/98; 521/145; 521/189 
Field of Search ................... 521/178, 145, 97, 98, 
521/189, 82 
~561 References Cited 
U.S. PATENT DOCUMENTS 
4,731,211 3/1988 Lee ........................................ 264/50 
Primaly Examiner-Morton Foelak 
Attorney, Agent, or Firm-R. Dennis Marchant; John R. 
Manning; Ronald F. Sandler 
[571 ABSTRACT 
Thermosetting fluoropolymer foams are made by mix- 
ing fluid form thermosetting fluoropolymer compo- 
nents having a substantial fluorine content, placing the 
mixture in a pressure tight chamber, filling the chamber 
with a gas, at relatively low pressure, that is unreactive 
with the fluoropolymer components, allowing the mix- 
ture to gel, removing the gelled fluoropolymer from the 
chamber and thereafter heating the fluoropolymer at a 
relatively low temperature to simultaneously cure and 
foam the fluoropolymer. The resulting fluoropolymer 
product is closed celled with the cells storing the gas 
employed for foaming. The fluoropolymer resins em- 
ployed may be any thermosetting fluoropolymer in- 
cluding fluoroepoxies, fluoropolyurethanes and 
fluoroacrylates. 
6 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19900007633 2020-03-24T03:02:48+00:00Z
1 
4,843,123 
CELLULAR THERMOSETTING 
FLUORODIEPOXIDE POLYMERS 
ORIGIN OF THE INVENTION 5 
The invention described herein was made by an em- 
ployee of the United States Government, and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
This is a divisionof application Ser. No. 867,987, filed 
May 29, 1986 U.S. Pat. No. 4,731,211. 
TECHNICAL FIELD 
This invention pertains to fluoropolymers and, more 
particularly, to cellular thermosetting fluorodiepoxide 
polymers. 
BACKGROUNDART 
Numerous fluoropolymers such as TEFLON, e.g. 
PTFE, FEP, PFA are now very widely used for coat- 
ings, electrical insulation and as structural components 
due to their superior properties in the areas of hydro- 
phobicity, chemical and thermal stability and electrical 25 
insulation. For some applications, fluoropolymers in 
cellular or foam form are particularly desirable because 
of their weight, dielectric constant and dissipation fac- 
tor. In terms of cost savings, the foams are preferred to 
the non-foams because less fluoropolymer material is 30 
used. These properties are often taken advantage of 
when using fluoropolymer foams in the production of 
wire products such as coaxial cables and power lines. 
The applications for these foams may be expanded as 
Generally these prior foams are made by processes 
which include mixing a thermoplastic fluoropolymer, in 
granular or powder form, with a blowing agent, such as 
a FREON or diisopropyl hydrazinedicarboxylate, and 
placing the mixture in a mold. The mold is heated to a 
very high temperature, for example 240" C. or higher, 
and subjected to a very high pressure in the order of 
I500 psi. After the fluoropolymer reaches a very high 
temperature it becomes fluid and is moldable and foam- 45 
able. A variety of methods, including the addition of 
additives such as nucleation agents, may be employed to 
facilitate the formation of a particular cell structure. 
One example of the prior art in cellular fluoropoly- 
mers includes mixtures of polymers or copolymers of 5o 
perfluorolfins with predetermined amounts of a hy- 
droxyl substituted hydrocarbon. In particular, an aque- 
ous dispersion of a sulfonated lauryl alcohol oxethylate 
and glycerol, a gas foaming agent, and polyetetrafluoro- 
ethylene (PTFE), is whipped until it appears as a stiff 55 
foam which is then heat-treated and finally sintered by 
placing the foam into a 400" oven where the foaming 
agent is evaporated and the plastic hardened. The final 
product is an open-cell thermoplastic. 
mers is that the methods of making them often employ 
blowing agents, nucleating agents, and other additives 
which may leave undesirable residues, in terms of a 
particular application, in the foam products in their final 
form. More importantly, the prior art is restricted to 65 
thermoplastic fluoropolymers products which are 
formed by high temperature sintering processes which 
are incompatable with the coating or encapsulation of 
15 
20 
the manufacturing processes are improved. 35 
40 
One problem with the prior art foamed fluoropoly- 60 
temperature sensitive parts, including some electronics 
parts. 
STATEMENT OF THE INVENTION 
Accordingly, it is an object of the invention to pro- 
vide thermosetting fluorodiepoxide polymer foams. 
It is another object of the invention to provide a 
process for making thermosetting fluorodiepoxide poly- 
mer foams. 
It is yet another object of the invention to provide a 
fluorodiepoxide polymer foam with a predetermined 
gas that is stored in a closed cell structure. 
It is still another object of the invention to provide a 
fluorodiepoxide polymer foam without undesirable resi- 
dues. 
Briefly, these and other objects are achieved by pro- 
viding a thermosetting fluorodiepoxide polymer foam 
closed cell product. 
DETAILED DESCRIPTION OF THE 
INVENTION 
The invention includes any cellular thermosetting 
fluorodiepoxide polymer product and the process of 
making these products, which process, for all the prod- 
ucts, will be essentially the same. The thermosetting 
fluorodiepoxide polymer systems have the same funda- 
mental characteristics, Le., a fluorodiepoxide resin is 
provided which can be cured to form a crosslinked solid 
polymer, by its mixture with a curing agent, a catalyst 
or both. The mixture then cures at a rate which is deter- 
mined as a function of temperature. For many systems, 
room temperature is often sufficient for the mixture to 
gel or set. The full cure often is completed by subjecting 
the mixture to a higher temperature. The curing tem- 
perature, which also functions to produce the foam 
structure, is related to the degree of cure in the gel. This 
type of thermosetting fluoropolymer system is to be 
distinguished from a thermoplastic fluorodiepoxide 
polymer system which does not ever cure in a tradi- 
tional sense, it only melts when heated to a high temper- 
ature and hardens when cooled. As previously noted, 
possible problems with creating a foam with a thermo- 
plastic system, as opposed to a thermosetting system 
and depending on the particular application, are the 
creation of undesirable residues resulting from the use 
of some of the traditional blowing agents and additives 
which are employed in thermoplastic fluoropolymers 
processes and the fact that foaming can only take place 
when the thermoplastic fluoropolymer material is fairly 
fluid, which, for these materials, is at a very high tem- 
perature. In contradistinction, thermosetting fluorodie- 
poxide polymers are fluid at or near room temperature 
when the fluorodiepoxide resin and curing agent are 
first mixed, fluid being defined for this purpose, as prior 
to any gellation. While the thermosetting fluorodiepox- 
ide polymer is in the fluid state, a predetermined unreac- 
tive gas can be dispersed into the chamber and into the 
fluid mixture under a moderate pressure. The gas will 
be trapped in the gelled polymer and foam the polymer 
when it is heat-cured. One example of such a thermoset- 
ting fluorodiepoxide polymer is made from the follow- 
ing fluorodiepoxide resin: 
4,843,123 
3 4 
(7) Heat-cure the gelled fluorodiepoxide polymer. 
The polymer will foam while heating during the 
final cure step of the process. 
Several important aspects of the invention are wor- 
gas has been noted and it is anticipated that for most 
applications a completely unreactive gas will be fa- 
vored. However, for some applications, a gas which is 
not completely unreactive may be employed so long as 
it does not inhibit the curing process. In the instant 
Rf 
0 
/ \  0 C A C F 3  I C-oCH2-c~-cH2 I / \  5 thy of note at this point. Foaming with an unreactive 
CHI- CH-CH20-C 
I 
CF3 
I 
CF3 
which may be cured by acuring agent such as an adduct 
amine with the formula: 
Y 
CF3 
I 
C-OCHZCH-CH~NHCH~CH~NH~ 
I 
H2NCH2CH2NHCH2CHCH2O-C 
I I I 
6 H  kF3 kF3 6 H  
Both of these compounds were developed at the U.S. 
Naval Research Laboratory. The adduct amine may be process, the entrapment of the gas in the resin-curing 
readily prepared by the known method of reacting a 25 agent mixture is completely unexpected because tradi- 
diepoxide with an excess of an diamine. In this case, tional physical concepts would lead one to believe that 
C,-fluorodiepoxide is reacted with an excess of ethylene the application of pressure with a gas would squeeze 
diamine. any gas out of the resin-curing agent mixture rather 
The fluorine content of these fluorodiepoxide poly- squeezing the applied gas into the mixture. Again, it 
mer formulations varies with the size of the perfluoroal- 30 should be emphasized that this unexpected result only 
kyl group, Rfand Rp. When those groups are large, the appears to occur when the fluorine content of the mix- 
ffuorine content of the formulation, in terms of weight, ture, by weight, is somewhere between 30% and #%, 
will be high, perhaps in the order of 50% or higher. A or higher. When this condition is met, the reaction with 
high fluorine content results in fluorodiepoxide poly- an unreactive gas is completely physical, not chemical, 
mer system with a novel property which makes it possi- 35 and completely predictable as well. In other words, as 
ble to disperse a gas into the fluorodiepoxide resin, long as a substantially unreactive gas is employed with 
curing agent mixture under a moderate pressure. The a thermosetting fluorodiepoxide resin-curing agent mix- 
above-noted highly fluorinated, two-component formu- ture that has a high enough fluorine content, the inven- 
lated fluoroepoxy compound may be viscous but it is tive process will work to produce the inventive prod- 
easy to remove a gas, such as air, by evacuation, which 40 uct. 
is introduced while mixing the two components. Just as The following are some specific examples of foaming 
it is easy to remove the gas from the compound, gas can processes for making thermosetting fluorodiepoxide 
also be readily dispersed into the fluorodiepoxide poly- polymer products. 
EXAMPLE NO. 1 mer compound under a moderate pressure. 
ting fluorodiepoxide polymer products may be de- A fluid compound was prepared by mixing, in a con- 
scribed as follows: tainer, 10.0 g. of the diglycidyl ether of 1,3-bis(2- 
(1) Mix the thermosetting fluorodiepoxide polymer hydroxy-hexafluoro-2-propyl)-5-heptadecafluoroctyl- 
fluid form components which usually comprise a benzene (designated as C8-fluorodiepoxide) and 3.4 g (a 
resin and a curing agent or a catalyst, or both. 50 stoichiometric amount) of the adduct amine of C6- 
(2) Deaerate the mixture in a vacuum. fluorodiepoxide with ethylenediamine (designated as 
(3) Place the fluid mixture in a chamber which is C6-adduct amine). After deaerating under a vacuum, 
structured to contain a gas under pressure. the compound was placed in a pressure chamber and 
(4) Fill the chamber with a gas that will not react the chamber was filled with oxygen from a compressed 
with the mixture. Typically the gas pressure in the 55 oxygen gas cylinder to a pressure of 45 psi. After 12 to 
chamber may reach several atmospheres. Note: 24 hrs. in the chamber room temperature, the com- 
The depth of foaming will vary with a variation of pound gelled to a transparent solid. The solid foamed to 
pressure and/or gas type. (More pressure, greater produce a cellular piece with oxygen stored in the re- 
depth.) sulting closed cell structure when it was removed from 
(5) Allow the mixture to gel or partially cure, nor- 60 the pressurized chamber and cured at B 70" C. for 2 hrs. 
mally at or near room temperature. When the mix- The fluorine content of this fluorodiepoxide resin-cur- 
ture is gelled, the gas is trapped in the polymer. ing agent mixture was 56%. 
EXAMPLE NO. 2 
(6) Remove the gelled fluorodiepoxide polymer from 
the chamber (or relieve the pressure in the cham- 
ber). Note: If the gas is removed before the mixture 65 The procedure of Example No. 1, including the mate- 
is sufficiently gelled, the formerly trapped gas will rials acted upon, was repeated except that compressed 
rupture any cell structure which has started to nitrogen was substituted for the oxygen and nitrogen 
form. was now stored in the cells of the final product. 
The general process used for producing thermoset- 45 
5 
4,843,123 
6 
given above. Any curing agent can be employed which 
is compatible with the fluorodiepoxide resin to form a 
fluid compound with a total fluorine content not less 
EXAMPLE NO. 3 
A fluid compound was Prepared by mixing 10.0 g. of 
C6-fluorodiepoxide and 1.48 g. Of 1,3-bis(-amino- than between 30% and 40% by weight or higher. 
ProPYl)-tetramethYldisilOXane. After deaerating under 5 
ber and the chamber was filled with nitrogen gas to a 
Pressure of 75 Psi* After 24 hrs* at temperature$ 
AlThough the availability of thermosetting fluoro- 
believed that this process is appliable to all themoset- 
ting fluoropolymers such as fluoropolyuretanes, fluoro- 
vacuum, the compound was placed in a pressure cham- polymers in the present state-of-art is very limited, it is 
the acylates, as long as they are fluid before gelling or 
70" C. for 2 hrs. after removal from the chamber. This 10 setting and their total fluorine content is not less than as 
compound had a 40% fluorine content. stated above. 
fluorodiepoxides may be better understood from the chosen to perform a specific function in addition to 
foaming. For example, oxygen may be chosen to pro- general fluorodiepoxide formula: 
l5 duce oxidation or combustion, sulfer hexafluoride (SF6) 
may be chosen to increase the dielectric properties of 
the foamed products made by the invention. Addition- 
ally, radioactive gases may be used. 
gelkd and foamed when it was cured at 
The short form designations of the above-noted The gases employed for the foaming process may be 
2o I claim: 
1. A foamed thermosetting fluorodiepoxide polymer 
2. The foamed thermosetting fluorodiepoxide poly- 
3. The foamed thermosetting fluorodiepoxide poly- 
4. The foamed thermosetting fluorodiepoxide poly- 
5. The foamed thermosetting fluorodiepoxide poly- 
product having a gas-filled closed cell structure. 
mer product of claim 1, wherein said gas is air. 
mer product of claim 1, wherein said gas is oxygen. 
mer product of claim 1 wherein said gas is nitrogen. 
C-OCH2 fi 
0 
I 
CF3 
/CHzO-C 
I 
CF3 
25 where Rfcan generally be set forth as Rf=CnFzn+i 
which corresponds to a short form fluoroepoxy desig- 
nation of C,-fluorodiepoxide. Where Rf equals CsFi7 
the designation is Cs~fluorodiepoxide and where Rf 
equals C6F13 the designation is C6-fluorodiepoxide. 
used c8- and C6-fluorodiepoxides. It is ex- 
tendable to all of-the homologues represented by the 
general formula CnF2,+, for Rf in the flurodiepoxide 
structural formula. Additionally, the curing agents for 
the fluorodiepoxide resins are not limited to the amines 
The methods illustrated by the examples noted above 30 mer product of claim 1 wherein said polymer is formed 
of components having a substantial fluorine content. 
, 6. The foamed thermosetting fluorodiepoxide Poly- 
mer product of claim 5 wherein said substantial fluorine 
content, by weight, is 30% or higher. 
35 * * * * *  
40 
45 
50 
55 
60 
65 


Cellular thermosetting fluorodiepoxide polymers

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