A resin composition for secondary coating of an optical fiber is a resin composition comprising: a photopolymerizable compound comprising a urethane (meth)acrylate having a number average molecular weight of 10000 or more and 40000 or less; and a photopolymerization initiator, the content of the urethane (meth)acrylate is 0.05 parts by mass or more and 15 parts by mass or less based on the total amount of the resin composition of 100 parts by mass, and the urethane (meth)acrylate is a reaction product of a polyol having a number average molecular weight of 1800 or more and 4500 or less, a diisocyanate, and a hydroxyl group-containing (meth)acrylate.

A resin composition for secondary coating of an optical fiber is a resin composition comprising: a photopolymerizable compound comprising a urethane (meth)acrylate having a number average molecular weight of 10000 or more and 40000 or less; and a photopolymerization initiator, the content of the urethane (meth)acrylate is 0.05 parts by mass or more and 15 parts by mass or less based on the total amount of the resin composition of 100 parts by mass, and the urethane (meth)acrylate is a reaction product of a polyol having a number average molecular weight of 1800 or more and 4500 or less, a diisocyanate, and a hydroxyl group-containing (meth)acrylate.

This resin composition for secondary coating of an optical fiber contains: at least one type of polyoxyalkylene monoalkyl ether compound selected from the group consisting of a polyoxyalkylene monoalkyl ether having a number average molecular weight of 2500-10,000 and a derivative of said polyoxyalkylene monoalkyl ether; a photopolymerizable compound; and a photopolymerization initiator.

This resin composition for secondary coating of an optical fiber contains: at least one type of polyoxyalkylene monoalkyl ether compound selected from the group consisting of a polyoxyalkylene monoalkyl ether having a number average molecular weight of 2500-10,000 and a derivative of said polyoxyalkylene monoalkyl ether; a photopolymerizable compound; and a photopolymerization initiator.

A reactive mixture comprising a Fire, Smoke and Toxicity retardant (FST) composition for making a polyisocyanurate and/or polyurethane (PIR/PUR) comprising material, said FST composition comprising: a) at least one compound having at least one ethylenically unsaturated moiety having a number average equivalent weight<160 g/mol, and b) optionally one or more radical initiator compound characterized in that the onset temperature for radical polymerization (T.sub.onset) of the ethylenically unsaturated compound with or without the radical initiator is 2° C. up to 40° C. lower than the maximum reaction temperature achieved during the process for making the PIR/PUR material (reaction exotherm (T.sub.reaction)).

A reactive mixture comprising a Fire, Smoke and Toxicity retardant (FST) composition for making a polyisocyanurate and/or polyurethane (PIR/PUR) comprising material, said FST composition comprising: a) at least one compound having at least one ethylenically unsaturated moiety having a number average equivalent weight<160 g/mol, and b) optionally one or more radical initiator compound characterized in that the onset temperature for radical polymerization (T.sub.onset) of the ethylenically unsaturated compound with or without the radical initiator is 2° C. up to 40° C. lower than the maximum reaction temperature achieved during the process for making the PIR/PUR material (reaction exotherm (T.sub.reaction)).

The present application provides a photopolymerization initiator having one or more ethylenic unsaturated bonds and one or more photopolymerization initiating functional groups in the molecule has been found. One or more kinds selected from an acrylamide group, an acrylate group, a vinyl group, an allyl group, a maleimide group, and the like can be suitably used as the ethylenic unsaturated bond, and a benzophenone compound having a specific structure can be suitably used as the photopolymerization initiating functional group.

The present application provides a photopolymerization initiator having one or more ethylenic unsaturated bonds and one or more photopolymerization initiating functional groups in the molecule has been found. One or more kinds selected from an acrylamide group, an acrylate group, a vinyl group, an allyl group, a maleimide group, and the like can be suitably used as the ethylenic unsaturated bond, and a benzophenone compound having a specific structure can be suitably used as the photopolymerization initiating functional group.

A photocurable composition is provided. A cured product formed by curing the photocurable composition has reworkability and excellent heat resistance while having flexibility. The photocurable composition includes a telechelic acrylic polymer having an acryloyl group at both ends; a polyfunctional acrylic polymer having acryloyl groups; a monofunctional acrylic monomer; and a fumed silica including at least one of a hydrophilic fumed silica or a fumed silica having a polar group. The photocurable composition has a Martens hardness of 0.07 to 0.75 N/mm.sup.2, where the Martens hardness is a hardness after the photocurable composition is cured.

A photocurable composition is provided. A cured product formed by curing the photocurable composition has reworkability and excellent heat resistance while having flexibility. The photocurable composition includes a telechelic acrylic polymer having an acryloyl group at both ends; a polyfunctional acrylic polymer having acryloyl groups; a monofunctional acrylic monomer; and a fumed silica including at least one of a hydrophilic fumed silica or a fumed silica having a polar group. The photocurable composition has a Martens hardness of 0.07 to 0.75 N/mm.sup.2, where the Martens hardness is a hardness after the photocurable composition is cured.