U.S. patent application number 11/057669 was filed with the patent office on 2005-08-04 for thermal protective composition and method of protecting a substrate from hyperthermal conditions.
Invention is credited to Feldman, Rubin, Rippe, James A. JR., Taylor, Edward W. JR..
Application Number | 20050171242 11/057669 |
Document ID | / |
Family ID | 22979229 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050171242 |
Kind Code |
A1 |
Taylor, Edward W. JR. ; et
al. |
August 4, 2005 |
Thermal protective composition and method of protecting a substrate
from hyperthermal conditions
Abstract
A composite system capable of protecting a substrate from a jet
fire including a lower layer of an active fire protective material
and an upper layer of a fire protective material. The upper layer
forms an open cell matrix when exposed to a jet fire to permit
passage of gasses from the lower layer to ambient. The upper layer
comprises a fill of refractory material and protects the system
during initial exposure to a hyperthermal condition. The upper
layer swells on exposure to hyperthermal conditions, but swells
less than the lower layer.
Inventors: |
Taylor, Edward W. JR.;
(Ballwin, MO) ; Feldman, Rubin; (Ladue, MO)
; Rippe, James A. JR.; (St. Louis, MO) |
Correspondence
Address: |
POLSTER, LIEDER, WOODRUFF & LUCCHESI
12412 POWERSCOURT DRIVE SUITE 200
ST. LOUIS
MO
63131-3615
US
|
Family ID: |
22979229 |
Appl. No.: |
11/057669 |
Filed: |
February 14, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11057669 |
Feb 14, 2005 |
|
|
|
10036717 |
Dec 21, 2001 |
|
|
|
6855401 |
|
|
|
|
60258138 |
Dec 22, 2000 |
|
|
|
Current U.S.
Class: |
523/179 ;
524/494; 524/495 |
Current CPC
Class: |
Y10T 442/131 20150401;
Y10T 442/2631 20150401; Y10T 428/249953 20150401; C09D 5/18
20130101; Y10T 428/24942 20150115; Y10T 442/114 20150401 |
Class at
Publication: |
523/179 ;
524/494; 524/495 |
International
Class: |
C08K 003/40; C08K
003/04 |
Claims
1. A thermally protective composition comprising a polymeric
binder, a flexibilizing agent, from 10% to 30% of a blowing agent
which changes from solid to gas at a hyperthermal temperature to
which the composition may be subjected, and at least 20% by weight
of a refractory filler.
2. The composition of claim 1 wherein the binder is an epoxy resin
modified with the flexibilizing agent, the composition comprising
about 35% to about 65% by weight of the modified epoxy resin.
3. The composition of claim 2 wherein the flexibilizing agent
comprises polysulfide, and wherein the modified epoxy resin is
cured with an amine.
4. The composition of claim 1 wherein the filler comprises both
particles and fibers.
5. The composition of claim 1 wherein the filler comprises ceramic
particles and glass fibers.
6. The composition of claim 1 wherein the filler comprises one or
more materials selected from the group consisting of glass,
graphite, and ceramic.
7. The composition of claim 1 wherein the filler comprises at least
25% by weight of the composition.
8. The composition of claim 7 wherein the filler comprises about
25% to 40%, by weight of the composition.
9. A thermally protective composition comprising a polymeric
binder, a blowing agent, and at least 7% by weight of the
composition of a refractory filler, the composition responding to
hyperthermal conditions by expanding about 10% to about 100% and
forming an open cell matrix.
10. The composition of claim 9 wherein the refractory filler
comprises both particles and fibers.
11. The composition of claim 9 wherein the filler comprises ceramic
particles and glass fibers.
12. The composition of claim 9 wherein the filler comprises one or
more materials selected from the group consisting of glass,
graphite, and ceramic.
13. The composition of claim 9 wherein the filler comprises at
least about 15% by weight of the composition.
14. The composition of claim 9 wherein the filler comprises about
25% to 30%, by weight of the composition.
15. The composition of claim 9 wherein the blowing agent comprises
10% to 30% by weight of the composition.
16. The composition of claim 9 comprising a flexibilizing
agent.
17. The composition of claim 16 wherein the composition comprises
about 35% to about 65% modified epoxy resin.
18. The composition of claim 17 wherein the epoxy resin is modified
with polysulfide and cured with an amine.
19. A method for protecting a substrate from hyperthermal
conditions comprising a first step of applying a layer of a first
polymeric active thermal protective composition to the substrate,
thereafter a second step of applying to the first layer an upper
layer of a second polymeric thermal protective composition which
when exposed to a fire or other hyperthermal condition swells to
form an open cell matrix to permit passage of gasses from the lower
layer to ambient, the second composition comprising a fill of a
refractory material comprising at least about seven percent of the
second composition by weight, and a step of embedding a mesh or
fabric reinforcement in the system.
20. The method of claim 19 wherein both the first composition and
the second composition comprise a polymeric binder and a gas
former, the second composition comprising less gas former by weight
than the first composition, the method providing a composite system
overlying the substrate.
21. The method of claim 20 wherein the upper layer is an epoxy
resin modified to increase its flexibility and elasticity.
22. The method of claim 20 wherein the reinforcement comprises a
graphite fabric.
23. The method of claim 20 wherein the reinforcement comprises a
metal mesh.
24. The method of claim 19 wherein lower layer is applied to a
cured thickness of about one to about twenty-five mm.
25. The method of claim 24 wherein the lower layer is less than 15
mm thick.
26. The method of claim 19 wherein the lower layer responds to
hyperthermal conditions by expanding to at least twice its original
thickness.
27. The method of claim 19 wherein the upper layer is applied to a
cured thickness of about one to about fifteen mm.
28. The method of claim 27 wherein the upper layer is less than
about six mm thick.
29. The method of claim 19 wherein the upper layer responds to
hyperthermal conditions by expanding to an average thickness no
more than twice its original thickness.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of application Ser. No.
10/036,717, filed Dec. 21, 2001, now U.S. Pat. No. 6,855,401, which
claims the benefit of United States Provisional application
60/258,138 filed Dec. 22, 2000, the disclosures of which are hereby
incorporated by reference.
STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] This invention relates to thermal protective coatings. It is
particularly useful as applied to coatings which are applied to
substrates to protect the substrate from extremely high intensity,
high velocity hyperthermal conditions.
[0004] Various compositions are known which provide protection
against fire and other thermal extremes. Presently, such
compositions generally include a polymeric binder and form a char
when exposed to fire or hyperthermal conditions. The char-forming
compositions may operate by various modalities. Several
char-forming, fire-resistive coatings are described in Deogon, U.S.
Pat. No. 5,591,791. Briefly, such coatings include ablative
coatings, which swell to less than twice their original thickness
when exposed to fire or other thermal extremes, intumescent
coatings such as those disclosed in Nielsen et al., U.S. Pat. No.
2,680,077, Kaplan, U.S. Pat. No. 3,284,216, or Ward et al., U.S.
Pat. No. 4,529,467, which swell to produce a char more than five
times the original thickness of the coating, and subliming
char-forming coatings of the type disclosed in Feldman, U.S. Pat.
No. 3,849,178, which undergo an endothermic phase change and expand
two to five times their original thickness to form a continuous
porosity matrix. The intumescent and subliming coatings are denoted
"active" thermal protective coatings. The coatings are also
sometimes applied to an intermediate structure which is then
applied to the substrate as set out in Feldman, U.S. Pat. No.
4,493,945.
[0005] The time required for a given temperature rise across a
predetermined thickness of the composition, under specified heat
flux, environmental, and temperature conditions, is a measure of
the composition's effectiveness in providing thermal protection to
an underlying substrate.
[0006] Eventually, the char is consumed by physical erosion and by
chemical processes, such as oxidation by oxygen in the air and by
free radicals produced by the coating or otherwise in a fire
environment, and protection is substantially reduced. Before the
char is totally consumed, degradation of the char layer leaves it
crumbled and without the necessary strength to sustain itself,
causing it to fail by being blown off or simply falling off
(spalling).
[0007] Various methods and structures have also been used or
proposed for applying these thermal protective coating materials.
The most frequent approach is to apply the materials directly to
the substrate, without additional structure. For many applications,
however, a reinforcing material, such as fiberglass fabric,
graphite fabric, or a wire mesh, has been embedded in the coating
material to strengthen the material and prevent it from cracking or
falling off the substrate under conditions of flame or thermal
extreme. Examples of this approach are found in Feldman, U.S. Pat.
No. 3,022,190, Billing et al, U.S. Pat. No. 3,913,290, Kaplan, U.S.
Pat. No. 3,915,777, and Billing et al, U.S. Pat. No. 4,069,075.
Sometimes the materials are first applied to a reinforcing
structure such as a flexible tape or flexible wire mesh, and the
combined structure is applied to the substrate. Examples of this
approach are found in Feldman, U.S. Pat. No. 3,022,190, Pedlow,
U.S. Pat. No. 4,018,962, Peterson et al, U.S. Pat. No. 4,064,359,
Castle, U.S. Pat. No. 4,276,332, and Fryer et al, U.S. Pat. No.
4,292,358. In these last-mentioned systems, the purpose of the
reinforcing structure may be both to strengthen the resulting
composite and to permit its application to a substrate without
directly spraying, troweling or painting the uncured coating
materials onto the substrate. In any of the foregoing methods and
structures, multiple layers are frequently applied to the substrate
to provide additional protection.
[0008] Presently known materials and methods, however, are not as
efficient, in terms of length of protection for a given weight of
protective material, as desirable. Efficiency is particularly
important because in many applications weight or volume is
critically limited. Moreover, heavily loading coating materials
with fire retardants may seriously impair their physical
characteristics and otherwise limit their suitability as coatings,
for example by limiting their film-forming characteristics or their
water-resisting characteristics.
[0009] Under certain extreme fire conditions, all of these known
coating systems have required excessive thickness and weight to
provide adequate protection. One of the environments in which such
extreme fire conditions can occur is in the vicinity of a delivery
pipe carrying flammable compressed gas or liquid, typically a
hydrocarbon, from one location to another location. A rupture in
the pipe or a failure of a valve or joint can result in a
high-temperature, high heat flux, high-velocity flame, frequently
termed a "jet fire." If the difference in pressure across the
rupture or opening is greater than about two-to-one, a choked flow
condition is produced at the aperture, and a supersonic flow of gas
is produced downstream of the aperture. The heat flux of these high
velocity gases is on the order of about 300 to 320 kilowatts per
square meter, and the temperature can typically be from
1,000.degree. C. to 1,500.degree. C. There have been standards
produced which define a jet fire and delineate test procedures for
assessing the effectiveness of protective coating systems. An
important standard is identified as OTI 95 634 "Jet Fire Resistance
Test Of Passive Fire Protection Materials" (Health and Safety
Executive (UK), Offshore Technology Report, 1996). This document is
incorporated herein by reference.
[0010] When exposed to the temperatures, heat fluxes, and
aerodynamic shear forces of a jet fire, presently known coating
systems erode and are quickly consumed or spall and fall off.
Ablative coatings tend to produce dense chars having good physical
and chemical resistance, but in standard jet fire tests they have
been found to allow an underlying substrate to reach the critical
temperature in a very short time. In the case of active coatings
which swell when exposed to thermal extremes, the degradations are
usually in the form of fissures which are formed in the char as a
result of differential thermal stresses produced by the high
thermal gradients and rapid erosion caused by shear forces.
[0011] To increase the strength of char layers during exposure to
thermal extremes, and to limit spalling and fissures, fabrics have
long been incorporated in the coating materials. As set out in
Feldman et al., U.S. Pat. No. 5,622,774, fiberglass fabric provides
an inexpensive, easy to install, reinforcement in many high
temperature applications. Jet fires, however, raise the fabric to
temperatures above the softening point of the glass (around
870.degree. C.), and the fiberglass fabric has disintegrated. Other
fabrics have therefore been required. Graphite cloth, as taught in
the foregoing Feldman et al., U.S. Pat. No. 5,622,774, and in
Castle et al., U.S. Pat. No. 5,580,648, Boyd et al., U.S. Pat. No.
5,433,991, and Kobayashi et al., U.S. Pat. No. 5,401,793, is one
choice. The graphite cloth may be either substantially pure carbon
or a precursor material, as is well-known in the art. Refractory
materials, such as quartz (Refrasil) fabric, are also used. Metal
mesh is inexpensive and widely used, but it is heavy and difficult
to install. Even when reinforced with fabric or mesh, however,
known protective systems are not very efficient in protecting
against a jet fire and therefore require thick, heavy coatings to
provide even limited protection.
[0012] The patents mentioned herein are all incorporated herein by
reference.
BRIEF SUMMARY OF THE INVENTION
[0013] One of the objects of one embodiment of the present
invention is to provide a thermal protective system which is more
efficient in protecting against jet fires than presently known
system.
[0014] Other objects will become apparent to those skilled in the
art in light of the following description.
[0015] In accordance with one aspect of the present invention,
generally stated, a composite system capable of protecting a
substrate from a jet fire is provided, the system comprising a
lower layer of an active fire protective material and an upper
layer of an ablative fire protective material, the ablative
material forming an open cell matrix when exposed to a jet fire to
permit passage of gasses from the lower layer to ambient.
[0016] In accordance with another aspect of the present invention,
generally stated, a composite system capable of protecting a
substrate from a jet fire is provided comprising a lower layer of
an active fire protective material which swells when exposed to a
fire or other hyperthermal condition and an upper layer of an
active fire protective material which swells when exposed to a fire
or other hyperthermal condition, the upper layer swelling less than
the lower layer, the upper layer comprising a fill of refractory
material comprising at least about seven percent of the upper layer
by weight.
[0017] In accordance with another aspect of the invention, a method
for protecting a substrate from hyperthermal conditions is provided
comprising a first step of applying a layer of a first active
thermal protective composition to the substrate, and thereafter a
second step of applying an upper layer of a second active thermal
protective composition to the first layer, the second composition
comprising a fill of a refractory material comprising at least
about seven percent of the second composition by weight.
Preferably, both the first composition and the second composition
comprise a polymeric binder and a gas former, the second
composition comprising less gas former by weight than the first
composition.
[0018] In some embodiments, a high-temperature mesh or fabric
reinforcement is embedded in the composite system. The
reinforcement may be of numerous materials. In one embodiment it is
graphite. In another it is metal, such as galvanized steel. In
others it is fiberglass of various types; a high temperature
polymer such as polyimide, polybenzoimidazole, or polyamide such as
Kevlar; a ceramic such as silica or zirconia; or a silicone, or a
combination of these materials. Other mesh or fabric reinforcements
may also be used, and the reinforcement may be free-floating in the
composite or pinned to the underlying substrate. In some
embodiments, the mesh or fabric is applied to the lower layer
either before or after the lower layer has substantially cured. If
the lower layer has substantially cured, an adhesive layer,
preferably in the form of a thin coat of the uncured upper layer,
may be applied to the lower layer, and the mesh or fabric is
embedded in the adhesive layer. In other embodiments, the mesh or
fabric is embedded in the upper layer. In other embodiments, the
mesh or fabric is embedded in the lower layer. In other
embodiments, particularly when a mesh is pinned to the substrate
and the thickness of the system is low, the mesh may extend through
into both layers of the system. In other embodiments, the amount
and size of chopped fibers in the upper layer is chosen to
substitute for the mesh or fabric. In other embodiments, no mesh or
fabric reinforcement is required because of the requirements of the
system. In other embodiments, the mesh or fabric is utilized to set
the system off from the substrate as in Feldman, U.S. Pat. No.
4,493,945.
[0019] In the preferred embodiments of the composite system, the
lower layer is applied directly to the substrate and adheres to it.
It will of course be understood that a primer is generally first
applied to the substrate to aid in adherence, in accordance with
generally accepted practice.
[0020] In the preferred embodiments, the lower layer is about 1-25
mm thick. In one embodiment, the lower layer is less than 15 mm
thick. In another embodiment, the lower layer is about 3 mm to
about 10 mm thick.
[0021] The lower layer responds to hyperthermal conditions by
expanding to at least twice its original thickness. In some
embodiments, the lower layer expands about two to about five times
its applied thickness. In other embodiments, the lower layer
expands from five to one hundred times its original thickness. The
lower layer preferably includes about 30% to about 65% polymeric
resin and more than 30% blowing agent (gas former). Numerous
useable formulations are known in the art, some examples being
given in the foregoing patents. Another is given in McGinniss et
al., U.S. Pat. No. 5,487,946. Others are commercially available,
for example Chartek 7 (Akzo Nobel/international Paint, Ltd.), Albi
Clad 800 (Albi Manufacturing division of Stanchem, Inc.), or
Thermo-Lag 3000, Thermo-Lag 2000, Thermo-Lag 440, Thermo-Lag 330,
or Thermo-Lag 220 (Nu-Chem, Inc.)
[0022] In the preferred embodiments, the upper layer is about 1-25
mm thick. In one embodiment, the upper layer is less than 15 mm
thick. In another embodiment, the upper layer is about 2 mm to
about 6 mm thick. When mesh or fabric reinforcement is used, it is
preferred that the upper layer be at least about 2.5 mm thick.
[0023] The upper layer composition forms a part of the present
invention both in combination with the lower layer and per se.
Thus, in accordance with another aspect of the invention, a
thermally protective composition is provided having a polymeric
binder, from 5% to 30% of a blowing agent which changes from solid
to gas at a hyperthermal temperature to which the composition may
be subjected, and at least 7% of a refractory filler.
[0024] The refractory filler preferably includes particles or
fibers, or both. The fillers preferably comprise glass, graphite,
or ceramic fibers and particles (granules). The glass may be of
various types. The ceramic may include, for example, metal oxides
such as silica, alumina, mullite, magnesium oxide, titanium
dioxide, and zirconia; metal carbides such as silicon carbide,
aluminum carbide, boron carbide, and zirconium carbide; metal
nitrides such as silicon nitride, boron nitride, and aluminum
nitride; metal silicates such as aluminum silicate, cordierite,
zircon, and steatite; and metal borides such as silicon
tetraboride, tungsten boride, and zirconium boride. The graphite
may be in the form of substantially pure carbon or may be a
precursor material which converts to substantially pure carbon
under fire conditions. Any fibers should be limited in length to no
more than about 7 mm for use in present-day spray applicators, but
longer fibers may be used when the upper layer is applied by other
methods such as troweling, brushing, rolling, or molding. In one
embodiment, the fillers comprise at least about 15% by weight of
the composition. In another embodiment they comprise about 20% to
30%, by weight of the composition. In other embodiments they
comprise at least 25% by weight of the composition. The inert
fillers increase the erosion resistance of the system and greatly
increase its effectiveness. The inert fillers are preferably chosen
to reradiate heat (as by reflection) from a high temperature fire
more effectively than the upper layer would without the
fillers.
[0025] The upper layer incorporates a small amount of gas forming
composition to ensure that an open porosity matrix is formed under
fire conditions. In one embodiment, gas formers comprise less than
30% by weight of the composition of the upper layer. In another
embodiment, gas formers comprise between about 10% and about 25% by
weight of the composition of the upper layer. The composition of
the upper layer is formulated to swell far less than the lower
layer under fire conditions, preferably on the order of 10% to 100%
of its initial thickness. The upper layer suppresses expansion of
the lower layer, but it does not prevent expansion of the lower
layer.
[0026] In presently preferred embodiments, the upper layer is
modified to increase its flexibility and elasticity, as with a
flexibilizing agent. In the presently most preferred embodiment,
the upper layer includes from about 35% to about 65% epoxy resin.
The resin is preferably modified to increase its flexibility and
elasticity, illustratively with polysulfide. It is preferably cured
with an amine. Other resins such as polyamides, polyimides,
acrylics, urethanes, polyisocyanurates, and the like may also be
useable. The polysulfide and amine curative components of the
presently preferred resin give it sufficient flexibility to permit
formation of a gas-permeable open porosity matrix on heating and
also permit swelling of the lower layer, particularly in areas of
highest heating. Only part of the gasses from the lower layer will
permeate through the upper layer. The other part will result in a
limited expansion of the lower layer. The upper layer is also
resistant to high-temperature stresses produced by having a very
high temperature on the surface of the layer and a much lower
temperature underneath it.
[0027] Additives may be added to the upper layer to improve its
properties in other ways. For example, boron or zinc may be added
either in elemental or combined form. Colorants, emissivity
controlling agents, rheology modifying agents, plasticizers, and
the like may also be added.
[0028] The upper layer also provides advantages to the system when
it has not been exposed to excessive heat or fire. It makes the
system more resistant to environmental conditions such as water,
salt, radiation, and corrosives, and makes it more resistant to
physical abrasion. One embodiment of the present invention has been
successfully tested under the immersion/freeze/dry cyclic test
program delineated in NORSOK M-501 Standard (Rev. 4, December
1999), both with and without a topcoat. Samples from that test
(without a scribe) have performed as well as a sample not subjected
to the cyclic test program when tested in sixty minute hydrocarbon
fire endurance tests (Norwegian Petroleum Directorate Standard NS
3904). These standards are incorporated herein by reference.
[0029] Unlike a traditional topcoat, the upper layer of the present
invention has a substantial thickness, of at least one millimeter,
preferably at least two millimeters, and it is compatible with the
composition of the lower layer. In preferred embodiments of the
present invention, the upper layer and lower layer include similar
resin systems, but differ in the amounts of gas-forming materials
and the amounts of refractory fillers in them.
[0030] Although not preferred in many applications envisioned for
the present invention, the upper layer may be used without the
lower layer in some applications, such as protecting pipes which do
not require long-duration protection from fire or other
hyperthermal conditions.
[0031] It has been found that the composites of the present
invention provide at least 30% longer protection under standard jet
fire testing procedures than would be provided by a system
including only the composition of the upper layer or of the lower
layer, even when applied to the full thickness of the composite
system. Preferred systems of the present invention provide at least
50% longer protection, and sometimes in excess of 100% longer
protection.
[0032] The system of the present invention may be utilized to
protect a wide variety of substrates. It is particularly useful in
protecting structural steel in hydrocarbon recovery or processing
facilities, such as deep sea drilling platforms and petroleum
processing plants. It also may be used to protect other substrates,
including, by way of example, other metals, plastics, piping,
flanges, fins, bulkheads, tanks, rocket launch gantries, and the
leading edges of hypersonic aircraft.
[0033] Other aspects of the present invention will be best be
understood in light of the following description.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0034] Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The following detailed description illustrates the invention
by way of example and not by way of limitation. This description
will clearly enable one skilled in the art to make and use the
invention, and describes several embodiments, adaptations,
variations, alternatives and uses of the invention, including what
we presently believe is the best mode of carrying out the
invention.
EXAMPLE 1
[0036] A composition for use as an ablative upper layer was
prepared containing 35% to 65% by weight of a flexible polymeric
resin (illustratively a modified epoxy resin, particularly an epoxy
polysulfide resin), 5% to 30% gas formers (illustratively polyol
spumifics, amine blowing agents, and phosphate acid producers), and
about 10% to about 40% refractory fillers. The illustrative
composition is a two-component modified epoxy having a nominal
formula as follows:
1 TABLE 1 Weight percent Melamine 5 Ammonium polyphosphate 10
Pentaerythritol 5 Epoxy resin (Bis Phenol A) 25 Polysulfide and
amine curative 25 Glass fibers (chopped) 5 Ceramic particles 25
EXAMPLE 2
[0037] A lower layer active thermal protective composition was
prepared containing 30% to 70% by weight of a polymeric resin
(illustratively a modified epoxy resin, particularly an epoxy
polysulfide resin) and 20% to 50% gas formers (illustratively
polyol spumifics, amine blowing agents, and phosphate acid
producers). The composition for use in the following tests was a
two-component epoxy-based thermally activated coating, which when
exposed to flame or thermal extreme, volatilizes at fixed
temperatures, exhibiting a small volume increase (greater than
twice the original thickness) through the formation of an open cell
matrix, and absorbs and blocks heat to protect the substrate
material. The composition included a polyfunctional alcohol, a
1,3,5-triazine-2,4,6-tri- amine, an epoxy resin and a polymer of
bis-(ethylene oxy)methane containing disulfide linkages and curable
terminal thiol groups (a polysulfide).
[0038] The exemplary composition is a two-component modified epoxy
having a nominal formula as follows:
2 TABLE 2 Weight percent Melamine 5 Ammonium polyphosphate 25
Pentaerythritol 10 Epoxy resin 30 Polysulfide 20 Glass fibers 5
Catalyst 5
[0039] A test fixture generally as set out in OTI 95634 dated 1996
was sprayed to a thickness of 3 mm with the lower layer
composition.
[0040] A graphite fabric was pressed into the lower layer before it
set. The lower layer was allowed to cure for 17 hours, and 3 mm of
the upper layer composition of EXAMPLE 1 was sprayed over the lower
layer. The composite was allowed to cure at 30.degree. C. for one
month.
EXAMPLE 3
[0041] The test article prepared in accordance with EXAMPLE 2 was
exposed to a jet fire in accordance with the procedure set out in
OTI 95634 dated 1996. The test showed that the composite structure
provided approximately sixty minutes of protection under the
conditions of the test.
[0042] Smaller scale tests indicate that the composite system
provides far greater protection than the protection given by a
thickness of either the upper layer or the lower layer alone equal
to the total thickness of the composite. The results of those tests
are summarized below:
3TABLE 3 Small scale jet fire simulations Temperature circa
1100.degree. C. Heat Flux circa 300 kilowatts/m2 Coating
Composition: A = lower coating, B = upper coating Test Article
Coating Composition Time to 400.degree. C. Flat Plate 6" .times. 6"
.times. 1/4" 3 mm of A and 3 mm of B 44 minutes 6" .times. 6"
.times. 1/4" 6 mm of A 27 minutes Pipe Diameter - 4" 5 mm of B 10
minutes Diameter - 4" 3 mm of A, 3 mm of B 26 minutes (Wall
Thickness: 3/8")
EXAMPLE 4
[0043] A full-scale test of a composite system in accordance with
the present invention was made in accordance with Offshore
Technology Report OTI 95 634. Upper layer and lower layer
compositions were formed as shown in Example 1 (Table 1) and
Example 2 (Table 2). The test specimen was primed with an epoxy
primer and coated with a nominal thickness of 3 mm of the lower
layer composition and a nominal thickness of 3 mm of the upper
layer composition reinforced with a sized woven carbon fiber fabric
with approximately 2.3 openings per square centimeter. The fabric
weighed about 105 grams per square meter, and the joint layers of
the cloth were overlapped. The overall thickness of the composite
system was 6 mm with individual measurements ranging between 5 mm
and 7 mm.
[0044] At the end of thirty minutes, average box temperature had
risen 250.degree. C. above ambient and average web temperature had
risen 239.degree. C. After seventy-five minutes, average box
temperature had risen 327.degree. C. above ambient and average web
temperature had risen 382.degree. C. Maximum rises at thirty
minutes were 428.degree. C. and 265.degree. C. respectively; at
seventy-five minutes they were 450.degree. C. and 411.degree.
C.
[0045] A test was also made in accordance with Offshore Technology
Report OTI 95 634 on a system comprising the upper layer
composition (Example 1, Table 1) alone. The test specimen was
primed with an epoxy primer and coated with a nominal thickness of
12 mm of the upper layer composition on the back of the box and 16
mm on the web. The entire structure was reinforced with a sized
woven carbon fiber fabric about 8 mm from the box and web surface.
An additional layer of fabric was used over the web only at a
nominal 12 mm from the web surface. The fabric had approximately
2.3 openings per square centimeter, weighed about 105 grams per
square meter, and the joint layers of the cloth were overlapped.
The average measured thickness of the system was 12.7 mm (10.5-16
mm) on the back of the box and 15.2 mm (13-17 mm) over the web of
the test specimen.
[0046] At the end of thirty minutes, average box temperature had
risen 121.degree. C. above ambient and average web temperature had
risen 175.degree. C. After seventy minutes, average box temperature
had risen 180.degree. C. above ambient and average web temperature
had risen 347.degree. C. After one hundred twenty minutes, average
box temperature had risen 207.degree. C. above ambient and average
web temperature had risen 474.degree. C. Maximum rises at thirty
minutes were 140.degree. C. and 225.degree. C. respectively; at
seventy minutes they were 210.degree. C. and 462.degree. C.; and at
one hundred twenty minutes they were 239.degree. C. and 628.degree.
C. After one hundred twenty minutes, all the fabric was intact, and
no metal substrate had been exposed by the jet fire.
[0047] A test was also made in accordance with Offshore Technology
Report OTI 95 634 on two systems comprising the lower layer
composition (Example 2, Table 2) alone. The test specimen was
primed with an epoxy primer and coated with a nominal thickness of
5 mm of the lower layer composition (test A) and 11 mm of the lower
layer composition (test B). In each test, the entire structure was
reinforced with a 19-gauge wire mesh with 12.7.times.12.7 mm
openings pinned to the substrate. The average measured thickness of
the system for test A was 4 mm (2.5-5 mm) on the back of the box
and 4.7 mm (3-7 mm) over the web of the test specimen. The average
measured thickness of the system for test B was 11 mm (9-14 mm) on
the back of the box and 11.4 mm (9-13 mm) over the web of the test
specimen.
[0048] At the end of thirty minutes, average box temperature of
test A had risen 352.degree. C. above ambient and average web
temperature had risen 473.degree. C.
[0049] At the end of thirty minutes, average box temperature of
test B had risen 200.degree. C. above ambient and average web
temperature had risen 180.degree. C. After seventy-four minutes,
average box temperature had risen 318.degree. C. above ambient and
average web temperature had risen 325.degree. C. Maximum rises at
seventy-four minutes were 604.degree. C. and 376.degree. C. Metal
mesh and metal substrate had been exposed by the jet fire.
[0050] In view of the above, it will be seen that the several
objects and advantages of the present invention have been achieved
and other advantageous results have been obtained.
[0051] As various changes could be made in the above constructions
without departing from the scope of the invention, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *