Fiber coatings with low pullout force
Fiber coatings with low Young's modulus, low fiber pullout force for fibers in the as-drawn state, and small time-dependent increases in pullout force as the fiber ages. The fiber coatings are cured products of coating compositions that include an oligomer formed from an isocyanate, a hydroxy acrylate compound and a polyol. The oligomer includes a polyether urethane acrylate and a di-adduct compound. The reaction mixture used to form the oligomer includes a molar ratio of isocyanate:hydroxy acrylate:polyol of n:m:p, where when p is 2, n is in the range from 3.0 to 5.0 and m is in the range from 1.50n-3 to 2.50n-5. Control of the n:m:p ratio leads to compositions that, when cured, provide coatings and cured products having low Young's modulus, low pullout force on glass, and weak variations with time as the fiber ages.
1. A coating for optical fibers comprising:
a polyol compound, said polyol compound having unsaturation less than 0.1 meq/g;
a mercapto-functional silane compound;
a Young's modulus less than 1.0 MPa; and
a pullout force less than 1.7 lbf/cm when configured with thickness 32.5 μm to surround and directly contact a glass fiber having a diameter of 125 μm in an as-drawn state, said pullout force increasing by less than a factor of 2.0 upon aging said coating on said glass fiber for at least 60 days.
2. The coating of claim 1 , wherein said Young's modulus is less than 0.8 MPa.
3. The coating of claim 1 , wherein said Young's modulus is less than 0.6 MPa.
4. The coating of claim 1 , wherein said pullout force is less than 1.5 lbf/cm.
5. The coating of claim 1 , wherein said pullout force is less than 1.3 lbf/cm.
6. The coating of claim 1 , wherein said pullout force increases by less than a factor of 1.9 upon aging said coating on said glass fiber for at least 60 days.
7. The coating of claim 1 , wherein said pullout force increases by less than a factor of 1.8 upon aging said coating on said glass fiber for at least 60 days.
8. The coating of claim 1 , wherein said coating has a tear strength greater than 30 J/m 2 .
9. The coating of claim 1 , wherein said coating has a tear strength greater than 40 J/m 2 .
10. The coating of claim 1 , wherein said coating has a tear strength greater than 50 J/m 2 .
11. The coating of claim 1 , wherein said coating has a tensile toughness greater than 500 kJ/m 3 .
12. The coating of claim 1 , wherein said coating has a tensile toughness greater than 700 kJ/m 3 .
13. The coating of claim 1 , wherein said coating has a tensile toughness in the range from 500 kJ/m 3 1200 kJ/m 3 .
14. The coating of claim 1 , wherein said coating is a cured product of a curable composition, the curable composition comprising:
a diisocyanate compound; and
a hydroxy (meth)acrylate compound;
wherein said diisocyanate compound, said hydroxy (meth)acrylate compound and said polyol compound are present in said composition in the molar ratio n:m:p, respectively, where n is in the range from 3.0 to 5.0, m is in the range from 1.50n-3 to 2.50n-5, and p is 2.
15. The coating of claim 14 , wherein said diisocyanate compound comprises a compound having the formula:
O═C═N—R 1 —N═C═O
wherein the group R 1 comprises an alkylene group.
16. The coating of claim 15 , wherein said group R 1 comprises a 4,4′-methylenebis(cyclohexyl) group.
17. The coating of claim 14 , wherein said polyol compound comprises a compound having the formula:
H—O R 2 —O x H
wherein the group R 2 comprises an alkylene group and x is between 40 and 100.
18. The coating of claim 14 , wherein n is in the range from 3.4 to 4.6 and m is in the range from 1.60n-3 to 2.40n-5.
19. The coating of claim 14 , wherein said polyol is polypropylene glycol having a number average molecular weight in the range from 3000 g/mol to 9000 g/mol.
20. The coating of claim 14 , wherein said cured product comprises:
an oligomer, said oligomer comprising:
a polyether urethane acrylate compound having the molecular formula:
and a di-adduct compound having the molecular formula:
wherein
R 1 , R 2 and R 3 are independently selected from linear alkylene groups, branched alkylene groups, or cyclic alkylene groups;
y is 1, 2, 3, or 4;
x is between 40 and 100;
said di-adduct compound is present in an amount of at least 1.0 wt %.
21. The coating of claim 20 , wherein said di-adduct compound is present in an amount of at least 2.35 wt %.
22. The coating of claim 14 , wherein said coating composition further comprises a photoinitiator.
23. An optical fiber comprising:
a glass core;
a glass cladding surrounding and in direct contact with said glass core; and
the coating of claim 1 , the coating surrounding and in direct contact with said glass cladding.