Molding composition

An injection molding composition comprising an ultrahigh molecular weight polyethylene material having an intrinsic viscosity of 10-30 dl/g at 135.degree. C. in decalin, said material resulting from a polymerization process consisting of the following two stages of polymerization reaction:

• (a) a first reaction stage wherein an ethylene monomer is polymerized in a reaction vessel in the presence of a composite catalyst comprising a solid component containing at least magnesium, titanium and/or vanadium and an organometallic compound and in the absence of hydrogen or in the presence of hydrogen at a low concentration to produce 75-99 parts by weight of polyethylene having an intrinsic viscosity of 12-32 dl/g at 135.degree. C. in decalin;
• and
• (b) a second reaction stage wherein a fresh feed of ethylene monomer is introduced in the same reaction vessel and polymerized in the presence of hydrogen at a higher concentration while retaining the reaction produce from the first reaction stage in said reaction vessel to produce 25-1 parts by weight of polyethylene having an intrinsic viscosity of 0.1-5 dl/g at 135.degree. C. in decalin.