U.S. patent number RE31,960 [Application Number 06/658,337] was granted by the patent office on 1985-07-30 for composites and methods for providing metal clad articles and articles produced.
This patent grant is currently assigned to Scott Bader Company Limited. Invention is credited to Cecil L. Phillips.
United States Patent |
RE31,960 |
Phillips |
July 30, 1985 |
Composites and methods for providing metal clad articles and
articles produced
Abstract
A composite for providing a metal clad article of thermosetting
resin includes a metal facing, a curable thermosetting resin and,
between the metal facing and the resin, a layer of adhesive
material. The adhesive material is capable of adhesion to the metal
facing and to the thermosetting resin on curing of the resin to
thereby bond the metal to the resin. The thermosetting resin may be
cured hot or cold, some adhesives being more suitable for one or
other method.
Inventors: |
Phillips; Cecil L. (Boughton,
GB2) |
Assignee: |
Scott Bader Company Limited
(GB3)
|
Family
ID: |
27449223 |
Appl.
No.: |
06/658,337 |
Filed: |
October 5, 1984 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
340405 |
Jan 18, 1982 |
04421827 |
Dec 20, 1983 |
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Foreign Application Priority Data
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Jan 21, 1981 [GB] |
|
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8101796 |
Jan 21, 1981 [GB] |
|
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8101797 |
Jun 19, 1981 [GB] |
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8118988 |
Oct 6, 1981 [GB] |
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8130121 |
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Current U.S.
Class: |
428/418; 156/330;
426/131; 428/116; 428/423.3; 428/423.7; 428/424.4; 428/424.7;
428/425.6; 428/425.8; 428/458; 428/463; 428/483; 428/520 |
Current CPC
Class: |
B32B
13/04 (20130101); B32B 27/04 (20130101); B32B
15/08 (20130101); Y10T 428/24149 (20150115); Y10T
428/31529 (20150401); Y10T 428/31797 (20150401); Y10T
428/31699 (20150401); Y10T 428/31928 (20150401); Y10T
428/31605 (20150401); Y10T 428/31554 (20150401); Y10T
428/31601 (20150401); Y10T 428/31576 (20150401); Y10T
428/31565 (20150401); Y10T 428/31681 (20150401); Y10T
428/31583 (20150401) |
Current International
Class: |
B32B
13/00 (20060101); B32B 13/04 (20060101); B32B
15/08 (20060101); B32B 27/04 (20060101); B29D
009/08 (); B29H 009/00 (); B32B 015/08 () |
Field of
Search: |
;428/425.8,418,463,423.3,423.7,424.4,483,520,425.6 ;156/330 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1431324 |
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Apr 1976 |
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GB |
|
2061834 |
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May 1981 |
|
GB |
|
Primary Examiner: Ives; Peter C.
Attorney, Agent or Firm: Townsend and Townsend
Claims
I claim:
1. A composite for providing a rigid metal clad article of
thermosetting resin which composite includes a metal facing, a
layer of adhesive material on the metal facing and, laid on the
layer of adhesive material, an uncured curable thermosetting resin,
the layer of adhesive material consisting essentially of a fully
precured thermosetting or a thermoplastics material and being
capable of adhesion to the metal facing and to the thermosetting
resin at least upon curing of said uncured resin to form an
adhesive bond with both the metal facing and the cured curable
thermosetting resin.
2. A composite according to claim 1, wherein the adhesive material
is effective upon cold curing of the said uncured curable
thermosetting resin.
3. A composite according to claim 1, wherein the adhesive material
is effective upon hot curing of said uncured curable thermosetting
resin.
4. A composite according to claim 1, wherein the adhesive material
is a fully cured thermosetting material selected from (a) a
thermosetting resin which contains polyurethane linkages, (b) an
acrylic resin, (c) an epoxy resin, (d) an unsaturated polyester,
(e) a nitrile rubber and (f) a polymer containing vinyl acetate
residues.
5. A composite according to claim 4, wherein the adhesive material
is a thermosetting resin selected from the group consisting of
acrylic, urethane and urethane/acrylic resin and nitrile
rubbers.
6. A composite according to claim 5, wherein the adhesive material
is a cured thermosetting resin selected from the group consisting
of a nitrile rubber, a two pot acrylic resin, a two pot urethane
resin and an acrylate-terminated polyurethane.
7. A composite according to claim 1, wherein the said curable
thermosetting resin includes reinforcing fibre.
8. A composite according to claim 1, wherein the metal facing is
selected fro the group consisting of stainless, mild or galvanised
steel, aluminum, copper, brass, phosphor bronze, zinc, nickel, tin,
titanium, molybdenum or chromium.
9. A rigid metal clad article of thermosetting resin consisting
essentially of a metal facing, a cured thermosetting resin layer
and, between the metal facing and the resin, a layer consisting
essentially of a fully cured thermosetting or thermoplastics
adhesive material, the article having been formed by applying to
the metal facing the layer of adhesive material, bonding the said
layer of adhesive material to the metal facing, which bonding is
effected, when the adhesive material is a thermoplastics material,
by heating the thermoplastics material and, when the adhesive
material is a thermosetting material, by curing the thermosetting
material, laying up on said layer of adhesive material an uncured
curable thermosetting resin and curing the said curable
thermosetting resin thereby bonding the adhesive material to the
resin to provide the said metal clad article, which said step of
curing the said curable thermosetting resin is, when the adhesive
material is a thermosetting material, carried out after the said
curing of the thermosetting material.
10. A metal clad article according to claim 9, wherein the
thermosetting resin layer includes reinforcing fibre.
11. A method of forming a rigid metal clad article which includes
the steps of applying to a metal facing a layer consisting
essentially of thermosetting or thermoplastics adhesive material
capable of adhesion to the metal facing, bonding the said layer of
adhesive material to the metal facing, which bonding is effected,
when the adhesive material is a thermoplastics material, by heating
the thermoplastics material and, when the adhesive material is a
thermosetting material, by fully curing the thermosetting material,
laying up on said layer of adhesive material an uncured curable
thermosetting resin and curing the said curable thermosetting resin
thereby bonding the adhesive material to the resin to provide the
said metal clad article, which step of curing the said curable
thermosetting resin is, when the adhesive material is a
thermosetting material, carried out after the said curing of the
thermosetting material.
12. A method according to claim 11, wherein the said curing step is
a cold curing step.
13. A method according to claim 11, wherein the adhesive material
is a thermosetting material selected from the group consisting of
nitrile rubbers and acrylic, urethane and urethane/acrylate
resins.
14. A method according to claim 11, wherein the said curing step is
a hot curing step.
15. A method according to claim 14, wherein the adhesive material
is a thermoplastics material which is a hot melt adhesive in the
form of a discrete layer.
16. A method according to claim 11 wherein the said step of curing
the adhesive material is a cold curing step.
Description
FIELD OF THE INVENTION
This invention relates to composites for providing metal clad
articles of thermosetting resin, methods of making the metal clad
articles and metal clad articles so produced.
BACKGROUND OF THE INVENTION
Fibre reinforced plastics (FRP) laminates especially those based on
thermosetting resins such as unsaturated polyesters, vinyl esters,
epoxides, phenolics, furans and silicones have found wide use in
industry. By correct choice of resin type and reinforcement the
laminates can be used in the production of pipes, ducts, tanks,
vessels for chemical plants, cladding and decorative panels for
building, containers, tanks and pipes for potable liquids and
foodstuffs, boats, cars and commercial vehicles, railway coaches,
and many other applications.
However there are some aggressive environments that attack some or
all the resin matrices that are used. This disadvantage has been
overcome in some instances by the use of thermoplastics such as
rigid polyvinyl chloride, polypropylene or fluorinated
ethylene/propylene copolymers as facings to the laminate. Even so
there are applications where metals such as aluminum or stainless
steel perform better than FRP or FRP with a thermoplastic facing
but where the lightness and load bearing properties of FRP would be
an advantage.
Very thin sheets of metals (e.g. stainless steel) down to about
0.008 cm thick are now available and many applications can be
foreseen where a material of this type with a FRP backing could be
used, namely decorative metal faced building panels, metal faced
sectional water tanks, metal lined pipes, ducts and tanks and metal
faced components for the transport industry. Unfortunately, little
or no adhesion can be obtained between stainless steel and
thermosetting resins such as standard unsaturated polyesters and
vinyl esters even with careful preparation of the stainless steel
surface. It has been stated that some resins such as epoxides or
polyurethanes are self bonding on to stainless steel (B.P. No.
2,061,834) but these suffer from other disadvantages such as cost
(epoxides) and low stiffness (polyurethanes).
We have found a way by which excellent adhesion can be obtained
between a metal and those thermosetting resins which are not
generally considered as being capable of bonding to metal.
SUMMARY OF THE INVENTION
According to the invention there is provided a composite for
providing a metal clad article, which composite includes a metal
facing, a curable thermosetting resin and, between the metal facing
and the resin, a layer of adhesive material capable of adhesion to
the metal facing and to the thermosetting resin upon curing of said
resin to form an adhesive bonding therewith.
On subjecting the composite to a curing operation, a metal clad
article in accordance with the invention is provided in which the
metal facing is efficiently and easily bound to the thermoset resin
by the adhesive.
A method aspect of the invention includes the steps of providing,
on the metal facing, a layer of adhesive material capable of
adhesion to the metal facing, laying up on said layer of adhesive
material a curable thermosetting resin, and curing the
thermosetting resin, thereby bonding the adhesive material to the
resin to provide the said metal clad article.
Any forming of the metal to a desired profile is carried out prior
to bonding it to the other materials. The method of the invention
is particularly applicable to the formation of profiled metal clad
laminates of fibre reinforced thermosetting resin.
It is valuable that the method of the invention is a lamination
onto the metal surface rather than the adhesion of the metal
surface to a preformed laminate. Thus the cladding of the metal
takes place at the same time as the formation/cure of the laminate
when the thermosetting resin is brought together with the adhesive
material and metal. This enables the adhesive material to bind with
the thermosetting resin of the laminate on curing thus providing a
surprisingly excellent adhesive bond between metal and
laminate.
Excellent adhesion may be obtained between the metal and
thermosetting resin by treating the metal surface with an adhesive
material selected from a wide range of primers/adhesives the choice
of which is explained in more detail hereinafter, allowing it to
dry or cure and applying the thermosetting resin plus reinforcement
(if required) in the uncured state and then curing the thermoset.
The thermosetting resins may be applied in combination with
reinforcement (if required) in either the wet state by standard
processes, e.g. hand lay-up, spray up, filament winding, resin
injection (with or without vacuum assistance) cold press moulding,
flexible bag moulding, rotational moulding and pultrusion and cured
at ambient, or elevated temperatures or as pre-impregnated material
or formulated moulding material such as sheet moulding compounds
(SMC or its "high performance" derivatives HMC, XMC), bulk moulding
compounds (BMC), dough moulding compounds (DMC) and granules etc.
pressed into contact with the treated surface and cured by heating
under conventional hot press moulding conditions.
The metals can be formed into shape before lamination for example
by pressing, cutting and welding, bending and stitching.
When the thermoset resin is reinforced, this is preferably achieved
using reinforcing fibres of, for example, glass, silica, carbon,
KEVLAR.RTM. and similar polyaramids, and natural fibres such as
jute.
The reinforcing fibre may be provided by at least one layer of
fibrous material and this is preferably preimpregnated with the
thermosetting resin ("prepreg"). Alternatively the fibres may be
distributed within the thermosetting resin, as for example is the
case with DMC.
Available adhesives are classified generally by their chemical
nature (Adhesives Directory 1981, Wheatland Journals Ltd,
Rickmansworth):
(a) Natural Products, e.g. starch, bone glue,
(b) Cellulosics, e.g. cellulose acetate,
(c) Elastomerics, e.g. natural rubber,
(d) Synthetic Rubbers, e.g. nitrile, Neoprene.RTM.,
styrene/butadiene,
(e) Thermoplastics, e.g. cyanocrylates, hot melts (e.g.
ethylene/vinyl acetate, polyamide) polyvinyl acetate, polyvinyl
butyral, acrylics and copolymers,
(f) Thermosets, e.g. addition polymers such as epoxides,
polyesters, vinyl esters, urethane acrylates, urethanes, anaerobic
acrylics or condensation polymers, e.g. phenol formaldehyde, urea
formaldehyde,
(g) Inorganic, e.g. sodium silicate.
We find that, in general, adhesives of groups (a), (b) and (g) do
not work. In particular, inorganic adhesives (g) tend to be too
rigid to form good bonds with the thermosetting resins forming the
laminate.
Preferred adhesive materials are those selected from group (f) and
certain members of groups (c), (d) and (e), though we find that
aqueous based adhesives within these latter groups in emulsion form
tend to be inferior. Such aqueous based adhesives may, however,
provide adequate adhesion on hot curing of the thermosetting resin
forming the laminate.
The adhesive capability of an adhesive material is regarded as good
if the resultant metal clad laminate has a lap shear of at least 3,
and preferably .gtorsim.3.5 Megapascals (MPa). It is strongly
preferred that the lap shear strength be no less than 2.5 MPa.
The choice of adhesive material depends upon the nature of the
thermosetting resin which is to form the laminate (the adhesive
material must be compatible with the resin) and the metal facing to
be provided. It depends also upon the conditions of curing to be
employed.
Some adhesive materials provide good results only when used with a
hot cured laminate and certain of the thermoplastics and natural
and synthetic rubbers fall into this category. Such hot curing is
generally carried out at a temperature in the range
100.degree.-200.degree. C., preferably 140.degree.-160.degree. C.,
more preferably 150.degree. C., and usually under pressure (about
1000-2000 psi, preferably 1500 psi).
On the other hand, other adhesive materials provide good results
when used with a cold cured or a hot cured laminate, these
including certain thermosetting resins and synthetic rubbers. Such
cold curing is generally carried out at about ambient temperature,
but may be followed by a "post-curing" step in which the material
is heated to say 30.degree.-120.degree. C., preferably at least
40.degree. C.
For excellent results both on cold and hot curing of the laminate,
an adhesive is selected which:
(a) provides a good key to the metal surface (there are certain
adhesives known to be useful for bonding metal to metal and some of
these, though not all, are useful in the method of the present
invention),
(b) is flexible, tough or resilient, i.e. having low modulus
and
(c) is curable by crosslinking with minimum shrinkage before
application of the laminating resin system.
Examples of adhesives which may give good results (though in some
cases hot curing of the laminate is required) are thermosetting
resins which contain polyurethane linkages and optionally
additionally include acrylic (especially acrylate) linkages or
terminal groups, acrylic resins (especially anaerobic acrylics),
epoxy resins, unsaturated polyesters (provided that they form
sufficiently flexible layers on curing), polymers containing vinyl
acetate residues, nitrile rubbers, polyolefine and nitrile hot melt
adhesives, cyanoacrylates, neoprene and natural rubbers.
Those adhesive materials which provide good results on hot curing
of the laminate include hot melt polyolefins which may contain
vinyl acetate residues.
Epoxy resins are also preferred for hot curing but will give
excellent results on cold curing of certain thermosetting resins
which form the laminate, e.g. epoxy thermosetting resins.
Some, though few adhesive materials, e.g. cyanoacrylates, give good
results on cold curing of the laminate, but not on hot curing.
Adhesives which, in general, give excellent results both on cold
and hot curing of the laminate include acrylics (especially
anaerobic acrylics), certain unsaturated polyesters as later
described, thermosetting resins which contain polyurethane linkages
and optionally additionally contain acrylic (especially acrylate)
linkages or terminal groups, and nitrile rubbers. In particular,
nitrile rubbers provide excellent adhesion when used with a cold
cured laminate.
This range of adhesives allows for a particularly wide choice of
metal, thermosetting resin and curing conditions and this
versatility is surprising. For example, although nitrile rubbers
are known adhesives they have, in general, been applied only by hot
curing in conventional adhesion processes. This contrasts with the
excellent results we obtain on cold curing.
Excellent results can be achieved on cold curing, especially with
the abovementioned range of adhesives. This enables the process to
be carried out without having to apply heat, thus saving energy and
rendering it easier and more economical to perform.
We also find that particularly excellent results may be achieved if
the adhesive is allowed or caused to cure completely before the
thermosetting resin is laid on it.
This is especially so for cold curable resins, e.g. epoxy resins,
acrylics, nitrile rubbers and urethanes.
An especially preferred adhesive is one containing polyurethane
linkages with terminal acrylate groups.
The preparation of a typical urethane/acrylate of this type is
described below.
1.0 M Sorbitol and 18.0 M .epsilon.-Caprolactone were charged to a
suitable reaction vessel and heated to 90.degree.-100.degree. C.
with stirring. A cloudy homogeneous dispersion was obtained to
which was added 0.2% p-toluene sulphonic acid. An exothermic
reaction began almost instantaneously and the temperature rose
peaking at 140.degree.-150.degree. C.
The batch was allowed to cool naturally for 15 minutes and was then
vacuum stripped. Less than 2% of charge weight was removed.
After stripping, the temperature was adjusted to
100.degree.-110.degree. C. and 3.5 M isophorone di-isocyanate was
added. A gentle exotherm began and the bath temperature was allowed
to rise to 120.degree.-130.degree. C. where it was controlled by
cooling.
When the exotherm was over, the batch was cooled to
90.degree.-95.degree. C. and 3.5 M 2-hydroxy ethyl acrylate and 100
ppm hydroquinone was added. A below the surface feed of air was
started and the temperature was adjusted to 80.degree.-85.degree.
C. The batch was maintained at this temperature until the
isocyanate content was less than 0.6% (equivalent to 95%
conversion). The batch was then dissolved in styrene to provide a
composition containing approximately 60% solids by weight.
Although the most successful treatments are found to be based on
anaerobic acrylics, urethanes, urethane/acrylics and nitrile
rubbers, certain other treatments are usable if the three
conditions above are fulfilled. For example, standard unsaturated
polyesters do not give any adhesion due to their being too rigid
and exhibiting too great a shrinkage on cure. However, using a
specially formulated unsaturated polyester with an elongation at
break (in cured form) of 50% and lower shrinkage than normal, good
bonding is achieved.
Again epoxy materials are well known metal adhesives but unless
well cured prior to the application of the thermosetting resin
which is to form the laminate (with resins other than epoxides)
they give rise to interfacial problems through either attack of
solvents on the partially cured epoxy or inhibition of the cure of
the FRP by substances leached from the partially cured epoxy.
The adhesive material may be used in any suitable form, e.g.,
dissolved in a solvent, as a melt, as a powder, or as a discrete
sheet of material. It may be a single- or two-component system.
Depending upon the form of adhesive selected, it may be applied to
the metal by, for example, brushing or spraying or simply laying it
upon the metal surface. As some adhesive materials are anaerobic,
i.e. only cure properly in the absence of air, a thin sheet of PTFE
can be laid over the coat of material and left in place until the
adhesive layer is cured, after which the sheet is removed before
subsequent lamination. An alternative, though less preferred method
of obtaining adhesion, is to apply the adhesive to the metal and
before it cures to apply reinforcement, e.g. glass chopped strand
mat, to the surface so than some of the fibres are in the adhesive
layer whilst most are protruding. Some adhesive materials are
available as hot melt films which can be melted on to the metal
before subsequent lamination or, if the whole structure is to be
cured by hot pressing, laid between the metal and the moulding
composition or pre-impregnated material.
The thermosetting resins used to make the laminates may, for
example, be unsaturated polyesters, vinyl esters, urethanes,
acrylates, epoxides, phenolic resins, furans, or silicones, and may
be copolymers, e.g. urethane/acrylates. Preferred resins are
unsaturated polyesters, phenolic resins, furan resins and epoxy
resins. They may be compounded with thixotropic agents e.g. gaseous
silicas, fillers e.g. natural and precipitated calcium carbonates,
clays, talc, mica, silica, hydraulic cements and pigments if
required. The curing of these laminates can be, in the case of
polyesters, vinyl esters and urethane acrylates, by organic
peroxides and heat, organic peroxides plus so called accelerators,
visible or U.V. light, electron beams and in the case of epoxides
by the well known curing agents and for furanes and phenolics the
various catalysts available.
The procedure is capable of being used with a wide range of metals
in thicknesses of 0.08 mm upwards but normally the thinnest
material would be used for economical reasons. The metals include
stainless steel, chromium, titanium, aluminum, tin, copper, lead,
zinc, phosphor bronze, nickel, molybdenum, galvanised steel, brass
and mild steel. Good bonds, as measured by lap shear and peel
strengths, can be obtained when the metals are solvent degreased
before application of the adhesive material but improved adhesion
can be obtained by abrasion followed by a solvent wipe, alkaline or
acid etching.
Particularly preferred metal clad laminates of the invention are
metal clad FRP laminates. Their structures combine the best
features of the metals and FRP which can be summarised as:
(i) the high strength to weight ratio of FRP giving components of
lower weight than if made wholly of metal,
(ii) the imperviousness of metals which prevents moisture and other
aggressive environments from attacking FRP and causing long term
loss of strength and blistering,
(iii) the chemical resistance of metal such as stainless steel,
titanium and nickel alloys which allows a choice of metal according
to the environment,
(iv) the desirable hygienic properties of metals such as stainless
steel for use in contact with foodstuffs and potable liquids,
(v) very good reverse impact resistance as large loads can be
sustained without failure of the metal facing,
(vi) the fire resistance of the metal facing and absence of smoke
which can be important for example inside a duct,
(vii) the electrical properties of metal, i.e. conductance and
shielding,
(viii) the decorative properties of metal, i.e. in building
panels.
Metal clad laminates of the invention are thus extremely versatile
and have a very wide range of uses particularly in structural
applications, for example, in the production of pipes, ducts,
tanks, vessels for chemical plants, cladding and decorative panels
for building, containers, tanks and pipes for potable liquids and
foodstuffs, boats, cars and commercial vehicles, railway coaches,
and many other applications.
There is no reason why the metal clad laminates should have only
one metal face; both faces could be metal and they need not be
similar metals. Similarly sandwich structures with light weight
cores can be formed having one or both faces of metal foils, e.g.
metal/primer/FRP/foam or honeycomb/FRP, or metal/primer/FRP/foam or
honeycomb/FRP/primer/metal.
DESCRIPTION OF PREFERRED EMBODIMENTS
Metal clad laminates embodying the invention, composites for
providing them and methods of metal clad laminate formation will
now be described in more detail with reference to the following
Examples which include some comparative examples. The presently
most preferred embodiments are those in which the laminate is cold
cured.
EXAMPLE 1
A thin sheet of stainless steel (0.25 mm thick) was solvent
degreased and coated with PERMABOND.RTM.F241 adhesive (one
component of a 2 pot acrylic system) and Permabond initiator No. 1
(hardener) at 200 g/m.sup.2. This layer was covered by a
polytetrafluoroethylene (PTFE) sheet until cured, when it was
peeled off. A glass fibre reinforced polyester laminate was then
laid up on the treated metal surface using CRYSTIC.RTM.272 (an
isophthalic acid based unsaturated polyester resin), suitably
catalysed and accelerated, and 4 layers of glass chopped strand mat
(450 g/m.sup.2) at a resin:glass ratio of 2.3:1. The polyester of
the resultant composite was then allowed to cure at ambient
temperature to form a metal clad laminate.
When the polyester had cured it was extremely difficult to separate
from the stainless steel facing (lap shear strength 3.5 MPa).
EXAMPLE IA
A sheet of stainless steel was coated with Permabond F241adhesive
and a piece of satin weave glass fibre fabric (340 g/m.sup.2) was
immersed in an acetone solution of Permabond Initiator No. 1 (9 pts
by weight acetone:1 part initiator) and the acetone allowed to
evaporate. The glass fibre was rolled on to the treated stainless
steel surface and good adhesion was obtained.
A glass fibre laminate was then laid up on the glass fabric using
Crystic 272, suitably catalysed and accelerated, and 4 layers of
glass chopped strand mat (450 g/m.sup.2) at a resin:glass ratio of
2.3:1.
After the GRP layers of the resultant composite had been allowed to
cure at ambient temperature it was extremely difficult to separate
them from the stainless steel facing.
EXAMPLE II-XX
The procedure of Example I was followed except that the treatments
shown in Table I was used.
TABLE I ______________________________________ Lap Shear Ex-
Strength ample Treatment/Type (MPa)
______________________________________ II CRYSTIC .RTM. 272
(Polyester) <1 III TENAXATEX .RTM. 3964 (Polyvinyl acetate 3
emulsion) IV DERAKANE .RTM. 411-45 (Vinyl ester) <1 V INDASOL
.RTM. NS240 (Natural rubber latex) <1 VI INDATEX .RTM. SE765
(Acrylic emulsion) <1 VII INDASOL .RTM. CS 1659 (Neoprene latex)
<1 VIII PERMABOND .RTM. E04 (2 pot epoxy RT cure) <1 IX as
VIII but cured 24 hours at 40.degree. C. 3 X CRODAFIX .RTM.
27-8-700 (Ethylene/vinyl 2 acetate emulsion) XI PERMABOND .RTM. C
(Cyanoacrylate with 3 PTFE sheet curing) XII PERMABOND .RTM. A
(Anaerobic - cured 30 3 mins at 150.degree. C. with PTFE sheet
curing) XIII PERMABOND .RTM. E15 (2 Pot epoxy - cured 24 4 hours at
RT) XIV as XIII but thereafter post-cured for 5.5 24 hours at
40.degree. C.) XV PERMABOND .RTM. ESP110 (1 pot epoxy - cured 4 5
mins at 160.degree. C.) XVI CRYSTIC .RTM. D4176A (Flexible
polyester 4 cured 18 hrs at RT) XVII as XVI but then post-cured for
18 hours 5.5 at 40.degree. C. XVIII CRODAGRIP .RTM. 14-00300 (2 pot
polyurethane) 5 XIX INDASOL .RTM. MS419NF (Nitrile rubber) 6 XX
Polyfunctional acrylate terminated 6.5 polymer containing urethane
linkages with 80 pphr talc as filler
______________________________________
EXAMPLE XXI
A sheet of stainless steel 0.25 mm thick was cut to conform to the
shape of a flat plate mould 100.times.260 mm. The metal sheet was
solvent degreased, coated with INDASOL.RTM.MS419NF (a nitrile
rubber adhesive) at 200 g/m.sup.2 and allowed to dry. The treated
metal was placed in the mould with the untreated side in contact
with the lower mould surface and the mould loaded with CRYSTIC M125
(a sheet moulding compound) and reinforcing fibres to cover 70% of
the surface area. The mould was closed and pressing of the
resultant composite took 4 minutes at 150.degree. C. under a
pressure of 1,500 p.s.i. to effect curing.
On opening the mould a stainless steel faced FRP sheet was obtained
which was extremely strong with good adhesion between the FRP and
the metal face (single lap shear strength 5.5 MPa).
EXAMPLES XXII-XXXVII
The procedure of Example XXI was followed except that the
treatments shown in Table II were used.
TABLE II ______________________________________ Lap Shear Strength
Example Treatment/Type (MPa) ______________________________________
XXII CRYSTIC .RTM. 272 (Polyester) <1 XXIII DERAKANE .RTM.
411-45 (Vinyl ester) <1 XXIV TENAXATEX .RTM. 4611 (nitrile
phenolic) <1 XXV NUTRIM .RTM. 5003 (Nitrile phenolic <1
ironed-on film) XXVI as XXV but cured 30 mins at 150.degree.C. 3
XXVII INDATEX .RTM. SE765 (Acrylic emulsion) <1 XXVIII TENAXATEX
.RTM.3964 (Polyvinyl acetate 2 emulsion XXIX PERMABOND .RTM. C
(Cyanoacrylate) 2 XXX INDASOL .RTM. NS240 (Natural rubber 3 latex)
XXXI INDASOL .RTM. CS1659 (Neoprene latex) 3 XXXII CRODAFIX .RTM.
27-8-700 (Ethylene/vinyl 3 acetate emulsion) XXXIII IGETABOND 7B100
(Polyolefine 3.5 copolymer hot melt) XXXIV CRODAGRIP .RTM. 14-00300
(2 pot poly- 4 urethane) XXXV Polyfunctional acrylate terminated 4
polymer containing urethane linkages with 80 pphr talc as filler
XXXVI PERMABOND .RTM. E04 (2 pot epoxy) 4.5 XXXVII PERMABOND .RTM.
F241 (2 pot acrylic 5.5 covered by PTFE sheet until cured)
______________________________________
EXAMPLE XXXIIIA
The procedure of Example XXXIII was also carried out using
Crystic.RTM.M225A sheet moulding compound (fire retardant grade).
On impact testing it was found that the GRP laminate could be
fractured without penetrating the stainless steel facing. There was
good adhesion between the FRP and metal face (single lap shear
stength 3.5 MPa). Furthermore, after curing, the laminate was
easily removed from the mould. The mould walls were of chrome
plated steel; hence the laminate did not adhere to them.
EXAMPLES XXXVIII-L
The same procedure as in Examples I-XX or XXI-XXXVII were used but
the stainless steel was replaced by thin sheets of other
metals.
______________________________________ Lap Shear Strength MPa
______________________________________ XXXVIII Aluminum as Ex. I 6
as Ex. XXI 5 XXXIX Copper as Ex. XIX 5.5 as Ex. XXXVII 4.5 XL Brass
as Ex. XVIII 4 as Ex. XXI 4 XLI Zinc as Ex. I 6.5 as Ex. XXXIV 4.5
XLII Phosphor Bronze as Ex. XX 6.5 as Ex. XXI 3.5 XLIII Nickel as
Ex. XX 7 as Ex. XXI 6 XLIV Tin as Ex. XX 5 as EX. XXXV 5 XLV
Titanium as Ex. XVIII 5 as Ex. XXXVI 4.5 XLVI Molybdenum as Ex. XIX
9 as Ex. XXXIV 7 XLVII as Ex. I 2 as Ex. XXXVII 5 XLVIII Chromium
as Ex. XV 4 as Ex. XXXVI 5 XLIX Mild Steel as Ex. XX 9 as Ex. XXI 7
L Galvanised as Ex. XIX 7.5 Steel as Ex. XXXIV 5.5
______________________________________
EXAMPLE LI
A sheet of stainless steel (0.5 mm thick) was solvent degreased and
coated with INDASOL.RTM.MS419NF (nitrile rubber adhesive) at 200
g/m.sup.2. This was allowed to dry and a glass reinforced phenolic
resin laminate laid up on the treated surface using 4 layers of
chopped strand mat (450 g/m.sup.2) at a resin:glass ratio of 3:1.
After the glass reinforced phenolic resin of the resultant
composite had been allowed to cure at ambient temperature it was
difficult to separate from the stainless steel and the bond had a
single lap shear strength of 3 MPa.
EXAMPLE LII
The same procedure as in Example LI was followed except that the
laminating resin was a QUAKER furane resin.
EXAMPLE LIII
A sheet of aluminum (0.5 mm thick) was solvent degreased and
treated with PERMABOND.RTM.E04 (a two pot epoxy) at 200 g/m.sup.2.
This was allowed to cure and a glass reinforced epoxide laminate
laid up on the treated surface using 4 layers of chopped strand mat
(450 g/m.sup.2) Epikote 828+Epicure at a resin:glass ratio of 3:1.
After the glass reinforced epoxide laminate of the resultant
composite had been allowed to cure at ambient temperature it was
extremely difficult to separate from the metal (lap shear strength
6 MPa).
EXAMPLES LIV-LVII
A sheet of aluminum (0.25 mm thick) was solvent degreased and
treated with INDASOL.RTM.MS419NF (nitrile rubber adhesive) at 200
g/m.sup.2. This was allowed to dry and one layer of 450 g/m.sup.2
chopped strand mat (CSM) with Crystic 272 at a resin:glass ratio of
2.5:1 was laid up on the treated surface. A 12.7 mm thick PVC foam
sheet was pushed into the wet resin layer and a 2 layer CSM (450
g/m.sup.2 per layer)-Crystic 272 laminate was laid up on top of the
foam to form a composite which, on curing at ambient temperature,
provided a stiff metal clad foam cured laminate structure.
This procedure was repeated using polyester foam as a replacement
core material, phenolic foam as a replacement core material and
polyurethane as a replacement core materal.
EXAMPLE LVIII
Metal faced sectional tank panels can readily be made using the
techniques developed.
A thin stainless steel sheet 4'4" square.times.0.5 mm thick had
four corner squares 2".times.2" cut from it and it was then folded
to give a tray shaped sheet 4'.times.4' flanges all round. The
corners were joined by welding or soldering. The inside surface of
the formed tray was solvent degreased and treated with a nitrile
rubber adhesive at 200 g/m.sup.2 and allowed to dry.
The shaped primed metal tray was then transferred to the female
tool in a press where it effectively became part of the tool. A
charge of sheet moulding compound (SMC) (Crystic.RTM.M125)
sufficient to give the required laminate thickness was then loaded
and the mould closed. Under the influence of pressure and heat the
SMC of the resultant composite flowed and cured so that when
released a stainless steel clad FRP sectional tank panel was
obtained. Th bond between the stainless steel and the FRP was
excellent and the panel had the following advantages over
traditional steel or unfaced SMS panels:
a. the external SMC face requires minimal maintenance,
b. the internal surface is a well known and trusted corrosion
resistant surface acceptable in the food industry,
c. the internal surface is impermeable and unlike SMC will not lose
mechanical properties or blister on long contact with water,
d. the internal surface is not broken when large impact loads are
applied to the outer surface.
Although the tray shape was made by cutting and welding the edges
it can also be made by drawing the metal.
Simila processes can be used to manufacture automotive body parts,
printed, circuit boards, filler plates and container panels
etc.
EXAMPLE LIX
Metal lined pipes were formed by using the following technique:
A thin stainless steel sheet (0.25 mm thick) 12 inches wide was
wound round a 12" diameter mandrel in a spiral fashion with a 1"
overlap. The overlap joints were sealed using
CRODAGRIP.RTM.14-00300 (a 2 pot polyurethane).
The complete surface of the stainless steel was then covered with
the same 2 pot polyurethane and allowed to dry to a layer 0.25 mm
thick.
Glass fibre rovings impregnated with CRYSTIC.RTM.272 (an
isophthalic acid based unsaturated polyester resin), suitably
catalysed and accelerated, were spirally wound on top of the primed
stainless steel to give a reinforced layer 5 mm thick.
After allowing the resin of the resultant composite to cure at
ambient temperature the pipe was removed from the mandrel.
The thin stainless steel liner provided a perfect barrier to a wide
range of chemical environments and the structural rigidity was
provided by the FRP winding.
Chemical tanks can be made by a similar process.
EXAMPLE LX
Metal lined ducts and pipes were made by an alternative technique
in which the 0.25 mm stainless steel sheet 36" wide was joined
longitudinally using an overlap joint and the metal chop bonded
together with Crodagrip .RTM.14-00300 (a two pot polyurethane). The
11" diameter metal liner was supported on a mandrel and the
exterior surface was coated with a polyfunctional acrylate
terminated polymer containing urethane linkages which had been
suitably catalysed and accelerated. The priming layer with allowed
to cure and glass rovings impregnated with DERAKANE .RTM.411-45,
suitably catalysed and accelerated, were spirally wound on top of
the primed metal to give a reinforced layer 5 mm thick. After
allowing the resin of the resultant composite to cure at ambient
temperature the 12" diameter metal lined pipe thus produced was
removed from the mandrel.
EXAMPLE LXI
Larger diameter pipes and tanks can be made by longitudinally
jointing more than one sheet of metal liner. This can be done by
using a fold stitching pistol, e.g. ATLAS COPCO Tagger 310, with a
jointing film of PTFE tape between the metal faces and then folding
over the jointed flange before applying a treatment of suitable
adhesive. Thus 4 sheet of stainless steel 36" wide were joined
together longitudinally as stated above to give the body of a
circular tank approximately 45" diameter. This was placed on a
mandrel and the external surface solvent degreased and coated with
INDASOL .RTM.MS419NF. When the coating was dry glass fibre rovings
impregnated with CRYSTIC.RTM.272, suitably catalysed and
accelerated, were spirally wound on top of the primed steel to give
a reinforced layer 5 mm thick. The resultant composite provided,
after curing at ambient temperature, a metal lined tank which was
removed from the mandrel.
EXAMPLE LXII
Thin aluminum sheet 0.45 mm thick was abraded, degreased and coated
with a polyfunctional acrylate terminated polymer containing
urethane linkages which contained 80 pphr talc filler, suitably
catalysed and accelerated, at 200 g/m.sup.2. After this had cured
CRYSTIC .RTM.272 resincontaining 33% by weight FILLITE.RTM. (silica
hollow microspheres) was suitably catalysed and accelerated and
poured onto the sheet to a depth of 10 mm. After this layer of the
resultant composite had been allowed to cure at ambient
temperature, one layer of 450 g/m.sup.2 glass chopped strand mat
was laid down and impregnated with catalysed and accelerated
CRYSTIC .RTM.272.
The resultant metal clad laminate could be used as a decorative
building panel with the aluminum surface providing good
weatherability.
EXAMPLE LXIII
Two sheets of stanless steel were solvent degreased treated with
INDASOL.RTM.MS419NF and allowed to dry. A layer of sheet moulding
compound was sandwiched between the two treated surfaces and the
resultant composite cured under heat and pressure. The double faced
metal coated laminate showed good adhesion at all the interfacial
bond lines.
Dissimilar metals can be used for each face to satisfy different
environmental conditions.
EXAMPLE LXIV
A sheet of stainless steel (0.25 mm thick) was solvent degreased
and treated with INDASOL.RTM.MS419NF and allowed to dry. A laminate
containing 6 layers of 300 g/m.sup.2 woven KEVLAR.RTM.
reinforcement and CRYSTIC.RTM.272 at a resin:fibre ratio of 1:1 was
laid up on the primed steel. After the resin of the resultant
composite had been allowed to cure at ambient temperature, the
resulting material was stronger and stiffer than an equivalent
glass reinforced laminate due to the inherent better properties of
KEVLAR fibres.
EXAMPLE LXV
A thin satin finish stainless steel sheet was pressed and drawn to
the shape of an automobile boot lid. It was degreased with solvent
and the inside surface coated with CRODAGRIP.RTM.14-00300 at 200
g/m.sup.2 which was allowed to cure. The shaped primed steel was
then placed in a two part mould and the requisite amount of
continuous strand glass fibre mat, tailored to fit the mould, laid
on to the primed surface. The mould was closed and suitably
catalysed and accelerated CRYSTIC.RTM.272 (an unsaturated polyester
resin) was injected into the mould until all the air in the mould
had been pushed out. Injection of resin then ceased and the resin
of the resultant composite was allowed to cure at ambient
temperature. When the mould was opened a FRP boot lid was obtained
with an attractive satin finish stainless steel face which had
excellent adhesion to the FRP.
In the above examples, various commercial products have been
described by trade names which are registered Trade Marks of the
following respective companies.
CRYSTIC-Scott Bader Company Limited.
DERAKANE-Dow Chemical Company.
TENAXATEX-Williams Adhesives Limited.
INDASOL-Industrial Adhesives Limited.
INDATEX-Industrial Adhesives Limited.
PERMABOND-Permabond Adhesives Limited.
CRODAFIX-Croda Adhesives Limited.
CRODAGRIP-Croda Adhesives Limited.
NUTRIM-Aluminium Developments Limited.
IGETABOND-Sumitomo Chemical Company Limited.
LEVLAR-E I du Pont de Nemours Inc.
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