Heat fusible-expandable mastic for automobile floor pans

The invention relates to a relatively inexpensive, non-blocking, low density sound deadening mastic material. Essentially, the composition of the improved sound deadening mastic material of this invention includes a mineral filler, an elastomer, a polymeric modifier and a foaming (or blowing) agent. The mastic material is particularly useful in sheet form for automotive applications.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to asphaltic based mastic materials particularly 
useful in vibration damping applications. 
2. Description of the Prior Art 
Important reductions in automobile noise level have been achieved by 
vibration damping of automobile floor panels, door panels, and roof panel 
sections. Compositions containing fillers dispersed in binders have been 
widely used to coat such metal surfaces to provide the desired sound 
deadening. For example, sheet materaials of heat softenable compositions 
including asphalt, fillers and natural and/or synthetic elastomers have 
been used in this application. Heat softenable sheet materials of this 
type are described in detail in U.S. Pat. No. 4,133,932, Australian Pat. 
No. 498,074 and Canadian Pat. No. 997,085. 
Sheet materials as described above are presently used in the automotive 
industry for sound deadening of metal floor panel sections. Essentially, 
the sheet material is placed on the floor panel section before the 
automobile body goes through the heating ovens for drying the paint 
finish. In response to the temperatures of the oven, the sheet material 
softens (or wilts) into conformity with the contour of the floor panel 
section and adheres to the metal surface. 
The automotive industry has established tests for acceptable sound 
deadening sheet materials. These tests require that the sheet materials 
soften into conformity with the contours of the panel section surface at 
the paint oven temperatures and provide a strong bond to the metal 
surface. At the same time, the softening of the sheet material must be 
controlled or restrained so that flowing or running of the thermoplastic 
material not exceed an established value at the oven temperatures or at 
higher temperatures. Particularly desired sound deadening sheet materials 
for floor panel sections are those having the capability of bonding 
directly to the metal surface without the need of applying adhesive layers 
to the metal and/or the sheet material surfaces. 
Another desirable performance characteristic of sound deadening sheet 
materials is that they be non-blocking or not stick together when stored 
in layers. The non-blocking feature permits the sheet materials to be 
stacked together during storage and transportation without the use of a 
release sheet between adjacent sheets. Sound deadening sheet materials 
requiring release sheets impose obvious disadvantages for an assembly line 
operation in terms of time, labor and costs. 
More recently, the automotive industry has been especially concerned with 
weight reduction in order to improve fuel efficiency. To this end, 
expandable or foamed, non-asphaltic, sound deadening sheet materials of 
reduced density have been considered. However, proposed foamed sound 
deadening sheet materials are relatively expensive and sound deadening 
sheet materials have been traditionally assigned a low cost status in the 
automotive industry. The increased expense is due primarily to the high 
concentration of polymer in the sheet material required to provide a 
foamed sheet material of acceptable functional integrity. An acceptable 
foamed sound deadening sheet material must provide a cellular structure 
which is sufficiently strong and resilient to sustain continuously applied 
pressures without breaking or permanently collapsing. 
A proposed bitumen containing foamable sound deadening material is 
described in German Ausligeschrift No. 2,824,681. The material is 
described as a non-self supporting mass foamable to the porous foamed 
structure comprising bitumen. Apparently the described material is 
designed to flow or run at elevated temperatures since the material is 
applied in the form of a foil 23 mm thick, reduced to a thickness of 11.5 
mm presumably by flowing and then expanded or foamed to provide a porous 
structure. Additionally, the Example describes the foamable mass as 
containing about 25 percent by weight bitumen mixed with about 75 percent 
by weight mineral filler and a heat activatable adhesive is used to bond 
the mass to the metal. 
The present invention is directed to the problem of providing a relatively 
inexpensive sound deadening sheet material which meets the desired flow 
characteristics at elevated temperatures, has the desirable surface 
adherent capability but is nonblocking and most importantly, can be 
expanded to provide a cellular structure of desirable and acceptable 
strength and integrity. 
SUMMARY OF THE INVENTION 
The present invention provides a relatively inexpensive, nonblocking, low 
density sound deadening sheet material. Essentially, the composition of 
the improved sound deadening sheet material of this invention includes a 
mineral filler, an elastomer, a polymeric modifier and a foaming (or 
blowing) agent. 
The sheet materials of this invention are highly filled, expandable mastic 
materials which meet the requirements of the automotive industry in terms 
of temperature dependent softening, restrained flow characteristics and 
effective adhesion. In use, the improved sheet materials may be applied 
for example, to an automobile floor panel section in the conventional 
manner. When heated in the oven, the sheet material softens into 
conformity with the contours of the metal surface with flowing or running 
characteristics of the heated material restrained within the established 
limits. At the same time, the softened sheet material is expanded or 
foamed to provide a final sound deadening sheet having a strong, 
compressible and resilient cellular structure firmly bonded to the metal 
surface.

DETAILED DESCRIPTION OF THE INVENTION 
The novel sound deadening sheet materials essentially comprise a dispersion 
of mineral or inorganic filler and elastomer in a binder system including 
asphalt and a polymeric modifier and a foaming or blowing agent. The 
composition and percent by weight of ingredients of sheet materials of 
this invention are set forth in Table I below: 
TABLE I 
______________________________________ 
Range Preferred 
______________________________________ 
Mineral Filler 25-65 35-60 
Elastomer 2-15 7-12 
Asphalt 2-20 4-16 
Polymeric Modifier(s) 
20-60 30-50 
Foaming Agent 0.5-5 0.5-3 
______________________________________ 
The sheet materials of this invention include mineral fillers and elastomer 
dispersed in a binder. Mineral fillers included in sheet materials of this 
invention may be one or more of the various finely divided inorganic 
materials such as ground limestone, preferably a dolomitic limestone, 
whiting, silica, kiln dust, barytes, calcium carbonate, clay, slate and 
mica among others. Fillers having particle sizes so that about 80% will 
pass a 200 mesh screen and none will be held on a 35 mesh screen have been 
suitably employed in the practice of the present invention. 
Rubber-like elastomers useful in the sound deadening sheet material 
composition may be natural rubber, synthetic polymer or copolymer rubbers, 
reclaim rubber or mixtures of such rubbers. Suitable synthetic rubbers 
include styrene-butadiene copolymer synthetic rubbers, butadiene-styrene 
block copolymers, butyl rubber, polyisobutylene, ethylene-propylene 
copolymers (EPM), ethylene-propylene-diene terpolymers (EPDM) and mixtures 
of these. A preferred range of Mooney values is from about 20 to about 60. 
In a preferred embodiment of the invention, the elastomer(s) include a 
combination of reclaim rubber(s) and synthetic rubber(s) with the reclaim 
rubber(s) preferably present in the greater proportion. For example a 
particularly preferred combination of elastomers involves a reclaim rubber 
in combination with ethylene propylene copolymers (EPM) and/or 
ethylene-propylene-diene copolymers (EPDM). 
As can be seen from Table I, the dispersed ingredients (filler and 
elastomer) can represent from about 30 to about 80 percent by weight of 
the sheet material composition but preferred sheet materials are those in 
which the dispersed ingredients represent from about 40 to about 70 
percent by weight. 
The asphalts include in the binder systems of the novel sheet materials are 
those which can wet the filler material for effective dispersion in the 
binder. The asphalts may be either natural asphalt or residue from the 
distillation of petroleum or mixtures of these and are commercially 
available in penetration values up to about 300 as determined by ASTM 
method D-5-73 at 77.degree. F. Softening points (Ball and Ring), as 
determined by ASTM method D-36-70 should be in the range of from about 
60.degree. F. to about 110.degree. F., preferably from about 60.degree. F. 
to about 80.degree. F. 
A variety of polymeric modifiers may be used in combination with the 
asphalts to provide sound deadening sheet materials of the invention. 
Essentially, a suitable polymeric modifier is an asphaltic compatible 
polymer(s) which provides binder systems presenting a degree of 
cohesiveness (or melt viscosity characteristics) at elevated temperatures 
having the requisite softening and restrained flow characteristics, but 
additionally having the capability for expansion to provide an internal 
cellular structure having a desirable degree of functional integrity. 
Preferred polymeric modifiers include polyolefins such as polyethylene, 
polypropylene, polybutene among others as well as copolymers of such 
polyolefins. Because cost is an important factor in sound deadening sheet 
materials, polyethylene is preferred. Preferred copolymers are asphaltic 
compatable ethylene copolymers containing from about 40% to about 98% 
preferably from about 60% to about 90% by weight ethylene with from about 
60% to about 2% preferably from about 40% to about 10% by weight of a 
mono-unsaturated polymerizable compound such as a lower alkyl, i.e. 6 
carbon atoms, acrylate, methacrylate, ethyl acrylate or ethyl acetate. 
Hydrocarbon oil or resin is preferably included as a polymeric modifier in 
relatively small percentages in the preferred binder systems to improve 
mixing of the asphalt with the mineral filler. For example, it has been 
found that the addition of gilsonite to the binder composition materially 
improves the breaking strength and tear strength of the sound deadening 
sheet material. Gilsonite is a natural hard thermoplastic hydrocarbon 
resin having a melting point of from about 130.degree. C. to about 
140.degree. C. and a penetration at 77.degree. F. (ASTM D-5-52) of less 
than one. 
The sheet materials of the present invention include a foaming (or blowing) 
agent effectively dispersed in the binder system. As those in the art 
know, foaming agents can be solid, liquid or gaseous substances which act 
as a source of gas which can produce an internal cellular structure in a 
polymeric mass. Foaming agents known to the art include physical foaming 
agents and chemical foaming or blowing agents. Chemical foaming agents are 
generally solid inorganic salts or organic materials which decompose at 
specific temperatures and generate a volume of gas sufficient to provide 
an internal cellular structure. In the practice of the present invention, 
chemical foaming agents and particularly chemical foaming agents of the 
organic type are especially preferred. 
In sound deadening sheet materials of this invention for use in automotive 
applications, the included foaming agent is one having a decomposition 
temperature coincident with the temperatures of the heating ovens. In 
present automotive assembly line operations, the temperature of these 
ovens range between about 140.degree. C. to about 200.degree. C. or higher 
and oven residence times of about 40 minutes are usually involved. 
Accordingly, automotive sound deadening sheet materials of this invention 
preferably include organic foaming agents having decomposition 
temperatures between about 140.degree. C. to about 200.degree. C. or 
higher. Such foaming agents are commercially available and include 
sulfonyl hydrazide types such as 4,4'oxy bis (benzenesulfonylhydrazide), 
azodicarbonamide types such as 1,1' azobisformamide and modified 
azodicarbonamide types. The sheet materials of this invention may be 
expanded or foamed by using foaming agents or foaming systems which can be 
activated at temperatures below 140.degree. C. or above 200.degree. C. For 
example, foaming agents such as those mentioned above may be used in 
combination with known catalysts for foaming agents such as amines (urea) 
or glycols (diethylene glycol). 
In the preferred sheet materials of this invention, the ingredients and 
respective amounts are selected to provide sheet material products having 
a minimum breaking tensile strength prior to foaming of 0.15 lb/mil 
thickness/inch width and a minimum tear strength prior to foaming of 50 
lbs/in. thickness. The breaking strength is determined according to ASTM D 
461 while the tear strength is determined according to ASTM D 624 Die "C". 
Additionally, preferred sheet materials of this invention have densities 
prior to expansion or foaming between about 70 to about 90 lbs/ft.sup.3. 
Representative particularly preferred sound deadening sheet material 
compositions are set forth in Table II below: 
TABLE II 
______________________________________ 
% by weight of sheet material 
Ingredient Range Preferred 
______________________________________ 
Inorganic Filler (Limestone) 
35-60 40-55 
Reclaim Rubber(s) (SBR) 
4-8 5-7 
Synthetic elastomers (EPM 
2-5 3-4 
and/or EPDM rubbers) 
Asphalt 4-10 5-9 
Polyethylene and/or Ethylene 
30-50 35-45 
acrylate copolymer 
Gilsonite 1-5 1.5-3.5 
Foaming Agent 0.5-3 0.75-2.00 
______________________________________ 
The above-described particularly preferred sheet materials may be 
compounded in any conventional manner as by mixing together the asphalt, 
polymers modifier(s), gilsonite, elastomer(s) and foaming agent in a high 
shear mixer (Banbury) and then adding the mineral filler to the mixture 
and mixing to uniformity at temperatures which will not cause activation 
of the blowing agent. The mixture is then formed into a sheet by calendar 
rolls or other suitable device. For use as a sound deadener for metal 
floor pans for automobiles, sheets are preferably from about 0.035 inch to 
about 0.150 inch in thickness. 
Sheet materials presented by way of this invention have the capability of 
softening into conformity with the contours of the metal sheet coupled 
with the requisite restrained flow characteristics as required in the 
tests described above. However, sheet materials of this invention also 
have the capability of being expanded internally to provide a cellular 
structure of a high degree of functional integrity. In other words the 
sheet materials of this invention are mastic-like and pliable at room 
temperature. At elevated temperatures however, they have a 
cohesiveness--or melt viscosity characteristics--which provide the 
requisite softening capability, the requisite flow resistant capability, 
the requisite adherent capability and the capability of being expanded to 
provide a strong, compressible and resilient cellular structure providing 
a high degree of functional integrity. The combination of these 
capabilities provide sound deadening sheet materials for the automotive 
industry which permit a weight reduction of about 30 percent without 
affecting the distinct combination of performance characteristics 
established by the industry for such sheet materials. 
The following Examples are given to aid in more fully understanding the 
invention and more fully appreciating the manners of making and using the 
invention. It is to be understood that the invention is not restricted to 
the particular procedures, materials or the like of the Examples. 
The sound deadener sheet for use with an automobile floor pan is merely 
laid on the upper surface of the floor pan and is required to soften into 
conformity with the contour of the floor pan during the heating used in 
finishing the automobile body, but must also not be softened to a 
condition in which it runs excessively so as to lose its uniformity or to 
run or flow beyond desired area limits. 
As shown in FIG. 1, tests for acceptance of sound deadener sheet material 
involve laying a 2.times.10" strip 10 of the sound deadener sheet across a 
metal sheet 12 contoured as shown in FIG. 1 and heating the assembly to 
320.degree. F. for one-half hour. The metal sheet 12 has a flat, 
horizontally disposed first section 14, a section 16 extending downward at 
right angles to the first section and a further horizontally disposed 
section 18. The section 18 is formed with small grooves 20. It is required 
that after the heating, the strip 10 have softened and sagged from its 
original position and flat shape shown in broken lines in FIG. 1 into 
conformity not only with the downwardly angled section 16 but also with 
the small grooves 20 so that there is not more than a 1/16" gap between 
the strip 10 and the contoured metal section 12 at any point. 
A further test to establish that the sheet does not flow or run excessively 
involves disposing a 2.times.6" strip 22 on the flat portion 14 of the 
contoured metal surface with a portion of the strip, as shown in broken 
lines in FIG. 1, extending beyond the edge that flat portion 14 by an 
amount which would bring the edge 26 against an upper score mark 28, on 
the downwardly extending portion 30 when the strip 22 has bent downwardly 
into engagement with the vertical portion 16 of the metal sheet 12. It is 
required that on heating the sample to 400.degree. F. the downwardly bent 
portion 30 of the strip 22 must not flow more than 3/8" in one hour, i.e. 
must not have flowed down to the lower score mark 32 on the vertical 
portion 16 of the metal surface. Additional requirements are that the 
sheet have a breaking tensile strength of at least 0.15 pound per mil 
thickness/inch width. 
EXAMPLE 1 
The following is a formula of a sound deadening sheet of the present 
invention for use in connection with an automobile floor panel section. 
______________________________________ 
Finely divided dolomitic limestone 
46 
Ethylene propylene rubber 
3.3 
Reclaim rubber.sup.2 5.7 
Asphalt.sup.3 5.7 
Ethylene - ethyl acrylate copolymer.sup.4 
36.0 
Gilsonite 1.8 
ZnO 0.5 
Foaming agent.sup.5 1.0 
______________________________________ 
.sup.1 An ethylene propylene copolymer sold by Enjay Chemical 
Company under the Trademark VISTALON 404. 
.sup.2 A whole tire reclaim rubber. 
.sup.3 A commercially available asphalt known as 22 L and sold by the 
Pioneer Division of Witco Chemical Company and having the 
following properties. 
Saybolt Viscosity - 900-150 sec. at 150.degree. 
ASTM D 88-56 
Ball and Ring Softening Point - 60-80.degree. F. 
ASTM D 36-70 
Specific Gravity at 60.degree. F. 0.96-0.98 
ASTM D 70-72 
Solubility in CS.sub.2 99.5 + % 
ASTM D 2042-66 
Solubility in Trichloroethylene 99.5 + % 
ASTM D 2042-66 
.sup.4 An ethylene-ethyl acrylate copolymer sold by Union Carbide 
under the designation CO-MER DPDA - 1969 Resin. 
.sup.5 A p,p'-oxybis-(benzenesulfonyl hydrazide) foaming agent sold 
by Naugatuck Chemicals under the Trademark CELOGEN .RTM. OT. 
All of the ingredients except the ethylene ethylacrylate copolymer and 
limestone were introduced to a laboratory sized internal mixer sold under 
the Trademark BANBURY (Model 00) and worked together for one minute. The 
copolymer and limestone were then added and all ingredients were worked 
together for two minutes or until the batch temperature reached 
250.degree. F. The mixture was discharged from the mixer and sheeted out 
between rolls of a calendar to a thickness of 0.060".+-.0.005". 
TEXT DATA 
All of the following test values are based on sheet materials conditioned 
in a controlled atmosphere of 23.degree. C..+-.2.degree. C. and 50%.+-.5% 
relative humidity for at least 24 hours prior to testing. 
Flexibility--Room Temperature (23.degree. C.+2.degree. C.) 
A 2".times.6" sample of the above prepared sheet material was bent 
180.degree. slowly around a 1" mandrel with either side up. 
No cracking was detected. 
Cold Temperature Flexibility -10.degree. C.+2.degree. C. 
A 2".times.6" sample of sheet material conditioned at -10.degree. 
C..+-.2.degree. C. for four hours was bent 180.degree. slowly around a 
temperature conditioned 2" mandrel with either side up. 
No cracking was detected. 
Bond Adhesion 
A 2".times.10" sample of sheet material was positioned on a flat metal test 
panel and the panel placed in an oven heated to 168.degree. 
C..+-.2.degree. C. for 30 minutes. 
Attempts to remove the foamed sheet material from the metal test panel 
resulted in cohesive failure. 
Heat Stability 
A 6".times.6" sample of sheet material was positioned on a flat metal test 
panel and the panel placed in an oven heated to 168.degree. 
C..+-.2.degree. C. for 40 minutes. 
No evidence of degredation, embrittlement or excessive blistering of the 
foamed sheet material was detected. 
Foamability 
A 6".times.6" sample of sheet material (0.060" thick) was placed on one 
corner of a 12".times.12" metal test panel and the test panel was placed 
in an oven heated to 168.degree. C..+-.2.degree. C. for 40 minutes. 
Measurements of foam height 2" inwardly from any edge of the foamed 
material was 0.120" or greater. The foamed sheet was strong, and had 
excellent performance characteristics in terms of compressibility and 
resiliency. 
A 2".times.10" sample of sheet material was placed on a metal test panel as 
shown in the Figure and the test panel was placed in an oven heated to 
168.degree. C..+-.2.degree. C. for 30 minutes. 
The foamed sheet material conformed to all contours of the test panel as 
illustrated in FIG. 1 and successfully passed the restricted flow 
requirements. 
Blocking 
The sheet material exhibited no blocking under normal handling and storage 
conditions. 
Breaking Tensile Strength--before foaming--greater than 0.15 lb/mil. 
thickness/inch width ASTM D 461. 
Tear strength--before foaming--greater than 50 lb/in. thickness. ASTM D 624 
Die "C". 
Density prior to foaming--80 lbs/ft 
EXAMPLE 2 
The following is a formula of another sound deadening sheet material of the 
present invention. 
______________________________________ 
% by weight 
______________________________________ 
Finely divided dolomitic limestone 
44.5 
Ethylene propylene rubber 
3.0 
Reclaim rubber 6.0 
Asphalt 6.0 
Polyethylene.sup.7 37.5 
Gilsonite 1.5 
ZnO 0.5 
Foaming Agent 1.0 
______________________________________ 
.sup.7 A polyethylene sold by Union Carbide under the designation DNDA 
4140. 
The ethylene propylene rubber, reclaim rubber, asphalt and foaming agent 
were the same as in Example 1. 
Sheet material of the above formula was prepared as in Example 1, 
conditioned as in Example 1 and subjected to all of the tests of Example 
1. The sheet material successfully passed all of the tests with 
substantially the same results as obtained for the sheet material of 
Example 1. 
EXAMPLE 3 
The following is a formula of still another sound deadening sheet material 
of the present invention. 
______________________________________ 
% by weight 
______________________________________ 
Finely divided dolometic limestone 
50 
Ethylene propylene rubber 
1.2 
Ethylene propylene diene rubber.sup.8 
5.3 
Asphalt 5.7 
Ethylene - ethyl acrylate copolymer 
18.7 
Polyethylene 16.7 
Gilsonite 1.5 
ZnO 0.5 
Foaming Agent.sup.9 1.0 
______________________________________ 
.sup.8 A terpolymer sold by E. I. DuPont de Nemours under the trademark 
NORDEL 2744. 
.sup.9 An azodicarbonamide foaming agent sold by Olin Chemicals Tradename 
KEMPORE 200. 
The ethylene propylene rubber, asphalt, ethylene--ethyl acrylate copolymer 
were the same as in Example 1. The polyethylene was the same as in Example 
2. 
Sheet material of the above formula was prepared as in Example 1, 
conditioned as in Example 1 and subjected to all the tests of Example 1. 
The sheet material successfully passed all of the tests with substantially 
the same results as obtained for the sheet materials of Example 1. 
EXAMPLE 4 
The following is a formula of still another vibration damping sheet 
material of this invention. 
______________________________________ 
% by weight 
______________________________________ 
Finely divided dolomitic limestone 
38 
Ethylene propylene rubber 
2.7 
Reclaim rubber 4.5 
Asphalt 4.5 
Ethylene - ethyl acrylate copolymer 
47 
Gilsonite 1.5 
ZnO 0.3 
Foaming Agent.sup.10 1.5 
______________________________________ 
.sup.10 The foaming agent includes 1.0 percent by weight of the sheet 
material composition of the p,p'-oxybis (benzenesulfonyl hydrazide) 
foaming agent of Example 1 and 0.5 percent by weight of the sheet materia 
of diethylene glycol. 
The ethylene propylene rubber, asphalt and ethylene--ethyl acrylate 
copolymer were the same as in Example 1. 
Sheet material of the above formula was prepared as in Example 1, 
conditioned as in Example 1 and subjected to all the tests of Example 1 
with the exception of the described foamability test. The sheet material 
successfully passed all of the tests with substantially the same results 
as obtained for the sheet materials of Example 1. 
The sheet material of this Example was subjected to the following 
foamability test: 
Foamability 
A 6".times.6" sample of sheet material (0.060" thick) was placed on one 
corner of a metal test panel and the test panel was placed in an oven 
heated at 135.degree. C. for 8 minutes. 
Measurements of foam height 2" in from any edge of the foamed material was 
0.120" or greater. The foamed sheet was strong and had excellent 
performance characteristics in terms of compressibility and resiliency. 
As can be seen from the above, the expansion or foaming was conducted at 
lower temperatures and shorter times than in the previous Examples. This 
sheet material was particularly useful as a sound deadening sheet material 
for an automotive roof section. 
Substantially the same results were obtained for a sheet material having 
substantially the same composition as the above formula, but using 0.5 
percent by weight of the sheet material composition of urea rather than 
diethylene glycol in combination with the foaming agent. 
Especially improved sound deadening performance characteristics can be 
obtained by using a foamable sheet material of this invention in 
combination with commercially available, non-foamable sound deadening 
sheet materials. FIG. 2 illustrates such a combination where a foamable 
sheet material 34 of this invention is bonded to metal substrate 36 and 
non-foamable sheet material 38 is bonded to sheet material 34. 
Non-foamable sheet material 38 is preferably a sheet material of the type 
described in U.S. Pat. No. 4,133,932 mentioned before. Preferably, sheet 
materials 34 and 38 are bonded together and in use, the bonded product is 
placed on an automotive metal panel section with sheet material 34 
communicating with the metal surface. 
In the description so far, the use of the sound deadening sheet in 
combination with automotive floor panel sections has been emphasized. 
However, it should be understood that the sheet materials can also be used 
in combination with other automotive panel sections such as door, roof, 
hood or other body sections to isolate adjacent panel sections to prevent 
flutter of unsupported sections. When used in combination with such 
sections they may be bonded to the section surface such as by pressure 
sensitive adhesives to hold the sheet materials in place until foamed in 
the ovens. 
In addition to automotive applications it is important to understand that 
the sheet materials provide relatively inexpensive foams having a high 
degree of functional integrity. Accordingly, the sheet materials can be 
used in various other applications where the softening and flow 
characteristics of the sheet material are not of such importance as in 
automotive applications. These other applications can include sound 
deadening as well as non-sound deadening applications. When used in such 
other applications, the sheet materials provide laminates in which the 
foamed sheet material is bonded to the surface of one or more substrates. 
The use of the sheet materials in such other applications is shown in 
FIGS. 3 and 4. 
The laminate shown generally as 40 in FIG. 3 includes a foamed sheet 
material of the invention 42 bonded to the surface of a substrate 44 by 
way of adhesive layer 46. It should be understood that substrate 44 may be 
applied to sheet material 42 before or after foaming and an adhesive layer 
46 is not always necessary. Effective bonding can oftentimes be directly 
achieved between sheet material 42 and substrate 44 particularly for 
example if substrate 44 is a metal. or if substrate 44 is a heat fusible 
material. Substrate 44 can be of a wide variety of materials such as 
metals, for example, a sheet of aluminum foil or plastic materials, for 
example, such as a vinyl or polyester sheet material. Other suitable 
substrate materials include wood, paper, fabric and glass or other vitrous 
materials among others. Substrate 44 is shown as a single sheet material, 
but may carry one or more substrates or carry other materials such as 
fibers. For example, substrate 44 may be the base of a rug and laminate 40 
including foamed sheet material 42 carrying the rug can be bonded to an 
automotive floor surface. 
The laminate shown generally as 50 in FIG. 4 includes a foamed sheet 
material 52 of the invention positioned between and bonded to the surfaces 
of substrates 54 and 56. Sheet material 52 may be bonded directly to one 
or both substrates as shown in the bond between sheet material 52 and 
substrate 54. Alternatively, sheet material 52 may be bonded to one or 
both substrates by way of an adhesive layer 58 as shown in the bond 
between sheet material 52 and substrate 56. Substrates 54 and 56 can be 
any of the materials mentioned above in the description of FIG. 2 or 
others. Substrates 54 and 56 can be the same or different materials 
depending upon the designed application for laminate 50. For example, 
substrate 54 may be a sheet of aluminum foil while substrate 56 may be a 
plastic sheet material impermeable to moisture. The resultant laminate 50 
provides a foamed sheet material positioned between and bonded to an 
aluminum foil sheet material on one surface and a plastic sheet material 
providing a moisture impermeable barrier layer on the other surfaces. 
Various modifications may be made to the above description relating to 
embodiments of the invention without departing from the spirit and scope 
of the invention defined in the claims. For example, in the description so 
far, the sheet material is thermoplastic in nature both before and after 
foaming. In other words, the sheet material can be resoftened and can 
flow--even excessively--if subjected to sufficiently high temperatures for 
sufficient times. Normally however, particularly in automotive sound 
deadening applications, the sheet material is never again subjected to the 
temperatures encountered in paint drying ovens. For applications in which 
higher temperatures for extended times may be encountered either at or 
after expansion of the sheet material, the thermoplastic nature of the 
sheet materials of this invention can be adjusted. The desired degree of 
adjustment can be achieved by using agents for cross-linking or curing the 
sheet material composition. For example, peroxides may be included in the 
sheet materials in varying amounts to provide a preselected degree of cure 
for the composition. Normally, the curing agent selected will be one 
having an activation temperature at or near the activation temperature of 
the blowing agent.