Fume duct circumferential joint sealant

Sealant compositions for sealing the circumferential joint between pairs of dual-laiminate fume duct sections, and a joint sealing method enabling strong bonding between the sealant and phenolic/glass and vinyl ester surfaces without sanding mating surfaces. A first preferred sealant consists of a resin including by weight: 20.0% Epon 862 novolac epoxy resin; 30.0% SU-2.5 Epon novolac epoxy resin; 20.0% Heloxy 48; 19.5% Epon 826 bisphenol A resin; 10.0% Heloxy 505; and 0.5% silane, and a hardener including: two cycloaliphatic amines, 94.0%; and an aromatic tertiary amine, 6.0%. A second preferred sealant consists of a resin including by weight: 39.5% aromatic epoxide resin; 40.0% Heloxy 48; 20.0% SU-2.5 Epon novolac epoxy resin; and 0.5% silane, and a hardener including: two cycloaliphatic amines, 94.0%; an aromatic tertiary amine, 5.5%; and an amino silane, 0.5%.

BACKGROUND OF THE INVENTION 
1. Field Of The Invention 
The present invention relates to fume ducts and more particularly to 
novolac epoxy resin and hardener compositions which enable an improved 
method for assembling fume duct sections wherein a composition is used as 
a sealant in constructing a circumferential joint bond between pairs of 
adjoining duct section ends. 
2. Description Of The Related Art 
Ductwork for corrosive vapor exhaust systems is used extensively in many 
diverse industries which utilize hazardous chemicals to process raw 
materials or perform manufacturing procedures, such as the semiconductor 
industry, the plating industry, and the pharmaceutical industry. Such 
ductwork also is required in the many research and development 
laboratories which use highly reactive, toxic or otherwise hazardous 
chemicals in conducting experiments. Use of such chemicals not only can 
put personnel in the work environment at risk to hazardous fumes, but also 
are potential sources of contamination of industrial processes or 
laboratory experiments. Consequently, vapors from such chemicals must be 
exhausted through leak-proof air ducts to 
PATENT safely remove them from work areas. Duct installations can be very 
large, consisting of many thousands of feet of ductwork which may be 
manifolded and connected to multiple exhaust fans. Because of the wide 
diversity of chemicals used in industrial and research applications, it is 
extremely difficult to provide a single material for fabricating ductwork 
which can withstand all the chemicals to which duct interiors may be 
exposed. Materials which have been used heretofore to fabricate fume 
exhaust ductwork include black steel, galvanized steel and stainless 
steel, as well as plastic materials such as polyvinylchloride, 
polypropylene, coated materials, and fiberglass reinforced plastics 
(FRP's). Over the past forty years the trend in materials has been away 
from metals and coated metals and toward the use of plastics, particularly 
FRP's. 
Various types of resins have been used in manufacturing FRP's including 
bisphenol fumarates, epoxies, chlorendic anhydrides, isopthalic or 
orthopthalic resins, and vinylester resins. Certain classes of resins are 
resistant to certain families of chemicals, but no single resin can resist 
all the chemicals used in industries such as semiconductor manufacturing. 
For example, polyesters generally have good resistance to acids and, to 
some degree, to caustics. However, they generally do not have good 
PATENT resistance to solvents, particularly halocarbons. Epoxies generally 
exhibit good resistance to caustics and solvents, but do not have good 
resistance to strong mineral acids. Various combinations of 
phenol/aldehyde resins have good resistance to most acids, but not to 
highly reactive combinations such as concentrated sulfuric acid and an 
oxidizer such as hydrogen peroxide. These resin systems also have poor 
resistance to liquid caustics. Thus, FRP resin compositions generally are 
poor choices for fume exhaust systems handling such types of materials. 
In addition to the problem of providing a duct material capable of 
resisting broad classes of chemical vapors, there is also the problem of 
providing adequate resistance to fire. Unlike metallic ducts, plastic 
ducts exhausting chemicals which can react exothermically with themselves 
or with duct surfaces pose the risk of being set on fire. A problem common 
to all plastics has been flammability. Plastics can burn rapidly and 
produce much smoke, creating hazards of their own. The plastics industry 
often refers to certain classes of materials as "fire-retardant." 
Typically such materials incorporate heat absorbent fillers, heat sinks 
such as aluminum trihydrate, and most commonly, halogenated resin systems 
that include antimony or boron compounds which interfere with combustion 
at the interface between a plastic surface and ambient air by functioning 
as a free radical trap depriving the surface fuel of oxygen. 
Resin systems and plastic fume exhaust ducts are described in U.S. Pat. 
Nos. 4,053,447; 4,076,873; and 4,107,127. In general, phenols and similar 
ring-structured molecules have excellent fire resistance characteristics 
and also generate low quantities of smoke. Fabrication costs are high for 
ducts made from phenolic resins because their curing generally requires 
heat and/or pressure. However, use of the phenol resorcinol in resin 
compositions can reduce or eliminate the necessity for using heat and 
pressure; some formulations can be cured at ambient (room) temperature. 
As described generally in the above-cited references, various types of 
aldehydes when used in conjunction with resorcinol or phenol/resorcinol 
(PRF) combinations enable curing of FRP resins. An excess of aldehydes to 
the hydroxyl radicals contained within the mix is necessary. 
Paraformaldehyde, furfuraldehyde or other aldehydes can be used alone or 
in combination with various types of phenol/resorcinol mixes. 
U.S. Pat. No. 5,298,299, which is incorporated in its entirety herein by 
reference, is directed to a composite fume duct having both good chemical 
resistance and good fire resistance properties. Ducts made in accordance 
with the invention described in that patent are generally tubular with a 
diametral size in the range of 2 inches to 84 inches, and have an inner 
laminate portion of chemically resistant material covered by and integral 
with an outer laminate portion of fire retardant material. The inner 
laminate is comprised of material such as fiberglass which is saturated 
with a chemically resistant resin such as a halogenated vinyl ester. The 
outer laminate which covers the inner laminate is similarly comprised of 
fabric or fiberglass material which is combined with a resorcinol or 
phenol/resorcinol type fire-retardant resin. 
The dual-laminate duct is formed by first coating a mylar wrapped mandrel 
tool with the chemically resistant resin and then wrapping the mandrel 
with successive layers of fabric material saturated with the resin. The 
outer fire-retardant laminate is then formed directly over the inner 
laminate by applying successive layers of a suitable fabric material 
saturated with the fire-retardant resin. The composite duct structure is 
then allowed to cure and harden before being removed from the mandrel. 
Ducts are fabricated as sections of standard length(s) which are 
transported to a job site and assembled there. Since a leak-proof joint is 
required between each pair of contiguous duct sections, even the smallest 
installation will have a considerable number of such joints. Therefore, 
reducing the time needed to assemble multi-section ductwork is significant 
to improving the profitability of businesses which install fume ducts. 
Because mechanical interfacing of section ends cannot by itself prevent 
leakage, a sealant must be applied circumferentially to each interface. 
Heretofore, the most time-consuming step in joining dual-laminate sections 
has been preparing the resin-impregnated surfaces to which the sealant 
must bond in order to effect a leak-proof seal. Specifically, these are 
surface areas near the ends of each duct section including: the opposed 
end portions of the inner laminate surface which is typically fiberglass 
saturated with a halogenated vinyl ester resin; the opposed end portions 
of the outer laminate surface which is typically fiberglass saturated with 
a phenol/resorcinol resin; and the exterior surfaces of a "slip" collar 
interposed internally between a pair of end sections, the collar surfaces 
typically being fiberglass saturated with a vinyl ester resin. Unless 
surfaces to be mated were first sanded, the interposing sealant layer 
would not adhere to the surfaces uniformly, resulting in porosities in the 
hardened sealant through which fumes could leak. 
Each joint must not only prevent fumes from escaping during day-to-day 
operation, but also must maintain integrity after prolonged exposure to 
corrosive or otherwise reactive chemicals. Also, a joint must not fail 
catastrophically in the event a flame propagates through the ductwork or, 
if exposed directly to heat, become a source of smoke particulates or 
other contaminants. 
Consequently, providing a sealant composition which facilitates joint 
assembly, withstands exposure to chemicals, and/or withstands exposure to 
flames is important to improving the state of the art of assembling and 
maintaining fume duct installations. 
OBJECTS OF THE INVENTION 
Accordingly, it is a primary object of the present invention to provide an 
improved method for joining fume duct sections. 
Another object of the invention is to provide an improved method for 
joining fume duct sections wherein each section has an inner laminate of 
fabric material such as fiberglass impregnated with a halogenated 
chemically resistant resin, and an outer laminate of fabric material such 
as fiberglass impregnated with a fire-retardant resin of PRF type 
comprised of phenol/resorcinol with an excess of aldehydes. 
A further object of the invention is to provide a sealant composition which 
can be applied directly to mating surfaces of duct fume joints without 
first requiring sanding of the surfaces. 
Yet another object of the invention is to provide a fume duct sealant 
composition that does not contain volatile organic solvent and is smoke 
and flame retardant. 
Other objects of the invention will become evident when the following 
description is considered with the accompanying drawings. 
SUMMARY OF THE INVENTION 
The above and other objects are met by the present invention which 
comprises sealant compositions for sealing the joint assembly between 
pairs of dual-laminate fume duct sections, and a joint assembly sealing 
method wherein high adhesive shear strength between mating joint surfaces 
is achieved without first sanding the surfaces. Each joint assembly 
includes two tubular fume duct section ends, each section including an 
inner fiberglass laminate impregnated with a halogenated resin and an 
outer fiberglass laminate impregnated with a PRF-type resin, and a 
fiberglass slip collar impregnated with a vinyl ester resin connecting the 
two section ends. A joint assembly may further include alternate layers of 
coarse and fine glass mesh saturated with sealant and wound around the 
joint seam. 
Each sealant composition includes a resin component and a hardener (curing) 
component. Resins of this invention include novolac epoxy resin and 
mixtures of novolac epoxy resins wherein the resin has an average 
molecular weight from about 300 to about 3,000, an epoxide equivalent from 
about 125 to about 300, and functionality from about 1.8 to about 6.0. 
Liquid hardener compositions which can be used to effect ambient cure of 
the novolac epoxy resins comprise primary, secondary and tertiary amines 
and mixtures thereof. Illustrative amines include 1,2-diaminocyclohexane, 
methylene-dicyclohexylamine and aromatic tertiary amine. 
Silanes may advantageously be incorporated into each component of a binary 
formulation to enhance the adhesive and bonding characteristics of the 
cured resin on a composite surface comprising resin and fiberglass. An 
illustrative silane which can be added to the resin component is 
.gamma.-glycidoxypropyltrimethoxy silane. A suitable silane which can be 
added to the curing component is .gamma.-aminopropyldimethoxy silane. 
Flame and smoke retardants may be added to the resin component of the 
formulation. Illustrative flame retardants include pentabromodiphenyl 
oxide and decabromodiphenyl oxide. 
There are no solvents in the binary formulation and no volatile organic 
compounds are evolved during the curing process. Accordingly, there is no 
outgassing when any of the resin systems described herein is used in the 
construction of a circumferential joint bond. 
A first preferred sealant consists of a resin including by weight: 20.0% 
Epon 862 novolac epoxy resin; 30.0% SU-2.5 Epon novolac epoxy resin; 20.0% 
Heloxy 48; 19.5% Epon 826 bisphenol A resin; 10.0% Heloxy 505; and 0.5% 
silane, and a hardener including: two cycloaliphatic amines, 94.0%; and an 
aromatic tertiary amine, 6.0%. 
A second preferred sealant consists of a resin including by weight: 39.5% 
aromatic epoxide resin; 40.0% Heloxy 48; 20.0% SU-2.5 Epon novolac epoxy 
resin; and 0.5% silane, and a hardener including: two cycloaliphatic 
amines, 94.0%; an aromatic tertiary amine, 5.5%; and an amino silane, 
0.5%. 
A more complete understanding of the present invention and other objects, 
aspects and advantages thereof will be gained from a consideration of the 
following description of the preferred embodiments read in conjunction 
with the accompanying drawings provided herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
I. INTRODUCTION 
While the present invention is open to various modifications and 
alternative constructions, the preferred embodiments shown in the drawings 
will be described herein in detail. It is to be understood, however, there 
is no intention to limit the invention to the particular forms disclosed. 
On the contrary, it is intended that the invention cover all 
modifications, equivalences and alternative constructions falling within 
the spirit and scope of the invention as expressed in the appended claims. 
II. DUCT JOINT PREATION AND ASSEMBLY 
FIGS. 1-4 show sequential steps in assembling a fume duct joint assembly 
10. Referring to FIG. 1, the joint assembly 10 includes end portions 12A, 
12B, respectively, of first and second dual-laminate duct sections 14A, 
14B, respectively, having a common generally tubular inner cross-sectional 
area 16, and, respectively, annular edges 18A, 18B, circumferential inner 
laminate surfaces 20A, 20B, and circumferential outer laminate surfaces 
22A, 22B. Disposed between end portions 12A and 12B is a slip collar 24 
including opposed first and second portions 26A, 26B, symmetric with 
respect to a circumferential rib 28 and having a generally tubular inner 
cross-sectional area 30 similar to but slightly smaller than the area 16 
so that collar portions 26A, 26B can be closely received within end 
portions 12A, 12B, respectively. Collar portions 26A, 26B have, 
respectively, circumferential inner surfaces 32A, 32B, circumferential 
outer surfaces 34A, 34B, and annular edges 36A, 36B. 
FIG. 2 shows the collar portion 26A closely received within the section end 
portion 12A, insertion of collar 24 within end portion 12A being limited 
by the rib 28 seating against edge 18A, thus forming a first portion 38A 
of a circumferential seam 40. Prior to inserting collar portion 26A, a 
single-layer coat of a sealant 50 is applied to surface 34A and edge 36A 
by brushing, rolling or spraying. Sealant 50 comprises a curable mixture 
of novolac epoxy resin and amine hardener and may further include a filler 
such as polyethylene fibers to provide a putty-like viscosity. 
With collar portion 26A already fitted within end portion 12A, FIG. 3 shows 
collar portion 26B closely received within section end portion 12B, the 
rib 28 seating against edge 18B to form a second portion 38B of seam 40. 
Prior to inserting collar portion 26B, a single-layer coat of the sealant 
50 is applied to surface 34B and edge 36B. Using a hot air gun (not 
shown), heat can be applied to joint assembly 10 to advance sealant 
curing. 
As shown in FIG. 4, sealant 50 is then applied into the seam 40, flowing 
between first and second interstices 52A, 52B between collar rib 28 and 
duct section edges 18A, 18B, respectively. Sufficient sealant is applied 
to form a circumferential surface 54 which is even with outer surfaces 
22A, 22B, thus sealing end portions 12A, 12B with a chemical-resistant 
barrier. 
As shown in FIGS. 5 and 6, joint assembly 10 is reinforced with a "lay-up" 
bond 60 formed by tightly winding alternate layers of fine mesh (boat 
cloth, "B") fiberglass sheeting and coarse mesh (woven roving, "W") 
fiberglass sheeting around the seam 40. Firstly, the sheeting is cut in 
individual wraps to be applied completely around the joint circumference. 
Depending on duct diameter, wraps are each 4 to 8 inches wide and are 
applied unsanded, symmetric with respect to seam 40. Secondly, the resin 
component of sealant 50 is applied using a paint roller to outer surfaces 
22A, 22B of duct end portions 12A, 12B, respectively, to "wet out" the 
surfaces. The layer of resin (not shown) should not be so thick as to 
cause excessive runs and drips. Thirdly, a first layer 62 of dry boat 
cloth is wound tightly around the joint, so that the cloth is pulled into 
seam 40. Using a paint roller the cloth outer surface then is wet out with 
the resin to smooth the joint and achieve a uniform surface. Fourthly, a 
layer 64 of dry woven roving is wound tightly around the layer 62 and then 
wet out in the same manner as layer 62. Fifthly, a second layer 66 of dry 
boat cloth is wound tightly around layer 64 and then wet out in the same 
manner as layers 62, 64. Alternate layers of boat cloth and woven roving 
are applied to complete the joint with boat cloth as the final layer. For 
example, for ducts having a diameter between 8 and 20 inches, the sequence 
of layers is B-W-B as in FIG. 5, the sheeting width is about 6 inches, and 
about 0.63 pounds per foot of duct circumferential perimeter of resin is 
used. For ducts having a diameter between 22 and 40 inches, the sequence 
of layers is B-W-B-W-B, the sheeting width is about 6 inches, and about 
0.75 pounds/foot of resin is used. For ducts having a diameter between 42 
and 60 inches, the sequence of layers is B-W-B-W-B-W-B, the sheeting width 
is about 6 inches, and about 0.88 pounds/foot of resin is used. 
Ill. PREFERRED RESIN COMPOSITIONS 
A. AL-133 Resin Composition 
Table 1 shows the composition of a first resin, AL-133, that can be used as 
the resin component in sealant 50. AL-133 is formulated by using chemicals 
provided by the manufacturers listed in Table 1. AL-133 includes by 
weight: 39.5% aromatic epoxide resin; 40.0% Heloxy 48 which is an 
aliphatic trifunctional epoxy; 20.0% SU-2.5 Epon novolac epoxy resin; and 
0.5% .gamma.-glycidoxypropyltrimethoxy silane. 
TABLE 1 
______________________________________ 
AL-133 Resin Composition 
Component Manufacturer Pctage 
______________________________________ 
Aromatic Epoxide 
CVC Specialty Chemicals, 
39.5 
Cherry Hill, NJ 
Heloxy 48 Shell Chemical Co. 
40.0 
Houston, TX 
SU-2.5 Epon Resin 
Shell Chemical Co. 
20.0 
Houston, TX 
Silane OSI Specialties, Inc. 
0.5 
Sistersville, WV 
______________________________________ 
B. AL-165 Resin Composition 
Table 2 shows the composition of a second resin, AL-165, that can be used 
as the resin component in sealant 50. AL-165 is formulated by using 
chemicals provided by the manufacturers listed in Table 2. AL-165 includes 
by weight: 48.0% Epon 862 novolac epoxy resin; 51.5% SU-2.5 Epon novolac 
epoxy resin; and 0.5% .gamma.-glycidoxypropyltrimethoxy silane. 
TABLE 2 
______________________________________ 
AL-165 Resin Composition 
Component Manufacturer Pctage 
______________________________________ 
Epon Resin 862 Shell Chemical Co. 
48.0 
Houston, TX 
SU-2.5 Epon Resin 
Shell Chemical Co. 
51.5 
Houston, TX 
Silane OSI Specialties, Inc. 
0.5 
Sistersville, WV 
______________________________________ 
C. AL-190 Resin Composition 
Table 3 shows the composition of a third resin, AL-190, that can be used as 
the resin component in sealant 50. AL-190 is formulated by using chemicals 
provided by the manufacturers listed in Table 3. AL-190 includes by 
weight: 20.0% Epon 862 novolac epoxy resin; 30.0% SU-2.5 Epon novolac 
epoxy resin; 20.0% Heloxy 48; 19.5% Epon 826 bisphenol A resin; 10.0% 
Heloxy 505 which is a multi-faceted novolac epoxy; and 0.5% 
.gamma.-glycidoxypropyltrimethoxy silane. 
TABLE 3 
______________________________________ 
AL-190 Resin Composition 
Component Manufacturer Pctage 
______________________________________ 
Epon Resin 862 Shell Chemical Co. 
20.0 
Houston, TX 
Heloxy 48 Shell Chemical Co. 
20.0 
Houston, TX 
SU-2.5 Epon Resin 
Shell Chemical Co. 
30.0 
Houston, TX 
Epon Resin 826 Shell Chemical Co. 
19.5 
Houston, TX 
Heloxy 505 Shell Chemical Co. 
10.0 
Houston, TX 
Silane OSI Specialties, Inc. 
0.5 
Sistersville, WV 
______________________________________ 
IV. PREFERRED HARDENER COMPOSITIONS 
A. Type-A Hardener Composition 
Table 4 shows the composition of a first hardener, Type-A, that can be used 
as the curative component in sealant 50. Type-A hardener is formulated by 
using chemicals provided by the manufacturers listed in Table 4. Type-A 
hardener includes by weight: a first cycloaliphatic amine, specifically 
1,2-diaminocyclohexane, 60.0%; a second cycloaliphatic amine, specifically 
methylene-dicyclohexylamine, 34.0%; and 6.0% Conac 10 which is an aromatic 
tertiary amine, specifically 2,4,6-Tris[(dimethylamino)methyl]phenol. 
TABLE 4 
______________________________________ 
Type-A Hardener Composition 
Component Manufacturer Pctage 
______________________________________ 
Cycloaliphatic - 
Air Products Co. 60.0 
Type 1 Allentown, PA 
Cycloaliphatic - 
Air Products Co. 34.0 
Type 2 Allentown, PA 
CONAC 10 Chempro Specialities, Inc. 
6.0 
Roswell, GA 
______________________________________ 
B. Type-B Hardener Composition 
Table 5 shows the composition of a second hardener, Type-B, that can be 
used as the curative component in sealant 50. Type-B hardener is 
formulated by using chemicals provided by the manufacturers listed in 
Table 5. Type-B hardener includes by weight: 60% 1,2-diaminocyclohexane; 
34.0% methylene-dicyclohexylamine; 5.5% Conac 10; and 0.5% amino silane, 
specifically .gamma.-aminopropyldimethoxy silane. 
TABLE 5 
______________________________________ 
Type-B Hardener Composition 
Component Manufacturer Pctage 
______________________________________ 
Cycloaliphatic - 
Air Products Co. 60.0 
Type 1 Allentown, PA 
Cycloaliphatic - 
Air Products Co. 34.0 
Type 2 Allentown, PA 
CONAC 10 Chempro Specialities, Inc. 
5.5 
Roswell, GA 
Amino Silane OSI Specialties, Inc. 
0.5 
Sistersville, WV 
______________________________________ 
V. SEALANT MIXING RATIOS 
Each of the six combinations of resins AL-133, AL-165, AL-190 and hardeners 
Type-A, Type-B is a preferred embodiment of the sealant 50. However, as 
detailed in Section VI infra, several embodiments are especially 
preferred. 
Mixing ratios by weight, for alternative embodiments of sealant 50 are as 
follows: 
133 parts of AL-133 resin to 51 parts of Type-A hardener; 
133 parts of AL-133 resin to 51 parts of Type-B hardener; 
100 parts of AL-165 resin to 44 parts of Type-A hardener; 
100 parts of AL-165 resin to 44 parts of Type-B hardener; 
100 parts of AL-190 resin to 37 parts of Type-A hardener; and 
100 parts of AL-190 resin to 37 parts of Type-B hardener. 
VI. ADHESIVE SHEAR STRENGTH TEST RESULTS 
A. Test Procedures 
In forming joint assembly 10, sealant 50 bonds to vinyl ester inner 
surfaces 20A, 20B of duct end portions 12A, 12B, respectively, and to 
outer surfaces 34A, 34B of vinyl ester collar portions 26A, 26B, 
respectively. Sealant 50 also bonds to outer phenolic/glass surfaces 22A, 
22B of duct end portions 12A, 12B, respectively, after being applied into 
and around seam 40. Thus, sealant 50 bonds directly to phenolic 
resin-impregnated surfaces 22A, 22B, and also bonds rib 28 of collar 24 to 
edges 18A, 18B of end portions 12A, 12B, respectively. In laid-up joint 
assemblies, the resin component of sealant 50 is used for impregnating and 
saturating layers of boat cloth and woven roving which are wound around 
seam 40, and so comprises the resin matrix for successive layers of 
fiberglass mesh that define a circumferential joint sheath. Consequently, 
in comparing how strongly a particular embodiment of the sealant will bond 
joint assembly components depending on whether bonded surfaces are or are 
not first sanded, the types of bonds which must be considered are 
phenolic-to-epoxy novolac and vinyl-to-epoxy novolac. 
Adhesive shear strength tests on double shear-type laminate specimens were 
performed by the Structural Composites Laboratory of the Civil Engineering 
Department at California State University, Long Beach. The tests were 
performed according to the method prescribed in ASTM D3165. In one series 
of tests, two sheets of phenolic resin-impregnated laminate, each 
approximately two feet square, were bonded together in a planar "sandwich" 
using one of the sealant embodiments as an adhesive, and then subjected to 
an increasing shearing force until failure occurred either in one or both 
sheets ("L"-type failure) or within the inter-sheet adhesive plane 
("A"-type failure). For each embodiment, five samples were tested after 
their adhering surfaces were sanded using a grit 40 sanding disk, and five 
samples were tested without their adhering surfaces sanded. Adhesive shear 
strength measurements for the five samples in each group were then used to 
calculate a mean and a standard deviation. In a second series of tests 
performed under the same conditions (i.e., six sealant compositions, 
sanded versus unsanded, five samples per case), two sheets of vinyl 
resin-impregnated laminate were used. 
B. Phenolic Laminates 
Table 6 compares mean adhesive shear strength (in lbs/in.sup.2 (psi)) and 
failure mode (A-type or L-type) for each embodiment bonding unsanded 
versus sanded phenolic resin-impregnated laminates. In almost all 
instances where surfaces were sanded, failure occurred in the laminate 
rather than the adhesive. For unsanded cases, the number of adhesive 
failures was higher. Regardless of the embodiment used as the adhesive, 
the mean value for an unsanded case was never greater than that for the 
corresponding sanded case. If the criterion for comparing unsanded 
vis-a-vis sanded shear strength performance is that the mean and standard 
deviation for an unsanded case be about the same as those for the 
corresponding sanded case, then the combinations (AL-165 resin; type-A 
hardener) and (AL-190 resin; type-B hardener) are especially preferred for 
applications where only phenolic-to-phenolic bonding is required. 
TABLE 6 
______________________________________ 
Phenolic Laminate Shear Test Results 
Unsanded Sanded 
Adhesive Shear 
Fail Adhesive Shear 
Fail 
R, H Strength (psi) 
Mode Strength (psi) 
Mode 
______________________________________ 
133, A 857 .+-. 147 
5L 893 .+-. 58 
5L 
165, A 836 .+-. 54 3L, 2A 837 .+-. 79 
5L 
190, A 1072 .+-. 99 
4L, 1A 1109 .+-. 162 
5L 
133, B 924 .+-. 94 4L, 1A 1138 .+-. 78 
5L 
165, B 774 .+-. 107 
5L 984 .+-. 86 
5L 
190, B 883 .+-. 39 5L 892 .+-. 41 
3A, 2L 
______________________________________ 
C. Vinyl Laminates 
Table 7 compares mean adhesive shear strength (in lbs/in.sup.2 (psi)) and 
failure mode (A-type or L-type) for each embodiment bonding unsanded 
versus sanded vinyl resin-impregnated laminates. Whether surfaces were 
sanded or unsanded, failure always occurred in the adhesive rather in the 
laminate. Regardless of the embodiment used as the adhesive, the mean 
value for an unsanded case was always less than that for the corresponding 
sanded case. Applying the same criterion for comparing unsanded vis-a-vis 
sanded shear strength performance, the combination (AL-133 resin; type-B 
hardener) is especially preferred for applications where only 
vinyl-to-vinyl bonding is required. 
TABLE 7 
______________________________________ 
Vinyl Laminate Shear Test Results 
Unsanded Sanded 
Adhesive Shear 
Fail Adhesive Shear 
Fail 
R, H Strength (psi) 
Mode Strength (psi) 
Mode 
______________________________________ 
133, A 1046 .+-. 88 
5A 1178 .+-. 168 
5A 
165, A 993 .+-. 108 
5A 1310 .+-. 117 
5A 
190, A 1190 .+-. 184 
5A 1444 .+-. 131 
5A 
133, B 1064 .+-. 128 
5A 1098 .+-. 121 
5A 
165, B 1034 .+-. 121 
5A 1120 .+-. 140 
5A 
190, B 1015 .+-. 109 
5A 1142 .+-. 123 
5A 
______________________________________ 
VII. ESPECIALLY PREFERRED EMBODIMENTS FOR DUAL-LAMINATE 
FUME DUCT JOINTS 
In the context of application as the sealant 50 for joint assembly 10 where 
both phenolic-to-phenolic and vinyl-to-vinyl bonding are required, the 
combinations (AL-190 resin; type-A hardener) and (AL-133 resin; type-B 
hardener) are especially preferred because according to the shear strength 
tests these embodiments result in the best overall performance. The ratio 
of mean adhesive shear strength for unsanded compared to sanded surfaces 
for the (AL-190 ; type-A) embodiment is 0.97 for phenolic laminates, and 
0.82 for vinyl laminates. The ratio of mean adhesive shear strength for 
unsanded compared to sanded surfaces for the (AL-133 ; type-B) embodiment 
is 0.81 for phenolic laminates, and 0.97 for vinyl laminates.