Blown-film conversion of Marlex® D170DK is established on heavy-duty form-fill-seal sack lines where the film must survive drop loading, tear propagation, and low-temperature flexing without gauge extension at seal zones. The resin is characterized by a nominal density of 0.917 g/cm³ per ASTM D1505 and a nominal melt index of 0.75 g/10 min per ASTM D1238 at 190°C and 2.16 kg. On a 75 mm single-screw extruder with a 30:1 L/D barrier screw and Maddock mixing section, melt temperature measured at the adapter is typically held between 190°C and 210°C. The die gap is maintained at 2.0–2.5 mm because narrower gaps drive shear rate upward and may produce sharkskin melt fracture at screw speeds above 80 rpm. A spiral mandrel die with blow-up ratio of 2.5:1 to 3.0:1 is used for gusseted open-mouth sacks, and frost-line height is controlled at 6–8 die diameters to retain dart impact while limiting excessive machine-direction orientation. Film produced at 125–150 µm gauge is converted into polymer granulate and fertilizer sacks with seal-bar temperatures between 150°C and 170°C. Food-contact compliance is routinely declared under FDA 21 CFR 177.1520(c) and Regulation (EU) No 10/2011 when the finished film contains only approved stabilizers and meets overall migration limits. Hexene comonomer distribution contributes to the tear and puncture performance required in this application; dart drop is measured by ASTM D1709, Elmendorf tear by ASTM D1922, and tensile properties by ASTM D882.

When D170DK Is Selected for Cast Stretch Film Despite Its 0.75 g/10 min Melt Index

Cast stretch line trials with D170DK encounter a measurable process conflict because conventional cast stretch grades are formulated at melt indices between 2.0 g/10 min and 4.0 g/10 min for low melt pressure and stable draw at high line speed. The 0.75 g/10 min melt index of D170DK raises melt pressure in flat-die systems and increases motor load on 30:1 L/D extruders. Published data for this specific configuration is limited. Melt temperature must be raised to 220–240°C to reduce viscosity, but the upper limit is set at 250°C because prolonged residence time above that threshold initiates oxidation gel formation in the melt film. Chill roll temperature is maintained at 15–25°C with an air gap of 150–250 mm to control edge bead and film width. D170DK is inherently non-tack; cling is generated by adding a tackifier masterbatch, commonly an EVA or polyisobutylene-based system, at converter-validated dosages in the 1–3 wt% range. Formulation tolerance is narrow because excess tackifier reduces film modulus and blocks unwind, while insufficient tackifier fails pallet-load retention. Machine-direction stretch force is tested by ASTM D5459, and cling strength is measured by ASTM D5458. The lower melt index also limits cast draw stability. Edge bead formation becomes more pronounced when film thickness is below 15 µm, and bubble-breathing control used in blown stretch is not available because the cast process has no internal air pressure. Converters selecting D170DK for cast stretch should verify melt pressure and ampacity margins on the die and extruder before production.

How Does Hexene Comonomer Alter Low-Temperature Dart Impact in Frozen-Food Film?

Frozen-food film converters typically run D170DK in a three-layer coextrusion where the resin forms the core or outer layers, with a food-contact sealant skin. The hexene short-chain branching of this grade lowers the crystalline plateau compared with butene-copolymer LLDPE of equivalent density, which translates into improved low-temperature impact resistance. Film gauge for frozen vegetable, seafood, and meat packaging is generally between 30 µm and 75 µm. After conditioning at −30°C for 24 h, dart impact is measured by ASTM D1709; the specific value depends on layer thickness and frost-line settings, but hexene copolymer films typically retain a higher percentage of room-temperature dart impact than butene-copolymer films at the same density and melt index. The resin’s 0.917 g/cm³ nominal density provides flexibility at freezer temperatures without the low-modulus limpness of lower-density ethylene copolymers. Heat sealing is evaluated by ASTM F88/F88M at sealing temperatures between 120°C and 150°C. The hot-tack window is relevant for vertical form-fill-seal equipment where the filled pouch drops immediately after sealing. Compliance with FDA 21 CFR 177.1520(c) and Regulation (EU) No 10/2011 applies only when the finished structure uses food-approved tie layers and sealants. D170DK is not an organoleptic barrier; strongly odorous frozen products may require an additional barrier layer unless sensory evaluation under EN 1230-1 demonstrates pack compliance.

In silage baling operations, D170DK is evaluated as a blown-film layer for wrap protection where puncture resistance during bale rotation and cling after stretching are the primary mechanical requirements. Typical film thickness is 25–50 µm, but D170DK alone does not provide an oxygen barrier comparable to EVOH or polyamide; oxygen transmission must be measured by ASTM D3985 for the final film structure. UV stabilization is mandatory for outdoor storage because the base resin contains no long-term UV inhibitor. A HALS stabilizer masterbatch is introduced at the converter’s validated let-down ratio, often in the 1–3 wt% range. The blown-film process uses a die gap of 1.8–2.5 mm, a blow-up ratio of 2.0:1 to 2.5:1, and melt temperatures between 190°C and 215°C to prevent thermal degradation of the UV additive. End-use puncture resistance is assessed by ASTM D5748, and tear resistance by ASTM D1922. The hexene comonomer reduces stress whitening in stretched film, but cling is formulated with a tackifier because D170DK has no inherent cling. Bale wrap exposed beyond one season to ultraviolet radiation must be evaluated for retained tensile and elongation per ASTM D882.

Can Liners and Industrial Waste Containment Film Requirements

Industrial can liners are converted from D170DK on heavy-gauge blown-film lines producing film between 100 µm and 250 µm. The resin’s hexene copolymer architecture supports high environmental stress crack resistance, which is measured by ASTM D1693 and is required for liners holding solvent-contaminated solids or alkaline cleaning residues. Extrusion conditions include a die gap of 2.0–3.0 mm, a blow-up ratio of 2.0:1 to 2.5:1, and melt temperatures between 190°C and 220°C. Puncture resistance is evaluated by ASTM D5748, and tear resistance by ASTM D1922. The film is not inherently UV stable; outdoor service requires carbon black at 2.0–2.5 wt% dispersion, and the dispersion quality is checked by ISO 18553. Heavy-metal and SVHC restrictions are verified under REACH and, when applicable, local landfill and incineration permits. The absence of plasticizers and migratory slip additives in D170DK simplifies compliance with many waste-containment specifications, but converters must confirm that welding or side-gusset sealing temperatures do not exceed 230°C to prevent polymer degradation at the seal fold. Bags which are stacked outdoors must be tested after UV exposure because surface oxidation can reduce tensile at break and increase tear propagation.

Coextruded Sealant Web Geometry and Hot-Tack Limits Are Set by the Resin Viscosity Curve

Coextrusion of D170DK as a sealant layer requires melt temperature control between 200°C and 230°C because the 0.75 g/10 min melt index increases viscosity relative to high-MI sealant grades. The resin is used in sealant webs for heavy packaging laminates where seal strength and stiffness are prioritized over low-temperature sealing. Sealant layer thickness is typically 10–25 µm. Heat-seal initiation is measured by ASTM F2029, and hot-tack strength is measured by ASTM F1921. D170DK has a hot-tack plateau at sealing temperatures above 120°C in most coextruded structures, but specific seal initiation depends on the adjacent tie resin and substrate. Adhesion to EMA- and EBA-based tie layers is generally stronger than to acid-modified EVA systems; converter trials determine the precise peel failure mode. The resin is not recommended for high-speed packaging lines requiring seal initiation below 100°C. Coextruded films must be checked for interfacial gel formation because temperature overshoot above 250°C in the sealant layer can generate oxidized specks that produce weak seal regions. Film clarity is measured by ASTM D1003, and haze values depend on layer distribution and die-lip surface condition.