Chevron Phillips Chemical mPact D350 is a metallocene-catalyzed linear low-density polyethylene resin supplied as free-flowing pellets. The grade is designated by the manufacturer as an ethylene-hexene copolymer produced with a single-site catalyst system. Representative nominal values published by the supplier for the neat resin include a density of 0.933 g/cm³ when determined under ASTM D1505 and a melt index of 0.5 g/10 min at 190 °C with a 2.16 kg load under ASTM D1238. The density positions D350 between conventional LLDPE film grades and medium-density polyethylene, which raises stiffness and creep resistance relative to lower-density film resins while retaining blown film drawability. Melt flow ratio, molecular weight distribution, and additive package are lot-dependent and are reported on the certificate of analysis rather than as single-point purchase specifications.

How Does the Hexene-1 Comonomer Distribution Affect Film Toughness in D350?

Single-site catalyst technology produces a narrower molecular weight distribution and a more homogeneous intermolecular comonomer distribution than a conventional Ziegler-Natta catalyst. In D350, the hexene-1 comonomer is distributed more uniformly across the molar mass distribution, reducing the low-molecular-weight, high-density fractions that typically limit dart impact resistance and environmental stress crack resistance. The solid-state morphology therefore contains fewer weak intercrystalline regions and a more uniform tie-molecule population. On production-scale blown film lines, the practical result is that dart impact resistance measured by ASTM D1709 Method A and Elmendorf tear propagation measured by ASTM D1922 are less sensitive to frost-line height variation than in comparable butene-based LLDPE. The same narrow distribution reduces shear thinning, and capillary rheometry under ISO 11443 shows higher shear viscosity at die-lip shear rates than a Ziegler-Natta resin of equivalent melt index. This difference must be addressed through screw design, die geometry, and melt pressure monitoring.

Extrusion of D350 on monolayer and coextruded blown film lines is conducted at melt temperatures of 190 °C to 230 °C. Supplier processing guidance indicates a die gap of 1.0 mm to 2.0 mm, depending on blow-up ratio and frost-line height. Because the resin exhibits a less pronounced shear-thinning response, die pressure on a single-screw extruder with a barrier screw and Maddock mixing section is normally higher than for a fractional-melt-index Ziegler-Natta LLDPE. Screen packs of 20/40/60 mesh are commonly used to protect the die, and pressure drop across the screen pack should be recorded at start-up and after purges. Blow-up ratios of 2.0:1 to 3.0:1 are typical for heavy-duty sack applications. A reduced frost-line height of 200 mm to 400 mm above the die is used when higher transverse direction tear resistance is required. Output on a 90 mm grooved-feed extruder with an L/D ratio of 30:1 is governed by screw speed, die diameter, and melt pressure; published line-speed data for D350 in specific structures is limited and should be established by trial on the actual line.

Mechanical Property Benchmarks for Heavy-Duty Packaging End Uses

For heavy-duty packaging films, property data are generated after conditioning at 23 °C ± 2 °C and 50 % ± 5 % relative humidity. Tensile yield strength and elongation at break are determined under ASTM D882 at a crosshead speed of 500 mm/min. Puncture resistance is evaluated by ASTM D5748 or an equivalent slow puncture method. The resin is used in industrial liners, heavy-duty sacks, agricultural films, and coextruded sealant webs where the balance of dart impact resistance and stiffness is evaluated according to ASTM D1709 and ASTM D790 or ISO 178. Low-temperature brittleness is assessed by ASTM D746; acceptance criteria are application-specific. In agricultural silage covers, ultraviolet stabilization is not part of the base resin specification unless a pre-compounded UV package is ordered. Film property values depend on thickness, die gap, blow-up ratio, frost-line height, and additive masterbatch loadings, so the current supplier datasheet must be consulted for the exact mechanical profile.

After film fabrication, heat seal performance is evaluated on laboratory sealers with controlled jaw temperature, sealing pressure of 0.28 MPa, and dwell time of 0.5 s. Seal initiation temperature is reported as the temperature at which seal strength reaches 8.9 N/25 mm under ASTM F88. Films based on D350 typically exhibit a broader hot-tack window than butene-based LLDPE because the uniform comonomer distribution reduces the crystalline melting range. Hot tack is measured under ASTM F1921. Surface coefficient of friction is controlled by erucamide slip and synthetic silica antiblock; the base pellet is not pre-lubricated unless specified. Corona treatment of film surfaces to 38 dyn/cm to 42 dyn/cm is used before printing or lamination. The resin can serve as a sealant web in coextruded films because the narrow molecular weight distribution lowers low-molecular-weight extractables that contribute to organoleptic defects. Seal performance at high line speeds must be validated with production-scale heat seal equipment, because laboratory dwell times do not reproduce the short contact times of form-fill-seal machinery.

When D350 Is Substituted for Ziegler-Natta Butene LLDPE in Coextruded Structures

Substitution of a butene-based Ziegler-Natta LLDPE with D350 in a coextruded film changes the property balance. The hexene-1 comonomer provides longer short-chain branches than butene-1, improving dart impact and tear resistance at equivalent density. The single-site catalyst narrows the molecular weight distribution and reduces the fraction of low-molar-mass chains. The following comparative profile is representative of a 25 µm monolayer blown film produced on a 3-layer line with a die gap of 1.2 mm and blow-up ratio of 2.5:1; values are normalized to a conventional Ziegler-Natta butene LLDPE of 0.918 g/cm³ and 1.0 g/10 min. The table reports directionally expected differences and the applicable test methods, not absolute specification limits for all fabrication conditions.

During handling and conversion, operational boundaries must be observed. D350 is supplied with a moisture content below 0.05 %. If storage conditions exceed 60 % relative humidity for extended periods, pre-drying in a desiccant dryer at 60 °C to 80 °C for 2 h to 4 h may be necessary to prevent surface defects on extruded film. The melt temperature should not exceed 260 °C to avoid thermal degradation and oxidized gel particle formation. Extended residence time at high temperature increases gel formation and should be minimized with appropriate extruder sizing and purge procedures. The narrow molecular weight distribution of D350 can increase motor load on single-screw extruders with shallow compression ratios or worn screws. Where nitrogen-containing additives or amine-based antifog concentrates are used, compatibility with the antioxidant package and organoleptic requirements should be verified before production. Fluoropolymer processing aids are sometimes added at 200 ppm to 500 ppm to reduce melt fracture in linear low-density polyethylene; the specific loading depends on die design, shear rate, and the carrier polymer.

Compliance with food-contact regulations is not a static resin property

Regulatory clearance for D350 depends on migration testing, end-use conditions, and the final fabricated article. The base resin can be evaluated for food-contact use under 21 CFR 177.1520(c), with extraction limits for the finished article governed by 21 CFR 177.1520(d). In the European Union, the relevant framework is Regulation (EU) 10/2011 and its amendments, with an overall migration limit of 10 mg/dm² for food-contact plastics. REACH registration under EC 1907/2006 and RoHS restriction under Directive 2011/65/EU are handled at the supplier level for the marketed polymer. Grade-specific certification must be obtained from the manufacturer for each regulatory application.