Thermally resistant radiation curable coatings for optical fiber
Described herein are coated optical fibers including an optical fiber portion, wherein the optical fiber portion includes a glass core and cladding section that is configured to possesses certain mode-field diameters and effective areas, and a coating portion including a primary and secondary coating, wherein the primary coating is the cured product of a composition that possesses specified liquid glass transition temperatures, such as below −82° C., and/or a viscosity ratios, such as between 25° C. and 85° C., of less than 13.9. Also described are radiation curable coating compositions possessing reduced thermal sensitivity, methods of coating such radiation curable coating compositions to form coated optical fibers, and optical fiber cables comprising the coated optical fibers and/or radiation curable coating compositions elsewhere described.
1. A radiation curable composition for coating an optical fiber comprising:
a reactive oligomer comprising at least one polymerizable group and a backbone derived from a diol comprising polypropylene glycol;
a reactive diluent monomer; and
one or more photoinitiators;
wherein the radiation curable composition possesses a first viscosity at 25° Celsius (C), a second viscosity at 55° C., and a third viscosity at 85° C.,
wherein the ratio of the first viscosity to the third viscosity is less than 14.4.
2. The radiation curable composition of claim 1 wherein, relative to the weight of the entire radiation curable composition:
the reactive oligomer is present in an amount of least about 40%;
the reactive diluent monomer is present in an amount from about 20 to about 50 wt. %; and
the one or more photoinitiators are present in an amount from about 0.1-5 wt. %.
3. The radiation curable composition of claim 2 , wherein the third viscosity is from about 0.03 to about 0.8 Pa·s.
4. The radiation curable composition of claim 3 , wherein the ratio of the first viscosity to the third viscosity is less than 12.
5. The radiation curable composition of claim 4 , wherein the ratio of the first viscosity to the third viscosity is from 5 to 10.
6. The radiation curable composition of claim 1 , wherein the composition further comprises an adhesion promoter.
7. The radiation curable composition of claim 6 , wherein the reactive oligomer comprises a urethane acrylate oligomer, wherein said urethane acrylate oligomer comprises the reaction product of an isocyanate, an acrylate, and a polypropylene glycol with a number average molecular weight as measured by size exclusion chromatography using a polystyrene standard in THF from 3,000 to 10,000;
and wherein the reactive oligomer comprises a number average from 0.9 to 3.1 (meth)acrylate endgroups.
8. The radiation curable composition of claim 7 , wherein the reactive oligomer comprises or consists essentially of urethane acrylate oligomer(s), and wherein the number average molecular weight of the reactive urethane oligomer is from about 8,000 to about 20,000 g/mol.
9. The radiation curable composition of claim 8 , wherein the molar ratio of the polypropylene glycol to the isocyanate is from 1:1 to 1:4, the molar ratio the polypropylene glycol to the acrylate is from 1:1 to 4:1, and the molar ratio of the isocyanate to the acrylate is from 1:1 to 4:1.
10. The radiation curable composition of claim 9 , wherein the reactive diluent monomer comprises one or more polymerizable groups, wherein the polymerizable groups comprise or consists essentially of acrylate groups.
11. The radiation curable composition of claim 10 , wherein the reactive diluent monomer comprises ethyl-hexyl acrylate, phenoxy-ethyl acrylate, or N-vinyl caprolactam.
12. The radiation curable composition of claim 10 , wherein the composition comprises at least two different reactive diluent monomers.
13. The radiation curable composition of claim 10 , wherein the third viscosity is from 0.01 Pa·s to 1 Pa·s.
14. The radiation curable composition of claim 13 , wherein the wherein the ratio of the first viscosity to the third viscosity is less than 13.
15. The radiation curable composition of claim 14 , wherein the ratio of the first viscosity to the third viscosity is from about 5 to about 13.
16. The radiation curable composition of claim 15 , wherein the ratio of the first viscosity to the third viscosity is from about 6 to about 9.
17. The radiation curable composition of claim 14 , wherein the ratio of the first viscosity to the second viscosity is less than 4.7.
18. The radiation curable composition of claim 17 , wherein the ratio of the first viscosity to the second viscosity is from about 2 to about 4.4.
19. The radiation curable composition of claim 13 , wherein the composition possesses a liquid glass transition temperature (Tg,rheo) from —113 to —82° C., wherein Tg,rheo is determined by fitting equation (8) to experimental viscosity versus temperature data for the radiation curable composition:
η
(
T
)
/
η
2
5
=
1
0
(
-
562.5
/
(
62.5
-
T
g
,
r
h
e
o
)
*
(
T
-
25
)
37.5
+
T
-
T
g
,
r
h
e
o
)
,
(
8
)
where η(T)is the viscosity of the composition at temperature, T, and η 25 is the first viscosity.
20. The radiation curable composition of claim 1 , wherein the photoinitiator comprises 4 -methyl benzophenone, 2,4,6-trimethyl benzophenone, dimethoxybenzophenone, 1-hydroxycyclohexyl phenyl ketone, phenyl(1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and 4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal, oligo-[2-hydroxy-2-methyl- 1-[4-(1-methylvinyl)phenyl]propanone]; 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl phenyl, bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone- 1, 2-benzyl-2-(dimethylamino)- 1 [4-(4-morpholinyl)phenyl]-1-butanone, 2-dimethylamino-2-(4-methyl-benzyl)- 1 -(4-morpholin-4-yl-phenyl)-butan- 1-one, 4-benzoyl-4′-methyl diphenyl sulphide, 4,4′-bis(diethylamino)benzophenone, and 4,4′-bis(N,N-dimethylamino)benzophenone (Michler's ketone), or mixtures thereof.