U.S. patent application number 10/420925 was filed with the patent office on 2004-02-05 for coated optical fibers.
Invention is credited to Alkema, Duurt, Buijsen, Paul, Cao, Huimin, Eekelen, Jan van, Johnson, Robert W., Nagelvoort, Sandra, Szum, David M..
Application Number | 20040022511 10/420925 |
Document ID | / |
Family ID | 29270548 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040022511 |
Kind Code |
A1 |
Eekelen, Jan van ; et
al. |
February 5, 2004 |
Coated optical fibers
Abstract
The present invention provides a coated optical fiber having a
primary coating and a secondary coating, wherein the primary
coating has good attenuation loss resistance and is obtained by
curing a composition having high cure speed.
Inventors: |
Eekelen, Jan van;
(Rozenburg, NL) ; Nagelvoort, Sandra;
(Vlaardingen, NL) ; Alkema, Duurt; (Den Haag,
NL) ; Buijsen, Paul; (Geleen, NL) ; Cao,
Huimin; (Addison, IL) ; Johnson, Robert W.;
(Algonquin, IL) ; Szum, David M.; (Crystal Lake,
IL) |
Correspondence
Address: |
PILLSBURY WINTHROP, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
29270548 |
Appl. No.: |
10/420925 |
Filed: |
April 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60374778 |
Apr 24, 2002 |
|
|
|
Current U.S.
Class: |
385/128 |
Current CPC
Class: |
C08G 18/40 20130101;
C08G 18/672 20130101; Y10S 525/932 20130101; C08G 18/672 20130101;
C09D 175/16 20130101; C09J 175/16 20130101; C08G 18/672 20130101;
C08G 18/4854 20130101; C03C 25/1065 20130101; G02B 6/02395
20130101; C08G 18/48 20130101 |
Class at
Publication: |
385/128 |
International
Class: |
G02B 006/22 |
Claims
What is claimed is:
1. A coated optical fiber comprising: (i) an optical fiber; (ii) a
primary coating; and (iii) a secondary coating; wherein (a) said
coated optical fiber has an attenuation increase of less than 0.650
dB/km at 1550 nm; (b) said primary coating is obtained by curing a
primary coating composition, said composition having a cure dose to
attain 95% of the maximum attainable modulus of less than 0.65
J/cm.sup.2; and (c) said primary coating has a Tg of less than
-35.degree. C.
2. The coated optical fiber of claim 1, wherein said primary
coating has an in-situ modulus is less than 0.56 MPa.
3. The coated optical fiber of claim 1, wherein said primary
coating has an in-situ modulus is less than 0.54 MPa.
4. The coated optical fiber of claim 1, wherein said primary
coating has an in-situ modulus is less than 0.52 MPa.
5. The coated optical fiber of claim 1, wherein said attenuation
increase is less than 0.500 dB/km.
6. The coated optical fiber of claim 1, wherein said primary
coating composition comprises an ethylenically unsaturated
oligomer.
7. The coated optical fiber of claim 6, wherein said oligomer is
prepared by reacting the following components: (1) one or more
polyisocyanates; (2) one or more polyols; and (3) one or more
hydroxyfunctional (meth)acrylates.
8. The coated optical fiber of claim 7, wherein said one or more
polyols includes polypropylene glycol.
9. The coated optical fiber of claim 7, wherein said one or more
polyols consists essentially of polypropylene glycol.
10. The coated optical fiber of claim 7, wherein said one or more
polyols includes a polyester polyol.
11. The coated optical fiber of claim 7, wherein said one or more
polyols each have a molecular weight of at least 3,000 g/mol.
12. The coated optical fiber of claim 7, wherein said one or more
hydroxyfunctional (meth)acrylates includes hydroxyethyl
acrylate.
13. The coated optical fiber of claim 1, wherein said primary
coating composition comprises one or more monomers.
14. The coated optical fiber of claim 13, wherein said one or more
monomers includes an alkoxylated acrylate monomer.
15. The coated optical fiber of claim 13, wherein said one or more
monomers includes an alkoxylated aliphatic polyacrylate
monomer.
16. The coated optical fiber of claim 1, wherein said cure dose is
below 0.55 J/cm.sup.2.
17. The coated optical fiber of claim 1, wherein said primary
coating has a Tg below -45.degree. C.
18. The coated optical fiber of claim 1, wherein said an optical
fiber is an optical glass fiber.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
provisional application No. 60/374,778, which was filed on Apr. 24,
2002.
FIELD OF THE INVENTION
[0002] The present invention relates to a coated optical fiber
comprising a primary and secondary coating, to a radiation curable
primary coating composition, to a combination of a primary and
secondary coating, and to a ribbon comprising at least one of said
coated optical fibers.
BACKGROUND OF THE INVENTION
[0003] Because optical fibers are fragile and easily broken, the
optical fibers are usually coated with a protective coating system,
for instance with a soft "cushioning" primary coating that is in
contact with the fiber and with a relatively hard secondary coating
surrounding the primary coating. In addition, the coating system
may be used to reduce attenuation, i.e. the loss of optical power
as light travels down a fiber, as a result of microbending of the
fiber. Providing such coatings should however not be at the expense
of the cure speed of coating compositions, as this would limit line
speeds in fiber drawing and therewith increase overall production
costs. Accordingly, one of the objects of the present invention is
to provide a coated optical fiber having a primary coating and a
secondary coating, wherein the primary coating has a high cure
speed and provides good attenuation resistance.
[0004] U.S. applications Ser. Nos. 09/989,703; 09/717,337; and
09/620,367 discuss primary coatings and microbending. All three
applications are hereby incorporated in their entirety by
reference.
SUMMARY OF THE INVENTION
[0005] The present invention provides a coated optical fiber having
a primary coating and a secondary coating, wherein the primary
coating provides good attenuation resistance and is obtained by
curing a composition having a high cure speed.
BRIEF DESCRIPTION OF THE FIGURES
[0006] FIG. 1 shows a schematic illustration for an in-situ modulus
test sample;
[0007] FIG. 2 is a photograph showing a set-up for measuring the
cavitation resistance
DETAILED DESCRIPTION OF THE INVENTION
[0008] The present invention provides a coated optical fiber having
a primary coating and a secondary coating, wherein the primary
coating provides good attenuation resistance and is obtained by
curing a composition having a high cure speed.
[0009] Preferably, the coated optical fiber has an attenuation
increase of less than 0.650 dB/km at 1550 nm, for instance less
than 0.5 or less than 0.4 dB/km at 1550 nm.
[0010] Preferably, the primary coating is obtained by curing a
primary coating composition, wherein the composition has a cure
dose to attain 95% of the maximum attainable modulus of less than
0.65 J/cm.sup.2, for instance less than 0.55 J/cm.sup.2, less than
0.45 J/cm.sup.2, or less than 0.35 J/cm.sup.2.
[0011] Preferably, the primary coating has an in-situ modulus of
less than 0.56 MPa, for instance less than 0.54 or 0.52 MPa.
Preferably, the primary coating also has a good in-situ modulus
retention, in particular under humid conditions. Accordingly, it is
preferred that the ratio of the in-situ modulus of the primary
coating after aging for 8 weeks at 85.degree. C. and at 85%
relative humidity to the initial in-situ modulus after cure is
greater than 0.5, for instance greater than 0.75 or greater than
0.9.
[0012] Furthermore, it is preferred that the primary coating has a
glass transition temperature below -10.degree. C., for instance
below -25.degree. C., -35.degree. C., or even below -45.degree. C.
The elongation to break of the primary coating is preferably at
least 75%, for instance at least 120% or at least 150%.
[0013] Generally, the Tg of the secondary coating is about
40.degree. C. or higher, for instance about 50.degree. C. or higher
or about 60.degree. C. or higher. The tensile modulus of the
secondary coating is preferably at least 200 MPa, for instance at
least 400 MPa or at least 500 MPa. The tensile modulus will
generally be below 3,000 MPa, for instance below 2,000 MPa. The
secondary coating will preferably have an elongation to break of at
least 2%, for instance at least 10% or at least 20%.
[0014] In order to, for instance, reduce thermal stresses in the
coating system, it is preferred that the ratio of the expansion
coefficient of the primary coating and the secondary coating is
below 3.0, for instance below 2.0, such as about 1.7.
[0015] The primary coating generally will be obtained by curing a
radiation curable coating composition based on (meth)acrylate
functional oligomers and radiation-curable monomers with
photoinitiator(s) and additives. Examples of additives include a
stabiliser and a silane coupling agent. The adhesion to the glass
as measured according to adhesion test described in WO 99/15473,
which is incorporated herein in its entirety by reference,
generally is at least about 5 g in force both at 50% RH and at 95%
RH (Relative Humidity). Preferably, the adhesion is at least about
10 g in force, for instance at least about 20 g in force, at least
about 50 g in force, or at least about 80 g in force, both at 50%
RH and 95% RH.
[0016] The primary coating composition of the present invention
generally comprise
[0017] (A) 20-98% by wt. of at least one oligomer having a
molecular weight of about 1000 or higher, for instance 20-80% by
wt. or 30-70% by wt.,
[0018] (B) 0-80% by wt. of one or more reactive diluents, for
instance 5-70% by wt., 10-60% by wt., or 15-60% by wt.,
[0019] (C) 0.1-20% by wt. of one or more photoinitiators for
initiation of a radical polymerisation reaction, for instance
0.5-15% by wt., 1-10% by wt., or 2-8% by wt.,
[0020] (D) 0-5% by wt. of additives,
[0021] wherein the total amount adds up to 100 wt. %.
[0022] Preferably, the oligomer (A) is a urethane (meth)acrylate
oligomer, comprising a (meth)acrylate group, urethane groups and a
backbone. (Meth)acrylate includes acrylate as well as methacrylate
functionality. The backbone is generally derived from a polyol
which has been reacted with a diisocyanate and hydroxy alkyl
acrylate. However, urethane-free ethylenically unsaturated
oligomers may also be used.
[0023] Examples of suitable polyols are polyether polyols,
polyester polyols, polycarbonate polyols, polycaprolactone polyols,
acrylic polyols, and the like. These polyols may be used either
individually or in combinations of two or more. Preferred polyols
include polyether polyols, e.g. polypropylene glycol polyols such
as Acclaim 4200 or Acclaim 4200N (commercially available from
Lyondell), optionally in combination with polyester polyols (e.g.
Priplast 3190, commercially available from Uniqema). There are no
specific limitations to the manner of polymerization of the
structural units in these polyols. Any of random polymerization,
block polymerization, or graft polymerization is acceptable.
Examples of suitable polyols, polyisocyanates and
hydroxylgroup-containing (meth)acrylates are disclosed in WO
00/18696, which is incorporated herein by reference.
[0024] The reduced number average molecular weight derived from the
hydroxyl number of these polyols is usually from about 50 to about
25,000, preferably from about 500 to about 15,000, more preferably
from about 1,000 to about 8,000, and most preferred, from about
1,500 to 6,000. In one embodiment, the polyol(s) used in preparing
the oligomer have a molecular weight of at least 2,500 g/mol, for
instance at least 3,000 g/mol or at least 4000 g/mol.
[0025] The ratio of polyol, di- or polyisocyanate (as disclosed in
WO 00/18696), and hydroxyl group-containing (meth)acrylate used for
preparing the urethane (meth)acrylate is generally determined so
that about 1.1 to about 3 equivalents of an isocyanate group
included in the polyisocyanate and about 0.1 to about 1.5
equivalents of a hydroxyl group included in the hydroxyl
group-containing (meth)acrylate are used for one equivalent of the
hydroxyl group included in the polyol.
[0026] In the reaction of these three components, an urethanization
catalyst such as copper naphthenate, cobalt naphthenate, zinc
naphthenate, di-n-butyl tin dilaurate, triethylamine, and
triethylenediamine, 2-methyltriethyleneamine, is usually used in an
amount from about 0.01 to about 1 wt % of the total amount of the
reactant. The reaction is carried out at a temperature from about
10 to about 90.degree. C., and preferably from about 30 to about
80.degree. C.
[0027] The number average molecular weight of the urethane
(meth)acrylate used in the composition of the present invention is
preferably in the range from about 1,200 to about 20,000 g/mol, for
instance from about 2,200 to about 10,000 g/mol. If the number
average molecular weight of the urethane (meth)acrylate is less
than about 1000 g/mol, the resin composition tends to vitrify at
room temperature; on the other hand, if the number average
molecular weight is larger than about 20,000, the viscosity of the
composition becomes high, making handling of the composition
difficult.
[0028] Suitable reactive diluents (B) are polymerizable
monofunctional vinyl monomers and polymerizable polyfunctional
vinyl monomers. Examples of these reactive diluents are disclosed
in WO 97/42130, which is incorporated herein in its entirety by
reference.
[0029] Preferred reactive diluents include alkoxylated alkyl
substituted phenol acrylate, such as ethoxylated nonyl phenol
acrylate, propoxylated nonyl phenol acrylate, vinyl monomers such
as vinyl caprolactam, isodecyl acrylate, and alkoxylated bisphenol
A diacrylate such as ethoxylated bisphenol A diacrylate. In one
embodiment, it is preferred to include one or more alkoxylated
aliphatic polyacrylates, for instance an alkoxylated aliphatic
diacrylate such as alkoxylated (e.g. propoxylated) neopentyl glycol
diacrylate. In another embodiment, it is preferred to include one
or more diluents comprising one or more aromatic rings. Aromatic
diluents may be helpful in embodiments where a comparatively high
refractive index is desired.
[0030] Preferably, the photoinitiators (C) are free radical
photoinitiators. Free-radical photoinitiators are generally divided
into two classes according to the process by which the initiating
radicals are formed. Compounds that undergo unimolecular bond
cleavage upon irradiation are termed Type I or homolytic photo
initiators.
[0031] If the excited state photoinitiator interacts with a second
molecule (a coinitiator) to generate radicals in a bimolecular
reaction, the initiating system is termed a Type II photoinitiator.
In general, the two main reaction pathways for Type II
photoinitiators are hydrogen abstraction by the excited initiator
or photoinduced electron transfer, followed by fragmentation.
[0032] Examples of suitable free-radical photoinitiators are
disclosed in WO 00/18696 which is incorporated herein in its
entirety by reference.
[0033] In one preferred embodiment of the present invention at
least one of the photoinitiators contains a phosphorous, sulfur or
nitrogen atom. It is even more preferred that the photoinitiator
package comprises at least a combination of a photoinitiator
containing a phosphorous atom and a photoinitiator containing a
sulfur atom.
[0034] In another preferred embodiment of the invention, at least
one of the compounds (C) is an oligomeric or polymeric
photoinitiator.
[0035] As an additive (D), an amine compound can be added to the
liquid curable resin composition of the present invention to
prevent generation of hydrogen gas, which causes transmission loss
in the optical fibers. As examples of the amine which can be used
here, diallylamine, diisopropylamine, diethylamine,
diethylhexylamine, and the like can be given.
[0036] In addition to the above-described components, various
additives such as antioxidants, UV absorbers, light stabilizers,
silane coupling agents (e.g. mercaptofunctional silane coupling
agents), coating surface improvers, heat polymerization inhibitors,
leveling agents, surfactants, colorants, preservatives,
plasticizers, lubricants, solvents, fillers, aging preventives, and
wettability improvers can be used in the liquid curable resin
composition of the present invention, as required.
[0037] In general, optical fibers are coated first with a primary
coating and subsequently with a secondary coating. Suitable
secondary coatings are disclosed, for instance, in U.S. Pat. No.
6,080,483, which is hereby incorporated in its entirety by
reference. The coatings can be applied as a wet-on-wet system
(without first curing of the primary) or as a wet-on-dry system.
The primary coating can be colored with a die, or secondary
coatings can be colored with pigments or dies, or a clear secondary
can be further coated with an ink. The primary and secondary
coatings generally have a thickness of about 30 .mu.m each. An ink
coating generally has a thickness of about 5 .mu.m (3-10
.mu.m).
[0038] The coated and preferably colored optical fibers can be used
in a ribbon comprising a plurality of said optical fibers,
generally in a parallel arrangement. The plurality of optical
fibers is further coated with one or more matrix materials in order
to obtain a ribbon. The present invention therefore further relates
to a ribbon comprising a plurality of coated and preferably colored
optical fibers, generally in a parallel arrangement, said coated
optical fiber comprising at least a primary coating according to
the present invention and preferably a secondary coating according
to the present invention.
[0039] The invention will be further elucidated by the following
examples, which should be regarded as illustrating the invention
and not as limiting the invention.
EXAMPLES
Examples 1-6 and Comparative Examples A-C
[0040] Primary coating compositions were prepared according to the
formulations listed in Table 1 below (amounts of ingredients listed
in weight % relative to total weight of the composition). Also
listed are physical properties of the primary coating (see below
for sample preparation and test methods).
1TABLE 1 Primary coating compositions Ingredients Ex. A Ex. 1 Ex. B
Ex. 2 Ex. 3 Ex. C Ex. 4 Ex. 5 Ex. 6 Oligomer 1.sup.a 68.60 66.15 --
-- -- -- 74.10 66.4 66.0 Oligomer 2.sup.b -- -- 52.66 -- -- 56.90
-- -- -- Oligomer 3.sup.c -- -- -- 77.10 66.20 -- -- -- --
Ethoxylated Nonyl Phenol Acrylate 7.0 5.0 21.43 -- 10.0 17.02 --
5.0 5.0 Tridecyl acrylate 7.0 -- -- -- -- -- -- -- -- Isodecyl
acrylate -- 8.5 -- 8.5 8.5 22.00 10.0 8.5 -- Phenoxyethylacrylate
-- 4.0 -- -- -- -- -- 4.0 4.0 Isobornyl acrylate -- -- 10.71 -- --
-- -- -- -- Lauryl acrylate -- -- 6.0 -- -- -- -- -- --
Propoxylated (3) Trimethylolpropane triacrylate -- 4.0 -- -- 5.0 --
4.0 4.0 4.0 Ethoxylated bisphenol diacrylate -- 2.0 -- -- 2.0 -- --
2.0 2.0 Vinyl Caprolactam 4.0 -- 6.31 5.0 -- -- -- -- --
Ethoxylated Aliphatic Acrylate (Ebecryl 111 from UCB 5.0 -- -- --
-- -- -- -- -- Chemicals) Propoxylated (2) Neopentyl Glycol
Diacrylate (SR9003) 4.0 4.0 -- 5.0 3.0 -- 6.0 4.0 4.0 Lucerine TPO
(photoinitiator) 1.3 1.5 1.58 1.3 1.3 1.71 1.3 1.5 2.3 Irgacure 184
(photoinitiator) 1.8 1.8 -- 1.8 1.8 1.00 1.8 1.8 1.8 Irganox 1035
(stabilizer) 0.3 -- 0.32 0.3 -- 0.34 -- -- -- Irganox 3790
(stabilizer) -- 1.4 -- -- 0.7 -- -- 1.4 1.4 Cyanox 1790
(stabilizer) -- -- -- -- -- -- 1.4 -- -- Tinuvin 123 -- 0.4 -- --
-- -- 0.4 0.4 -- Silane coupling agent 1.0 1.25 1.0 1.0 1.5 1.0 1.0
1.0 1.0 Properties Viscosity (mPas) 5656 6134 7500 8500 6673 8100
8761 6329 5850 Tensile Strength (MPa) 0.7 2.36 1.3 0.8 1.8 0.9
1.085 11.89 2.56 Elongation at break (%) 230 184 170 150 160 160
171 163 173 Secant modulus (MPa) 0.7 0.98 0.9 0.9 0.86 1.5 1.14
1.06 0.98 Cure dose to attain 95% of modulus (J/cm.sup.2) 0.21 0.47
0.3 ND 0.32 0.7 0.51 ND ND Tg(.degree. C.) -51 -47.4 ND ND -23.2
-45 -50.4 ND ND Measured shear modulus G.sub.measured (MPa) 0.145
0.16 0.22 0.17 0.16 ND ND ND ND Primary coating thickness (micron)
34 28 30 30 27 ND ND ND ND In-situ Modulus (MPa) 0.58 0.55 0.89
0.65 0.54 ND ND ND ND Microbending attenuation increase @ 1310 nm
(dB/km) 0.185 0.116 0.512 0.184 0.117 0.2 0.213 ND ND Microbending
attenuation increase @ 1550 nm (dB/km) 0.709 0.365 1.473 0.405
0.375 0.454 0.628 ND ND Microbending attenuation increase @ 1700 nm
(dB/km) 2.61 1.168 3.807 0.960 1.148 1.54 1.806 ND ND
.sup.aprepared by reacting Acclaim4200, toluenediisocyanate, and
hydroxyethylacrylate in the presence of catalyst and stabilizer.
.sup.bprepared by reacting PTGL2000 (polytetrahydrofuran poyol with
Mw of about 2000), isophoronediisocyanate and hydroxyethylacrylate
in the presence of catalyst and stabilizer. .sup.cprepared by
reacting Acclaim4200N, Priplast3190, isophoronediisocyanate, and
hydroxyethylacrylate in the presence of catalyst and
stabilizer.
[0041] Cavitation resistance of above primary coatings was also
measured (see below for test method and sample preparation).
Several experiments were conducted per primary coating composition.
The absolute data value was substantially scattered, however,
possibly due to differences in the angle in which the razor blade
touched the sample coated optical fibers, resulting in inaccurate
force distributions. The general trend observed was (starting with
the sample having the best cavitation resistance): Example
A>Example 1>Examples B, 2, and 3.
[0042] The caviation resistance of Example C and Examples 4-6 was
not determined.
[0043] In addition, the cavitation resistance of a commercial
coated optical fiber was measured. Again, there was substantial
scattering in the data, but the the cavitation resistance appeared
to be in the range of Example 1. The in-situ modulus of the primary
coating of the commercial fiber was determined to be 0.58 MPa. The
commercial primary coating is believed to be obtained by curing a
composition having a cure dose of 0.4 J/cm.sup.2.
[0044] Test Methods
[0045] (i) Cure Dose
[0046] The cure speed of the compositions was determined as the
cure dose required to attain 95% of the maximum attainable modulus.
This cure dose was determined by Dose vs. Modulus curve analysis.
Hereto, 6 radiation-cured sample films of each composition were
prepared, with each sample film being obtained by applying an
approximately 75 microns thick composition layer on a plate and
subsequently curing the composition layer. Each composition layer
was cured with a different dose: 0.2, 0.3, 0.5, 0.75, 1.0, and 2.0
J/cm.sup.2 respectively. Six specimens were cut from the center
portion of each prepared sample film. A Universal Testing
Instrument, INSTRON Model 4201 equipped with a suitable personal
computer and software "Series IX Materials Testing System" was used
to measure the modulus of each specimen. The modulus measurements
were then entered into the software package and the calculations
were automatically performed with a determination of the average
modulus for each film sample. The dose-modulus curve was then
created by plotting the modulus values vs. the dose and by fitting
a curve through the data points. The "cure dose" of the coating
composition was determined to be the dose at which 95% of the
ultimate secant modulus is attained.
[0047] (ii) Tensile Strength, Elongation and Modulus Test
Method
[0048] The tensile strength, elongation and secant modulus of cured
samples were tested using a universal testing instrument, Instron
Model 4201 equipped with a personal computer and software "Series
IX Materials Testing System." The load cells used were 4.4 Kg
capacity. The ASTM D638M was followed, with the following
modifications.
[0049] A drawdown of each material to be tested was made on glass
plate and cured using a UV processor. A minimum of eight test
specimens, having a width of 12.7.+-.0.005 mm and a length of 12.7
cm, were cut from the cured film. To minimize the effects of minor
sample defects, sample specimens were cut parallel to the direction
in which the drawdown of the cured film was prepared. If the cured
film was tacky to the touch, a small amount of talc was applied to
the film surface using a cotton tipped applicator.
[0050] The test specimens were then removed from the substrate.
Caution was exercised so that the test specimens were not stretched
past their elastic limit during the removal from the substrate. If
any noticeable change in sample length had taken place during
removal from the substrate, the test specimen was discarded.
[0051] If the top surface of the film was talc coated to eliminate
tackiness, then a small amount of talc was applied to the bottom
surface of test specimen after removal from the substrate.
[0052] The average film thickness of the test specimens was
determined. At least five measurements of film thickness were made
in the area to be tested (from top to bottom) and the average value
used for calculations. If any of the measured values of film
thickness deviates from the average by more than 10% relative, the
test specimen was discarded. All specimens came from the same
plate.
[0053] The crosshead speed was set to 25.4 mm/min, and the
crosshead action was set to "return at break". The crosshead was
adjusted to 50.8 mm jaw separation. The air pressure for the
pneumatic grips was turned on and set to approximately 1.5
Kg/cm.sup.2. After the Instron test instrument had been allowed to
warm-up for fifteen minutes, it was calibrated and balanced
following the manufacturer's operating procedures.
[0054] The temperature near the Instron instrument was measured and
the humidity was measured at the location of the humidity gauge.
This was done just before beginning measurement of the first test
specimen.
[0055] Specimens were only analyzed if the temperature was within
the range 23.+-.1.0.degree. C. and the relative humidity was within
50.+-.5%. The temperature was verified as being within this range
for each test specimen. The humidity value was verified only at the
beginning and the end of testing a set of specimens from one
plate.
[0056] Each test specimen was tested by suspending it into the
space between the upper pneumatic grips such that the test specimen
was centered laterally and hanging vertically. Only the upper grip
was locked. The lower end of the test specimen was pulled gently so
that it has no slack or buckling, and it was centered laterally in
the space between the open lower grips.
[0057] While holding the specimen in this position, the lower grip
was locked.
[0058] The sample number was entered and sample dimensions into the
data system, following the instructions provided by the software
package.
[0059] The temperature and humidity were measured after the last
test specimen from the current drawdown was tested. The calculation
of tensile properties was performed automatically by the software
package.
[0060] The values for tensile strength, % elongation, and secant,
or segment, modulus were checked to determine whether any one of
them deviated from the average enough to be an "outlier." If the
modulus value was an outlier, it was discarded. If there were less
than six data values for the tensile strength, then the entire data
set was discarded and repeated using a new plate.
[0061] (iii) Viscosity
[0062] The viscosity was measured using a Physica MC10 Viscometer.
The test samples were examined and if an excessive amount of
bubbles was present, steps were taken to remove most of the
bubbles. Not all bubbles need to be removed at this stage, because
the act of sample loading introduces some bubbles.
[0063] The instrument was set up for the conventional Z3 system,
which was used. The samples were loaded into a disposable aluminum
cup by using the syringe to measure out 17 cc. The sample in the
cup was examined and if it contains an excessive amount of bubbles,
they were removed by a direct means such as centrifugation, or
enough time was allowed to elapse to let the bubbles escape from
the bulk of the liquid. Bubbles at the top surface of the liquid
are acceptable.
[0064] The bob was gently lowered into the liquid in the measuring
cup, and the cup and bob were installed in the instrument. The
sample temperature was allowed to equilibrate with the temperature
of the circulating liquid by waiting five minutes. Then, the
rotational speed was set to a desired value which will produce the
desired shear rate. The desired value of the shear rate is easily
determined by one of ordinary skill in the art from an expected
viscosity range of the sample.
[0065] The instrument panel read out a viscosity value, and if the
viscosity value varied only slightly (less than 2% relative
variation) for 15 seconds, the measurement was complete. If not, it
is possible that the temperature had not yet reached an equilibrium
value, or that the material was changing due to shearing. If the
latter case, further testing at different shear rates will be
needed to define the sample's viscous properties. The results
reported are the average viscosity values of three test
samples.
[0066] (iv) Glass Transition Temperature
[0067] The elastic modulus (E'), the viscous modulus (E"), and the
tan delta (E"/E'), which is an indication of the material's
T.sub.g, of the examples were measured using a Rheometrics Solids
Analyzer (RSA-11), equipped with: 1) a personal computer having
MS-DOS 5.0 operating system and having Rhios.RTM. software (Version
4.2.2 or later) loaded, and 2) a liquid nitrogen controller system
for low-temperature operation.
[0068] The test samples were prepared by casting a film of the
material, having a thickness in the range of 0.02 mm to 0.4 mm, on
a glass plate. The sample film was cured using a UV processor. A
specimen approximately 35 mm (1.4 inches) long and approximately 12
mm wide was cut from a defect-free region of the cured film. For
soft films, which tend to have sticky surfaces, a cotton-tipped
applicator was used to coat the cut specimen with talc powder.
[0069] The film thickness of the specimen was measured at five or
more locations along the length. The average film thickness was
calculated to.+-.0.001 mm. The thickness cannot vary by more than
0.01 mm over this length. Another specimen was taken if this
condition was not met. The width of the specimen was measured at
two or more locations and the average value calculated to .+-.0.1
mm.
[0070] The geometry of the sample was entered into the instrument.
The length field was set at a value of 23.2 mm and the measured
values of width and thickness of the sample specimen were entered
into the appropriate fields.
[0071] Before conducting the temperature sweep, moisture was
removed from the test samples by subjecting the test samples to a
temperature of 80.degree. C. in a nitrogen atmosphere for 5
minutes. The temperature sweep used included cooling the test
samples to about -60.degree. C. or about -80.degree. C. and
increasing the temperature at about 1/minute until the temperature
reached about 60.degree. C. to about 70.degree. C. The test
frequency used was 1.0 radian/second. The DMA instrument produced a
plot of the data on the computer screen. The temperature at which
E' is 1,000 MPa and E' is 100 MPa was calculated from this plot, as
well as the tan delta peak. The temperature corresponding with the
tan delta peak is reported as the glass transition temperature
(Tg).
[0072] (v) In-situ Modulus
[0073] A glass optical fiber (single mode fiber having a field
diameter of 10.5 micron) was coated using a primary composition
according to Table 1 and a commercial secondary composition. The
thus obtained coated fiber was then placed in a metal sample
fixture, as schematically shown in FIG. 1: A small portion of the
coating layer was stripped in the middle of the fiber; the length
of the bottom part of the fiber was cut to be exactly 1 cm; the
bottom of the fiber was inserted into a micro tube in the fixture;
the micro tube consisted of two half hollow cylinders; its diameter
was made to be the same as the fiber outer diameter; the fiber was
tightly gripped after the screw was tightened; the gripping force
on the secondary coating surface was uniform and no significant
deformation occurred in the coating layer. The fixture with the
fiber was then mounted on DMA (same instrument as used to determine
the glass transition temperature). The metal fixture was clamped by
the bottom grip. The top grip was tightened, pressing on the top
portion of the coated fiber to the extent that it crushed the
coating layer. The DMA was set to the shear sandwich mode to
measure the shear modulus of the primary coating. Under the force
F, the primary coating layer is sheared with a displacement D while
essentially no deformation occurs in the stiff secondary coating.
The shear strain S (=D/T.sub.p) was set to be 0.05. With this low
level of strain and stress, the deformation was proven to be in the
linear viscoelastic region and no delamination occurred at the
interface of glass and primary coating. The shear modulus G was
thus obtained (values indicated in Table 1). This shear modulus G
was then corrected for stretch of the glass during measurement by
the following formula:
1/G.sub.corrected32 1/G.sub.measured-1/G.sub.glass, wherein
G.sub.glass was taken to be 0.85 MPa.
[0074] G corrected was then further corrected by adjusting for the
real thickness of the primary coating (the thickness assumed when
obtaining G.sub.measured was always 30 micron), resulting in
G'.sub.corrected See Table 1 for the real thickness of the primary
coatings. Finally, the in-situ modulus E was calculated with the
following formula:
E=2(1+v)G.sub.corrected=3G'.sub.corrected, wherein v is the primary
coating Poisson ratio=0.5.
[0075] (vi) Cavitation Resistance
[0076] A Sutherland.RTM. 2000 rub tester was equipped with a
fixture, replacing the heavy weight test block that this rub tester
normally uses. See FIG. 2. The left side of the fixture was locked
into a joint on the tester moving arm. The bottom side was equipped
with a razor blade holder. The razor blade, with the back facing
down, was vertically sitting on the Q-panel, with the razor blade
back edge being in complete contact with the Q-panel surface. The
distance from the center of the razor blade holder to the joint is
.about.1.5 in. The moving distance of the razor blade is .about.1.5
inch in half cycle. The weight of the fixture with the razor blade
is .about.200 g. The fixture was raised and a coated optical fiber
was taped on the Q-panel perpendicular to the edge of the razor
blade back and in the center position. Microscope immersion oil was
droppped on the fiber to reduce friction. The fiber had been
previously prepared by drawing a glass optical fiber (single mode
fiber having a field diameter of 10.5 micron) and coating it with
the use of a primary composition according to Table 1 and a
commercial secondary composition.
[0077] The count number of the Sutherland.RTM. 2000 rub tester was
then preset as 3 (3 cycles, 6 times back and force in total) and
speed 3 was selected (85 cycles/min). The razor blade was
subsequently lowered over the fiber and the test was started. At
the end of the cycle 3, the razor blade was raised from the fiber
by hand (the moving arm runs one more slow cycle before it stops.
To avoid the possible delamination caused by this slow rub, the
razor blade should be lifted over the fiber before this slow
rub).
[0078] The rubbed portion (i.e. 1.5 inch) of the fiber was then
examined under the microscope at 40.times. magnification. The
number of cavities observed was noted. The more cavities observed,
the poorer the cavitation resistance.
[0079] (vii) Microbending
[0080] A glass optical fiber (single mode fiber having a field
diameter of 10.5 micron) was coated using a primary composition
according to Table 1 and a commercial secondary composition. The
microbending resistance of the fiber was determined by determining
the attenuation of the coated optical fiber before and after
winding the fiber around a drum (diameter 600 mm) covered with
sandpaper (40 .mu.m Alox grade by 3M.TM.). The winding force was
kept constant at 4N. The attenuation increase (difference between
attenuation before and after winding) was determined at various
wavelengths (as indicated in Table 1).
* * * * *