POLYETHYLENE FIBER

1 . An ultrahigh molecular weight polyethylene fiber containing ethyl branches as side chains wherein,

the polyethylene fiber satisfies a ratio of the number of ethyl branches per 1000 carbon atoms (C 2 H 5 /1000C) to an elongation stress of the polyethylene fiber (MPa) {(C 2 H 5 /1000C)/(elongation stress)} of 2 to 30 ethyl branches per 1000 carbon atoms/MPa.

2 . The ultrahigh molecular weight polyethylene fiber according to claim 1 , wherein the polyethylene fiber further satisfies all the requirements below in creep measurement at the measurement temperature of 70° C. under a measurement load of 6.6 g/dtex:

a creep rate is not larger than 9.0×10 −8 sec −1 ;

an elongation is not larger than 2.7% when 24 hours have elapsed since start of the measurement;

an elongation is not larger than 5.0% when 96 hours have elapsed since start of the measurement; and

a time until an elongation reaches 3.0% is not less than 30 hours.

3 . The ultrahigh molecular weight polyethylene fiber according to claim 1 , wherein the polyethylene fiber further satisfies below:

a number of ethyl branches per 1000 carbon atoms (C 2 H 5 /1000C) is larger than 1.1.

4 . The ultrahigh molecular weight polyethylene fiber according to claim 1 , wherein the polyethylene fiber further satisfies below:

a melting point peak temperature in a first temperature rising is not higher than 141° C., and

a heat amount is not larger than 134 Jig in a range from 70° C. to 150° C. in which the melting point peak temperature is reached in a second temperature rising,

wherein, the peak temperature in the first temperature rising and the heat amount in the second temperature rising are values obtained when, in the differential scanning calorimetry (DSC measurement), a temperature of the polyethylene fiber is increased from 30° C. to 200° C. at a rate of 10° C./imin (first temperature rising) and the polyethylene fiber is retained at 200° C. for five minutes, the temperature is thereafter reduced from 200° C. to 30° C. at a rate of 10° C./min and the polyethylene fiber is retained at 30° C. for five minutes, and the temperature is thereafter increased from 30° C. to 200° C. at a rate of 10° C./min (second temperature rising).

5 . The ultrahigh molecular weight polyethylene fiber according to claim 1 , wherein the polyethylene fiber further satisfies below:

a tensile strength is not less than 20 cN/dtex.

6 . A use of the ultrahigh molecular weight polyethylene fiber according claim 1 , wherein the use is at least one selected from the group of a braid, a twisted yarn, a fishing line, a rope, and a net; wherein the braid, the twisted yarn, the fishing line, the rope, and the net contains the polyethylene fiber.