Epoxy foams using multiple resins and curing agents

An epoxy foam comprising a plurality of resins, a plurality of curing agents, at least one blowing agent, at least one surfactant and optionally at least one filler and the process for making. Preferred is an epoxy foam comprising two resins of different reactivities, two curing agents, a blowing agent, a surfactant, and a filler. According to the present invention, an epoxy foam is prepared with tailorable reactivity, exotherm, and pore size by a process of admixing a plurality of resins with a plurality of curing agents, a surfactant and blowing agent, whereby a foamable mixture is formed and heating said foamable mixture at a temperature greater than the boiling temperature of the blowing agent whereby said mixture is foamed and cured.

BACKGROUND OF THE INVENTION 
The invention relates to an epoxy foam and a process for making the same. 
More particularly, this invention relates to a tailorable epoxy foam 
encapsulant formed using at least two resins and at least two curing 
agents. 
In the fabrication of electronic devices and circuits, the electronic 
devices are protected from the adverse effects of the environment by 
filling the empty spaces between components on the device with a potting 
material that encapsulates these components. If the electronic device is 
used outdoors, such as in automotive, aircraft, marine, or building 
applications, the potting or encapsulant material must be stable enough to 
provide protection over extreme outdoor temperatures and humidity 
conditions, as well as mechanical stresses. Additionally, the encapsulant 
material can serve to isolate the protected devices from human intrusion. 
In some applications, future access to the device is desired and so the 
encapsulant must be capable of isolating the device for a period of time 
but must have mechanical and structural characteristics to allow 
subsequent removal of the encapsulant. Consequently, such encapsulants 
must possess suitable thermal, mechanical and electrical properties. 
Epoxy compounds have been widely used as adhesives, encapsulants and 
coatings for a variety of applications. Epoxy compounds typically have 
good insulating properties and excellent adhesion, and are easy to 
process. However, flexibilized epoxies usually have poor thermal 
stability, hydrolytic stability and mechanical properties; and 
consequently, have not been used for elastomeric applications. Rather, 
polyurethane or silicone potting compositions have been used for these 
applications. However, polyurethanes are more difficult to process due to 
their tendency to foam when in contact with moisture-containing surfaces. 
Silicones have the disadvantage of being poor adhesives and are also 
mechanically weak and costly. 
Epoxy foam encapsulants have a general composition that includes a resin, a 
curing agent, a surfactant, a blowing agent and a filler or nucleating 
agent. The resin, curing agent and surfactant, as well as the curing 
conditions, are chosen to yield a specific foam encapsulant structure. The 
mixture is cast into a mold and heated to form and cure the encapsulant. 
Gormley et al. (U.S. Pat. No. 4,090,986, issued on May 23, 1978) describe 
an epoxy foam composition which uses a delta-1-tetrahydrophthalic 
anhydride epoxy resin with an amine curing agent to form a thermoset epoxy 
foam. Hermansen et al. (U.S. Pat. No. 5,457,165, issued on Oct. 10, 1995) 
note that there are various resins which may be used in forming an 
encapsulant; diglycidyl ethers are commonly used. Hermansen et al. also 
describe an encapsulant which uses two resins to tailor the property of 
the formed encapsulant to provide both dry heat and humid heat stability. 
The invention according to Hermansen et al. differs from other formed 
encapsulants in that the invention utilizes more than one resin to tailor 
specific properties of the encapsulant to achieve desired properties. 
Russick and Rand (Sandia National Laboratories Technical Report 
SAND98-2538, Albuquerque, N. Mex., December, 1998, incorporated by 
reference herein) describes a new epoxy foam encapsulant that utilizes 
multiple resins and curing agents to control the reactivity, exotherm, and 
pore size and therefore the mechanical, thermal, and electrical properties 
of the formed epoxy foam encapsulant. Such control allows for epoxy foams 
of larger volumes without excessive reactivity and exotherm which could 
lead to lowered pot life, premature curing prior to filling void volume, 
or burn out of the foam. 
Useful would be a foam encapsulant without carcinogenic constituents that 
has tailorable mechanical, thermal, and electrical properties that allow 
encapsulation of a component such as electromechanical components or 
instrumentation that sufficiently isolates the material from the outside 
environment with adequate thermal/mechanical properties to allow removal 
so that the encapsulated component can be accessed. 
SUMMARY OF THE INVENTION 
According to the present invention, an epoxy foam is provided, comprising a 
plurality of resins, a plurality of curing agents, at least one blowing 
agent, at least one surfactant; and optionally at least one filler. 
Preferred is an epoxy foam comprising two resins of different 
reactivities, two curing agents, a blowing agent, a surfactant, and a 
filler. More preferred is an epoxy foam wherein the two resins are Epon 
830 and Epon 8121. 
Also according to the present invention is a process of making an epoxy 
foam with tailorable properties, comprising admixing a plurality of resins 
with a plurality of curing agents, a surfactant and blowing agent, whereby 
a foamable mixture is formed and heating said foamable mixture at a 
temperature greater than the boiling temperature of the blowing agent 
whereby said mixture is foamed and cured. 
The epoxy foam according to the present invention can be employed in a kit, 
wherein the kit comprises a premixed component consisting essentially of 
the curing agents, a premixed component consisting essentially of the 
epoxy resins, the surfactant and the nucleating agent, and a component 
consisting essentially of the blowing agent. 
DESCRIPTION OF SPECIFIC EMBODIMENTS 
Epoxy foams are formed by cross-linking reactions between epoxy resins and 
curing agents that create a three-dimensional covalent bond network. There 
are numerous commercially available epoxy resins and curing agents that 
are used to achieve epoxy foams with different thermal, mechanical, and 
electrical properties. A type of epoxy resin that is commonly used is 
diglycidyl ether of bisphenol A (DGEBPA). Examples of these are: the solid 
Epon 1001, Epon 1002, Epon 1004, Epon 1007 and Epon 1009; and the liquid, 
Epon 826, Epon 828 and Epon 830, manufactured by Shell Chemical Corp. 
Also, the following epoxy resins may be used: the solid ERL-2002, 2003 and 
3001 and the liquid ERL 2772, 2774 and 3794 manufactured by Bakelite Co. 
of the Union Carbide Plastics Division. Any epoxy resin that is comparable 
to the above listed epoxy resins may be used regardless of the 
manufacturer. 
The addition of a curing agent to the epoxy resin causes the liquid resin 
to cure or harden into a rigid cross-linked polymer. When the resin is 
intimately mixed with a stoichiometric amount of a curing agent containing 
labile hydrogen atoms, the epoxy ring opens and reacts with the curative. 
Most cured epoxy foams are produced using one of three types of curing 
agents, which are amines, polyphenols, and anhydrides. Cure is achieved by 
polyaddition with no by-product formation, and the cure reaction between 
epoxy resins and curatives is exothermic which, in some cases, can evolve 
a considerable amount of heat. Control of evolved heat can be an important 
consideration in an epoxy foam. Because a foamed epoxy is an insulating 
material, (i.e., having low thermal conductivity), heat unable to escape 
from the center of a sufficiently large sample may actually char or burn 
the interior of the foam. 
Aside from a resin and curing agent, other constituents used to make an 
epoxy foam generally include a blowing agent, a surfactant, and a filler 
or nucleating agent (hereafter referred to as a filler). Because epoxies 
normally react with the curing agent without evolving volatiles, the 
addition of a blowing agent is required. The blowing agent may be a 
chemical agent, that thermally decomposes and evolves gas due to the heat 
of the exothermic epoxy reaction, or a physical agent, which simply 
vaporizes at its boiling temperature to liberate gas. Chemical agents 
include ammonium carbonate, sodium bicarbonate, and sulfonyl hydrazide. 
Physical agents include liquid solvents such as toluene, fluorocarbons 
(FCs), chlorofluorocarbons (CFCs), and hydrochlorofluorocarbons (HCFCs). 
Surfactants are used in epoxy foams to promote foaming and stabilization of 
the subsequent cellular structure. A surfactant generally serves to 
decrease the surface tension of the pre-cure composition and thereby 
promote increased expansion, smaller cells, and more uniform cell size and 
texture of the expanded formed product. The surfactants used in 
polyurethane foam systems, such as silicone-based surfactants, are the 
same ones generally used in epoxy foams. The cell structure can be greatly 
affected by the surfactant, which in turn influences the properties of the 
resultant foam. 
Fillers are added to epoxy foam formulations for reasons including lowering 
cost, adding color, reducing exotherms, and controlling shrinkage rates. 
Fillers in the form of fine particles (for example, carbon black or fumed 
silica) may also serve as nucleating agents. Small particles provide sites 
for heterogeneous nucleation which allow for initiation and subsequent 
growth of foam cells. In heterogeneous nucleation, gas molecules driven by 
supersaturation preferentially form nucleation sites on the solid/fluid 
interfaces of the nucleating agent. The ultimate cell size is determined 
by other factors including the exotherm, the rate of cure, the amount of 
blowing agent, and interactions between the epoxy and surfactant. 
There are several important parameters that must be considered in the 
development of a foam with a desirable cellular structure. First, the 
rheology of the epoxy mixture during the rise of the foam is vitally 
important. As the epoxy and curing agent cross-link and cure, the liquid 
becomes more viscous. The viscosity increase is necessary to retain the 
cell structure created during the rise of the foam. An epoxy that does not 
become sufficiently viscous to maintain a cellular structure during the 
rise of the foam will coalesce and collapse. An epoxy that becomes 
extremely viscous and gels too early may prematurely terminate the foam 
rise, not allowing for full expansion. 
Another important processing parameter closely related to foam rheology is 
the epoxy cure rate, which is dependent on the processing temperature, as 
well as the chosen resins or curing agents. A very fast reacting 
epoxy-curative system with a large exotherm may result in a cure rate, 
which does not allow sufficient processing time for the foam to rise. 
Furthermore, an excessive amount of heat from a large exotherm could 
result in burn out of the interior regions of the foam. Conversely, an 
extremely slow reacting epoxy may not become viscous and gel within an 
appropriate amount of time to establish a cellular structure during the 
foam rise, requiring addition of external heat or a reaction accelerator 
to increase the cure rate. Other processing parameters which affect epoxy 
foam quality and cell structure are surface tension and cell nucleation. 
Surfactant is added at an appropriate level to control the surface tension 
of the fluid. As already noted, the surfactant can have a significant 
influence on cell size and foam morphology. The addition of fine 
particulates such as carbon black or fumed silica can be added to 
facilitate the nucleation of a great number of small foam pores. 
Therefore, epoxy foam encapsulants of different cellular structure and 
therefore different mechanical, thermal and electrical properties, can be 
formed by tailoring the choice of resins, curing agents and processing 
conditions. 
According to the present invention, the epoxy foam comprises a plurality of 
resins, a plurality of curing agents, a surfactant, a blowing agent, and a 
filler. More particularly, the invention comprises two resins of different 
reactivities, two curing agents that cure at different rates that function 
to provide a desired foam structure, a surfactant that functions to lower 
the surface tension of the epoxy mixture and stabilize the foam structure 
established by the blowing agent, and a filler. Dual resins and dual 
curing agents of varying reactivities permit the adjustment of the resin 
ratio, curing agent ratio, or both, to achieve a desired foam pore size, 
density, or volume. A more reactive formulation utilizing a greater 
relative amount of the highly reactive resin and/or curing agent could be 
used in applications where smaller foam cells are desired and foam volume 
is small. Such a formulation creates a faster curing epoxy system that 
results in early termination of foam cell growth and expansion. A less 
reactive formulation employing a lesser relative amount of the highly 
reactive resin and/or curing agent may be used in applications where 
larger foam cells are permissible or desired and where foam volume is 
large. A less reactive formulation creates a slower curing epoxy system 
that results in late termination of foam cell growth and expansion. 
Control of pore size and density, combined with control of the particular 
constituents chosen for the epoxy foam formulation also allow control of 
mechanical, thermal, and electrical properties of the resulting epoxy 
foam. 
More particularly, preferred in the present invention are the resins EPON 
830 (manufactured by Shell Corporation), a diglycidyl ether of bisphenol A 
resin, which is a high viscosity resin with relatively low reactivity 
which raises the initial viscosity of the epoxy foam mixture and EPON 8121 
(manufactured by Shell Corporation), a bisphenol resin with acrylated 
phenols, that is highly reactive compared with other commercially 
available resins and which cures rapidly with epoxy curing agents. Also 
preferred are the curing agents ANCAMINE 2049 (manufactured by Air 
Products & Chemical Corporation), a compound consisting essentially of 
3-3'-dimethylmethylenedi(cyclohexylamine) and EPI-CURE 3270 (manufactured 
by Shell Corporation), a compound consisting essentially of n-aminoethyl 
piperazine, diethylene triamine, and nonyl phenol. ANCAMINE 2049 is a 
cycloaliphatic amine curing agent which has a long cure time, relative to 
other commercially available curing agents, with epoxy resins and serves 
to increase the glass transition temperature of the cured epoxy, thereby 
increasing mechanical stability at higher temperatures. EPI-CURE 3270 is 
an aliphatic amine curing agent which is more reactive and cures faster 
that the ANCAMINE 2049. The preferred blowing agent is FC-72 Electronic 
Fluid (manufactured by 3M Corporation), a perfluorinated solvent 
(primarily compounds with 6 carbons), and having a boiling point 
(56.degree..degree.C.) which allows the solvent to boil at a point in the 
epoxy cure to form bubbles (pores in the material) thereby forming a foam. 
The preferred surfactant is DC-193 Surfactant (manufactured by Air Product 
& Chemical Corporation), an ethylene oxide-propylene oxide siloxane block 
polymer. This surfactant lowers the surface tension of the epoxy mixture 
sufficiently to allow foam structure to form and stabilize. Common fillers 
or nucleating agents include a carbon black filler, such as Cabot Monarch 
280 carbon black (manufactured by Cabot Corporation), fumed silica or 
titanium dioxide. This filler serves as a nucleating agent to promote 
uniform cell structure throughout the epoxy foam sample. 
An important part of the present invention is that reactivity and exotherm 
of the epoxy foam can be controlled by using appropriate proportions of 
these resins, curing agents, surfactant, blowing agent, and filler. Larger 
volume foams tend to have higher exotherms (i.e., evolved heat) which 
accelerate the cure of the epoxy. Exhibiting control of the epoxy 
reactivity and exotherm would be necessary to foam large volumes. As shown 
in the Examples, by varying the proportion of these constituents, 
reactivity can be tailored to achieve the desired foam volume and geometry 
and thermal, mechanical and electrical properties. 
In the process of the present invention, a plurality of resins is 
physically mixed with a surfactant and filler or nucleating agent, 
generally at approximately room temperature. A blowing agent is added to 
the resulting mixture and physically mixed. Preferably the blowing agent 
is added incrementally because it is a volatile solvent which tends to 
evaporate until it is mixed into the epoxy resin. A plurality of curing 
agents is physically mixed with the mixture of resins, surfactant, filler, 
and blowing agent. The resulting mixture is heated, at a temperature 
greater than the boiling temperature of the blowing agent and cured for a 
period of time generally greater than one hour and up to several days to 
provide the resulting epoxy foam. 
In one embodiment, an epoxy foam encapsulant was desired with properties 
similar to a product, called Ablefoam.RTM., now discontinued by Ablestick 
Corporation. An epoxy foam encapsulant was desired that had similar 
mechanical, thermal and electrical properties but that did not use toxic 
components, particularly methylene dianiline, and could also be tailored 
to have either a nominal density of approximately 10 lb/ft.sup.3 or 20 
lb/ft.sup.3. 
Example 1 describes the composition and process of making of the epoxy foam 
encapsulant with a nominal density of approximately 20 lb/ft.sup.3. 
Example 2 describes the composition and process of making of the epoxy 
foam encapsulant with a nominal density of approximately 10 lb/ft.sup.3. 
The constituents used to make the epoxy foams of Example 1 and Example 2 
differ primarily in the surfactant and blowing agent. The epoxy foam of 
Example 2 has a significantly higher proportion of surfactant and blowing 
agent than Example 1, thus providing a lower viscosity during epoxy foam 
formation. The epoxy foam of Example 2 is thus tailored to have a lower 
density (approximately 11 lb/ft.sup.3 compared with 22 lb/ft.sup.3) and 
higher nominal cell size than the foam of Example 1 (approximately 400 mm 
compared with 200 mm in Example 1). 
Russick and Rand (Sandia National Laboratories Technical Report 
SAND98-2538, Albuquerque, N. Mex., December, 1998) describe the results of 
tests to compare the mechanical, thermal and electrical properties of the 
epoxy foam encapsulants of the present invention with the corresponding 
properties of the product for which a replacement was desired. The tests 
demonstrated that the mechanical properties, specifically the compressive 
strength and modulus and tensile strength and modulus, were slightly 
better for the epoxy foam encapsulant of Examples 1 and 2 compared with 
the discontinued Ablefoam.RTM. product. The glass transition temperature 
and coefficient of thermal expansion for both materials were approximately 
the same. Also, the dielectric constant and dissipation factors for the 
materials of Examples 1 and 2 were similar to the discontinued 
Ablefoam.RTM. product. This embodiment demonstrated the capability to 
tailor specific properties in an epoxy foam encapsulant using multiple 
resins and curing agents. An important advantage was the capability to 
choose resins and curing agents that did not contain carcinogenic 
compounds. 
Comparative Example 1 and Example 3 demonstrate the utility of having 
multiple epoxy resins and curing agents to be able to develop a suitable 
epoxy foam encapsulant with desired properties. In Comparative Example 1, 
a small-volume epoxy foam patch was needed to repair an epoxy foam 
encapsulant on an existing electronics-based system. A formulation was 
prepared using two epoxy resins but only one curing agent that achieved 
properties compatible with the existing but now discontinued epoxy foam. 
However, this formulation proved inadequate when used in large volumes. 
Experimentation demonstrated that an epoxy foam encapsulant could be 
foamed suitable for use in large volume applications with the desired 
properties by using multiple resins as well as multiple curing agents. 
Example 3 provides the composition and process of making of such an epoxy 
foam encapsulant.

Examples of practice of the present invention are as follows. 
EXAMPLE 1 
The following ingredients were used at the specified quantities to make an 
epoxy foam sample: 
Epon 830 epoxy resin (Shell Corporation): 20.11 g 
Epon 8121 epoxy resin (Shell Corporation): 13.36 g 
Ancamine 2049 curing agent (Air Products & Chemical Corporation): 8.63 g 
Epi-cure 3270 curing agent (Shell Corporation): 8.77 g 
DC-193 surfactant (Air Products & Chemical Corporation): 1.02 g 
FC-72 blowing agent (3M Corporation): 2.09 g 
Cabot Monarch 280 carbon black (Cabot Corporation) 0.68 g 
The procedure for preparation of the epoxy foam sample was as follows: The 
Epon 830 resin was weighed out in a mixing container at room temperature. 
The Epon 8121 resin was weighed out in the mixing container at room 
temperature. The DC-193 surfactant was weighed out in the mixing container 
at room temperature. The Monarch 280 carbon black was weighed out in the 
mixing container at room temperature. The contents of mixing container 
were mixed thoroughly with a spatula for about 2 minutes. The FC-72 
blowing agent was added to contents of the mixing container and stirred 
together. The FC-72 was added incrementally until the desired weight was 
achieved (FC-72 is added incrementally since it is a volatile solvent that 
tends to evaporate until it is mixed into the epoxy resin mixture). The 
Ancamine 2049 curing agent was weighed out in the mixing container at room 
temperature. The Epi-cure 3270 curing agent was weighed out in mixing 
container at room temperature. The contents in the mixing container were 
mixed thoroughly with a spatula for about 2 minutes. After mixing, 36.3 g 
of the epoxy formulation were weighed out in a 4" I.D..times.1/2" thick 
aluminum mold preheated at 65.degree..degree.C. The mold was sealed and 
returned to a 65.degree..degree.C. forced convection oven to cure for 4 
hours. 
The resulting epoxy foam sample had a density of 0.347 g/cc (22 
lb/ft.sup.3) and had a nominal cell size of about 200 mm. 
EXAMPLE 2 
The following ingredients were used at the specified quantities to make an 
epoxy foam sample: 
Epon 830 epoxy resin: 10.03 g 
Epon 8121 epoxy resin: 6.67 g 
Ancamine 2049 curing agent: 4.33 g 
Epi-cure 3270 curing agent: 4.50 g 
DC-193 surfactant: 0.84 g 
FC-72 blowing agent: 2.50 g 
Cabot Monarch 280 carbon black: 0.33 g 
The Epon 830 resin, Epon 8121 resin, DC-193 surfactant, and Monarch 280 
carbon black were weighed out in a mixing container at room temperature. 
The contents of mixing container were mixed thoroughly with a spatula for 
about 2 minutes. The FC-72 blowing agent was added to contents of mixing 
container, and stirred together. The FC-72 was added incrementally until 
the desired weight was achieved (FC-72 is added incrementally since it is 
a volatile solvent that tends to evaporate until it is mixed into the 
epoxy resin mixture). The Ancamine 2049 curing agent was weighed out in 
the mixing container at room temperature. The Epi-cure 3270 curing agent 
was weighed out in mixing container at room temperature. All the contents 
in the mixing container were mixed thoroughly with a spatula for about 2 
minutes. After mixing, 18.2 g of the epoxy formulation was weighed out in 
a 4" I.D..times.1/2" thick aluminum mold preheated at 65.degree..degree.C. 
The mold was sealed and returned to a 65.degree..degree.C. forced 
convection oven to cure for 4 hours. 
The resulting epoxy foam sample had a density of 0.174 g/cc (10.9 
lb/ft.sup.3) and had a nominal cell size of about 400 mm. 
COMATIVE EXAMPLE 1 
The following ingredients were used at the specified quantities to make an 
epoxy foam patch to be compatible with an existing epoxy foam formulation, 
called Ablefoam.RTM., now discontinued by Ablestick Corporation. The epoxy 
foam patch is not made according to the present invention as only one 
curing agent is used in this formulation. 
Epon 828 epoxy resin: 85% of resin 
Epon 8121 epoxy resin: 15% of resin 
Epi-cure 3270 curing agent: 21.4 phr 
DC-193 surfactant: 1.0 phr 
HCFC-141b blowing agent: 5.0 phr (manufactured by Allied Signal Corp.) 
Cabosil M-7D: 2.0 phr (manufactured by Cabot Corp.) 
The stepwise procedure for preparation of the epoxy foam sample was as 
follows: 
The Epon 828 resin, the Epon 8121 resin, the DC-193 surfactant, and the 
Cabosil M-7D were weighed out in the mixing container at room temperature. 
The contents of mixing container were mixed thoroughly with a spatula for 
about 2 minutes. The HCFC-141b blowing agent was added to contents of 
mixing container, and stirred together. The blowing agent was added 
incrementally until the desired weight was achieved. The Epi-cure 3270 
curing agent was weighed out in mixing container at room temperature. All 
the contents in the mixing container were mixed thoroughly with a spatula 
for about 2 minutes. After mixing the epoxy formulation was used as a 
patch in an electronic system that had previously been encapsulated with 
the Ablefoam.RTM. foam and for which a patch was required. The system was 
sealed and returned to a 70.degree..degree.C. forced convection oven to 
cure. 
The resulting epoxy foam patch had properties consistent with the 
Ablefoam.RTM. foam. 
EXAMPLE 3 
While the epoxy foam formulation of Comparative Example 1 was sufficient 
for small-volume patching, the formulation was not suited for more general 
large volume applications because that formulation had a very short pot 
life (i.e., processing time prior to cure). Further experimentation 
revealed that epoxy foam formulations having multiple epoxy resins and 
multiple curing agents could be tailored to have the desired thermal, 
mechanical, and electrical properties by varying the proportion of the 
varying constituents. 
The following ingredients were used at the specified quantities to make an 
epoxy foam sample of cylindrical geometry with a diameter of 3 inches and 
a length of 8 inches. The standard curative ratio was modified to cause 
the formulation to be less reactive and allow for sufficient cure time 
such that the foam could rise sufficiently to fill the larger volume mold: 
Epon 830 epoxy resin: 132.9 g (60% of resin) 
Epon 8121 epoxy resin: 88.7 g (40% of resin) 
Ancamine 2049 curing agent: 65.2 g (29.5 phr) 
Epi-cure 3270 curing agent: 38.7 g (17.5 phr) 
DC-193 surfactant: 6.8 g (3.0 phr) 
FC-72 blowing agent: 13.3 g (6.0 phr) 
Cabot Monarch 280 carbon black: 4.4 g (2.0 phr) 
The stepwise procedure for preparation of the epoxy foam sample was as 
follows: 
The Epon 830 resin, the Epon 8121 resin, the DC-193 surfactant, and the 
Monarch 280 carbon black were weighed out in the mixing container at room 
temperature. The contents of mixing container were mixed thoroughly with a 
spatula for about 2 minutes. The FC-72 blowing agent was added to contents 
of mixing container, and stirred together. The FC-72 was added 
incrementally until the desired weight was achieved (FC-72 is added 
incrementally since it is a volatile solvent that tends to evaporate until 
it is mixed into the epoxy resin mixture). The Ancamine 2049 curing agent 
was weighed out in the mixing container at room temperature. The Epi-cure 
3270 curing agent was weighed out in mixing container at room temperature. 
All the contents in the mixing container were mixed thoroughly with a 
spatula for about 2 minutes. After mixing, 300 g of the epoxy formulation 
was weighed out in a 3" I.D..times.8" long cylindrical aluminum mold 
preheated at 65.degree. C. The mold was sealed and returned to a 
65.degree. C. forced convection oven to cure for 4 hours. 
The resulting epoxy foam sample had a density of 20 lb/ft.sup.3 and had a 
nominal cell size of about 250 mm. 
EXAMPLE 4 
20 lb/ft.sup.3 Density Epoxy Foam Kit 
A premixed epoxy foam kit has been developed for an epoxy foam formulation 
for a foam density of approximately 20 lb/ft.sup.3. The kit consists of 
three components which are blended together to form the epoxy foam 
mixture. The epoxy foam kit makes weighing and mixing the materials more 
convenient for the operator because only three components are involved 
rather than the seven individual starting materials. The kit consists of 
Component A, which includes two epoxy resins, a surfactant, and a 
nucleating agent, Component B, which includes a blowing agent, and 
Component C which includes the two curing agents. 
The following is the composition of Components A, B, and C that make up the 
20 lb/ft.sup.3 density epoxy foam kits: 
Component A: 
Epon 830 epoxy resin: 57.1 wt % 
Epon 8121 resin: 38.1 wt % 
DC-193 surfactant: 2.9 wt % 
Monarch 280 carbon black: 1.9 wt % 
Component B: 
FC-72 blowing agent: 100 wt % 
Component C: 
Ancamine 2049 curing agent: 62.8 wt % 
Epi-cure 3270 curing agent: 37.2 wt % 
The following are the final amounts of Components A, B, and C to make an 
epoxy foam mixture for 20 lb/ft.sup.3 foam density: 
Component A: 66.5 wt % 
Component B: 3.8 wt % 
Component C: 29.7 wt % 
To prepare the epoxy foam, Component A is weighed out in a mixing container 
at room temperature. Component B is added to contents of mixing container 
and stirred. Component B is added incrementally until the desired weight 
is achieved (FC-72 is added incrementally since it is a volatile solvent 
that tends to evaporate until it is mixed into the epoxy resin mixture). 
Component C is weighed out in the mixing container at room temperature. 
All the contents in the mixing container are mixed thoroughly with a 
spatula for about 2 minutes. After mixing, the epoxy formulation is 
weighed out in a mold preheated at 65.degree..degree.C. The mold is sealed 
and returned to a 65.degree..degree.C. forced convection oven to cure for 
4 hours. 
EXAMPLE 5 
10 lb/ft.sup.3 Density Epoxy Foam Kit 
A premixed epoxy foam kit has been developed for an epoxy foam formulation 
for a foam density of approximately 10 lb/ft.sup.3. The kit consists of 
three components which are blended together to form the epoxy foam 
mixture. The epoxy foam kit makes weighing and mixing the materials more 
convenient for the operator because only three components are involved 
rather than the seven individual starting materials. The kit consists of 
Component A, which includes two epoxy resins, a surfactant, and a 
nucleating agent, Component B, which includes a blowing agent, and 
Component C which includes the two curing agents. 
The following is the composition of Components A, B, and C for the 10 
lb/ft.sup.3 density epoxy foam kits: 
Component A: 
Epon 830 epoxy resin: 56.1 wt % 
Epon 8121 resin: 37.4 wt % 
DC-193 surfactant: 4.7 wt % 
Monarch 280 carbon black: 1.9 wt % 
Component B: 
FC-72 blowing agent: 100 wt % 
Component C: 
Ancamine 2049 curing agent: 62.8 wt % 
Epi-cure 3270 curing agent: 37.2 wt % 
The following are the final amounts of Components A, B, and C that are 
required for making the epoxy foam mixture for 10 lb/ft.sup.3 foam 
density: 
Component A: 63.3 wt % 
Component B: 8.9 wt % 
Component C: 27.8 wt % 
The processing procedure is similar to that described in Example 4 to 
prepare the 20 lb/ ft.sup.3 epoxy foam formulation. 
The invention has been described in detail above and in the specific 
examples. Further variations will be apparent to those skilled in the art. 
The true scope of the invention is to be found in the appended claims.