TPC (Japan) HDPE KF138D is processed as a monolayer blown film for dry cereal liners and non-greasy snack packaging only after the conversion line is qualified under EU Regulation No 10/2011 Annex I and EN 1186-1:2002 for overall migration; specific migration of olefin oligomers is measured by EN 13130-1:2004, and North American shipments fall under FDA 21 CFR §177.1520 paragraph (c), which imposes n-hexane extractive limits according to food contact temperature and fat type. On a conventional blown-film line the resin is extruded through a single-screw extruder with L/D 28:1 and a spiral mandrel die with die gap 1.4 mm to 1.8 mm; melt temperature is maintained at 200 °C to 210 °C, die body 5 °C to 10 °C below the melt set point, blow-up ratio 2.2:1 to 3.0:1, and frost-line height 550 mm to 750 mm. This envelope produces film of 15 µm to 25 µm for terminal cereal liners, cracker sleeves, and non-greasy snack pouches. At that gauge, film is tested for dart impact by ASTM D1709 Method A, Elmendorf tear by ASTM D1922, tensile properties by ASTM D882, and moisture vapor transmission by ASTM F1249 at 38 °C and 90% RH; HDPE film of this class typically exhibits machine-direction tensile strength of 30 MPa to 45 MPa, elongation at break of 400% to 800%, and moisture vapor transmission in the range 3 g·m^-2·d^-1 to 8 g·m^-2·d^-1. Processors should not transfer these properties to finished packs without confirming lot-specific tensile and barrier data, because slight density variation within the HDPE family shifts water vapor transmission more than thickness variation of the same percentage.

What Happens to Dart Impact Retention When Post-Consumer Recyclate Is Let Down into KF138D?

Post-consumer recycled high-density polyethylene is let down into KF138D at 10 wt% to 25 wt% in non-food refuse sack and building-film applications using gravimetric dosing at the main feed throat; the recycled fraction is screened through an 80/120/80 mesh screen pack to remove gel particles above 250 µm. This is not a food-contact application, and the blend is controlled under packaging heavy-metal limits of 94/62/EC with total lead, cadmium, mercury, and hexavalent chromium below 100 mg/kg; under REACH, the recycled fraction must be sourced through a documented authorized recycler because contaminant composition directly shifts dart impact and melt-pressure stability. Though HDPE is not hygroscopic, surface moisture from storage at relative humidity above 60% can generate microbubbles at melt temperature; when feedstock has been stored in unsealed silos or bags, pre-drying at 70 °C for 2 h to 4 h is applied before extrusion. On the extrusion side, the let-down blend increases melt elasticity and narrows the bubble stability window; processors commonly raise die temperatures by 3 °C to 5 °C and reduce screw speed by 8% to 12% relative to neat KF138D to avoid melt fracture at the die lip. Dart impact retention measured by ASTM D1709 Method A typically degrades non-linearly with recycle addition; published data for this specific KF138D/PCR configuration is limited, and the relationship becomes steep when the recycled fraction contains more than 3 wt% polyethylene wax contamination from label adhesives. Terminal products are non-food heavy-gauge refuse sacks and building-site film; these are converted on bottom-seal or side-seal bag machines with seal settings adjusted upward by 5 °C to 10 °C because the PCR fraction broadens the seal melting endotherm.

Three-Layer Coextrusion with EVA Sealing Skins and a KF138D Core

Three-layer blown film lines for frozen seafood and liquid paste packaging use KF138D as the central stiffness and moisture-barrier layer at 55 wt% to 70 wt%, with ethylene-vinyl acetate copolymer skins at 15 wt% to 20 wt% per layer and, when required, an anhydride-modified polyethylene tie layer at 5 wt% to 10 wt%. The EVA skins are selected with vinyl acetate content of 6% to 12% to lower heat-seal initiation below 85 °C to 95 °C; this is confirmed by heat-seal strength testing under ASTM F88/F88M and hot-tack testing under ASTM F1921. The KF138D core layer is extruded through a three-layer spiral mandrel die with layer ratio control better than ±2%; melt temperature per layer is set at 205 °C to 215 °C for the HDPE core and 185 °C to 200 °C for the EVA skins to limit thermal degradation of vinyl acetate groups. Film gauge of 45 µm to 80 µm is produced at a die gap of 1.6 mm to 2.0 mm. From a compliance standpoint, EVA skins are not always accepted for direct fatty food contact; for high-fat applications, the skin layer is replaced with an LLDPE skin or a polyolefin plastomer meeting EU 10/2011 and FDA 21 CFR §177.1520, and migration of the EVA layer through the core is prevented by the continuous HDPE core layer. The terminal products are three-layer coextruded pouches and liner films where the outer skins provide low-temperature puncture resistance and seal through residual moisture, while the KF138D core provides creep resistance and moisture vapor transmission below 5 g·m^-2·d^-1 at 38 °C and 90% RH.

When Gauge Falls Below 15 µm, Bubble Geometry Becomes the Dominant Control

On high-stalk extrusion lines producing T-shirt carrier bags and produce bags from KF138D at 7 µm to 14 µm, the stalk height is maintained between 2.0 and 3.5 die diameters to separate molecular orientation from bubble expansion; this geometry shifts the orientation balance toward the machine direction and permits a blow-up ratio of 3.0:1 to 4.5:1 without losing bubble stability. Frost-line height is critically limited to ±50 mm; excursions above this band produce visible gauge bands at the collapsing frame and reduce tear resistance measured by ASTM D1922. Melt temperature is set at 195 °C to 210 °C, the die gap is narrowed to 0.8 mm to 1.2 mm, and internal bubble cooling is used to raise specific output without exceeding 8 °C of frost-line temperature drift. At this gauge, film is tested for gauge uniformity by ISO 4593 or ASTM D6988, with maximum acceptable variation of ±5% from the mean for registered converting on high-speed bag machines; the carrier film is printed by flexography only after corona treatment is confirmed at a wetting tension of at least 38 mN/m by ASTM D2578. Terminal products are printed and unprinted T-shirt grocery sacks, produce bags, and inner bin liners; holes at the bag mouth are punched after sealing, and the film must resist Elmendorf tear propagation in the machine direction at values which are strongly dependent on orientation ratio but generally decline when the blow-up ratio falls below 2.5:1.

Heavy-duty liner production using KF138D as the viscosity backbone at 80 µm to 150 µm is carried out on low-shear blown-film extruders with L/D 30:1 and screw cooling, because the high melt viscosity of the grade raises melt temperature through adiabatic shear heating; screw speed is limited to 80 rpm to 120 rpm depending on extruder diameter from 65 mm to 90 mm. The melt temperature is kept below 220 °C, and the die gap is increased to 1.8 mm to 2.2 mm to reduce die-lip shear stress and delay shark-skin melt fracture. In this application KF138D is typically blended with 15 wt% to 25 wt% metallocene LLDPE to raise dart impact at freezer temperatures; the blend is assessed for dart impact by ASTM D1709 Method B, slow puncture by ASTM D5748, and tensile impact by ISO 8256. Terminal products are free-standing FIBC liners, drum liners, and heavy-gauge industrial sacks; FIBC liners are fabricated to fit 1,000 kg flexible intermediate bulk containers, and the film must pass 60° tear propagation and crease-flex tests specified by the FIBC manufacturer rather than a single harmonized standard. Compliance for hazardous goods liners is limited to the packaging certification of the assembled FIBC under UN 13H2 or UN 13H4, not to the liner film alone.

Sealing KF138D Through Coextruded Tie Layers on Vertical Form-Fill-Seal Equipment

On vertical form-fill-seal lines for frozen vegetables and ice-glazed foods, KF138D is used as a component layer in a coextruded film at total thickness of 35 µm to 55 µm, with the HDPE core at 40 wt% to 60 wt% and the sealant layer at 25 wt% to 35 wt%; the sealant is selected from LLDPE or plastomer because the high-density core alone requires sealing temperatures above 130 °C, which destabilizes the VFFS jaw cycle. Seal initiation temperature is measured by ASTM F88/F88M across a temperature gradient of 90 °C to 140 °C; the film is released for production when seal strength exceeds 10 N/15 mm at 110 °C and 0.3 s dwell. Hot-tack strength is tested under ASTM F1921 at a simulated filling temperature of 5 °C to account for frozen product contact immediately after sealing. The HDPE layer contributes dimensional stability and puncture resistance to the pack, measured by ASTM F1306 slow puncture; the low-temperature ductility of the total structure is evaluated by ASTM D1709 Method B after conditioning at -18 °C for 24 h. Compliance for frozen food packaging follows FDA 21 CFR §177.1520 for the HDPE core and the appropriate olefin polymer regulation for the sealant; when the pack is marketed in the European Union, overall migration is tested by EN 1186-1:2002 using food simulant A for frozen non-fatty foods. Terminal products are pillow packs and cushion packs for frozen vegetables, prepared meals, and ice-glazed seafood.

Agricultural silage cover and bale wrap produced with KF138D as a dense, stiff layer in a multi-layer structure differs from conventional LDPE silage covers because the HDPE layer is used at 10 wt% to 20 wt% of the total coextruded film to reduce oxygen transmission and increase puncture resistance against stalk puncture. The film is typically 150 µm to 200 µm in total thickness, and the HDPE layer is embedded between LLDPE skins at a die gap of 2.0 mm to 2.4 mm; UV stabilization is introduced through a hindered amine light stabilizer masterbatch at 3 wt% to 6 wt% in the outer skin only, because the HDPE core has no direct sunlight exposure after installation. Oxygen permeability is measured by ASTM D3985 at 23 °C and 0% RH, and the target is below 2,000 cm³·m^-2·d^-1·bar^-1 for the total structure to limit aerobic spoilage at the silage surface. Terminal products are silage bags, horizontal silage covers, and bale wrap films; the operational boundary is that HDPE-based films have lower puncture elongation at subzero temperatures than metallocene LLDPE films, so the edges must be protected from direct mechanical stress by rope-reinforced hems or sandbag anchoring, and the film is not recommended for bale wrapping at ambient temperatures below -20 °C unless the LLDPE skins exceed 60 wt% of the structure.