Sinopec-SK (Wuhan) HDPE HD5502 is a high-density polyethylene extrusion blow molding grade. The nominal density is 0.955 g/cm³ when tested under ISO 1183-1:2019, and the melt flow index is 0.35 g/10 min at 190 °C/2.16 kg under ISO 1133-1:2022. The resin is supplied as natural granules with a stabilizer package that is intended for repeated extrusion heat history in blow molding lines. Processors using 60–75 mm grooved-barrel extruders with 24:1 to 30:1 L/D have reported that melt temperatures above 215 °C generate oxidative gel particles during residence times beyond 8 min, while temperatures below 185 °C produce parison curl and wall-thickness non-uniformity in containers above 500 mL. These boundaries are line-specific and require validation with the installed die and accumulator geometry.

Food-contact extrusion blow molding of pasteurized milk and drinking water bottles consumes HD5502 in 200 mL to 1 L formats. The process uses a melt temperature of 190–210 °C, a die head temperature of 195–205 °C, a parison die gap of 1.8–2.2 mm, and blow air pressure of 0.6–0.8 MPa. Mold temperature is held between 15 °C and 30 °C; for an 8-station wheel running 500 mL round bottles, cycle times normally fall between 12 s and 18 s. The formulation for opaque dairy bottles begins at 100 phr HD5502 plus 0.5–1.0 phr white pigment masterbatch; no external slip or antiblock concentrate is required because the cooled mold releases HDPE surfaces without blocking. Regrind must come from the same food-contact-approved lot and is maintained at or below 20 wt% unless migration testing under EN 1186-1:2002 demonstrates that a higher closed-loop scrap ratio still meets the overall migration limit of 10 mg/dm² under EU Regulation (EU) No 10/2011. Terminal articles must satisfy olefin polymer requirements under 21 CFR 177.1520(c) and GB 4806.7-2016 where Chinese food-contact compliance applies. HD5502 is not intended for hot-fill above 60 °C, retort, or autoclave conditions; sidewall deformation and closure-seal failure become the limiting factors above that service window. If surface condensation occurs during cold-weather storage, pre-drying at 70 °C for 1–2 h in a desiccant dryer prevents surface splay. Wall-thickness consistency in multi-cavity tooling depends on vertical die centering, uniform parison drop speed, and shot-to-shot regrind feed stability.

The compliance checks below are repeated across the downstream sectors because food-contact, household chemical, automotive, and industrial packaging each cross different regulatory thresholds. The table consolidates the usual boundary conditions; none of the listed criteria replaces lot-specific migration or extraction testing on the finished article.

What Limits ESCR Retention in HD5502 When Bleach and Alkaline Cleaners Are Packed?

The dominant failure mode in household and industrial chemical packaging is environmental stress cracking at the pinch-off seam and along sharp corners. HD5502 is used for 1 L, 5 L, and 25 L bottles for sodium hypochlorite, alkaline cleaners, and diluted agrochemical formulations. The injection of 100 phr HD5502 with 2.0–3.0 phr chemical-resistant pigment masterbatch and, when outdoor storage is anticipated, 0.2–0.3 phr hindered amine light stabilizer is typical. Post-consumer recyclate is excluded from dangerous goods packaging, and in-house regrind is held at or below 15 wt% because calcium carbonate or oxide residues from recycled streams act as crack initiators. Extrusion blow molding on accumulator-head machines for 5–25 L containers is operated at a melt temperature of 190–200 °C and a mold temperature of 20–25 °C. The parison die gap is set between 2.0 mm and 2.8 mm for a 20 L jerrycan, and the tail flash weld must be compressed with sufficient clamp force to produce a cold-weld bulge of 1.0–1.5 mm; a thin or sharply folded tail weld is the usual site of ESCR failure. Incoming resin is tested by the converter against ASTM D1693-15b condition A; blow-molded panels are preferred over compression-molded plaques because internal stresses from parison stretching shift the F50 value downward. The certificate of analysis from Sinopec-SK is compared against the internal minimum F50 for the specific bottle design, but published data for this exact container configuration is limited and must be generated on the filling line. Terminal containers for sodium hypochlorite are usually rated under UN 3H1 jerrican requirements when the product is classified for dangerous goods transport; stack and drop testing follow the applicable UN model regulations rather than a single resin property. Processors should avoid melt temperatures above 210 °C during start-up purging because oxidative gels introduced into the parison reduce ESCR by creating local stress concentrations. The same constraint applies to hold-up points in the die head; a clean polymer flow path with no dead spots is required for bleach packaging.

In personal care packaging, HD5502 is converted into 200–750 mL cylindrical and oval bottles for shampoos, conditioners, and body washes. The converter blends 100 phr HD5502 with 1.5–3.0 phr pearlescent or opaque color masterbatch and adds 0.1–0.2 phr processing aid only when high-gloss surface finish or faster parison drop is required on shuttle presses. Because surfactants can stress-crack HDPE, incoming resin is evaluated by ASTM D1693-15b condition A; the certificate of analysis is compared against the minimum F50 value written into the end-use specification. Extrusion blow molding uses melt temperatures of 190–205 °C and mold temperatures of 18–28 °C. Tall flat-sided bottles are produced with parison programming; the die gap is opened at the top and bottom to prevent sidewall thinning. Pinch-off strength is monitored by filled-bottle drop testing under ASTM D2463-15 at 1.2 m and 23 °C, with additional cold-climate drops at -10 °C for distribution into northern markets. Terminal articles must meet the low-odour and sensory requirements of cosmetic packaging; volatile carriers in the masterbatch must remain below the declaration threshold, and any processing aid must be covered by a food-contact or cosmetic-positive list when the bottle is used for leave-on cosmetic formulas. HD5502 does not provide PET-like clarity; opaque, matte, or coloured bottles are the realistic design envelope. Oval containers with a high cross-sectional aspect ratio require an elliptically shaped die bushing because HD5502 exhibits intermediate die swell; the die minor axis is typically reduced by 10–20% relative to the finished bottle minor axis to compensate for swell.

Open-Head Pails and UN-Rated Drum Inserts: Cold Impact, Stack Load, and Parison Programming

Large accumulator-head machines convert HD5502 into 10–30 L open-head pails, gasket-sealed lids, and drum inserts for lubricants, inks, and industrial intermediates. The compound formulation for outdoor storage is 100 phr HD5502 plus 1.5–2.5 phr carbon black masterbatch and 0.1–0.3 phr hindered amine light stabilizer. For pigmented indoor pails, the carbon black masterbatch is replaced by 2.0–3.0 phr of a compatible color concentrate. Melt temperature is controlled at 190–205 °C, mold temperature at 15–25 °C, and blow air pressure at 0.7–0.9 MPa. The die gap is programmed from 2.0 mm at the base to 2.8 mm at the shoulder to maintain a wall thickness of 1.2–1.8 mm in the finished pail sidewall.

The cold-impact requirement eliminates marginal pinch-off welds. Filled pails are conditioned at -18 °C for 24 h and then dropped from a height determined by the UN packaging test program for the packing group; the pail must not leak or lose contents. Stack load is evaluated at 40 °C for 28 days with a static load representative of warehouse stacking. HD5502 passes these tests only when the pinch-off tail is fully compressed and the pigment masterbatch is free of moisture; visible bubbles at the pinch-off seam are classified as a batch reject. The resin is not specified for continuous contact with food, and processors should not blend post-consumer regrind into UN-rated pails unless the regrind source is verified against the same formulation and the finished pail passes all drop and stack tests. Published data for this specific HD5502 pail configuration is limited; internal validation on the production line is mandatory because design wall thickness and handle attachments shift failure points independently of resin type.

HD5502 can be converted into 0.5–2.0 mm extruded sheet for thermoformed food trays, industrial dunnage, and returnable transit trays. The sheet line uses an 80 mm barrier screw and a flat die; barrel zone temperatures are set at 180–215 °C, and the die temperature is held at 195–210 °C to reduce die lines. The extrudate enters a three-roll stack with roll temperatures of 70–90 °C for matte sheet and 90–110 °C for polished sheet. Edge trim and start-up scrap are granulated, dried below 0.1% moisture, and fed back at up to 30 wt%. Higher regrind ratios shift the sheet flexural modulus and increase thermoforming web sag; beyond 30 wt%, the sheet may require a higher melt temperature or slower line speed to maintain gauge. Thermoforming is performed at sheet surface temperatures of 160–175 °C, with plug assist required for draw ratios above 2.5:1. Terminal trays and inserts use the stiffness imparted by the 0.955 g/cm³ density of HD5502. Food-contact sheet must comply with 21 CFR 177.1520(c) and EU Regulation (EU) No 10/2011; industrial sheet is tested for heavy metals under Directive 94/62/EC, where the sum of cadmium, mercury, lead, and chromium VI must remain below 100 mg/kg. HD5502 sheet is unsuitable for transparent blisters or deep-draw thin-wall packaging; it is intended for rigid, thick-gauge applications where high melt strength is not required.

When Windshield Washer Reservoirs Are Blow Molded from HD5502 Instead of a Higher-Melt-Strength Automotive HDPE

Windshield washer reservoirs and coolant overflow bottles represent an automotive blow molding segment where wall thickness around insert fittings is the primary process variable. The formulation is 100 phr HD5502 plus 1.5–2.5 phr carbon black masterbatch and 0.1–0.2 phr heat stabilizer top-up when under-hood service temperatures approach 85 °C. Extrusion blow molding on an accumulator head uses a melt temperature of 190–200 °C and a mold temperature of 15–25 °C. The parison is programmed to deliver 2.0–3.0 mm wall sections at the pump and sensor bosses; local thinning below 1.5 mm at the insert is a known cause of vibration-induced cracking. Terminal reservoirs are tested under OEM fluid compatibility protocols, typically involving exposure to 50/50 methanol-water washer fluid at 80 °C for 1,000 h, followed by pressure cycling between 0 MPa and 0.07 MPa. Published data for HD5502 in this exact automotive configuration is limited; the resin is not intended for pressurized coolant expansion tanks above 0.1 MPa or for continuous service above 90 °C. Odour and volatile organic content must be validated against the relevant OEM specification because cockpit and under-hood airflow can carry low-molecular-weight residuals into the cabin. HD5502 provides the ESCR required for washer fluid and coolant overflow but is not a substitute for high-molecular-weight HDPE grades specified for fuel tanks.