EP3830186A1

EP3830186A1 - Polyethylene composition having improved environmental stress cracking resistance

Info

Publication number: EP3830186A1
Application number: EP19742340.3A
Authority: EP
Inventors: Anantharaman Dhanabalan; Mark Johannes Boerakker; Maria Soliman; Radha Kamalakaran
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2018-07-27
Filing date: 2019-07-17
Publication date: 2021-06-09
Also published as: CN113195619A; CN113195619B; WO2020020716A1

Abstract

A polyethylene composition having increased environmental stress crack resistance comprises a polymer blend of a high density polyethylene (HOPE) and a styrenic block copolymer (SBC). The styrenic block polymer is at least one of a non-hydrogenated styrene- isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer. In a method of forming a polyethylene composition having increased environmental stress crack resistance, a high density polyethylene (HOPE) is modified by combining the HOPE with a styrenic block copolymer (SBC) of at least one of a non- hydrogenated styrene-isoprene-styrene (SIS) block copolymer and a styrene-butadiene- styrene (SBS) block copolymer.

Description

POLYETHYLENE COMPOSITION HAVING IMPROVED ENVIRONMENTAL STRESS

CRACKING RESISTANCE

TECHNICAL FIELD

[0001 ] The invention relates to high density polyethylene compositions that have improved environmental stress crack resistance.

BACKGROUND

[0002] Synthetic polymeric materials, particularly thermoplastic resins, are widely used in the manufacturing of a variety of end-use articles ranging from medical devices to food containers. Conventional propylene based polymeric materials have long been used in processes like thermoforming, blow molding, coating, etc., requiring high melt strength which could be achieved by increasing molecular weight and broadening of molecular weight distribution. Molecular weight and molecular weight distribution can be modified in the polymerization process itself by choosing particular process conditions and catalysts.

[0003] Polypropylene (PP) has widely been used to produce caps and closures. To achieve a necessary cap strength, however, an inner liner (e.g., made from ethylene vinyl acetate (EVA), polyvinylchloride (PVC), butyl rubber, or the like) is typically required to achieve the requisite seal properties and organoleptic properties. Such two-layer caps are costly. On the other hand, high density polyethylene (HDPE) typically possesses requisite stiffness, flow properties, and better organoleptic properties for making one-piece closures, such as screw caps. HDPE, however, mostly lacks in its ability to resist cracking over time (as measured by environmental stress cracking resistance (ESCR) testing). Hence, there is a need to improve ESCR performance of HDPE compositions.

[0004] Attempts have been made to improve such performance. These include the incorporation of C₄, O_Q, and/or Cs comonomers used during polymerization, which may be carried out in the vapor phase or in solution. Fine-tuning the molecular weight distribution (bi- or multi-modal) has also been used, as well as blending the polyethylene with other polymers. Cross-linking of silane grafted polyethylene has also been used.

[0005] Given the growing trend of down-gauging of the plastic parts (for example, caps and closure, bottles and containers) and the use of plastic containers for storing aggressive chemicals (bleach bottles), an enhanced ESCR performance of plastics even at a lower thickness becomes more vital. For instance, a weight reduction of bottle caps from 3 g to 1.8 g - 2.0 g, as currently demanded by many brand-owners, while still keeping its ESCR performance, is an emerging challenge.

[0006] While various methods exist to increase ESCR properties of polyethylene, many of these suffer in that they are cost prohibitive or applicable only to the method of making the starting polyethylene materials instead of to existing polyethylene materials. Thus, there is a continuing need for polyethylene-based compositions having increased ESCR, particularly for those that are suitable for cap and closure applications.

SUMMARY

[0007] A polymer composition having increased environmental stress crack resistance comprises a polymer blend of a high density polyethylene (HDPE) and a styrenic block copolymer (SBC). The SBC is at least one of a styrene-isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer.

[0008] In certain embodiments, the HDPE is at least one of a unimodal HDPE, bimodal HDPE, and multimodal HDPE. The styrenic block copolymer may have a weight average molecular weight (Mw) of from 20,000 to 80,000. In some embodiments, the styrenic block copolymer may have a styrene content of from 5 wt.% to 40 wt.% by total weight of the styrenic block copolymer.

[0009] The styrenic block copolymer may comprise a mixture of styrene-isoprene-styrene (SIS) block copolymer and styrene-butadiene-styrene (SBS) block copolymer in certain embodiments.

[0010] The styrenic block copolymer content may be from 0. 1 wt.% to 20 wt.% by total weight of the polymer blend in some applications.

[001 1 ] The polymer blend may provide a molded article having an ESCR of at least 30 hours as determined by ASTM D1693-15B. In certain instances, the polymer blend may provide a molded article having an ESCR of from 30 hours to 1000 hours as determined by ASTM D1693-15B method.

[0012] In particular embodiments, the HDPE is a copolymer with comonomers selected from C₃ to C10 olefin monomers, with the comonomers being present in the HDPE copolymer in an amount of from 2 wt.% or less. In other embodiments, the HDPE is a copolymer with comonomers selected from C₃ to C10 olefin monomers, with the comonomers being present in the HDPE copolymer in an amount of from 1 wt.% or less. In some embodiments, the HDPE is a neat HDPE.

[0013] The HDPE may be unimodal HDPE having a melt flow ratio at 190 °C and 2.16 kg or 21 .6 kg of 0.2 dg/min to 50 dg/min and/or a density of 945 kg/m³to 965 kg/m³. In other cases, the HDPE is bimodal and may have a melt flow ratio at 190 °C and 2.16 kg or 21.6 kg of 0.2 dg/min to 50 dg/min and/or a density of 945 to 965 kg/m³. In the context of the present invention, density of the HDPE may be determined in accordance with ISO 1 183-1 (2012), method A, and the melt flow rate in accordance with ISO 1 133-1 (201 1 ).

[0014] In particular embodiments, the polymer composition may include an additive of at least one of a nucleating agent, a heat conductive agent, a tie agent, an antiblocking agent, an antistatic agent, an antioxidant, a neutralizing agent, an acid scavenger, a blowing agent, a crystallization aid, a dye, a flame retardant agent, a filler, an impact modifier, a mold release agent, an oil, another polymer, a pigment, a processing agent, a reinforcing agent, a stabilizer, an UV resistance agent, a clarifying agent, a slip agent, a flow modifying agent, and combinations thereof.

[0015] The HDPE is a multimodal HDPE in particular applications and the styrenic block copolymer content may range from 0.1 wt.% to 2 wt.% by total weight of the polymer blend.

[0016] The polymer blend may be formed into an article of manufacture. The article may be at least one of a film, a molded part, a container, a beverage container cap, a lid, a sheet, a pipe, a pipe coupling, a bottle, a cup, a tray, a pallet, and a toy. The article may be formed by at least one of injection molding, blow molding, compression molding, sheet extrusion, film blowing, pipe extrusion, profile extrusion, calendaring, and thermoforming.

[0017] In a method of forming a polyethylene composition having increased environmental stress crack resistance, a high density polyethylene (HDPE) is modified by combining the HDPE with a styrenic block copolymer (SBC) of at least one of a non-hydrogenated styrene- isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer.

BRIEF DESCRIPTION OF THE DRAWINGS [0018] For a more complete understanding of the embodiments described herein, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying figure, in which:

[0019] FIG. 1 is a stained transmission electron microscope (TEM) image of a polymer blend of bimodal HDPE incorporated with 5 wt.% of styrene-isoprene-styrene (SIS) linear block copolymer.

DETAILED DESCRIPTION

[0020] It has been discovered that the environmental stress crack resistance (ESCR) of high density polyethylene (HDPE) can be increased by incorporating an additive of a styrenic block copolymer (SBC) of at least one of a styrene-isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer. The styrenic block copolymer is incorporated into the HDPE by polymer melt blending. The amount and the type of the styrenic block copolymer incorporated into the HDPE is selected so that the processability of the HDPE remains relatively unaffected while its ESCR performance is enhanced.

[0021 ] The HDPE polymers used in the polymer blend can include those prepared by any of the polymerization processes, which are in commercial use (e.g., a“high pressure” process, a slurry process, a solution process and/or a gas phase process) and with the use of any of the known catalysts (e.g., multisite catalysts such as Ziegler Natta catalysts, and/or single site catalysts such as chromium or Phillips catalysts, metallocene catalysts, and the like).

[0022] The HDPE can be unimodal, bimodal HDPE or a combination of these. As used herein, where the phrase or term “high density polyethylene” or “HDPE” are used without characterization as unimodal, bimodal or multimodal HDPE, the phrase or term should be construed as referring to any or all of them. Bimodal HDPE can be made using an advance cascade process. HDPE can be obtained from a commercial vendor. Non-limiting examples of suitable commercially available HDPE include those HDPE polymers marketed as SABIC^® HDPE CC253 and SABIC^® HDPE CC254 (SABIC^®, Kingdom of Saudi Arabia). In certain aspects, the polymer blends of the present invention do not include polypropylene. In some embodiments, the polymer blends do not include linear low density polyethylene (LLDPE).

[0023] The HDPE can be characterized by various properties such as a melt flow rate (MFR) at 190 °C and 2.16 kg and / or 21.6 kg, a density, ESCR, tensile strength at yield, tensile modulus, tensile elongation at yield, Charpy notched impact strength (-30 °C), hardness or combinations thereof. The density of the unimodal, bimodal HDPE can be from 945 kg/m³ to 965 kg/m³, or at least, equal to, and/or between any two of 945 kg/m³, 950 kg/m³, 955 kg/m³, 960 kg/m³, and 965 kg/m³.

[0024] It should be noted in the description, if a numerical value, concentration or range is presented, each numerical value should be read once as modified by the term "about" (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the description, it should be understood that an amount range listed or described as being useful, suitable, or the like, is intended that any and every value within the range, including the end points, is to be considered as having been stated. For example,“a range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific points within the range, or even no point within the range, are explicitly identified or referred to, it is to be understood that the inventor appreciates and understands that any and all points within the range are to be considered to have been specified, and that inventor possesses the entire range and all points within the range.

[0025] In some embodiments, all or a portion of the HDPE component is unimodal. MFR of unimodal HDPE at 190 °C and 2.16 kg and/or 21.6 kg can be from 0.2 dg/min to 50 dg/min or at least, equal to, and/or between any two of 0.2 dg/min, 0.3 dg/min, 0.4 dg/min, 0.5 dg/min, 0.75 dg/min, 1 dg/min, 1.25 dg/min, 1 .5 dg/min, 1.75 dg/min, 2 dg/min, 3 dg/min, 4 dg/min, and 5 dg/min, 6 dg/min, 7 dg/min, 8 dg/min, 9 dg/min, 10 dg/min, 1 1 dg/min, 12 dg/min, 13 dg/min, 14 dg/min, 15 dg/min, 16 dg/min, 17 dg/min, 18 dg/min, 19 dg/min, and 20 dg/min, 21 dg/min, 22 dg/min, 23 dg/min, 24 dg/min, 25 dg/min, 26 dg/min, 27 dg/min, 28 dg/min, 29 dg/min, 30 dg/min, 31 dg/min, 32 dg/min, 33 dg/min, 34 dg/min, 35 dg/min, 36 dg/min, 37 dg/min, 38 dg/min, 39 dg/min, 40 dg/min. 41 dg/min, 42 dg/min, 43 dg/min, 44 dg/min, 45 dg/min, 46 dg/min, 47 dg/min, 48 dg/min, 49 dg/min and 50 dg/min. In particular embodiments, the MFR is from 0.5 dg/min to 5 dg/min at 190 °C and with 2.16 kg load.

[0026] Tensile modulus and/or flexural modulus of unimodal HDPE can be from 1000 MPa to 1300 MPa, or at least, equal to, and/or between any two of 1000 MPa, 1050 MPa, 1 100 MPa, 1 150 MPa, 1200 MPa, 1250 MPa, and 1300 MPa, as measured by ISO 527-2. Tensile and/or flexural strength at yield of unimodal HDPE can be from 20 MPa to 40 MPa, or at least, equal to, and/or between any two of 20 MPa, 25 MPa, 30 MPa, 35 MPa, and 40 MPa, as measured by ISO 527-2. [0027] In some embodiments, all or a portion of the HDPE component is bimodal and/or multimodal. Bimodal HDPE can have a MFR at 190 °C and 2.16 kg and/or 21 kg of from 0.2 dg/min to 20 dg/min or at least, equal to, and/or between any two of 0.2 dg/min to 20 dg/min or at least, equal to, and/or between any two of 0.2 dg/min, 0.3 dg/min, 0.4 dg/min, 0.5 dg/min, 0.75 dg/min, 1 dg/min, 1.25 dg/min, 1.5 dg/min, 1 .75 dg/min, 2 dg/min, 3 dg/min, 4 dg/min, and 5 dg/min, 6 dg/min, 7 dg/min, 8 dg/min, 9 dg/min, 10 dg/min, 1 1 dg/min, 12 dg/min, 13 dg/min, 14 dg/min, 15 dg/min, 16 dg/min, 17 dg/min, 18 dg/min, 19 dg/min, and 20 dg/min, 21 dg/min, 22 dg/min, 23 dg/min, 24 dg/min, 25 dg/min, 26 dg/min, 27 dg/min, 28 dg/min, 29 dg/min, 30 dg/min, 31 dg/min, 32 dg/min, 33 dg/min, 34 dg/min, 35 dg/min, 36 dg/min, 37 dg/min, 38 dg/min, 39 dg/min, 40 dg/min. 41 dg/min, 42 dg/min, 43 dg/min, 44 dg/min, 45 dg/min, 46 dg/min, 47 dg/min, 48 dg/min, 49 dg/min and 50 dg/min. In particular embodiments, the MFR is from 0.5 dg/min to 5 dg/min at 190 °C and with 2.16 kg load.

[0028] Tensile modulus of bimodal HDPE can be from 1000 MPa to 1300 MPa, or at least, equal to, and/or between any two of 1000 MPa, 1050 MPa, 1 100 MPa, 1 150 MPa, 1200 MPa, 1250 MPa and 1300 MPa, as measured by ASTM D638. Tensile strength at yield of bimodal and multimodal HDPE can be from 20 MPa to 40 MPa, or at least, equal to, and/or between any two of 20 MPa, 25 MPa, 30 MPa, 35 MPa, and 40 MPa, as measured by ASTM D638.

[0029] The Charpy notched impact strength of the HDPE component at -30 °C can be from 3 kJ/m² to 12 kJ/m² or at least, equal to, and/or between any two of 3 kJ/m², 4 kJ/m², 5 kJ/m², 6 kJ/m², 7 kJ/m², 8 kJ/m², 9 kJ/m², 10 kJ/m², 1 1 kJ/m² and 12 kJ/m².

[0030] In certain embodiments, the HDPE component of the polymer blend will constitute homopolymers of ethylene. These may include homopolymers solely of neat HDPE. In other embodiments, however, the HDPE may include a polymer blend with non-HDPE polyethylene. These may include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and medium density polyethylene (MDPE). When such non-HDPE polyethylene is used it may be present in the HDPE polymer component in an amount of from 2 wt.%, 1.5 wt.%, 1 wt.%, 0.5 wt.%, 0.1 wt.% or less.

[0031] In other embodiments, the HDPE component can include copolymers of ethylene with at least one C3 to C10 alpha olefin. Typically, this will be at least one of the alpha olefins of butene, hexene, and/or octene. In some embodiments the HDPE is a copolymer with 1-butene (polyethylene-1 -butene) or 1 -hexene (polyethylene-1 -hexene). When such copolymers are used, the non-ethylene comonomer may be present in the HDPE copolymer in an amount of from 2 wt.%, 1.5 wt.%, 1 wt.%, 0.5 wt.%, 0.1 wt.% or less. In particular embodiments, there is no butene or no C₃ to C10 alpha olefin comonomer.

[0032] In certain embodiments, the HDPE may be an un-functionalized neat HDPE with no functional groups along the polymer chain. In particular embodiments, the HDPE polyethylene does not include any anhydride modified HDPE.

[0033] The HDPE component, as described above, is used as a polymer blend in combination with styrenic block copolymers (SBCs). The SBCs used are those linear triblock copolymers formed from block chains of styrene and diene monomers having the general structure A— B— A, where A constitutes a polystyrene block and B constitutes a diene polymer block, such as polyisoprene or polybutadiene. To impart the desired ESCR characteristics of the final product, the SBC is used in an amount of from 0.1 wt.% to 20 wt.% by total weight of the polymer blend. In particular embodiments, the SBC is used in an amount of from 0.1 wt.% to 20 wt.% by total weight of the polymer blend or at least, equal to, and/or between any two of 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 wt.%, 1.5 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, 1 1 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, and 20 wt.% by total weight of the polymer blend. In particular embodiments, the SBC is used in an amount of from 0.1 wt%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, or 5 wt.% to 6 wt.%, 7 wt.%, 10 wt.%, 1 1 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, or 15 wt.% by total weight of the polymer blend, with from 0.5 wt.% to 15 wt.% being particularly useful.

[0034] In other embodiments, lesser amounts of SBC may be used, with the SBC being used in an amount at least, equal to, and/or between any two of 0.10 wt%, 0.15 wt%, 0.20 wt.%, 0.25 wt%, 0.30 wt.%, 0.35 wt%, 0.40 wt.%, 0.45 wt%, 0.50 wt.%, 0.55 wt%, 0.60 wt%, 0.65 wt.%, 0.70 wt.%, 0.75 wt%, 0.80 wt.%, 0.85 wt%, 0.90 wt.%, 0.95 wt%, 1.00 wt.%, 1 .10 wt%, 1.15, 1.20 wt%, 1.25 wt%, 1.30 wt%, 1.35 wt%, 1.40 wt%, 1.45 wt%, 1.50 wt%, 1 .55 wt%, 1 .60 wt%, 1.65 wt%, 1.70 wt%, 1.75 wt%, 1.80 wt%, 1.85 wt%, 1 .90 wt%, 1.95 wt%. and 2.0 wt.%.

[0035] The SBC component of the polymer blend may be a hydrogenated or non- hydrogenated SBC block copolymer. As used herein, non-hydrogenated SBC block copolymers may be those SBCs, such as SIS, wherein from 30% or more of the polydiene block is unsaturated. In particular embodiments, the non-hydrogenated block copolymers may be those SBCs wherein from 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% to less than 100% or 100% of the polydiene block is unsaturated.

[0036] In particular embodiments, the SBC is a styrene-isoprene-styrene (SIS) block copolymer. The SIS block copolymer may be a hydrogenated or non-hydrogenated SIS block copolymer. In many instances, the SIS block copolymer is a non-hydrogenated block copolymer wherein from 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% to less than 100% or 100% of the polyisoprene block is unsaturated.

[0037] The SIS block copolymer component of the polymer blend may have a polystyrene or styrene monomer content of from 5 wt.% to 40 wt.% by total weight of the SIS block copolymer, more particularly from 7 wt.% to 30 wt.%, and still more particularly from 10 wt.% to 20 wt.%, with the remainder of the SIS block copolymer being composed of polyisoprene or isoprene monomer units.

[0038] The SIS component of the polymer blend may have a weight average molecular weight (Mw) of from 20,000 to 80,000 with respect to polystyrene standard or at least, equal to, and/or between any two molecular weights of 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000 and 80,000. In certain embodiments, the Mw of the SIS is from 40,000 to 60,000, 65,000, or 70,000. In the context of the present invention, the molecular weight is to be understood as expressed in g/mol.

[0039] A non-limiting example of a suitable commercially available SIS block copolymer is that marketed as KRATON^®-1 161 , available from Kraton Corporation, Houston, Texas.

[0040] In other embodiments, the SBC is a styrene-butadiene-styrene (SBS) block copolymer. The SBS block copolymer may be a hydrogenated or non-hydrogenated SIS block copolymer. If a non-hydrogenated SBS block copolymer is used, from 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% to less than 100% or 100% of the polybutadiene block may be unsaturated.

[0041] The SBS block copolymer may have a polystyrene or styrene monomer content of from 5 wt.% to 40 wt.% by total weight of the SBS block copolymer, more particularly from 7 wt.% to 30 wt.%, and still more particularly from 10 wt.% to 20 wt.%, with the remainder of the SBS block copolymer being composed of polybutadiene or butadiene monomer units. [0042] The SBS component of the polymer blend may have a weight average molecular weight (Mw) of from 20,000 to 80,000 or at least, equal to, and/or between any two molecular weights of 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000 and 80,000. In certain embodiments, the Mw of the SIS is from 40,000 to 60,000, 65,000, or 70,000.

[0043] A non-limiting example of a suitable commercially available SBS block copolymer is that marketed as LG501 S, LG501W, LG41 1 S, LG41 1W, LG41 1 H, LG502S, available from LG Chem Ltd., Jeonnam, South Korea.

[0044] In certain embodiments, the styrenic block copolymer may comprise a mixture of SIS and SBS block copolymers, as have each been described individually above. The relative amount of SIS in the mixture of SIS and SBS used in the polymer blend may range from greater than 0 wt.% to less than 100 wt.% by total weight of the block copolymer mixture, with the balance of the block copolymer mixture being made up of SBS. More particularly, the amount of SIS in the mixture of SIS and SBS used in the polymer blend may range from 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, 30 wt.%, 40 wt.%, 50 wt.%, 60 wt.%, 70 wt.%, 80 wt.%, 90 wt.% or more, with the balance of the block copolymer mixture being SBS.

[0045] The polyethylene compositions can further include at least one additive. Non-limiting examples of additives include a nucleating agent, a heat conductive agent, a tie agent, an antiblocking agent, an antistatic agent, an antioxidant, a neutralizing agent, an acid scavenger, a blowing agent, a crystallization aid, a dye, a flame retardant agent, a filler (hard or soft), an impact modifier, a mold release agent, an oil, another polymer, a pigment, a processing agent, a reinforcing agent, a stabilizer (including light stabilizers), an UV resistance agent, a clarifying agent, a slip agent, a flow modifying agent, and combinations thereof. In certain embodiments, no carbon black is present in the HDPE composition.

[0046] Non-limiting examples of nucleating agents include calcium carbonate (CaCOs), barium sulfate (BaS0₄), silica (S1O2), kaolin, talc, mica, titania (T1O2), alumina (AI2O3), a zeolite, mono-or polycarboxylic aromatic acid, a dye, a pigment, metal carboxylates, metal aromatic carboxylate, hexahydrophthalic acid metal salts, stearates, organic phosphates, bisamides, sorbitols, or a combination thereof. A non-limiting example of metal aromatic carboxylate includes sodium benzoate. [0047] In certain aspects, a heat conductive additive is present in the polymer blend in an amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, and 1.0 wt. % by total weight of the polymer blend. Non-limiting examples of heat conductive additive include, aluminum oxide, titanium dioxide, graphitic compounds, graphenes, boron nitride, aluminum nitride, zinc oxide.

[0048] In certain aspects, a tie molecule is present in the polymer blend in amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, and 1.0 wt. % by total weight of the polymer blend. Non- limiting examples of tie molecules include, linear low density polyethylene, low density polyethylene, medium density polyethylene.

[0049] In certain aspects, a filler is present in the polymer blend in amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1 .0 wt. %, 2.0 wt. %, 3.0 wt. %, 4.0 wt. %, 5.0 wt. %, 6.0 wt. %, 7.0 wt. %, 8.0 wt. %, 9.0 wt. %, 10.0 wt. %, 20.0 wt. %, 30.0 wt. % by total weight of the polymer blend. The filler can be a hard filler. Non-limiting examples of hard filler include, inorganic particulate fillers such as silica, calcium carbonate, inorganic layered fillers such as clays, mica. The filler can be a soft filler. Non-limiting examples of soft filler include, immiscible particulate elastomeric/polymeric resins. The filler can also be a hollow filler. Non-limiting examples of hollow filler include, glass microspheres, plastic microspheres, ceramic microspheres such as cenospheres made up of alumino silicate microspheres, metallic microspheres made up of aluminum and copper/silver microspheres, phenolic microspheres.

[0050] In certain aspects, a light stabilizer is present in the polymer blend in an amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, and 1.0 wt. % by total weight of the polymer blend. The light stabilizer can be a hindered amine light stabilizer. The term“hindered amine light stabilizer” refers to a class of amine compounds having certain light stabilizing properties. Non-limiting examples, of hindered amine light stabilizers (HALS) include 1 -cyclohexyloxy- 2,2,6,6-tetramethyl-4-octadecylaminopiperidine; bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(1 -acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(1 ,2,2,6,6- pentamethylpiperidin-4-yl) sebacate; bis(1 -cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; bis(1 -acyl-2, 2,6,6- tetramethylpiperidin-4-yl) sebacate; bis(1 ,2,2,6,6-pentamethyl-4-piperidyl) n-butyl-3,5-di-tert- butyl-4-hydroxybenzyl malonate; 2,4-bis[(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4- yl)butylamino]-6-(2-hydroxyethyl amino-s-triazine; bis(1-cyclohexyloxy-2, 2,6,6- tetramethylpiperidin-4-yl) adipate; 2,4-bis[(1-cyclohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]- 6-chloro-s-triazine; 1-(2-hydroxy-2-methylpropoxy)-4-hydroxy-2,2,6,6-tetramethylpiperidine; 1-(2-hydroxy-2-methylpropoxy)-4-oxo-2,2,6,6-tetramethylpiperidine; 1-(2-hydroxy-2-methyl propoxy)-4-octadecanoyloxy-2,2,6,6-tetramethyl piperidine; bis(1-(2-hydroxy-2- methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;bis(1-(2-hydroxy-2- methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl) adipate; 2,4-bis{N-[1 -(2-hydroxy-2-methyl propoxy)-2,2,6,6-tetramethylpiperidin-4-yl]-N-butylamino}-6-(2-hydroxyethylamino)-s-triazine; 4-benzoyl-2,2,6,6-tetramethylpiperidine; di-(1 ,2,2,6,6-pentamethylpiperidin-4-yl) p- methoxybenzylidenemalonate; 2,2,6,6-tetramethylpiperidin-4-yl octadecanoate; bis(1- octyloxy-2,2,6,6-tetramethylpiperidyl) succinate; 1 ,2,2,6,6-pentamethyl-4-aminopiperidine; 2- undecyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro[4,5]decane; tris(2,2,6,6-tetramethyl- 4-piperidyl) nitrilotriacetate; tris(2-hydroxy-3-(amino-(2,2,6,6-tetramethylpiperidin-4-yl)propyl) nitrilotriacetate; tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1 ,2,3,4-butane-tetracarboxylate; tetrakis(1 ,2,2,6,6-pentamethyl-4-piperidyl)-1 ,2,3,4-butane-tetracarboxylate; 1 ,1 '-(1 ,2- ethanediyl)-bis(3,3,5,5-tetramethylpiperazinone); 3-n-octyl-7,7,9,9-tetramethyl-1 ,3,8- triazaspiro[4.5]decan-2,4-dione; 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1 ,3,8- triazaspiro[4.5]decane-2,4-dione; 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidin-2,5- dione; 3-dodecyl-1-(1 ,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione; N,N'-bis-formyl- N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine; reaction product of 2,4- bis[(1-cyclohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazine with N,N'-bis(3- aminopropyl)ethylenediamine);condensate of 1 -(2-hydroxyethyl)-2,2,6,6-tetramethyl-4- hydroxypiperidine and succinic acid; condensate of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)- hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-1 ,3,5-triazine; condensate of N,N'- bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylenediamine and 4-cyclohexylamino-2,6- dichloro-1 ,3,5-triazine; condensate of N,N'-bis-(2,2,6,6-tetramethyl-4- piperidyl)hexamethylenediamine and 4-morpholino-2,6-dichloro-1 ,3,5-triazine; condensate of N,N'-bis-(1 ,2,2,6,6-pentamethyl-4-piperidyl)hexamethylenediamine and 4-morpholino-2,6- dichloro-1 ,3,5-triazine; condensate of 2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethyl piperidyl)-1 ,3,5-triazine and 1 ,2-bis(3-aminopropylamino)ethane; condensate of 2-chloro-4,6- di-(4-n-butylamino-1 ,2,2,6,6-pentamethylpiperidyl)-1 ,3,5-triazine and 1 ,2-bis-(3- aminopropylamino)ethane; a reaction product of 7,7,9,9-tetramethyl-2-cycloundecyl-1-oxa- 3,8-diaza-4-oxospiro[4,5]decane and epichlorohydrin; poly[methyl, (3-oxy-(2, 2,6,6- tetramethylpiperidin-4-yl)propyl)]siloxane, CAS#182635-99-0; reaction product of maleic acid anhydride-CI 8-C22-oolefin-copolymer with 2,2,6,6-tetramethyl-4-aminopiperidine; oligomeric condensate of 4,4'-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-[(2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2- chloro-4,6-bis(dibutylamino)-s-triazine; oligomeric condensate of 4,4'- hexamethylenebis(amino-1 ,2,2,6,6-pentaamethylpiperidine) and 2,4-dichloro-6-[(1 , 2, 2,6,6- pentaamethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; oligomeric condensate of 4,4'-hexamethylenebis(amino-1- propoxy-2,2,6,6-tetramethyl piperidine) and 2,4-dichloro-6-[(1 -propoxy-2,2,6,6- tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; oligomeric condensate of 4,4'-hexamethylenebis(amino-1- acyloxy-2,2,6,6-tetramethyl piperidine) and 2,4-dichloro-6-[(1 -acyloxy-2,2,6,6- tetramethylpiperidin-4-yl)butylamino]-s-triazine end-capped with 2-chloro-4,6- bis(dibutylamino)-s-triazine; and product obtained by reacting (a) with (b) where (a) is product obtained by reacting 1 ,2-bis(3-aminopropylamino)ethane with cyanuric chloride and (b) is (2,2,6,6-tetramethyl piperidin-4-yl)butylamine. Also included are the sterically hindered N-H, N-methyl, N-methoxy, N-hydroxy, N-propoxy, N-octyloxy, N-cyclohexyloxy, N-acyloxy and N- (2-hydroxy-2-methylpropoxy) analogues of any of the above mentioned compounds. Non- limiting examples of commercial light stabilizer are available from BASF under the trade name Uvinul® 4050H, 4077H, 4092H, 5062H, 5050H, 4092H, 4077H, 3026, 3027, 3028, 3029, 3033P, and 3034 or Tinuvin® 622.

[0051 ] Anti-static agents can be used to inhibit accumulation of dust on plastic articles. Antistatic agents can improve the electrical conductivity of the plastic compositions, and thus dissipate any surface charges, which develop during production and use. Thus, dust particles are less attracted to the surface of the plastic article, and dust accumulation is consequently reduced. In certain aspects of the present invention, the antistatic agent can be a glycerol monostearate. The polymer blend can include an anti-static agent in an amount of at least, equal to, and/or between any two 0.01 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, and 1 wt. % by total weight of the polymer blend.

[0052] A lubricant can be added to a polymer blend to improve the mold-making characteristics. The lubricant can be a low molecular compound from a group of fatty acids, fatty acid esters, wax ester, fatty alcohol ester, amide waxes, metal carboxylate, montanic acids, montanic acid ester, or such high molecular compounds, as paraffins or polyethylene waxes. In certain aspects of the present invention, the lubricant is a metal stearate. Non- limiting examples of metal stearates include zinc stearate, calcium stearate, lithium stearate or a combination thereof, preferably calcium stearate. The polymer blend can include a lubricant in an amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, and 1 wt. % by total weight of the polymer blend.

[0053] An antioxidant can provide protection against polymer degradation during processing. Phosphites are known thermal oxidative stabilizing agents for polymers and other organic materials. The antioxidant can be a phosphite-based antioxidant. In certain aspects phosphite-antioxidants include, but are not limited to, triphenyl phosphite, diphenylalkyl phosphites, phenyldialkyl phosphites, tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert- butylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert- butylphenyl)pentaerythritol diphosphite tristearyl sorbitol triphosphite, and tetrakis(2,4-di- tertbutylphenyl)-4,4'-biphenylene diphosphonite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite. The polymer blend can include an antioxidant in an amount of at least, equal to, and/or between any two of 0.01 wt.%, 02 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, and 0.1 wt. % by total weight of the polymer blend. Non-limiting examples of commercially available antioxidants include Irganox 1010 available from BASF, or Doverphos S9228T available from Dover Chemical Company.

[0054] In forming the composition, the various components of the HDPE and SBC, which may be in the form of pellets, powder, flakes or fluff, along with any additives, can be dry blended. These materials combined in a customary mixing machine, in which the HDPE and SBC are mixed with the optional additives. The optional additives can be added at the end or during the processing steps to produce the polymer blend. Suitable machines for such mixing are known to those skilled in the art. Non-limiting examples include mixers, kneaders and extruders. These materials are then fed directly into the feed zone of an extruder. In certain aspects, the process can be carried out in an extruder and introduction of the additives may occur during processing. Non-limiting examples of suitable extruders include single-screw extruders, counter-rotating and co-rotating twin-screw extruders, planetary-gear extruders, ring extruders, or co-kneaders. The process can be performed at a temperature from 160 °C to 300 °C.

[0055] In some embodiments, the HDPE and SBC, and optionally one or more additives, used to produce the polymer blend of the present invention can be melt-extruded by following typical procedures of weighing the required amounts of the HDPE, SBC and other additives, followed by dry blending, and then feeding the mixture into a main feeder of a twin-screw co-rotating extruder (length/diameter (L/D) ratio of 25:1 or 40:1 ) to obtain the final composition. The HDPE, SBC, or blend thereof can be subjected to an elevated temperature for a sufficient period of time during blending. The blending temperature can be above the softening point of the polymers. In certain aspects, the extrusion process can be performed at a temperature from 160 °C to 300 °C. The SBC can be added along with other additives in-line and prior to pelletization of the HDPE resin during the production process. The amounts of SBC combined with the HDPE can be adjusted to provide those weight amounts previously discussed.

[0056] Additives can be premixed or added individually to the polymer blend or the different components thereof. By way of example, the additives of the present invention can be premixed such that the blend is formed prior to adding it to the HDPE or the SBC. The additive- containing blend thereof can be subjected to an elevated temperature for a sufficient period of time during blending and/or incorporation of additives. Incorporation of additives into the polymer resin can be carried out, for example, by mixing the above-described components using methods customary in process technology. The blending temperature can be above the softening point of the polymers. In certain aspects, a process can be performed at a temperature from 160 °C to 300 °C. Such“melt mixing” or“melt compounding” results in uniform dispersion of the present additives in the HDPE and/or SBC.

[0057] Articles (e.g., caps) that are manufactured from the blend of HDPE and SBC can have a higher ESCR than articles of manufacture made from HDPE without the SBC (i.e., the HDPE used to prepare the blend). In some embodiments, the articles of manufacture of the present invention have an ESCR that is 200% to 1000% greater than the ESCR values of HDPE articles of manufacture with the same configuration using the same HDPE without the use of the SBC. The ESCR values can be at least, equal to, and/or between any two of 200%, 300%, 400%, 500%, 600%, 700%, 800%, 900%, 1000% and 2000% greater than the ESCR HDPE values without the use of SBC. As exemplified in the Examples section and throughout the specification, polymer blend containing articles of manufacture of the present invention can have an ESCR values from at least 20 hours to 1000 hours (e.g., 20, 30, 40, 50, 60, 70, 80, 90, 100, 1 10, 120, 130, 140, 150, 160, 170, 180, 190, 200, 300, 400, 500, 600, 700, 800, 900, 1000, and 2000 and any range or value there between and including the endpoints). In contrast HDPE articles of manufacture without the SBC, can have an ESCR values of less than but not equal to 20 hours.

[0058] The polymer blend compositions formed as described are normally collected as pellets, which can be stored for a time or employed immediately in a forming process. The forming processes can include injection molding, blow molding, compression molding, sheet extrusion, film blowing, pipe extrusion, profile extrusion, calendaring, thermoforming, rotomolding, or combinations thereof. The final formed articles can be, for instance, molded parts, sheets, films, or fibers. Examples of molded parts include a cap, a bottle cap, a container, a lid, a sheet, a pipe, a pipe coupling, a bottle, a cup, a tray, a pallet, or a toy, or combinations thereof. Caps can be injection and/or compression molded. The caps may be threaded or non- threaded caps for selectively closing off openings to bottles or other containers. Such caps can be used in a variety of food and non-food applications. By way of example, caps that include the polymer blend of the present invention can be used with containers for storing carbonated beverages, pressurized beverages, or the like.

[0059] The following examples serve to further illustrate various embodiments and applications.

EXAMPLES

EXAMPLE 1

[0060] Styrene-isoprene-styrene (SIS) linear block copolymer, available as KRATON-1 161 , having a weight average Mw of 63,000 (as per polystyrene standard) and a styrene content of 15 wt. % was dry mixed as powder or flakes in different amounts of from 5 wt.% to 15 wt.% with commercially available HDPE. The HDPE used was SABIC^® HDPE CC253 and SABIC^® HDPE CC254. SABIC^® HDPE CC253 is a unimodal HDPE having a MFR at 190 °C and 2.16 kg of 1.8 dg/min and a density of 952 kg/m³. SABIC^® HDPE CC254 is a bimodal HDPE having a MFR at 190 °C and 2.16 kg of 2.1 dg/min and a density of 953 kg/m³. For comparison purposes, neat HDPE without any SBC was also tested. The different mixtures were fed into a hopper of a ZSK- 25 mm 6 barrel twin-screw extruder with an L/D ratio of 25:1. The operating parameters used are set forth in Table 1 below:

Table 1

[0061 ] The torque measured during the melt extrusion of the neat and formulated HDPE with the SIS was in the range of 28-34%, indicating that the processibility of HDPE was not hampered significantly with the incorporation of SIS.

EXAMPLE 2

[0062] The pellets obtained after the melt extrusion of Example 1 were compressed molded into 1.85 mm to 1.95 mm thick sheets at a temperature of 195 °C to 210 °C, with a holding time of 5 min and a cooling time of 5 min. No visual inhomogeneity was evident in the compression molded sheets. The compression molded sheets, both the neat and formulated HDPE, were then evaluated for ESCR performance according to ASTM D1693-15B method (Bell Test).

[0063] The compression molded sheets were cut into test specimens having a length of 38 mm and width of 13 mm. A notch of 0.5 mm depth was created at the center of each test specimen prior to storing it in a conditioned environment of 23 °C and humidity of 55% RH. The conditioned specimens were U-bent with the aid of a jig. Ten of the bent specimens for each neat and formulated HDPE materials were placed in an aluminum sample holder and subsequently placed inside a test tube filled with 10% v/v aqueous solution of Igepol CO-630 (nonylphenoxy poly(ethyleneoxy) ethanol, CAS 68412-54-4). The mouth of the test tube was closed with a rubber cork wrapped with an aluminum foil. The test specimens placed in the test tube filled with Igepol CO-630 aqueous solution was immersed in a silicone oil bath maintained at 50 °C. The time it took to observe the formation of cracks in the test specimens were regularly noted. The time taken for 50% of the specimens (i.e., 5 out of the 10 specimens) to fail (i.e., crack) were reported to infer the ESCR performance of the given composition.

[0064] The ESCR performance of the neat HDPE and formulated HDPE incorporating the SIS are presented in Table 2 below:

Table 2

[0065] As can be seen from Table 2, the observed time for 50% of the samples to fail for unimodal (CC253) and bimodal (CC254) HDPE was 12 and 16 hrs, respectively. A 2-3 fold increase of time for 50% of the specimens to fail was found for those HDPE compositions incorporating SIS block copolymer at 5 wt.% to 15 wt.%.

[0066] Melt mass flow rate (MFR) of neat bimodal HDPE resin (CC254) measured at 190 °C with a load of 2.16 Kg by ISO 1133-1 :201 1 method, along with that of blends of bimodal HDPE and different loading of KRATON-1 161 are depicted in the Table 3 below. The standard deviation observed during the MFR measurements was 0.1 g/10 min.

Table 3

[0067] As can be seen from Table 3, the observed MFR value for bimodal (CC254) HDPE was 2.0 g/10 min. In comparison, the MFR value for the bimodal HDPE composition incorporating 5 wt.%, 10 wt.%, and 15 wt.% KRATON-1161 is 2.2 g/10 min - 2.3 g/10 min. This result indicates that the melt viscosity/flow characteristics of HDPE resins have slightly increased with the incorporation of KRATON-1 161 , in addition to the superior ESCR performance of such KRATON-1161 incorporated HDPE compositions.

[0068] The stained transmission electron microscope (TEM) image of a blend of bimodal HDPE (CC254) incorporated with 5 wt.% KRATON-1161 is depicted in FIG.1. TEM samples were prepared by cryo-microtoming the ESCR test specimen at -120 °C, followed by the staining with Ru for 2 minutes. As seen from FIG. 1 , the KRATON-1 161 is finely dispersed within the HDPE matrix with aggregate size ranging from 0.1 pm to 1 pm. Banded type spherulites of HPDE matrix can be seen in all blends which contained 5 wt.%-15 wt.% of KRATON-1 161. The number density of KRATON-1 161 domains is found to increase with increasing loading of KRATON-1161 in the HDPE matrix. [0069] The percentage crystallinity of bimodal HDPE (CC254) was found to increase from 65% to 75%, 78% and 82% with the incorporation of 5% wt, 10 wt.%, and 15 wt.% of KRATON-1161 , respectively. [0070] While the invention has been shown in some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes and modifications without departing from the scope of the invention based on experimental data or other optimizations considering the overall economics of the process. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Claims

1. A polyethylene composition having increased environmental stress crack resistance, the composition comprising a polymer blend of a high density polyethylene (HDPE) and a styrenic block copolymer (SBC) of at least one of a styrene-isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer.

2. The composition of claim 1 , wherein the HDPE is at least one of a unimodal HDPE, and a bimodal HDPE.

3. The composition of any one of claims 1-2, wherein the styrenic block copolymer has a weight average molecular weight (Mw) of from 20,000 to 80,000 g/mol.

4. The composition of any one of claims 1-3, wherein the styrenic block copolymer has a styrene content of from 5 wt.% to 40 wt.% by total weight of the styrenic block copolymer.

5. The composition of any one of claims 1-4, wherein the styrenic block copolymer comprises a mixture of styrene-isoprene-styrene (SIS) block copolymer and styrene- butadiene-styrene (SBS) block copolymer.

6. The composition of any one of claims 1-5, wherein the styrenic block copolymer content is from 0. 1 wt.% to 20 wt.% by total weight of the polymer blend.

7. The composition of any one of claims 1-6, wherein the polymer blend provides a molded article having an ESCR of at least 30 hours as determined by ASTM D1693-15B, preferably of from 30 to 1000 hours.

8. The composition of any one of claims 1-7, wherein the HDPE is a copolymer with comonomers selected from C3 to C10 olefin monomers, the comonomers being present in the HDPE copolymer in an amount of from 2 wt.% or less, preferably of from 1 wt.% or less.

9. The composition of any one of claims 1-8, wherein the HDPE is unimodal and has a melt flow ratio at 190 °C and 2.16 kg or 21.6 kg of 0.2 dg/min to 50 dg/min and/or a density of 945 kg/m³to 965 kg/m³, wherein the density of the HDPE is determined in accordance with ISO 1183-1 (2012), method A, and the melt flow rate in accordance with ISO 1 133- 1 (201 1 ).

10. The composition of any one of claims 1-8, wherein the HDPE is bimodal and has a melt flow ratio at 190 °C and 2.16 kg or 21.6 kg of 0.2 dg/min to 50 dg/min and/or a density of 945 to 965 kg/m³, wherein the density of the HDPE is determined in accordance with ISO 1183-1 (2012), method A, and the melt flow rate in accordance with ISO 1 133-1 (201 1 ).

11. The composition of any one of claims 1 -10, further comprising an additive of at least one of a nucleating agent, a heat conductive agent, a tie agent, an antiblocking agent, an antistatic agent, an antioxidant, a neutralizing agent, an acid scavenger, a blowing agent, a crystallization aid, a dye, a flame retardant agent, a filler, an impact modifier, a mold release agent, an oil, another polymer, a pigment, a processing agent, a reinforcing agent, a stabilizer, an UV resistance agent, a clarifying agent, a slip agent, a flow modifying agent, and combinations thereof.

12. The composition of any one of claims 1-1 1 , wherein the polymer blend is formed into an article of manufacture, preferably wherein the article is at least one of a film, a molded part, a container, a beverage container cap, a lid, a sheet, a pipe, a pipe coupling, a bottle, a cup, a tray, a pallet, and a toy.

13. The composition of claim 12, wherein the article is formed by at least one of injection molding, blow molding, compression molding, sheet extrusion, film blowing, pipe extrusion, profile extrusion, calendaring, and thermoforming.

14. A method of forming a polyethylene composition having increased environmental stress crack resistance, the method comprising modifying a high density polyethylene (HDPE) by combining the HDPE with a styrenic block copolymer (SBC) of at least one of a styrene-isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer, present in an amount of from 0.1 wt.% to 20 wt.% by total weight of the polymer blend.

15. Use in a polymer blend comprising high-density polyethylene of a styrenic block

copolymer (SBC) of at least one of a styrene-isoprene-styrene (SIS) block copolymer and a styrene-butadiene-styrene (SBS) block copolymer, present in an amount of from 0.1 wt.% to 20 wt.% by total weight of the polymer blend, preferably of from 5.0 wt.% to 15 wt.%, for increase of the environmental stress crack resistance of a polymer composition comprising the blend.