U.S. patent application number 14/895300 was filed with the patent office on 2016-05-05 for medium- or high-voltage electric device.
The applicant listed for this patent is NEXANS. Invention is credited to Ruben Briceno Garcia, Lucile Carteron, Philippe Cassagnau, Phillippe Chaumont, Francoise Fenouillot, Yannick Goutille, Laurent Keromnes, Jean-Michel Marty.
Application Number | 20160125975 14/895300 |
Document ID | / |
Family ID | 49237305 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160125975 |
Kind Code |
A1 |
Briceno Garcia; Ruben ; et
al. |
May 5, 2016 |
MEDIUM- OR HIGH-VOLTAGE ELECTRIC DEVICE
Abstract
The invention relates to an electrical device (1,20,30)
comprising a cross-linked layer (3, 4, 5, 21, 22, 23, 31, 32)
produced from a polymer composition comprising: at least one
polymer A comprising at least one epoxy function; and a
cross-linking agent B comprising at least one reactive function
that can react with the epoxy function of said polymer A in order
to allow the cross-linking of said polymer A. The device is
characterised in that the polymer composition also comprises a
compound C comprising: at least one aromatic group; and a reactive
group that can physically interact with the hydroxyl function
formed by the opening of said epoxy function during the
cross-linking of polymer A.
Inventors: |
Briceno Garcia; Ruben;
(Villeurbanne, FR) ; Marty; Jean-Michel; (Sainte
Foy Lyon, FR) ; Carteron; Lucile; (Lyon, FR) ;
Goutille; Yannick; (Velleurbanne, FR) ; Keromnes;
Laurent; (Chaponost, FR) ; Fenouillot; Francoise;
(L'isle D'abeau, FR) ; Chaumont; Phillippe;
(Vaulx-en-Velin, FR) ; Cassagnau; Philippe;
(Millery, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEXANS |
Paris |
|
FR |
|
|
Family ID: |
49237305 |
Appl. No.: |
14/895300 |
Filed: |
June 3, 2014 |
PCT Filed: |
June 3, 2014 |
PCT NO: |
PCT/FR2014/051316 |
371 Date: |
December 2, 2015 |
Current U.S.
Class: |
174/84R |
Current CPC
Class: |
H01R 4/10 20130101; H01B
3/40 20130101; H01B 3/441 20130101; C08F 224/00 20130101; H01B
3/447 20130101 |
International
Class: |
H01B 3/44 20060101
H01B003/44; C08F 224/00 20060101 C08F224/00; H01R 4/10 20060101
H01R004/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2013 |
FR |
1355102 |
Oct 1, 2013 |
FR |
1359471 |
Claims
1. An electrical device having a crosslinked layer obtained from a
polymer composition comprising: at least one polymer A comprising
at least one epoxy functional group, and a crosslinking agent B
comprising at least one reactive functional group capable of
reacting with the epoxy functional group of said polymer A in order
to make possible the crosslinking of said polymer A, wherein the
polymer composition additionally comprises a compound C comprising:
at least one aromatic group, and a reactive group capable of
interacting physically with the hydroxyl functional group formed by
the opening of said epoxy functional group during the crosslinking
of the polymer A.
2. The device as claimed in claim 1, wherein the compound C is
different from the polymer A and from the crosslinking agent B.
3. The device as claimed in claim 1, wherein the compound C is an
antioxidant.
4. The device as claimed in claim 1, wherein the reactive group of
the compound C is a hydrogen atom.
5. The device as claimed in claim 1, wherein the reactive group of
the compound C is in the form of a hydroxyl (OH) group and/or of an
amine (NH) group.
6. The device as claimed in claim 1, wherein the aromatic group of
the compound C is a benzene group or one of its derivatives.
7. The device as claimed in claim 1, wherein the aromatic group
together with the reactive group form a phenol group.
8. The device as claimed in claim 7, wherein the phenol group is
disubstituted in the ortho position.
9. The device as claimed in claim 7, wherein the phenol group is a
di(tert-butyl)-4-hydroxyphenyl group.
10. The device as claimed in claim 1, wherein the aromatic group
together with the reactive group form an aminobenzene group, the
amine of which is of the primary or secondary type.
11. The device as claimed in claim 1, wherein the polymer
composition comprises at most 10 parts by weight of compound C per
100 parts by weight of polymer(s) in the composition.
12. The device as claimed in claim 1, wherein the polymer A
comprises at least one compound chosen from glycidyl esters.
13. The device as claimed in claim 1, wherein the polymer A
comprises at most 10% by weight of epoxy functional group.
14. The device as claimed in claim 1, wherein the polymer A
comprises at least 0.1% by weight of epoxy functional group.
15. The device as claimed in claim 1, wherein the epoxy functional
group of the polymer A is grafted to said polymer.
16. The device as claimed in claim 1, wherein the polymer A is a
copolymer obtained from at least two monomers, one of the monomers
comprising said epoxy functional group.
17. The device as claimed in claim 1, wherein the polymer A
additionally comprises at least one acrylate functional group.
18. The device as claimed in claim 1, wherein the crosslinking
agent B is a polymer compound or a nonpolymer compound.
19. The device as claimed in claim 1, wherein the reactive
functional group of the crosslinking agent B is chosen from an
anhydride functional group, a carboxyl functional group and an
amine functional group.
20. The device as claimed in claim 19, wherein the amine functional
group of the crosslinking agent is a primary amine or a secondary
amine.
21. The device as claimed in claim 1, wherein the crosslinking
agent B comprises at least two reactive functional groups.
22. The device as claimed in claim 19, wherein the crosslinking
agent comprises an amine functional group and a carboxyl functional
group.
23. The device as claimed in claims 19 and 21, characterized in
that the crosslinking agent comprises two amine functional
groups.
24. The device as claimed in claim 1, wherein said device is an
electric cable comprising an elongated electrically conducting
component surrounded by said crosslinked layer.
25. The device as claimed in claim 1, wherein said device is an
electric cable accessory, said accessory comprising said
crosslinked layer.
26. The device as claimed in claim 25, wherein the accessory is an
electric cable joint or termination.
27. The device as claimed in claim 1, wherein the crosslinked layer
is an electrically insulating layer.
28. The device as claimed in claim 1, wherein the crosslinked layer
is a semiconducting layer.
29. The device as claimed in claim 1, wherein said device further
comprises a first semiconducting layer (3) surrounding the
elongated electrically conducting component (2), an electrically
insulating layer (4) surrounding the first semiconducting layer (3)
and a second semiconducting layer (5) surrounding the electrically
insulating layer (4), the crosslinked layer being at least one of
these three layers.
Description
[0001] The present invention relates to an electrical device of the
electric cable or electric cable accessory type. It typically but
not exclusively applies to the fields of low-voltage (in particular
of less than 6 kV), medium-voltage (in particular from 6 to 45-60
kV) or high-voltage (in particular greater than 60 kV, and which
can range up to 800 kV) power cables, whether they are direct
current or alternating current.
[0002] Power cables typically comprise a central electrical
conductor and at least one electrically insulating layer
crosslinked by techniques well known to a person skilled in the
art, in particular by the peroxide route.
[0003] The peroxide route is tending to be increasingly avoided
with respect to the decomposition products of peroxide, which
exhibit disadvantages during the manufacture of the cable, indeed
even once the cable is in the operational configuration. This is
because, during the crosslinking, the peroxides decompose and form
crosslinking by-products, such as, in particular, methane,
acetophenone, cumyl alcohol, acetone, tert-butanol,
.alpha.-methylstyrene and/or water. The formation of water from
cumyl alcohol is relatively slow and can occur after several
months, indeed even a few years, once the cable is in the
operational configuration. The risk of breakdown of the crosslinked
layers is thus significantly increased. In addition, if the methane
formed during the crosslinking stage is not discharged from the
crosslinked layers, risks related to the explosiveness of methane
and its ability to ignite cannot be ignored. This gas can also
cause damage once the cable is put into service. Even if solutions
exist for limiting the presence of methane within the cable, such
as, for example, heat treating the cable in order to accelerate the
diffusion of methane outside the cable, they become lengthy and
expensive when the thickness of the crosslinked layers is high.
[0004] Mention may be made, as example of crosslinking process not
using the peroxide route, of the document U.S. Pat. No. 4,826,726,
which describes a heat-resistant electric cable comprising an
elongated electrical conductor surrounded by a crosslinked layer
obtained from a composition comprising an ethylenic copolymer
comprising an oxirane functional group and a polymeric compound, as
crosslinking agent, of the copolymer of ethylene and of unsaturated
dicarboxylic acid anhydride type.
[0005] However, once said composition has been crosslinked, the
layer obtained does not exhibit optimum properties of tensile
strength and elongation at break, in particular during the life of
the electric cable (cf. aging).
[0006] The aim of the present invention is to overcome the
disadvantages of the techniques of the prior art by providing an
electrical device, of the electric cable or electric cable
accessory type, comprising a crosslinked layer, the manufacture of
which significantly limits the presence of crosslinking
by-products, such as, for example, methane and/or water, while
guaranteeing optimum mechanical properties (tensile strength and
elongation at break) during the life of the electrical device.
[0007] A subject matter of the present invention is an electrical
device comprising a crosslinked layer obtained from a polymer
composition comprising: [0008] at least one polymer A comprising at
least one epoxy functional group, and [0009] a crosslinking agent B
comprising at least one reactive functional group capable of
reacting with the epoxy functional group of said polymer A in order
to make possible the crosslinking of said polymer A, characterized
in that the polymer composition additionally comprises a compound C
comprising: [0010] at least one aromatic group, and [0011] a
reactive group capable of interacting physically with the hydroxyl
functional group formed by the opening of said epoxy functional
group during the crosslinking of the polymer A.
[0012] By virtue of the invention, the crosslinked layer makes it
possible to avoid the use of organic peroxide while guaranteeing,
on the one hand, a high level of crosslinking and, on the other
hand, very good mechanical properties of the type consisting of
tensile strength and elongation at break according to French
standard NF EN 608 11-1-1, during the life of the electrical
device.
[0013] In addition, the crosslinked layer of the invention exhibits
the advantage of being economical, easy to process, in particular
by extrusion, and easy to manufacture since it does not require
resorting to restrictive venting processes.
[0014] The Compound C
[0015] The reactive group of the compound C is in particular
capable of interacting physically with the hydroxyl functional
group which is formed during the crosslinking of the polymer A with
the compound B. In other words, the reactive group of the compound
C is not capable of interacting chemically with the hydroxyl
functional group formed from the epoxy functional group of the
polymer A during the crosslinking of the polymer composition. It
thus does not modify the chemical structure of said hydroxyl
functional group; in particular, it is not capable of forming a
chemical bond of the covalent type with said hydroxyl functional
group.
[0016] More particularly, said reactive group is capable of forming
van der Waals' bonds and/or hydrogen bonds with the hydroxyl groups
originating from the epoxy functional groups of the polymer A, once
opened.
[0017] The compound C makes it possible to significantly limit,
indeed even to prevent, the epoxy functional groups liable to have
not reacted during the crosslinking of the polymer composition from
reacting chemically by etherification with the hydroxyl groups
originating from the epoxy functional groups, once opened.
[0018] The compound C will thus sterically hinder the hydroxyl
groups originating from the epoxy functional groups already opened
and will thus significantly limit, indeed even prevent, the
etherification of the epoxy functional groups liable to have not
reacted during the crosslinking.
[0019] The compound C can be different from the polymer A and from
the crosslinking agent B. It is preferably an organic compound.
[0020] The compound C can be a polymeric or nonpolymeric
compound.
[0021] "Nonpolymeric compound" is understood to mean a compound
other than a polymer. In other words, this compound does not in
particular result from the covalent linking of a large number of
identical or different monomer units and more particularly does not
result from the covalent linking of at least two identical or
different monomer units.
[0022] Particularly preferably, the compound C is an
antioxidant.
[0023] The reactive group of the compound C can be a hydrogen atom,
in particular in the form of a hydroxyl (OH) group and/or of an
amine (NH) group, it being possible for the amine to be of the
primary or secondary type.
[0024] The aromatic group of the compound C can be a benzene group
or one of its derivatives.
[0025] According to a first alternative form, the aromatic group
together with the reactive group can form a phenol group.
[0026] Preferably, the phenol group is disubstituted in the ortho
position.
[0027] Mention may be made, by way of examples, of the following
compounds, comprising at least one phenol group disubstituted in
the ortho position: [0028]
2-methyl-4,6-bis[(octylthio)methyl]phenol (Irgastab KV10; CAS No.
110553-27-0); [0029] benzenepropanoic acid,
3,5-bis(1,1-dimethylethyl)-4-hydroxy-,
1,1'-(2,2-bis((3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)-1-oxopropox-
y)methyl)-1,3-propanediyl) ester (Irganox 1010; CAS No. 6683-19-8);
[0030] 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid
octadecyl ester (Irganox 1076; CAS No. 2082-79-3); [0031]
1,3,5-trimethyl-2,4,6-tris[3',5'-di(tert-butyl)-4'-hydroxybenzyl]benzene
(Irganox 1330; CAS No. 1709-70-2); [0032] thiodiethylene
bis{3-[3,5-di(tert-butyl)-4-hydroxyphenyl]propionate} (Irganox
1035; CAS No. 41484-35-9).
[0033] Particularly preferably, the phenol group is a
di(tert-butyl)-4-hydroxyphenyl group. Mention may be made, by way
of examples, of Irganox 1010, Irganox 1076, Irganox 1330 or Irganox
1035.
[0034] In this first alternative form, the compound C can thus be
Irganox 1035 or else a compound which is not Irganox 1035.
[0035] According to a second alternative form, the aromatic group
together with the reactive group form an aminobenzene group, the
amine of which is of the primary or secondary type. Mention may be
made, by way of examples, of 1,2-dihydro-2,2,4-trimethylquinoline
or poly(1,2-dihydro-2,2,4-trimethylquinoline) (CAS No.
26780-96-1).
[0036] The compound C of the invention can additionally comprise a
thioether group. Mention may be made, by way of examples, of
Irgastab KV10 or Irganox 1035.
[0037] The polymer composition in accordance with the invention can
comprise at most 10.0 parts by weight of compound C per 100 parts
by weight of polymer(s) in the composition, preferably at most 5.0
parts by weight of compound C per 100 parts by weight of polymer(s)
in the composition, preferably at most 2.0 parts by weight of
compound C per 100 parts by weight of polymer(s) in the composition
and particularly preferably at most 1.0 part by weight of compound
C per 100 parts by weight of polymer(s) in the composition.
[0038] The polymer composition in accordance with the invention can
comprise at least 0.01 part by weight of compound C per 100 parts
by weight of polymer(s) in the composition and preferably at least
0.1 part by weight of compound C per 100 parts by weight of
polymer(s) in the composition.
[0039] In the present invention, when reference is made to "100
parts by weight of polymer(s)", this is understood to mean
preferably the polymer or polymers other than the crosslinking
agent B and the compound C in the polymer composition (when the
crosslinking agent B and/or the compound C are in the polymer
form).
[0040] The Polymer A
[0041] The epoxy functional group (i.e., the epoxide functional
group) or the polymer A is more particularly an oxirane functional
group (i.e., an ethylene oxide group).
[0042] Preferably, the epoxy functional group can be contributed by
a compound comprising said epoxy functional group, it being
possible for this compound to be chosen from glycidyl esters. Thus,
the polymer of the invention can comprise glycidyl ester
groups.
[0043] The polymer A of the invention can comprise at most 10% by
weight of epoxy functional group and preferably at most 5% by
weight of epoxy functional group.
[0044] The polymer A of the invention can comprise at least 0.1% by
weight of epoxy functional group and preferably at least 1% by
weight of epoxy functional group.
[0045] According to a first alternative form, the epoxy functional
group of the polymer A can be grafted to said polymer. The polymer
comprising at least one epoxy functional group of the invention is,
according to this first alternative form, an epoxy-grafted polymer.
In other words, the polymer according to the invention can be a
polymer comprising at least one epoxy functional group grafted to
the macromolecular chain (i.e., main chain or backbone) of said
polymer. The ends of the macromolecular chain of the polymer may or
may not for their part be grafted with the epoxy functional
group.
[0046] According to a second alternative form, the polymer
comprising at least one epoxy functional group of the invention can
be a copolymer obtained from at least two monomers, one of the two
monomers comprising said epoxy functional group. Said monomer
comprising said epoxy functional group can be chosen from the
following compounds: butenecarboxylic acid monoglycidyl ester,
glycidyl methacrylate, glycidyl acrylate, methylglycidyl acrylate,
methylglycidyl methacrylate, itaconic acid glycidyl ester,
7,8-epoxy-1-octyl methacrylate, itaconic acid methylglycidyl ester,
7,8-epoxy-1-octyl vinyl ether, vinyl glycidyl ether, allyl glycidyl
ether and 2-methyl-2-propenyl glycidyl ether.
[0047] Mention may be made, by way of example, as polymer
comprising at least one epoxy functional group, of a copolymer of
ethylene and glycidyl methacrylate.
[0048] The polymer A of the invention is more particularly an
organic polymer, making it possible in particular to shape the
polymer composition by extrusion.
[0049] The polymer A can comprise at least one polyolefin. The term
"polyolefin" as such means generally olefin polymer of the olefin
homopolymer or copolymer type. Preferably, said olefin polymer is a
noncyclic olefin polymer.
[0050] In the present invention, it will be preferable to use an
ethylene polymer (ethylene homo- or copolymer) or a propylene
polymer (propylene homo- or copolymer).
[0051] The first alternative form of the invention can be used with
an epoxy-grafted olefin homopolymer or an epoxy-grafted olefin
copolymer.
[0052] The second alternative form of the invention can be used
with a copolymer obtained from an olefin monomer and a monomer
comprising at least one epoxy functional group, as described
above.
[0053] The polymer composition of the invention can comprise more
than 50.0 parts by weight of polymer(s) comprising at least one
epoxy functional group (i.e., polymer A) per 100 parts by weight of
polymer(s) (i.e., polymer matrix) in the polymer composition;
preferably at least 70 parts by weight of polymer(s) A per 100
parts by weight of polymer(s) in said polymer composition; and
particularly preferably at least 90 parts by weight of polymer(s) A
per 100 parts by weight of polymer(s) in said polymer
composition.
[0054] In the present invention, when reference is made to "100
parts by weight of polymer(s)", this is understood to mean
preferably the polymer or polymers other than the crosslinking
agent B and the compound C in the polymer composition (when the
crosslinking agent B and/or the compound C are in the polymer
form).
[0055] Particularly advantageously, the constituent polymer or
polymers of the polymer composition are solely one or more
olefin-based polymer(s) (i.e., olefin homopolymer and/or
copolymer).
[0056] In a specific embodiment, the polymer of the invention can
additionally comprise at least one acrylate functional group. This
acrylate functional group advantageously makes it possible to
render the polymer of the invention supple and more flexible.
[0057] According to a first alternative form, the acrylate
functional group can be grafted to the polymer of the invention.
The polymer of the invention is, according to this first
alternative form, an acrylate-grafted polymer. In other words, the
polymer according to the invention can be a polymer comprising at
least one acrylate functional group grafted to the macromolecular
chain (i.e., main chain or backbone) of said polymer. The ends of
the macromolecular chain of the polymer may or may not, for their
part, be grafted with the acrylate functional group.
[0058] According to a second alternative form, the polymer of the
invention can be a copolymer obtained from at least two monomers,
one of the two monomers comprising said acrylate functional group.
Mention may be made, by way of example, of the terpolymer of
ethylene, methyl acrylate and glycidyl methacrylate.
[0059] The Crosslinking Agent B
[0060] The crosslinking agent B of the invention can be a polymeric
compound or a nonpolymeric compound. Preferably, the crosslinking
agent is other than the polymer A.
[0061] It will be preferable to use a nonpolymeric compound as
compound B since this type of crosslinking agent advantageously
makes it possible to improve the resistance to electrical
breakdowns of the crosslinked layer, in particular according to the
standard IEC 62539, at 20.degree. C., based on the Weibull
distribution.
[0062] When the crosslinking agent of the invention is of the
"nonpolymeric" type, it does not result from the covalent linking
of a large number of identical or different monomer units and
preferably it does not result from the covalent linking of at least
two identical or different monomer units.
[0063] The reactive functional group of the crosslinking agent is
capable of reacting with the epoxy functional group of the said
polymer in order to make possible the crosslinking of said polymer.
It will react directly with the epoxy functional group after
opening the epoxy during a rise in temperature.
[0064] The reactive functional group of the crosslinking agent can
be chosen from an anhydride functional group, a carboxyl functional
group and an amine functional group.
[0065] When the crosslinking agent comprises at least one amine
functional group, the amine functional group is a primary or
secondary amine.
[0066] In a specific embodiment, the crosslinking agent can
comprise at least two reactive functional groups. These two
reactive functional groups can be identical or different and can be
chosen without distinction from an anhydride functional group, a
carboxyl functional group and an amine functional group.
[0067] The crosslinking agent can preferably comprise an amine
functional group and a carboxyl functional group.
[0068] The crosslinking agent can preferably comprise two amine
functional groups.
[0069] Mention may be made, as examples of nonpolymeric
crosslinking agent, of amino acids, diamines, anhydrides, Lewis
acids or Bronsted acids.
[0070] The preferred nonpolymeric crosslinking agent of the
invention is chosen from: [0071] a nonpolymeric compound comprising
at least one amine functional group and at least one carboxyl
functional group, i.e. an amino acid, [0072] a nonpolymeric
compound comprising at least one anhydride functional group,
preferably in combination with a crosslinking catalyst, and [0073]
one of their mixtures.
[0074] The amino acid typically comprises two functional groups: a
carboxyl --COOH functional group and an amine functional group
which is preferably of the primary amine --NH.sub.2 type. The
carbon chain separating the carboxyl functional group from the
amine functional group can comprise from 1 to 50 carbon atoms and
preferably from 1 to 20 carbon atoms. Conventionally, the carboxyl
and amine functional groups can be positioned at the ends of the
main carbon chain of said amino acid, the main carbon chain
preferably being an unbranched chain. The amino acid can also be an
.alpha.-amino acid, which is defined by the fact that the amine
functional group is bonded to the carbon atom adjacent to the
carboxyl functional group (the .alpha. carbon).
[0075] Mention may be made, as preferred example, of
11-aminoundecanoic acid.
[0076] When the crosslinking agent is a nonpolymeric compound
comprising an anhydride functional group, the composition can
additionally comprise a crosslinking catalyst or, in other words,
said nonpolymeric compound comprising an anhydride functional group
is combined, in the polymer composition, with a crosslinking
catalyst.
[0077] The nonpolymeric compound comprising an anhydride functional
group is more particularly an organic compound. In other words, the
nonpolymeric compound comprising an anhydride functional group is
composed solely of carbon and of hydrogen and optionally of
oxygen.
[0078] More particularly, said nonpolymeric compound comprising an
anhydride functional group additionally comprises an aliphatic
chain comprising at least five carbon atoms, it being possible for
this chain to be saturated or unsaturated.
[0079] Mention may be made, by way of example, of dodecenylsuccinic
anhydride.
[0080] Mention may be made, as examples of polymeric crosslinking
agent, of copolymers of olefin and unsaturated monocarboxylic acid,
copolymers of olefin and unsaturated dicarboxylic acid or
copolymers of olefin and unsaturated dicarboxylic acid anhydride.
The olefin cited for these copolymers is preferably ethylene.
[0081] The polymer composition in accordance with the invention can
comprise an amount of crosslinking agent B in an amount necessary
and sufficient to obtain the crosslinked layer.
[0082] By way of example, the polymer composition in accordance
with the invention can comprise at most 15.0 parts by weight of
crosslinking agent B per 100 parts by weight of polymer(s) in the
composition, preferably at most 10.0 parts by weight of
crosslinking agent B per 100 parts by weight of polymer(s) in the
composition and preferably at most 5.0 parts by weight of
crosslinking agent B per 100 parts by weight of polymer(s) in the
composition.
[0083] The polymer composition in accordance with the invention can
comprise at least 0.1 part by weight of crosslinking agent B per
100 parts by weight of polymer(s) in the composition and preferably
at least 0.5 part by weight of crosslinking agent B per 100 parts
by weight of polymer(s) in the composition.
[0084] In the present invention, when reference is made to "100
parts by weight of polymer(s)", this is understood to mean
preferably the polymer or polymers other than the crosslinking
agent B and the compound C in the polymer composition (when the
crosslinking agent B and/or the compound C are in the polymer
form).
[0085] Filler-Comprising Polymer Composition
[0086] The polymer composition of the invention can additionally
comprise a filler.
[0087] The filler of the invention can be an inorganic or organic
filler. It can be chosen from a flame-retardant filler and an inert
filler (or noncombustible filler).
[0088] By way of example, the flame-retardant filler can be a
hydrated filler chosen in particular from metal hydroxides, such
as, for example, magnesium dihydroxide (MDH) or aluminum
trihydroxide (ATH). These flame-retardant fillers act mainly by the
physical route by decomposing endothermically (e.g., release of
water), which has the consequence of lowering the temperature of
the crosslinked layer and of limiting the propagation of the flames
along the electrical device. The term "flame retardant properties"
is used in particular.
[0089] For its part, the inert filler can be chalk, talc, clay
(e.g., kaolin), carbon black or carbon nanotubes.
[0090] According to a first alternative form, carbon black, as
electrically conducting filler, may be preferred in order to obtain
a semiconducting crosslinked layer and may be introduced into the
polymer composition in an amount sufficient to render the
composition semiconducting.
[0091] According to a second alternative form, carbon black may be
used in a small amount in order to improve the dielectric
properties of an electrically insulating layer.
[0092] The polymer composition can comprise at least 5 parts by
weight of fillers per 100 parts by weight of polymer in the
composition, preferably at least 10 parts by weight of filler per
100 parts by weight of polymer in the composition and more
preferably still at least 20 parts by weight of filler per 100
parts by weight of polymer in the composition.
[0093] The addition of a filler as described in the invention can
result in a rise in temperature during the processing of the
polymer composition and for this reason bring about premature
crosslinking of the polymer composition. Thus, in order to prevent
any premature crosslinking of the polymer composition, it is
preferable for the addition of the filler to be carried out so that
there is no premature crosslinking of the polymer composition
during its processing. More particularly, the crosslinking agent
can advantageously be added to the polymer composition in a stage
separate from and subsequent to that of the addition of the
filler.
[0094] According to another characteristic of the invention and in
order to guarantee an "HFFR" (Halogen-Free Flame Retardant)
electrical device, the electrical device, or in other words the
components which make up said electrical device, preferably does/do
not comprise halogenated compounds. These halogenated compounds can
be of any nature, such as, for example, fluoropolymers or
chloropolymers, such as polyvinyl chloride (PVC), halogenated
plasticizers, halogenated inorganic fillers, and the like.
[0095] Additives
[0096] The composition can typically additionally comprise
additives in an amount of 5 to 20 parts by weight per 100 parts by
weight of polymer in the composition. The additives are well known
to a person skilled in the art and can, for example, be chosen from
protective agents (e.g., UV stabilizers, agents for combating
copper), processing aids (e.g., plasticizers, viscosity reducers)
and pigments.
[0097] As mentioned above, the polymer composition can also
comprise a crosslinking catalyst in order to help in the
crosslinking. This crosslinking catalyst can more particularly be
used when the nonpolymeric crosslinking agent of the invention
comprises a reactive functional group of the anhydride type.
[0098] The crosslinking catalyst can be a catalyst of the Lewis
base type or, in other words, a nucleophilic chemical entity, one
of the constituents of which has a pair or more of free or
nonbonding electrons on its valence layer.
[0099] By way of examples, the crosslinking catalyst can be chosen
from imides, tertiary amines, imidazoles and one of their
mixtures.
[0100] Crosslinking catalysts of phenol type would be preferred in
the context of the invention, this catalyst being in particular a
Lewis base, such as, for example,
2,4,6-tris(dimethylaminoethyl)phenol.
[0101] When the polymer composition comprises a crosslinking
catalyst, in particular in the presence of a nonpolymeric
crosslinking agent comprising a reactive functional group of the
anhydride type, the polymer composition can comprise from 0.01 to
2.0 parts by weight of crosslinking catalyst per 100 parts by
weight of polymer and preferably from 0.05 to 1.0 part by weight of
crosslinking catalyst per 100 parts by weight of polymer.
[0102] The Crosslinked Layer and the Electrical Device
[0103] In the present invention, the crosslinked layer can be
easily characterized by the determination of its gel content
according to the standard ASTM D 2765-01.
[0104] More particularly, said crosslinked layer can advantageously
have a gel content, according to the standard ASTM D 2765-01, of at
least 40%, preferably of at least 50%, preferably of at least 60%
and particularly preferably of at least 70%.
[0105] The electrical device of the invention can be an electric
cable or an electric cable accessory.
[0106] According to a first embodiment, the device according to the
invention is an electric cable comprising an elongated electrically
conducting component surrounded by said crosslinked layer.
[0107] According to a second embodiment, the device according to
the invention is an electric cable accessory, said accessory
comprising said crosslinked layer. Said accessory is more
particularly intended to be used in combination with at least one
electric cable, the crosslinked layer being intended to surround at
least one end of an electric cable. The accessory can in particular
be an electric cable joint or termination.
[0108] The crosslinked layer of the invention can be an
electrically insulating layer or semiconducting layer.
[0109] According to a first embodiment, the crosslinked layer of
the invention can be an electrically insulating layer.
[0110] The crosslinked layer of this first embodiment in addition
advantageously exhibits a significantly improved resistance to
electrical breakdown.
[0111] More particularly, "electrically insulating layer" is
understood to mean a layer, the electrical conductivity of which
can be at most 1.10.sup.-9 S/m (siemens per meter) (at 25.degree.
C.).
[0112] When the electrical device of the invention is an electric
cable, at least two alternative forms of this first embodiment are
possible.
[0113] According to a first alternative form of the first
embodiment, the crosslinked layer of the invention is directly in
physical contact with the elongated electrically conducting
component. Reference is made, in this case, in particular to
low-voltage cable.
[0114] The polymer composition used to form the low-voltage cable
preferably comprises at least one filler, as defined above in the
invention.
[0115] In addition, the polymer of the invention can advantageously
comprise said acrylate functional group.
[0116] According to a second alternative form of the first
embodiment, the electric cable of the invention additionally
comprises a first semiconducting layer and a second semiconducting
layer, the first semiconducting layer surrounding the elongated
electrically conducting component, the electrically insulating
layer surrounding the first semiconducting layer and the second
semiconducting layer surrounding the electrically insulating layer.
Reference is made, in this case, in particular to medium- or
high-voltage cable.
[0117] The polymer composition used to form the medium- or
high-voltage cable and more particularly the electrically
insulating layer of said cable preferably does not comprise filler
or else does not comprise filler in an amount sufficient to modify
the electrical properties of the electrically insulating layer.
[0118] In addition, the polymer of the invention can advantageously
not comprise said acrylate functional group.
[0119] According to a second embodiment, the crosslinked layer of
the invention can be a semiconducting layer. This semiconducting
layer can be at least one of the semiconducting layers of a medium-
or high-voltage cable as defined above.
[0120] Consequently, the polymer composition of the invention can
additionally comprise an electrically conducting filler in an
amount sufficient to render the polymer composition semiconducting.
Mention may be made, for example, as electrically conducting
filler, of carbon black.
[0121] More particularly, "semiconducting layer" is understood to
mean a layer, the electrical conductivity of which can be at least
1.10.sup.-9 S/m (siemens per meter), preferably at least
1.10.sup.-3 S/m, and preferably can be less than 1.10.sup.3 S/m (at
25.degree. C.).
[0122] When the electrical device of the invention is an electric
cable, the latter can comprise a first semiconducting layer
surrounding the elongated electrically conducting component, an
electrically insulating layer surrounding the first semiconducting
layer and a second semiconducting layer surrounding the
electrically insulating layer, the crosslinked layer of the
invention being at least one of these three layers, preferably at
least two of said three layers and preferably said three layers.
Reference is made, in this case, in particular to medium- or
high-voltage cable.
[0123] In the present invention, the elongated electrically
conducting component of the electric cable can be a metal wire or a
plurality of metal wires, which is/are or is/are not twisted, in
particular made of copper or of aluminum, or one of their
alloys.
[0124] When the electrical device of the invention is an electric
cable accessory, said accessory more particularly surrounds at
least one end of an electric cable, said end being that which is
intended to be combined with said accessory.
[0125] The accessory can typically be a hollow longitudinal body,
such as, for example, an electric cable joint or termination, in
which at least a portion of an electric cable is intended to be
positioned.
[0126] The accessory comprises at least one semiconducting
component and at least one electrically insulating component, these
components being intended to surround an end of an electric cable.
The semiconducting component is well known for controlling the
geometry of the electric field, when the electric cable, in
combination with said accessory, is under voltage.
[0127] The crosslinked layer of the invention can be said
semiconducting component and/or said electrically insulating
component.
[0128] When the accessory is a joint, the latter makes it possible
to connect together two electric cables, the joint then
surrounding, in part, these two electric cables. More particularly,
the end of each electric cable intended to be connected is
positioned inside said joint.
[0129] When the device of the invention is an electric cable
termination, the latter surrounds, in part, an electric cable. More
particularly, the end of the electric cable intended to be
connected is positioned inside said termination.
[0130] The crosslinked layer of the invention can be a layer
extruded or a layer molded by processes well known to a person
skilled in the art. When the electrical device is an electric
cable, the crosslinked layer is preferably an extruded layer. When
the electrical device is an electric cable accessory, the
crosslinked layer is preferably a molded layer.
[0131] Another subject matter of the invention is a process for the
manufacture of an electrical device of the electric cable type
according to the invention, characterized in that it comprises the
following stages: [0132] i. extruding the polymer composition
around an elongated electrically conducting component, in order to
obtain an extruded layer, and [0133] ii. crosslinking the extruded
layer of stage i.
[0134] Stage i can be carried out by techniques well known to a
person skilled in the art, using an extruder.
[0135] During stage i, the temperature within the extruder should
preferably not exceed the temperature of opening of the epoxy
functional group with the polymer, in order to prevent any
crosslinking within the extruder. By way of example, the
temperature for processing the polymer composition by extrusion is
less than 200.degree. C. and preferably less than 150.degree.
C.
[0136] There is thus obtained, at the extruder outlet, a layer
extruded around said electrically conducting component which may or
may not be directly in physical contact with said electrically
conducting component.
[0137] At the extruder outlet, the extruded layer is thus a
"noncrosslinked" layer.
[0138] "Noncrosslinked" is understood to mean a layer, the gel
content of which according to the standard ASTM D 2765-01 is at
most 20%, preferably at least 10%, preferably at least 5% and
particularly preferably 0%.
[0139] Prior to stage i, the constituent components of the polymer
composition of the invention can be mixed, in particular with the
polymer A in the molten state, in order to obtain a homogeneous
mixture. The temperature within the mixer can be sufficient to
obtain a polymer A in the molten state but is limited in order to
prevent the opening of the epoxy functional group of the polymer
and thus the crosslinking of the polymer A.
[0140] The homogeneous mixture is then granulated by techniques
well known to a person skilled in the art. These granules can
subsequently feed an extruder in order to carry out stage i.
[0141] Stage ii can be carried out by the thermal route, for
example using a steam tube or a bath of molten salt, these
techniques being well known to a person skilled in the art. By way
of example, the crosslinking temperature is less than 300.degree.
C. and preferably less than or equal to 250.degree. C.
[0142] At the extruder outlet, the composition extruded in the form
of a layer around the electrically conducting component can
subsequently be subjected to a temperature sufficient in order to
be able to open the epoxy functional group of the polymer A and
thus to cause the crosslinking agent to react with the opened epoxy
functional group. An extruded and crosslinked layer is then
obtained.
[0143] Other characteristics and advantages of the present
invention will become apparent in the light of the description of a
nonlimiting example of an electric cable according to the invention
made with reference to the figures.
[0144] FIG. 1 represents a diagrammatic view in cross section of an
electric cable according to a preferred embodiment in accordance
with the invention.
[0145] FIG. 2 represents a diagrammatic view of an electrical
device according to the invention comprising a joint in
longitudinal section, this joint surrounding the end of two
electric cables.
[0146] FIG. 3 represents a diagrammatic view of an electrical
device according to a first alternative form of the invention
comprising a termination in longitudinal section, this termination
surrounding the end of a single electric cable.
[0147] FIGS. 4a to 4f exhibit spectra of infrared absorbance as a
function of the time (0 h, 24 h, 96 h and 168 h) for crosslinked
layers in accordance with the invention and not in accordance with
the invention.
[0148] FIG. 5 exhibits histograms of tensile strength according to
the French standard NF EN 60811-1-1 at 0 h, 24 h, 96 h and 168 h
for crosslinked layers in accordance with the invention and not in
accordance with the invention.
[0149] FIG. 6 exhibits histograms of elongation at break according
to the French standard NF EN 60811-1-1 at 0 h, 24 h, 96 h and 168 h
for crosslinked layers in accordance with the invention and not in
accordance with the invention.
[0150] For reasons of clarity, only the components essential for
the understanding of the invention have been represented
diagrammatically, this being done without observing a scale.
[0151] The medium- or high-voltage power cable 1, illustrated in
FIG. 1, comprises an elongated central conducting component 2, in
particular made of copper or of aluminum. The power cable 1
additionally comprises several layers positioned successively and
coaxially around this conducting component 2, namely: a first
semiconducting layer 3 referred to as "inner semiconducting layer",
an electrically insulating layer 4, a second semiconducting layer 5
referred to as "outer semiconducting layer", an earthing and/or
protective metal shield 6 and an external protective cladding
7.
[0152] The electrically insulating layer 4 is an extruded and
crosslinked layer obtained from the polymer composition according
to the invention.
[0153] The semiconducting layers are also extruded and crosslinked
layers which can be obtained from the polymer composition according
to the invention.
[0154] The presence of the metal shield 6 and of the external
protective cladding 7 is preferential but not essential, this cable
structure being as such well known to a person skilled in the
art.
[0155] FIG. 2 represents a device 101 comprising a joint 20
surrounding, in part, two electric cables 10a and 10b.
[0156] More particularly, the electric cables 10a and 10b
respectively comprise an end 10'a and 10'b which are intended to be
surrounded by the joint 20.
[0157] The body of the joint 20 comprises a first semiconducting
component 21 and a second semiconducting component 22 separated by
an electrically insulating component 23, said semiconducting
components 21, 22 and said electrically insulating component 23
surrounding the ends 10'a and 10'b respectively of the electric
cables 10a and 10b.
[0158] This joint 20 makes it possible to electrically connect the
first cable 10a to the second cable 10b, in particular by virtue of
an electrical connector 24 positioned at the center of the joint
20.
[0159] At least one of the components chosen from the first
semiconducting component 21, the second semiconducting component 22
and said electrically insulating component 23 can be a crosslinked
layer as described in the invention.
[0160] The first electric cable 10a comprises an electrical
conductor 2a surrounded by a first semiconducting layer 3a, an
electrically insulating layer 4a surrounding the first
semiconducting layer 3a, and a second semiconducting layer 5a
surrounding the electrically insulating layer 4a.
[0161] The second electric cable 10b comprises an electrical
conductor 2b surrounded by at least one first semiconducting layer
3b, an electrically insulating layer 4b surrounding the first
semiconducting layer 3b, and a second semiconducting layer 5b
surrounding the electrically insulating layer 4b.
[0162] These electric cables 10a and 10b can be those described in
the present invention.
[0163] At said end 10'a, 10'b of each electric cable 10a, 10b, the
second semiconducting layer 5a, 5b is at least partially denuded in
order for the electrically insulating layer 4a, 4b to be at least
partially positioned inside the joint 20, without being covered
with the second semiconducting layer 5a, 5b of the cable.
[0164] Inside the joint 20, the electrically insulating layers 4a,
4b are directly in physical contact with the electrically
insulating component 23 and the first semiconducting component 21
of the joint 20. The second semiconducting layers 5a, 5b are
directly in physical contact with the second semiconducting
component 22 of the joint 20.
[0165] FIG. 3 represents a device 102 comprising a termination 30
surrounding a single electric cable 10c.
[0166] More particularly, the electric cable 10c comprises an end
10'c intended to be surrounded by the termination 30.
[0167] The body of the termination 30 comprises a semiconducting
component 31 and an electrically insulating component 32, said
semiconducting component 31 and said electrically insulating
component 32 surrounding the end 10'c of the electric cable
10c.
[0168] At least one of the components chosen from the
semiconducting component 31 and the electrically insulating
component 32 can be a crosslinked layer as described in the
invention.
[0169] The electric cable 10c comprises an electrical conductor 2c
surrounded by a first semiconducting layer 3c, an electrically
insulating layer 4c surrounding the first semiconducting layer 3c,
and a second semiconducting layer 5c surrounding the electrically
insulating layer 4c.
[0170] This electric cable 10c can be that described in the present
invention.
[0171] At said end 10'c of the electric cable 10c, the second
semiconducting layer 5c is at least partially denuded in order for
the electrically insulating layer 4c to be at least partially
positioned inside the termination 30, without being covered with
the second semiconducting layer 5c of the cable.
[0172] Inside the termination 30, the electrically insulating layer
4c is directly in physical contact with the electrically insulating
component 32 of the termination 30. The second semiconducting layer
5c is directly in physical contact with the semiconducting
component 31 of the joint 30.
EXAMPLES
1. Filler-Free Electrically Insulating Compositions
[0173] Filler-free crosslinkable compositions, the amounts of the
compounds of which are expressed in parts by weight per 100 parts
by weight of polymer, the polymer being in this instance solely
Polymer/Epoxy, are collated in table 1 below. Compositions I1 to I6
are in accordance with the invention, whereas compositions C1 and
C2 correspond to comparative compositions.
TABLE-US-00001 TABLE 1a Compositions I1 I2 I3 I4 I5 C1
Polymer/Epoxy 100 100 100 100 100 100 Crosslinking 0.75 0.75 0.75
0.75 0.75 0.75 agent Irgastab KV10 1.0 0 0 0 0 0 Irganox 1010 0 0.5
0 0 0 0 Irganox 1076 0 0 0.9 0 0 0 Irganox 1330 0 0 0 0.44 0 0
Irganox 1035 0 0 0 0 0.45 0 Irganox PS802 0 0 0 0 0 0.58
TABLE-US-00002 TABLE 1b Compositions I6 C2 Polymer/Epoxy 100 100
Crosslinking agent 0.75 0.75 Aromatic amine 0.3 0 Nonaromatic amine
0 0.15
[0174] The compounds of tables 1a and 1b have the following
origins: [0175] Polymer/Epoxy is a copolymer of ethylene and
glycidyl methacrylate (GMA) sold by Arkema under the reference
Lotader AX8840, this copolymer comprising 8% by weight of GMA;
[0176] Crosslinking agent is 11-aminoundecanoic acid sold by
Sigma-Aldrich under the reference 11-Aminoundecanoic acid; [0177]
Irgastab KV10 is an antioxidant sold by BASF under the reference
Irgastab KV10 (CAS No. 110553-27-0); [0178] Irganox 1010 is an
antioxidant sold by BASF under the reference Irganox 1010 (CAS No.
6683-19-8); [0179] Irganox 1076 is an antioxidant sold by BASF
under the reference Irganox 1076 (CAS No. 2082-79-3); [0180]
Irganox 1330 is an antioxidant sold by BASF under the reference
Irganox 1330 (CAS No. 1709-70-2); [0181] Irganox 1035 is an
antioxidant sold by BASF under the reference Irganox 1035 (CAS No.
41484-35-9); [0182] Irganox PS802 is an antioxidant sold by BASF
under the reference Irganox PS802 (CAS No. 693-36-7); [0183]
Aromatic amine is the antioxidant
1,2-dihydro-2,2,4-trimethylquinoline sold by Flexsys under the
reference Flectol TMQ (CAS No. 26780-96-1); and [0184] Nonaromatic
amine is the antioxidant N,N'-diethylhydroxylamine (tertiary amine)
sold by Sigma-Aldrich under the reference N,N-Diethylhydroxylamine
(CAS No. 3710-84-7).
[0185] The compositions collated in tables 1a and 1b are processed
as follows.
[0186] In a first step, for each composition (I1 to I6, C1 and C2),
the crosslinking agent and the antioxidant are mixed with the
polymer in the molten state in an internal mixer of twin-screw or
Buss type, the temperature within the mixer not exceeding
130.degree. C. in order to prevent the opening of the epoxy
functional group of the polymer and to thus prevent the
crosslinking of the polymer. The homogeneous mixture thus obtained
is subsequently granulated.
[0187] In a second step, the granules are subsequently introduced
into a single-screw extruder and extruded at a maximum temperature
of 130.degree. C., in order to prevent any crosslinking of the
polymer in the extruder.
[0188] The extrusion is carried out around a copper conducting wire
with a section of 1.5 mm.sup.2. An electric cable comprising an
extruded and noncrosslinked layer in direct contact with the
conducting wire is obtained.
[0189] In a third step, the extruded layer is crosslinked by
supplying heat, at a temperature of 200.degree. C., said electric
cable being passed inside a steam tube under a steam pressure of 15
bar.
2. Semiconducting Compositions
[0190] A crosslinkable semiconducting composition I7 in accordance
with the invention, the amounts of the compounds of which are
expressed in parts by weight per 100 parts by weight of polymer,
the polymer in this instance being solely Polymer/Epoxy, is
collated in table 2 below.
TABLE-US-00003 TABLE 2 Composition I7 Polymer/Epoxy 100 Amino acid
0.38 Antioxidants 1.5 Carbon black 42.9
[0191] The compounds of table 2 have the following origins: [0192]
Polymer/Epoxy is a copolymer of ethylene and glycidyl methacrylate
(GMA) sold by Arkema under the reference Lotader AX8840, this
copolymer comprising 8% by weight of GMA; [0193] Amino acid is an
11-aminoundecanoic acid sold by Sigma-Aldrich under the reference
11-Aminoundecanoic acid; [0194] Antioxidants is a mixture of 0.5
part by weight of Irganox PS802 and of 1.0 part by weight of
Irganox 1035, these antioxidants being sold by BASF; and [0195]
Carbon black is carbon black sold by Cabot under the reference
Carbon Black VXC500.
[0196] Composition I7 in table 2 is processed according to the same
procedure as that described for the compositions of tables 1a and
1b, except for the fact that the carbon black is first of all mixed
with the molten polymer and then the crosslinking agent and the
antioxidants are incorporated in said mixture. The addition of the
crosslinking agent in a stage separate from and subsequent to the
addition of the carbon black makes it possible to prevent any
premature crosslinking of the polymer composition which may occur
subsequent to the rise in temperature brought about by the addition
of the carbon black. The crosslinking agent is thus added to the
filler-comprising mixture once the mixture has cooled to a
temperature of less than 130.degree. C.
3. Characterization of the Crosslinked Compositions
[0197] 3.1. Infrared Absorbance Spectra
[0198] FIGS. 4a to 4d exhibit spectra of infrared absorbance as a
function of the time (0 h, 24 h, 96 h and 168 h) for crosslinked
layers in accordance with the invention (compositions I2, I3, I4
and I6).
[0199] For the compositions according to the invention, these
absorbance spectra show that, during aging, up to 168 h, compound C
of the invention performs its role perfectly, namely it prevents
the etherification reactions since the peaks in the vicinity of
1200 cm.sup.-1 remain stable and are characteristic of the
stability in the number of ether functional groups formed. In
addition, the peak in the vicinity of 915 cm.sup.-1, corresponding
to the epoxy functional group, also remains unchanging.
[0200] FIGS. 4e to 4f exhibit spectra of infrared absorbance as a
function of the time (0 h, 24 h, 96 h and 168 h) for crosslinked
layers not in accordance with the invention (compositions C1 and
C2).
[0201] These absorbance spectra show that, during aging and
starting from 24 h for composition C1 and from 96 h for composition
C2, the antioxidant used does not succeed in preventing the
etherification reactions since the peaks in the vicinity of 1200
cm.sup.-1 vary, this variation being characteristic of the
etherification of the epoxy groups of the polymer A.
[0202] 3.2 Tensile Strength Test
[0203] FIG. 5 exhibits histograms of tensile strength according to
the French standard NF EN 60811-1-1, at 0 h, 24 h, 96 h and 168 h,
for crosslinked layers in accordance with the invention
(compositions I2, I3, I4 and I6) and not in accordance with the
invention (compositions C1 and C2).
[0204] It is clearly apparent that, after aging for 168 h, the
compositions according to the invention exhibit a tensile strength
(i.e., maximum strength achieved before breaking) of at least 10
mPa, in contrast to compositions C1 and C2, which exhibit a
strength of at most 8 mPa.
[0205] 3.3. Elongation at Break Test
[0206] FIG. 6 exhibits histograms of elongation at break according
to the French standard NF EN 60811-1-1, at 0 h, 24 h, 96 h and 168
h, for crosslinked layers in accordance with the invention
(compositions I2, I3, I4 and I6) and not in accordance with the
invention (compositions C1 and C2).
[0207] It is clearly apparent that, after aging for 168 h, the
compositions according to the invention exhibit a deformation at
elongation (i.e., maximum elongation achieved before breaking) of
at least 280%, in contrast to compositions C1 and C2, which exhibit
a deformation of at most 70%.
* * * * *