Chevron Phillips Marlex D143FK is a metallocene-catalyzed linear low-density polyethylene (mLLDPE) film resin. The grade is produced with a 1-hexene comonomer and is supplied as pellets containing a proprietary antioxidant, slip, and antiblock system. Nominal base-resin density is 0.916 g/cm³ when tested in accordance with ASTM D1505 or ISO 1183-1; nominal melt index is 1.0 g/10 min when tested in accordance with ASTM D1238 or ISO 1133-1 at 190°C/2.16 kg. Unlike high-pressure LDPE, D143FK has a linear backbone with controlled short-chain branching rather than long-chain branching; unlike conventional C4 Ziegler-Natta LLDPE, the metallocene catalyst system narrows the short-chain branching distribution and reduces the low-molecular-weight, highly branched fraction. Film property claims are therefore referenced to standard test methods on converted film, not to resin parameters alone.

The table below lists published nominal resin properties; film properties are deliberately excluded because they vary with gauge, orientation, and processing history.

How Does D143FK Differ from Conventional Ziegler-Natta Butene-Based LLDPE Film Grades?

At equal density (0.916 g/cm³) and equal melt index (1.0 g/10 min), a butene-based Ziegler-Natta LLDPE typically contains a broader distribution of comonomer placement and a larger fraction of low-molecular-weight, highly branched chains. These species plasticise the amorphous phase and can lower seal initiation temperature, but they also increase the extractable fraction and may reduce hot-tack performance. D143FK is a hexene-based metallocene resin; temperature rising elution fractionation shows a narrower branch distribution, and triple-detection gel permeation chromatography confirms lower long-chain branching than LDPE. On film, the practical comparison is made with ASTM F88 seal strength, ASTM F1921 hot tack, ASTM D1709 dart impact, ASTM D1922 Elmendorf tear, ASTM D1003 haze, and ASTM D2457 gloss. A converter changing from a C4 Ziegler grade to D143FK may observe lower seal initiation temperature and lower haze at the same film thickness; published data for this specific comparison is limited and should be confirmed on the target line.

Against an octene-based metallocene film resin of equivalent density, D143FK occupies a different position in the stiffness/toughness balance. Hexene-based grades of this class may show higher secant modulus measured by ASTM D882 but comparatively lower dart impact and tear propagation when evaluated by ASTM D1709 and ASTM D1922. The decision to use D143FK over a C8 mLLDPE should therefore depend on whether the package requires stiffness for machineability or extreme puncture and tear resistance for abusive distribution. Direct published comparative data for D143FK is limited; converter trials remain the authoritative basis for grade substitution.

On a monolayer blown-film line equipped with a grooved-feed single-screw extruder of 24:1 to 30:1 L/D, a barrier screw, and a dual-lip air ring, D143FK is processed with a die gap of 1.5 mm to 2.5 mm and a blow-up ratio of 2.0:1 to 2.8:1. Melt temperature at the adapter is maintained between 193°C and 232°C. Higher setpoints are used for high-output lines, but hold-up above 240°C should be minimised to avoid oxidative gel formation. Compared with a high-pressure LDPE of similar melt index, D143FK produces higher screw torque and head pressure because the low-shear viscosity is higher; the pressure before the screen pack should be monitored against the extruder manufacturer’s maximum. A sudden pressure rise above baseline indicates screen blinding or feed starvation rather than a change in resin melt index. Surface melt fracture at high shear rates is controlled by adding a fluoropolymer processing aid at 500 ppm to 1,000 ppm and by raising the final die zone temperature toward the upper processing limit. Frost line height is set between 1 and 3 die diameters; a lower frost line preferentially increases MD orientation and MD tear, while a higher frost line improves TD tear but may reduce gauge uniformity.

Capillary rheometry of D143FK at 190°C and 210°C reveals shear-thinning behaviour typical of metallocene LLDPE. At low shear rate, apparent viscosity is higher than that of a comparable high-pressure LDPE; at extrusion shear rates above 100 s⁻¹, the viscosity difference narrows. The practical consequence is that processability limitations are concentrated in the feed and compression zones rather than at the die lips. A reverse-temperature profile is often used: feed zone 150°C to 170°C, compression zone 180°C to 200°C, and metering zone 200°C to 220°C. However, the optimum profile is screw-specific; a barrier screw with a Maddock mixing section can homogenise the melt without excessive shear heating.

Film Property Testing Matrix and Standard Designations

Specification compliance for D143FK films is not determined by nominal resin properties alone but by a test matrix conducted on film samples conditioned at 23°C and 50% RH according to ASTM D618. Tensile properties, including secant modulus, yield strength, and elongation at break, are measured by ASTM D882 / ISO 527-3. Tear resistance is measured by Elmendorf tear, ASTM D1922 / ISO 6383-2; dart impact by ASTM D1709 Method A or Method B; puncture energy by ASTM D5748. Optical performance is quantified by ASTM D1003 / ISO 14782 for haze and ASTM D2457 / ISO 2813 for gloss at 45°. Coefficient of friction is measured by ASTM D1894 / ISO 8295. Seal strength is tested on a calibrated heat sealer using ASTM F88, and hot tack by ASTM F1921. Water vapour transmission rate is measured by ASTM F1249 / ISO 15106-2. Because film thickness, gauge distribution, and orientation state change test results, numerical pass/fail values should be established on the target line, not transferred from another converter’s data.

Thermal analysis by differential scanning calorimetry per ASTM D3418 typically shows a broad melting endotherm for D143FK due to short-chain branching. The peak melting temperature is lower than HDPE and higher than very-low-density ethylene copolymers; cooling rate and film quenching history shift the crystalline content and therefore the film modulus. Cast film quenched at high chill roll temperature may develop lower crystallinity and improved clarity but lower dimensional stability. These effects should be characterised on the target line rather than inferred from resin pellet data.

Cast film conversion of D143FK is run on a flat-die line with chill roll temperature between 15°C and 30°C and an air gap in the range of 5 to 15 cm. The grade is used as a high-clarity skin or sealant layer where optical quality is specified by ASTM D1003 haze and ASTM D2457 gloss. In a three-layer cast line, D143FK may be paired with a polypropylene or HDPE core; the viscosity ratio between adjacent layers should not exceed 1:3, and layer distribution should be verified by cross-section microscopy or FT-IR mapping if gauge uniformity is outside tolerance. Die temperature is commonly set between 200°C and 230°C; the lower end protects optical quality, while the upper end reduces melt viscosity at high line speed. Extended residence time at the upper temperature can generate oxidised gel particles, which appear as fisheyes. If fisheyes appear after a line stoppage, the die should be purged with a high-MI LDPE before restarting D143FK feed.

Regrind from edge trim and start-up scrap may be re-introduced into the film layer at levels up to 20% by weight if the scrap is clean and ground without excessive frictional heat. Repeated extrusion should be monitored for melt index shift by ASTM D1238; an increase above the baseline indicates chain scission, and the regrind ratio should be reduced. D143FK is compatible with other polyolefins in multilayer reclaim streams, but mixed-colour scrap or high-slip scrap can alter haze measured by ASTM D1003 and coefficient of friction measured by ASTM D1894.

When D143FK Replaces LDPE in High-Clarity Sealant Layers

Substituting D143FK for high-pressure LDPE in a sealant layer changes bubble or curtain mechanics because D143FK exhibits less strain hardening. In blown-film coextrusion, the operator should expect a more sensitive bubble and may need to reduce the blow-up ratio by 0.2 to 0.5 units or raise the frost line by 1 to 2 die diameters to maintain stability. Extruder temperature profiles should be set with a feed zone of 160°C to 180°C, a metering zone of 200°C to 230°C, and a die setting of 215°C to 230°C. The sealant layer thickness should be optimised by measuring seal strength per ASTM F88 and hot tack per ASTM F1921; a layer that is too thin reduces weld integrity, while a layer that is too thick increases raw material use and may alter flex-crack resistance. When D143FK is used with an ethylene-vinyl acetate tie layer, melt indices of the adjacent layers should be within 0.5 g/10 min to minimise interfacial distortion. Published data for this specific configuration is limited; converter trials remain the authoritative method for validating sealant replacement.

Storage and handling of D143FK follow standard polyolefin practice. The resin should be stored below 50°C, away from ultraviolet light and strong oxidisers, and used within 12 months of the production date when kept in sealed packaging. Drying is not required under ambient relative humidity below 60% RH; if silo condensation or bulk-handling moisture entrapment occurs, hopper drying at 60°C to 70°C for 2 to 4 hours is sufficient. Food-contact status must be verified through the manufacturer’s regulatory certification. Polyethylene resins such as D143FK are generally referenced under FDA 21 CFR 177.1520 and EU Regulation 10/2011, but specific migration limits and end-use restrictions depend on film structure, additives, and sterilization or filling temperatures. Compliance testing under EU Regulation 10/2011 requires migration kinetics studies with food simulants according to the intended contact conditions; the low extractable fraction of metallocene LLDPE may reduce total migration, but additive migration and oligomer content must still be verified. The converter retains responsibility for compliance testing on the final article.

In vertical form-fill-seal packaging, D143FK is evaluated on lines running cycle rates of 40 to 120 packages per minute, depending on bag size and film gauge. The critical parameters are hot-tack strength measured by ASTM F1921, seal-through-contamination performance, and slip consistency during film transport. The coefficient of friction should be measured by ASTM D1894 because metal roll surfaces, film tension, and temperature shift the dynamic friction baseline. Seal jaw temperature should be mapped from 120°C to 160°C using ASTM F88 seal-strength curves and ASTM F1921 hot-tack curves; the appropriate setpoint is the lowest jaw temperature that yields the minimum seal strength specified by the package design. If pouch failure occurs at the seal edge, the failure mode should be distinguished between adhesive peel and cohesive film tear to determine whether the sealant layer or the film orientation is the limiting variable.