Polyethylene

1 . A polyethylene polymer satisfying the following conditions of 1) to 4):

1) A melt index (MI) of 0.5 g/10 min to 40 g/10 min, as measured at 190° C. under a load of 2.16 kg according to ASTM D1238;

2) A molecular weight distribution (MWD) of 2.3 to 2.6;

3) A crystallinity of 63% to 71%, as measured using a differential scanning calorimeter (DSC) according to ASTM F2625; and

4) A crystal relaxation temperature (T cr ) of 42° C. to 50° C., as measured using dynamic mechanical analysis (DMA).

2 . The polyethylene polymer of claim 1 , wherein the melt index (MI) is 18 g/10 min to 40 g/10 min, as measured at 190° C. under a load of 2.16 kg according to ASTM D1238.

3 . The polyethylene polymer of claim 1 , wherein an abrasion resistance is 0.2 mg/cm 3 or less, as measured according to ASTM D5264.

4 . The polyethylene polymer of claim 1 , wherein the polyethylene polymer is a copolymer of ethylene and an alpha-olefin.

5 . The polyethylene polymer of claim 4 , wherein the alpha-olefin includes one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicosene, norbornene, norbornadiene, ethylidene norbornene, phenyl norbornene, vinyl norbornene, dicyclopentadiene, 1,4-butadiene, 1,5-pentadiene, 1,6-hexadiene, styrene, alpha-methylstyrene, divinylbenzene, and 3-chloromethylstyrene.

6 . The polyethylene polymer of claim 1 , wherein the polyethylene polymer is prepared by copolymerizing ethylene and an alpha-olefin in the presence of a catalyst composition including a metallocene compound represented by Chemical Formula 1:

wherein, in Chemical Formula 1,

B is boron,

M is a Group 4 transition metal,

R 1 to R 4 are each independently hydrogen, C 1-20 alkyl, C 3-20 cycloalkyl, or C 6-20 aryl, or optionally R 1 and R 2 or R 3 and R 4 are bonded to each other to form a substituted or unsubstituted C 6-60 aromatic ring,

R 5 and R 6 are each independently C 1-20 alkyl, C 3-20 cycloalkyl, or C 6-20 aryl, or optionally R 5 and R 6 are bonded to each other to form a C 3-60 aliphatic ring or a C 6-60 aromatic ring,

X 1 and X 2 are each independently C 1-20 alkyl or —O(CO)R′, wherein R′ is C 1-20 alkyl,

Q is a substituted or unsubstituted C 2-60 hetero ring including any one or more selected from the group consisting of N, O, and S,

Y and Y′ are elements constituting Q,

Y is N, O, or S,

Y′ is N or C.

7 . The polyethylene polymer of claim 6 , wherein R 1 to R 4 are each independently hydrogen or methyl, or optionally R 1 and R 2 or R 3 and R 4 are bonded to each other to form a benzene ring or a 1,2,3,4-tetrahydronaphthalene ring, wherein the benzene ring or the 1,2,3,4-tetrahydronaphthalene ring is unsubstituted or substituted with 1 to 4 substituents selected from the group consisting of methyl, tert-butyl, and 4-tert-butyl phenyl.

8 . The polyethylene polymer of claim 6 , wherein R 5 and R 6 are each independently methyl or phenyl, or optionally R 5 and R 6 are bonded to each other to form a cyclooctane ring.

9 . The polyethylene polymer of claim 6 , wherein the compound represented by Chemical Formula 1 is any one of compounds represented by the following structural formulae:

10 . The polyethylene polymer of claim 6 , wherein the catalyst composition further includes one or more cocatalyst compounds selected from the group consisting of compounds represented by Chemical Formulae 2 to 4:

[Al(R 10 )—O] a -  [Chemical Formula 2]

wherein, in Chemical Formula 2,

R 10 is halogen or C 1-20 hydrocarbyl substituted or unsubstituted with halogen; and

a is an integer of 2 or more,

D(R 11 ) 3   [Chemical Formula 3]

wherein, in Chemical Formula 3,

D is aluminum or boron; and

R 11 is halogen or C 1-20 hydrocarbyl substituted or unsubstituted with halogen,

[L-H] + [ZA 4 ] − or [L] + [ZA 4 ] −   [Chemical Formula 4]

wherein, in Chemical Formula 4,

L is a neutral or cationic Lewis base;

H is a hydrogen atom;

Z is a group 13 element; and

plural As are each independently C 6-20 aryl or C 1-20 alkyl, of which one or more hydrogen atoms are substituted with halogen, C 1-20 hydrocarbyl, C 1-20 alkoxy, or phenoxy.