High-molecular-weight HDPE 5020 with a nominal melt flow rate of 0.20 g/10 min under ASTM D1238 at 190°C and 2.16 kg load, and a nominal density near 0.950 g/cm³ under ASTM D1505, is converted into thin-gauge blown film for T-shirt carrier sacks, refuse sacks, and industrial liners on grooved-feed single-screw extruders. The screw diameter is commonly 45 mm to 65 mm with an L/D 30:1 barrier screw, a spiral mandrel die of 100 mm to 200 mm, and a dual-lip air ring. Melt temperature is maintained between 195°C and 225°C; higher temperatures reduce bubble load but increase oxidation risk in the gel-permitting polymerization stabiliser system. The die gap is set between 1.2 mm and 1.8 mm when final gauge is targeted at 8 µm to 30 µm, with blow-up ratio held between 3.0:1 and 4.5:1 and frost-line height corrected within 400 mm to 800 mm after concentric annulus alignment. Gauging is controlled by capacitance or nucleonic back-scatter heads to maintain a transverse thickness tolerance of ±2 µm on a 20 µm film, because draw resonance and melt surge in the low-melt-index material cause side-gauge deviation if the air ring is not centered within 0.5 mm. The extruder barrel temperature profile is set with a feed section at 160°C to 180°C, a compression section at 190°C to 210°C, and a metering section at 210°C to 225°C. Bubble internal pressure is maintained at 0.2 kPa to 0.8 kPa relative to ambient for a 3.0:1 blow-up ratio, and continuous screen-pack monitoring at the breaker plate is required below 35 MPa; pressure above 45 MPa at the screen indicates gel or crosslinked contamination and is corrected by a screen change before bubble instability appears.

Film mechanicals are assessed under ASTM D882 for tensile yield and break in both machine and transverse direction, ASTM D1922 for Elmendorf tear, ASTM D1709 Method A for dart drop impact, and ASTM D1003 for haze. Because the resin is densified and tends toward high tear and dart drop but limited clarity, converter formulations typically incorporate 2 wt% to 10 wt% LLDPE or LDPE at the hopper throat to widen the bubble margin and lower internal haze; addition above 15 wt% is avoided for T-shirt bag rigidity unless a lower top-load requirement applies to refuse liners. Slip erucamide is metered at 400 ppm to 1,000 ppm and synthetic silica antiblock at 1,000 ppm to 2,500 ppm, but the exact load is set after a 48-hour migration trial on a pilot line producing 20 µm film because roll-blocking failure appears only after winding pressure and storage time. Where the finished film is placed into indirect food contact as a prepack liner, compliance is verified on the final article under 21 CFR 177.1520(c) 2.1 or Regulation (EU) No 10/2011, and migration testing is performed according to EN 1186 and EN 13130 methods applied to the actual film gauge and food simulant exposure conditions.

What Processing Window Controls Parison Hang Time in 25-L HDPE Jerrycans?

Accumulator-head extrusion blow moulding of tight-head jerrycans and open-top pails from 5 L to 60 L uses the low melt flow rate of HDPE 5020 to limit parison elongation during the drop. The melt is discharged from the accumulator die at 190°C to 230°C; below 190°C the parison surface shows melt fracture and the pinch-off zone can delaminate, whereas above 230°C parison sag becomes measurable in lengths longer than 800 mm when the die gap is not programmed. The accumulator head volume is matched at 1.0 to 1.3 times the shot weight, and the die gap is profiled in 0.1 mm increments through the parison stroke to add mass at the top sealing shoulder and at the bottom pinch-off. Die swell on diameter is observed in the range of 1.8:1 to 2.4:1 for this low-MFR high-density resin, so the blow ratio is set between 2.0:1 and 3.0:1 and the mould is adjusted only after the first article is sectioned to measure wall thickness distribution. Pre-blow air is introduced at 0.05 MPa to 0.15 MPa for 0.2 s to 0.6 s to stop the parison from collapsing before the mould closes; final blow air at 0.6 MPa to 0.9 MPa is maintained until the part reaches 80°C to 90°C at the inner wall, after which the part is ejected. Blow pin geometry is matched to the neck finish, with a land length of 8 mm to 12 mm for a 50 mm neck; too short a land causes flash into the seal area, too long increases pressure drop and slows bottle cooling.

Cooling water enters the mould at 5°C to 20°C, with a minimum flow rate of 3.5 m³/h per mould half on a 20-L tool to keep the inner parison surface below the crystal growth range long enough for dimensional stabilisation. Cycle time on a single-station accumulator machine for a 20-L jerrycan is typically 55 s to 80 s depending on pre-blow sequencing and flash thickness. Regrind from pinch-off tail and top flash is metered at 15 wt% to 25 wt%, but the addition is permitted only if the source is clean internal scrap of the same grade. Any external or contaminated regrind is excluded when the container is submitted for hazardous material approval under 49 CFR 178.509, ADR 6.1.5, IMDG 6.1.5, or IATA Packing Instruction Y as applicable. Finished containers are checked with a wall-thickness sectioning jig at the shoulder, sidewall, and pinch-off line, and leak tested on a closed-loop pressure test at 20 kPa to 40 kPa with pressure decay not exceeding 1 kPa/60 s depending on the UN marking group. Environmental stress-crack resistance of the pinch-off and flash-free sidewall is screened under ASTM D1693-B in 100% Igepal CO-630 at 50°C, but the resin supplier datasheet value must be verified on the produced article because weld lines reduce the effective value relative to plaque-moulded sheets, and the magnitude depends on tool geometry.

On a six-station shuttle or wheel blow moulding machine, HDPE 5020 can be converted into 500 mL to 5 L industrial chemical and agrochemical bottles with thinner walls than accumulator-head jars, but with a narrower melt-temperature band because the continuous extruder does not provide the same parison programming depth as an accumulator head. Melt temperature is controlled at 180°C to 210°C at the die, and the parison drop length is limited to less than 300 mm to prevent taper. The mould closes with a clamp force of 8 to 25 tonnes per cavity, and blow air is introduced at 0.6 MPa to 0.8 MPa through a needle system after pre-blow at 0.1 MPa to 0.3 MPa for the first 0.3 s to 0.8 s to stabilise the tube. Cooling time is governed by wall thickness and mould temperature, which is held at 8°C to 20°C on the cavity and 6°C to 18°C on the core pin; exceeding this band improves gloss but extends cycle time and creates post-mould shrinkage variation. Regrind usage on wheel machines is limited to 10 wt% to 15 wt% because the thin neck and thread zone of a 500-mL bottle is more sensitive to loss of elongation at break than a large jerrycan wall. Additive masterbatches for UV protection in agrochemical bottles are dosed at 2 wt% to 5 wt%, but the article must still pass the labelled chemical compatibility test under the relevant Good Laboratory Practice protocol because amine-based antistatic additives and certain liquid formulations can alter stress-crack resistance of the neck thread during storage at 40°C for 28 days. Top-load resistance is measured on the empty container under ASTM D2659 at a crosshead speed of 12.5 mm/min. Published data for the use of HDPE 5020 in six-station wheel machines is limited; converters predominantly qualify it on accumulator-head equipment before transferring to continuous wheel tools.

When Roll-Stack Sheet Lines Run HDPE 5020 Instead of a Higher-MFR Sheet Resin

Extrusion of 0.5 mm to 2.0 mm HDPE sheet from HDPE 5020 through a 75 mm single-screw extruder with L/D 30:1, gear pump, and screen changer produces blanks for vacuum-formed dunnage trays and interlayer sheets. Because the 0.20 g/10 min melt is higher in viscosity than typical high-MFR sheet HDPE, head pressure at the die rises and is controlled between 40 MPa and 60 MPa on the pressure transducer before the gear pump. Melt temperature at the flexible-lip die is maintained at 200°C to 240°C; temperatures above 240°C create die-lip oxidation and gel streaks after 8 h of continuous running. The roll stack is set with an initial roll at 80°C to 100°C, a middle roll at 70°C to 90°C, and a final roll at 50°C to 70°C, with a roll gap decreased in 0.05 mm steps until the desired sheet flatness is reached without edge tear. Trim from the sheet edges is ground and reintroduced at 20 wt% to 35 wt% as fluff, but addition above 35 wt% can create gel specks and thickness bands in a 1.0 mm sheet because the lower bulk density of fluff and higher moisture regain require vented-barrel degassing. Moisture in reprocessed fluff above 0.1 wt% causes splay marks on the sheet surface; therefore the fluff is pre-dried at 70°C for 2 h when stored in unheated wet areas.

Thermoforming of the sheet into transport trays is run on a contact or shuttle process at a sheet surface temperature of 160°C to 180°C, a vacuum level of -60 kPa to -80 kPa, and a forming cycle of 8 s to 15 s. Deep-draw trays with depth-to-width ratios above 0.5 cause wall thinning at the tray corners; thus the sheet is thickness-profiled during extrusion to add 0.2 mm to 0.5 mm margin in the corner zones for trays with a draw depth above 100 mm. Compliance is limited to industrial non-food contact unless final article testing under Regulation (EU) No 10/2011 or 21 CFR 177.1520 demonstrates migration below the assigned specific migration limit. For direct export into electrical and electronics accessory packaging, the sheet is screened against REACH candidate-list substances and RoHS restricted heavy metals using IEC 62321 digest methods when proof of conformity is required.

Twin-Wall Drainage Pipe Extrusion Vacuum Calibration Requirements

Corrugated twin-wall pipes of 150 mm to 600 mm nominal outside diameter can be extruded from HDPE 5020 on a twin-screw or grooved-feed single-screw line feeding a corrugator with vacuum calibration blocks. The melt temperature at the pipe die is maintained between 210°C and 230°C; higher temperatures reduce the vacuum calibration retention of the corrugated profile, while lower temperatures cause the outer ribs to solidify before filling the block depressions. The inner wall is extruded through a separate die mandrel at 0.5 mm to 0.9 mm wall thickness, and the outer corrugated shell is drawn into aluminium mould blocks with a vacuum of -20 kPa to -35 kPa and a haul-off speed correlated to the corrugator pitch within ±0.5%. The corrugator mould blocks are operated at 35°C to 50°C, and the cooling water circuit uses a closed-loop temperature variation of ±1°C across the width; asymmetric cooling causes the pipe to spiral or exhibit out-of-roundness measured under EN 13476-3 as a maximum out-of-roundness of 5% of nominal outside diameter.

Pipe ring stiffness is tested under ISO 9969 at a deflection of 3%, and the product is classified according to EN 13476-3 if the converter seeks CE marking for non-pressure underground drainage. Because the lower MFR may increase back pressure in the spiral mandrel distribution system, the melt pump inlet pressure is monitored at 25 MPa to 35 MPa to avoid overheating due to shear. The final pipe is impact tested at 0°C using the staircase or batch method under EN 744 to confirm that the chosen HDPE grade has sufficient resistance to crack propagation in the oriented corrugation root; producers may require a resin lot-to-lot ESCR check under ASTM D1693-B because not all 0.20 g/10 min HDPE lots exhibit the same comonomer distribution. The specific formulation must meet the long-term hydrostatic strength requirements of ISO 9080 when the finished pipe is evaluated under ISO 12162 at 20°C and 50 years if the grade is qualified for pressure service. Published data for pressure-rated HDPE 5020 configurations is limited; conversion of this grade into pressure pipes requires a producer-audited stress-rupture regression.