A blend comprising a high molecular weight, high density polyethylene (HMW HDPE) and a linear low density polyethylene (LLDPE) is disclosed. The blend comprises from about 50 wt. % to about 80 wt. % of HMW HDPE. The HMW HDPE has a density greater than about 0.94 g/cc and a melt index MI.sub.2 less than about 0.1 dg/min. The blend also comprises about 20 wt. % to about 50. wt % of LLDPE. The LLDPE has a density within the range of about 0.90 to about 0.93 g/cc and an MI.sub.2 within the range of about 0.5 to about 5 dg/min. The LLDPE is a copolymer of ethylene with 1-hexene that has a dart drop impact strength of greater than about 500 grams as measured by ASTM D1709/A. The blend shows increased resistance to environmental stress cracking.
A multiphase polymeric material comprises a first rigid continuous phase and a second elastic phase dispersed in the first phase. The multiphase polymeric material may be formed into polymeric strips and used to make a cellular confinement system which is suitable for use in cold areas.
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.
Melt blended HDPE compositions for single and dual wall corrugated HDPE pipe and associated fabricated and molded fittings and accessories with enhanced physical properties and processing and environmental stress crack resistance (ESCR) characteristics and associated blend methods are disclosed in which virgin or recycled homopolymer and/or copolymer HDPE resin components are blended. The invention discloses methods for 1) selecting and determining the relative weight fractions of the HDPE blending components that provide specific physical properties and processability of HDPE blended compositions associated with density and melt index respectively and specific values of environmental stress crack resistance (ESCR) associated with specific molecular parameters and 2) for determining from molecular parameters, the ESCR of linear polyethylene resins and blended compositions within a class having similar densities. The invention reduces the cost of raw materials to corrugated HDPE pipe manufacturers by enabling the use of virgin prime commodity HDPE resins and/or wide and off specification prime HDFE resins in place of single stream specialty HDPE resins and favorably impacts the environment by providing the capability of utilizing recycled HDPE resins in place of prime HDPE resins in the manufacture of corrugated HDPE pipe.
A thick film produced from a polyolefin blend is disclosed. The film is prepared from a blend having a density from 0.935 to 0.955 g/cm.sup.3 and comprising LLDPE and greater than 50% by weight HDPE having a density greater than 0.955 g/cm.sup.3. The film has a modulus in the machine direction from about 75,000 to about 130,000 psi and improved machine direction tear strength.
The invention provides a polyethylene composition comprising a melt blend of (i) a bimodal high molecular weight high density polyethylene resin having a NCTL stress crack resistance of about 200 hours or greater, and (ii) a high density polyethylene resin selected from the group consisting of a homopolymer high density polyethylene resin, a copolymer high density polyethylene resin, and mixtures thereof, wherein the composition has a minimum NCTL stress crack resistance of 24 hours. In another embodiment, a polyethylene composition comprises a melt blend of the bimodal high molecular weight high density polyethylene resin and a linear low density polyethylene resin. The bimodal high molecular weight high density polyethylene resin can be a commodity film grade resin, the homopolymer and copolymer resins can be milk bottle grade and detergent bottle grade, respectively, and the linear low density polyethylene resin can be a film grade. The compositions are especially useful for manufacture of profile and corrugated pipe and/or pipe fitting applications, and chemical waste applications including sanitary sewer or irrigation piping systems.
