In monolayer blown film conversion for retail T-shirt bags, PetroChina Jilin HDPE 9455F is typically dry-blended rather than compounded when warehouse humidity is maintained below 60% RH and incoming pellet moisture remains below 0.05 wt% by Karl Fischer titration under ISO 15512:2019. The dry blend commonly comprises 93.0–95.0 wt% 9455F, 4.0–6.0 wt% high-opacity white masterbatch, and 0.8–1.2 wt% slip/antiblock masterbatch. The white concentrate frequently contains 60 wt% rutile TiO₂ dispersed in an LDPE carrier with a melt flow rate of 8 g/10 min at 190 °C/2.16 kg, while the slip/antiblock concentrate combines 5 wt% erucamide and 10 wt% synthetic silica in the same carrier. Formulation control is judged by statistically stable colour difference of <1.5 Delta E across the printed web and by retained dart impact after masterbatch addition, not by visual inspection alone.

Extrusion on a 55–75 mm grooved-feed extruder with 25:1–30:1 L/D and a barrier screw fitted with a Maddock mixing section normally holds melt temperature between 190 °C and 210 °C at the die inlet. Die gap is set at 1.0–1.4 mm, die diameter at 250–400 mm, and blow-up ratio between 3.5:1 and 4.5:1 to produce film at 8–15 µm gauge. Frost line height is maintained at 6–8 die diameters beneath a dual-lip air ring; lowering the frost line below 5 die diameters has been observed on commercial lines to increase blocking at the collapsing frame and generate gauge bands at the winder. Output stability is a function of die circumference rather than screw speed alone, and typical high-stalk HDPE lines run at 0.9–1.3 kg/h per mm of die circumference. Film tensile properties are measured under ISO 527-3:2018, dart drop impact under ASTM D1709-15A Method A, and tear propagation under ISO 6383-2:1983.

During bag converting, the film is gusseted, perforated, heat-sealed and die-cut into T-shirt bags with punched handles. Seal initiation temperature is determined by hot-tack testing under ASTM F1921-12; typical rotary heat-seal jaw settings are 160–175 °C at 0.5–1.0 s dwell and 2.0–3.5 bar pressure. Seal strength is required to exceed 60% of the film tensile at break under ISO 527-3:2018, with failure located outside the seal zone. Converter trials indicate that edge trim regrind can be reintroduced up to 15 wt% without breaching dart impact specifications when melt temperature is limited to 210 °C, but gel counts above 0.5 gel/m² generally require a 200 µm screen pack change. The terminal article is a folded block of printed T-shirt sacks rated for retail collection loads of 8–12 kg, while the finished film roll must maintain a thickness tolerance of ±8% across the layflat width.

What Limits Drawdown Stability in Heavy-Gauge Industrial Sack Film When Internal Bubble Cooling Is Not Installed?

Low drawdown stability in heavy-gauge refuse sacks and construction debris bags produced from 9455F is governed by the interaction between bubble cooling rate, melt viscosity, and extrusion pressure. The resin is formulated with 96.0–97.5 wt% 9455F, 2.5–3.0 wt% carbon black masterbatch, 0.2–0.5 wt% fluoropolymer processing aid, and 0.05–0.10 wt% antioxidant concentrate to reduce gel formation at elevated back pressures. The carbon black masterbatch is based on 40 wt% furnace black in an HDPE carrier, because an LDPE carrier reduces the tensile modulus of the finished sack below the minimum run-point required for heavy wet waste. Drawdown stability is evaluated by recording bubble diameter at the frost line and web tension oscillation on the haul-off; a tension deviation exceeding ±15% during 10 min of continuous operation generally predicts gauge variation outside ±10% at the winder.

Heavy-gauge film is produced at 60–150 µm thickness on extruders with 30:1 L/D barrier screws, die diameters of 350–500 mm, and die gap 1.6–2.0 mm. Blow-up ratio is reduced to 2.0:1–3.0:1 to limit transverse orientation, and frost line height is held at 5–7 die diameters. Without internal bubble cooling, melt temperature is often lowered to 190–200 °C to compensate for low air-ring heat transfer, but this raises extruder pressure drop by 10–15% compared with processing at 210 °C; the fluoropolymer processing aid is therefore mandatory when die pressure exceeds 420 bar. Gauge uniformity is measured with a capacitance gauge and controlled to ±10% in both machine and transverse directions. Mechanical testing under ISO 527-1:2019 and ISO 527-3:2018 focuses on machine-direction tensile yield, while puncture resistance is evaluated according to ASTM D5748-19 or ISO 7765-1. Finished refuse sacks must comply with EN 13592:2017 for household waste collection, including dimensional stability and sealing integrity; industrial sacks used for construction debris are additionally tested for filled-bag drop impact under ASTM D5276-19.

Terminal products include gusseted refuse sacks, rubble sacks, and industrial can liners for 120 L, 240 L and 660 L wheeled containers. The seal configuration differs from retail bags: wide bottom seals of 8–15 mm are used with dual heated jaws to compensate for thickness variation. The converter must monitor film-to-film blocking force because carbon black absorbs infrared and raises film surface temperature at the winder; blocking force above 80 g/cm according to ASTM D3354-15 can stop high-speed bag separation in dispensing equipment. Pre-drying of the resin itself is not generally required, but regrind stored under humid conditions above 60% RH should be dried at 80 °C for 2 h to prevent downstream edge curl and seal porosity.

Where agricultural storage covers require UV resistance and mechanical strength at -20 °C, monolayer construction from 9455F is usually replaced by a three-layer coextrusion in which the resin forms the structural core. Layer distribution on a three-layer blown film line with extruder diameters of 70 mm, 90 mm and 70 mm and a 300–500 mm die is typically 20/60/20 by volume. The core layer consists of 92.0–94.0 wt% 9455F, 5.0–6.0 wt% UV masterbatch, and 1.0–2.0 wt% white TiO₂ concentrate; the outer layers are formulated with lower-density polyethylene or EVA copolymers to provide cling and low-temperature flexibility. The UV masterbatch contains a hindered amine light stabiliser system delivered at 10 wt% active in an LLDPE carrier, dosed to achieve 0.5–0.8 wt% active HALS in the final film. Process settings are shifted to a die gap of 1.4–1.8 mm, blow-up ratio 2.5:1–3.5:1, and melt temperature 200–215 °C because the EVA skin requires lower viscosity than the HDPE core. The line must be purged with LLDPE after shutdown because 9455F and EVA can form interfacial gels if residence time exceeds 20 min at 215 °C.

Mechanical evaluation of the finished cover follows ISO 527-3:2018 before and after accelerated weathering under ISO 4892-2:2021; a tensile retention of at least 50% after 2000 h of xenon-arc exposure is a common acceptance criterion for silage pile covers. Puncture and tear requirements are set by ASTM D5748-19 and ISO 6383-2:1983. The terminal articles are silage pile covers, temporary greenhouse side sheeting, and agricultural fumigation films with total thickness 80–150 µm. Compliance under REACH Regulation (EC) No 1907/2006 Annex XVII restricts the use of certain plasticisers in skin layers, and the converter must verify that the finished article meets specific migration limits if any layer is intended for direct contact with feed.

Low-Temperature Dart Impact Retention in Frozen Poultry Package Liners

Blending 10–20 wt% linear low-density polyethylene into 9455F lowers the ductile-to-brittle transition of monolayer liner film used in frozen poultry packaging, but reduces tensile modulus measured under ISO 527-3:2018. A converter-grade blend containing 85 wt% 9455F, 15 wt% octene LLDPE with density 0.918 g/cm³, 0.5–1.0 wt% slip masterbatch, and 0.2 wt% polymer processing aid is blow-extruded at 30–60 µm gauge. The blended formulation shows a measurable loss of dart impact at -20 °C when the LLDPE content exceeds 20 wt% because the frost line height must be increased to 8–10 die diameters to prevent bubble fluttering; above this frost line, machine-direction orientation drops and the bubble becomes more prone to edge tear. The bubble is run with blow-up ratio 3.0:1–4.0:1 and die gap 1.2–1.6 mm.

The key specification is dart drop impact at -20 °C under ASTM D1709-15A, with typical acceptance values of 100–140 g at 40 µm, while unmodified 9455F monolayer films of identical gauge often fall below 60 g under the same conditioning protocol of 24 h at -20 °C. Seal strength after side-seal conversion is determined by hot-tack testing under ASTM F1921-12 at 140–160 °C jaw temperature. For direct food contact, the finished liner must comply with FDA 21 CFR 177.1520(c) for olefin polymers and the relevant migration limits in EU No 10/2011 Annex I and II; compliance is not automatically transferred from the resin certificate to the printed film because slip additives and converter-applied inks or coatings can alter overall migration. Terminal products include side-seal bags, pillow pouches, and dump-bin liners for frozen whole poultry, cut poultry parts, and frozen seafood. Production lines that combine 9455F with LLDPE should avoid purge materials based on mineral-filled polypropylene because the abrasive filler accelerates barrel wear and can leave black specks after 2–3 h of continuous operation.

When 9455F Is Extruded as the Structural Core of Multiwall Shipping Sacks, Layer Viscosity Matching Determines Interlayer Adhesion

In three-layer multiwall sack structures, the melt viscosity of 9455F at 210 °C and a shear rate of 300 s⁻¹ should be within 35% of the adjacent skin-layer melt viscosity to avoid interfacial instability and delamination. The structure is commonly 15/70/15 by volume, with LDPE-based skins for heat sealing and a 9455F core for tear resistance and dead-fold. The LDPE skin resin with a melt flow rate of 2–4 g/10 min enables sealability, while the core layer is dry-blended with 2.0–3.0 wt% calcium carbonate masterbatch to control slip and reduce blocking in the finished roll. Die gap is 1.8–2.4 mm, blow-up ratio 2.5:1–3.0:1, and melt temperature 200–215 °C. Interfacial adhesion is measured on a 25 mm wide strip using a 180° peel test under ASTM D903-98; adhesion values below 1.5 N/25 mm indicate that the viscosity ratio has drifted too high.

Terminal products are HDPE film liners laminated to woven polypropylene or kraft paper in multiwall shipping sacks for pet food, mineral additives, and dry chemical powders. The film provides puncture resistance in transport, while the outer paper or woven fabric carries print and load stability. The film roll is corona-treated to 42–46 dyn/cm and tested for wetting tension under ASTM D2578-23 before lamination. Compliance for chemical packaging requires that the finished sack pass the drop test of ASTM D5276-19 after filling with 25 kg of product; for mineral feed packaging, the converter must also verify compliance with FDA 21 CFR 177.1520(c) if the inner liner is positioned as a direct feed contact layer. Equipment operators must limit melt temperature to 220 °C because thermal degradation of the LDPE skin generates odour compounds that migrate into sorbate-based pet food after 48 h of sealed storage at 40 °C.

Caliper deviation below ±1 µm is more decisive than tensile yield strength in glass interleaving film produced from 9455F. The film is used between glass containers during transit and storage to prevent pressure marks, surface scratches, and microbial adhesion. It is extruded at 10–20 µm gauge with a die gap of 0.8–1.2 mm, blow-up ratio 2.0:1–3.0:1, and high-stalk bubble geometry to maintain flat orientation. The converter commonly adds 0.3–0.6 wt% food-contact antistatic masterbatch containing an ethoxylated amine or glyceride, because static build-up on the film surface leads to mis-sheet insertion on high-speed glass interleaving machines. Film-to-metal and film-to-film static decay times are measured according to ASTM D257-14; an acceptance criterion of <2.0 s decay from 5000 V to 500 V at 23 °C and 50% RH is typical for automatic sheet insertion equipment.

Published third-party data specific to 9455F in glass interleaving film is limited, so converters establish caliper capability through roll map studies across the layflat width. A caliper deviation above ±1.5 µm at the edges can produce wavy sheet formation and cause double-sheet pickup on the vacuum head of glass packaging lines. The film must be wound at near-zero taper tension, typically 20–40 N/m, to avoid blocking; blocking force is measured by ASTM D3354-15. When the finished film is intended for food or beverage glass containers, the antistatic additive and the base polymer must comply with FDA 21 CFR 177.1520 and EU No 10/2011; antistatic agents based on lauryl diethanolamide may require specific migration evaluation under the assigned specific migration limit. The terminal product is a hard roll of interleaving film supplied with a width tolerance of ±1 mm and splice-free length up to 6000 m depending on gauge.