High-output blown-film lines running TPC HDPE KM698A as the neat resin for thin-gauge T-shirt bag production operate within a melt temperature window of 180–210°C and a blow-up ratio of 3.0–4.5:1; the high molecular weight distribution is reflected in a melt mass-flow rate of 0.08 g/10 min at 190°C/2.16 kg under ISO 1133-1:2022 and a high-load melt mass-flow rate of 8.0 g/10 min at 190°C/21.6 kg, with a density of 0.949 g/cm³ under ISO 1183-1:2019. Where pellet surface moisture exceeds 0.01 wt% after storage at relative humidity above 60%, pre-drying at 80°C for 2 h is necessary; otherwise surface moisture migrates into the melt film and forms microvoids at the die lip. The processing window is deliberately narrow: below 170°C the high molecular weight tail produces unmelted gel particles that emerge as fisheyes in the web, and above 220°C oxidative chain scission generates gel specks and destabilises bubble height at frost-line heights from 4 to 8 die diameters. In formulation, the resin is charged at 100 phr as the base matrix; 3.0–5.0 wt% linear low-density polyethylene C6 or C8 is added to raise dart impact under ASTM D1709-16a and reduce seal puckering, 2.0–4.0 wt% of a 60% TiO₂ white masterbatch supplies opacity for printed bags, and 0.5–1.5 wt% of a 10% synthetic silica antiblock masterbatch prevents blocking on high-speed converting. Downstream processing is performed on a grooved-feed single-screw extruder with L/D 30:1 and a barrier screw with a Maddock mixer, feeding a spiral-mandrel die of 150–250 mm diameter and 1.0–2.0 mm die gap; melt filtration across 60/80/100 mesh screen packs holds pressure before the screen at 25–40 MPa, and a dual-lip air ring plus online capacitance gauging maintains gauge variability within ±8% for a 12 µm web. The specification anchor is ASTM D4976-12a for polyethylene film and sheeting, with GB/T 21661-2020 applying to plastic shopping bags in export markets; direct food-contact status is not assigned to the resin itself but can be supported under FDA 21 CFR 177.1520 only when the finished bag uses compliant additive masterbatches and migration testing under EU No 10/2011 is completed on the final article. Terminal forms on this setting are high-density T-shirt bags, produce roll bags, point-of-sale bag bundles, and small bin liners from 8–18 µm web.

What Controls Bubble Stability When KM698A Is Let Down with Post-Consumer Recyclate at 20 wt%?

At a let-down of 20 wt% post-consumer HDPE recyclate into KM698A, bubble stability is governed less by the melt index of the virgin fraction than by contaminant gel load, melt-elasticity mismatch, and pellet-feeding uniformity of the recycled stream. The formulation benchmark is 80 wt% KM698A and 20 wt% PCR-HDPE; the working window is 10–30 wt% recyclate, with the lower limit set by cost and the upper limit set by gauge instability and gel-induced film breaks. Downstream processing on a single-screw blown-film line with a grooved-feed section requires a continuous screen changer with 100/120/150 mesh screens; pressure before the screen is typically 18–28 MPa at 190–205°C melt temperature, and a pressure drift of 2–5 MPa per shift indicates filter blinding from paper fiber, cap liner remnants, or oxidised gel. On production lines equipped with gravimetric metering, pellet segregation between virgin KM698A and irregular PCR-HDPE is reduced by feeding the recycled fraction through a separate side-feeding hopper rather than by dry tumble blending; this avoids melt-pressure oscillations of more than 3 MPa at the screw tip. In practice, bubble breaks are most frequent when the recyclate contains small amounts of polypropylene caps or closures; polypropylene forms discrete unmelted islands at HDPE melt temperatures and acts as a tear-initiation site under ASTM D1922-15. The compliance frame for non-food grocery sacks is EN 15343:2007 for recycled content traceability and EU Directive 94/62/EC on packaging and packaging waste; food-contact use is not supported unless the recyclate carries an EFSA suitability opinion and the finished article passes EU No 10/2011 migration testing. Published data for film property retention above 30 wt% PCR-HDPE specifically with KM698A is limited; qualification must therefore include pilot-line let-down followed by dart impact testing under ASTM D1709-16a and MD tensile testing under ASTM D882-18. The resulting sacks are refuse sacks, retail grocery sacks, and municipal recycling bags in gauges from 12–25 µm.

Calcium Carbonate Masterbatch Addition and Low-Temperature Puncture in Heavy-Duty Liner Film

In heavy-duty liner extrusion, the formulation uses KM698A at 100 phr as the matrix and a calcium carbonate masterbatch at 5–15 wt%; the masterbatch is typically based on 80% CaCO₃ in an LLDPE carrier and is added for density, opacity, and cost-adjusted stiffness. Addition above 15 wt% produces a cliff-edge effect in low-temperature puncture resistance; published data for this specific masterbatch concentration with KM698A is limited, but industrial practice on 350–600 mm spiral-mandrel die lines indicates that heavy-duty refuse sacks loaded above 15 wt% show a marked reduction in MD tear retention under ASTM D1922-15 and puncture resistance under ASTM D5748-19, particularly at handling temperatures between −10°C and 5°C. The production process runs a die gap of 2.0–2.8 mm, a blow-up ratio of 2.5–3.5:1, and a frost-line height of 500–900 mm; a dual-lip air ring with chilled air at 12–18°C is required to stabilize the wider bubble and prevent melt conditioning differences between the flattened edges and centre of the web. Melt temperature is held at 185–205°C; below 175°C the filler masterbatch increases screw torque and can produce surface roughness at the die lip, while above 210°C oxidative degradation of the LLDPE carrier in the masterbatch creates gel specks in the film. Compliance for refuse sacks is anchored to EN 13592:2017 for household waste sacks and to REACH 1907/2006 Annex XVII for the calcium carbonate masterbatch and processing aids; ASTM D4976-12a remains the specification reference for polyethylene film and sheeting. Product types under this route include heavy-duty refuse sacks, industrial liners for dry bulk containers, construction-site waste bags, and compactor bags in thicknesses from 30–70 µm.

Coextruded Cereal Liner Structures Rely on a 0.08 g/10 min Melt Mass-Flow Rate for Layer Uniformity

A three-layer coextruded cereal liner uses KM698A in the outer skin layers at 40–60 wt% of total structure, with an LLDPE C8 core at 30–50 wt%, and optional white masterbatch at 3.0–5.0 wt% in the skins. The KM698A fraction is selected not for melt strength alone but because its low melt mass-flow rate of 0.08 g/10 min under ISO 1133-1:2022 reduces layer-thickness variation when the melt stream passes through a three-layer spiral mandrel die; the high molecular weight distribution narrows the viscosity ratio between the skin and core polymers at a die temperature of 190–205°C. Downstream processing on an internal bubble cooling line uses a die gap of 1.8–2.2 mm, a blow-up ratio of 2.0–2.8, and a frost-line height of 3–6 die diameters; the IBC airflow is adjusted to maintain bubble diameter within ±2% across the lay-flat. For food-contact use, the finished structure falls under FDA 21 CFR 177.1520 for olefin polymers and EU No 10/2011 for plastic food contact materials; overall migration testing must demonstrate ≤ 10 mg/dm² on the final article, and the liner supplier must verify that the white masterbatch and any processing aids are also listed in the relevant framework. Because HDPE is a moisture barrier but a weak oxygen barrier, the structure is suited to dry cereal, cracker, and snack liners rather than oxygen-sensitive dry powders; if an EVOH barrier layer is introduced, maleic anhydride-grafted PE tie layers at 5–8 wt% per adhesive layer are required because HDPE and EVOH do not intermix without interfacial adhesion. End-use articles produced from this structure include cereal box liners, cracker liners, dry snack pouches, and boxed dry mix liners from 20–40 µm total structure.

When Powdered Detergent Box Liners Require Heat-Seal Integrity at 130–150°C Jaw Temperatures

For powdered detergent box liners, the heat-seal window is set by the melting range of HDPE and by the need to avoid burn-through at high jaw pressure. The film formulation uses KM698A at 100 phr; 2.0–4.0 wt% of an erucamide/synthetic silica slip-antiblock masterbatch reduces coefficient of friction below 0.30 under ASTM D1894-14, 3.0–5.0 wt% of a white masterbatch provides opacity, and 0.5–1.0 wt% of a 10% ethoxylated amine antistat masterbatch prevents powder deposition on the seal area when handling detergent dust. Downstream converting occurs on vertical form-fill-seal machines with heated jaws set to 130–150°C, dwell 0.6–1.2 s, and sealing pressure 2–4 bar; the KM698A molecular weight distribution stabilizes the melt curtain during seal-bar contact, but the seal window remains narrower than LLDPE grades, so jaw temperature must not exceed 150°C to avoid seal thinning and film snap-back after the jaw opens. Compliance for non-food detergent packaging is anchored to ASTM D4976-12a, REACH 1907/2006, and RoHS 2011/65/EU; direct food-contact status is not required, but the finished article must still meet the factory’s standard for extractable heavy metals if the packed product is exported to markets that enforce packaging toxicity rules. The converted material feeds box liners for powdered detergent, dry chemical liners, and powder mix pouches in thicknesses from 30–70 µm.