499 results about "Environmental stress cracking" patented technology

A dual reactor solution process gives high density polyethylene compositions containing a first ethylene polymer and a second ethylene polymer which have a good balance of processability, toughness, and environmental stress crack resistance combined with good organoleptic properties. The polyethylene compositions are suitable for compression molding or injection molding applications and are particularly useful in the manufacture of caps and closures for bottles.

The invention relates to a method for producing an ethylene polymer, comprising performing polymerization of ethylene in co-presence of hydrogen using a trialkylaluminum compound-carried chromium catalyst, wherein the chromium catalyst is obtained by calcination-activating a chromium compound that is carried on an inorganic oxide carrier in a non-reducing atmosphere to convert chromium atoms in the chromium compound into hexavalent chromium atoms for at least a portion thereof, and treating with a trialkylaluminum compound in an inert hydrocarbon solvent to carry thereon and removing to dry the solvent so that the chromium atoms are not over-reduced by the trialkylaluminum compound, and to an ethylene polymer suitable for blow molded articles obtained by the production method. The ethylene polymer of the invention have improved environment stress crack resistance (ESCR) and impact resistance in a good balance and are suitable for molded blow articles, in particular large size blow molded articles.

A dual reactor solution process gives high density polyethylene compositions containing a first ethylene copolymer and a second ethylene copolymer and which have good processability, toughness, and environmental stress crack resistance combined with good organoleptic properties. The polyethylene compositions are suitable for compression molding or injection molding applications and are particularly useful in the manufacture of caps and closures for bottles.

Resins comprising a relatively high-density, low-molecular-weight polyethylene component and a relatively low-density, high-molecular-weight ethylene copolymer component and methods of making the resins are disclosed. The rheological polydispersity of the high-density component exceeds that of either the resin or the low-density component. The resins are valuable for making films, sheets, coatings, pipes, fibers, and molded articles having a favorable balance of good stiffness and excellent environmental stress crack resistance.

The present invention relates to a polyolefin that has high environmental stress cracking resistance (ESCR), a high impact property, and an excellent die swell property, and a method of preparing thesame. According to the method of preparing polyolefin of the present invention, a supported hybrid metallocene catalyst and an alpha olefin comonomer having 4 or more carbon atoms are used to obtain polyolefin having the bimodal or multimodal molecular weight distribution curves during the single reactor polymerization. The polyolefin has excellent processability, a melt flow rate ratio (MFRR) that is useful to processing, excellent shapability, impact strength, tensile strength, in particular, environmental stress cracking resistance (ESCR) and full notch creep test (FNCT), thus being used tomanufacture the blow molded product.

This invention discloses the production and use of a polyethylene composition comprising a metallocene-produced linear low density polyethylene and a multi modal high density polyethylene prepared from either a Ziegler-Natta or a metallocene catalyst system. The resulting polyethylene composition is suitable for preparing articles having improved environmental stress crack resistance, rigidity, contact transparency, gloss as well as good processing capabilities.

Disclosed is a polyethylene composition having faster crystallization rate and improved environmental stress cracking resistance. The polyethylene composition comprises a multimodal polyethylene and a nucleating agent. The multimodal polyethylene comprises from 25 to 50 wt % of a low molecular weight ethylene homopolymer component, from 25 to 50 wt % of a medium molecular weight ethylene copolymer component and from 25 to 50 wt % of a high molecular weight ethylene copolymer component. The polyethylene composition has an environmental stress cracking resistance (ASTM D1693, Condition B in 100% Igepal) greater than or equal to 40 days and a crystallization half time less than or equal to 70% of the crystallization half time of the multimodal polyethylene without nucleating agent.

A high density polyethylene moulding composition having a multimodal molecular weight distribution, having a density according to ISO 1183 at 23° C. in the range of 945 to 965 kg / m3 and an MFR190 / 2 according to ISO 1133 in the range of 0.05 to 25 g / 10 min, said polyethylene moulding composition comprising at least three ethylene polymer fractions having distinct molecular weights: A) 15 to 50 wt % of a low molecular weight ethylene homopolymer fraction with a weight average molecular weight Mw in the range of 15 to 40 kg / mol; B) 15 to 50 wt % of a medium molecular weight ethylene homopolymer fraction with a weight average molecular weight Mw in the range of 70 to 180 kg / mol; and C) 15 to 50 wt % of a high molecular weight ethyleve copolymer fraction with a weight average molecular weight Mw in the range of 200 to 400 kg / mol; and wherein the composition has: a tensile modulus according to ISO 527-2: 1993 measured on compression moulded samples of at least 800 MPa; a Charpy impact strength CIS (23° C.) according to ISO 179:2000 measured on V- notched samples produced by compression moulding of at least 30 kJ / m2; and an environmental stress crack resistance ESCR measured as FNCT full notch creep test according to ISO / DIS 16770.3 at 50° C. and 6 MPa of at least 20 h.