Agricultural liquid storage and sprayer tank bodies

Icorene 3560 G BUE 5720 is charged as a 35-mesh powder into cast aluminum moulds at a shot weight of 5.6 kg/m² for a 6 mm nominal wall, a loading that yields a fused wall density within 0.930–0.938 g/cm³ after the biaxial cycle. The BUE 5720 package contains a blue pigment and a hindered amine light stabilizer; therefore, additional ultraviolet masterbatch is limited to 0.5–1.0 wt% only when colour matching to a specified RAL value is required, while clean in-house regrind from the same grade is capped at 20 wt%. At 30 wt% regrind, ASTM D1693 method B F50 environmental stress-crack resistance decreases below 700 h in 10% Igepal at 50°C, which is below the five-year service requirement for chemical-carrying agricultural tanks. At ambient relative humidity above 60%, the powder is pre-dried at 70°C for 60 min before charging; moisture levels above 200 ppm cause steam pitting on the inner wall of the tank. The moulding line is a single-lobe shuttle rotational moulder with a 4.0:1 primary-to-secondary axis ratio and an oven set point of 290°C to 300°C; peak internal air temperature is held at 198°C to 208°C for 4 to 6 min. Part release occurs after forced-air cooling to 80°C and water mist cooling to 60°C to reduce flange warpage. Compliance references for the finished articles include ASTM D1998-21 for upright polyethylene storage tanks, EN 13341 for static thermoplastic tanks, and NSF/ANSI/CAN 61 for installations where drinking water is stored and grade-specific certification must be recorded; material conformity is verified under ISO 1872-1 and REACH 1907/2006 Annex XVII. Terminal products from this process include 150 L saddle tanks for crop sprayers, 1,000 L horizontal transfer tanks, and 5,000 L vertical storage cylinders.

Marine navigation buoy hulls moulded from this linear low-density polyethylene are dry-charged at 8.8 kg/m² of effective mould surface for an 8 mm outer-wall specification, with an additional 10% allowance for the top lifting ring and mooring bracket bosses. Because the hollow shell is post-filled with closed-cell polyurethane foam at 32–40 kg/m³, regrind above 10 wt% is excluded; lower molecular weight fractions from reprocessing reduce slow-crack resistance at the polyethylene–foam interface and promote stress cracking when the shell flexes under mooring shock loads. Mold release is maintained at 0.10–0.20 g/m² of PTFE-based external release; higher deposition rates leave residue that degrades adhesion of the antifouling topcoat on buoy daymarks. The rotational cycle uses a 4:1 rotation ratio, oven set point 300°C, and peak internal air temperature 200°C to 210°C; the shell is demoulded only after the inner-wall surface has cooled below 60°C, measured by infra-red pyrometry, to prevent foam exotherm softening. Compliance testing for the moulded buoy shell includes ISO 4892-3 for UV weathering, ASTM D256 Izod impact at -20°C, and colour retention under IALA Recommendation R1001 daymark classes. Terminal products are 1.2–2.4 m diameter channel buoys, 300–1,500 L mooring buoys, marker floats, and dock fender shells.

What limits ESCR performance in chemical secondary containment decks?

Secondary containment decks and spill pallets do not fail by tensile yield; they fail by slow crack growth when the stored liquid acts as a stress-cracking agent at the fusion line between separately sintered powder particles. For this grade, the controlling test is ASTM D1693 condition B F50 in 10% Igepal CO-630 at 50°C; virgin rotomoulded coupons typically exceed 1,000 h, while the same tooling with 25 wt% post-industrial regrind returns 600–800 h due to a broader lamellar thickness distribution across the powder fusion boundary. The loading formula for chemical bunds is therefore fixed at 100 phr as-supplied Icorene 3560 G BUE 5720 powder, 15 wt% maximum same-grade regrind, 2.0 wt% carbon black masterbatch only when black decks are specified, and 0.2 wt% maximum zinc stearate release. This formulation supports compliance with EPA 40 CFR 112.7 secondary containment capacity, 40 CFR 264.175 for hazardous waste containment where applicable, and the resin is evaluated under ASTM D1998-21 and REACH 1907/2006. The process uses double-wall rotational moulding with a 5 mm top deck and 4 mm internal rib walls, mould surface temperature 285°C to 295°C, peak internal air temperature 205°C to 215°C, and a cooling rate of 1.0–1.5 K/s through the crystallization plateau of 118°C to 105°C to minimise internal stress in the sump corners. Desktop demoulding is allowed at 70°C wall temperature; earlier removal at 85°C produces 3–5 mm of corner lift in deck sections. Terminal products include 2-drum and 4-drum spill pallets, modular containment berm sections, and 1,000 L containment sumps.

Rainwater harvesting vessels in the 2,000 L to 20,000 L range are rotomoulded from the same powder when non-potable outdoor storage is specified, eliminating the need for post-moulding liner systems. The charge weight is calculated as 4.7 kg/m² for a 5 mm wall, plus 8% for the inlet and outlet bosses. In-house regrind is capped at 25 wt%; post-consumer scrap is not introduced into the formulation because the lot-to-lot variability in moisture and pigment residue alters the powder bulk density from 0.30–0.35 g/cm³ to below 0.28 g/cm³, causing short shots at the upper dome. The moulding cycle uses an oven set point of 280°C to 290°C and a peak internal air temperature of 195°C to 205°C. Cooling is executed in two stages: ambient forced air to 85°C, followed by water mist to 65°C; the water mist stage is interrupted if the mould parting line sensor exceeds a 12°C difference between top and bottom shell halves, to limit ovality. Finished vessels are checked against EN 13341 for static thermoplastic tanks and ASTM D1998-21 for upright polyethylene tanks; raw material conformity under REACH 1907/2006 and RoHS 2011/65/EU is documented. Terminal products include 5,000 L above-ground cisterns, 10,000 L underground retention tanks, and fire suppression water reservoirs where non-potable supply is acceptable.

When cooling rate differentials distort thick-wall traffic barrier sections

Water-ballast highway barriers and crash cushions moulded from this resin have internal vertical baffles that create wall-thickness gradients from 6 mm in the outer skin to 14 mm at the baffle intersection. This geometry produces differential cooling rates of 0.8–1.6 K/s between the thick and thin regions during the crystallisation window, so the process holds forced-air cooling until the thickest section reaches 82°C before switching to water mist; otherwise the thinner upper wall freezes first and the thick lower rib continues to crystallise, generating 5–8 mm of inward bow across the face. The charge formula is 100 phr as-supplied powder, 25 wt% maximum same-grade regrind, and 0.5 wt% additional hindered amine stabilizer only for desert installations where total UV radiation exceeds 120 kLy/yr. The moulding machine is a carousel-type machine with a 4.5:1 rotation ratio, oven set point 305°C to 315°C, peak internal air temperature 210°C to 220°C, and heated mould surface temperature 270°C to 285°C. Production experience shows that mould-open temperature is the dominant parameter controlling flatness; releasing the part above 65°C leads to corner lift beyond the 3 mm/m flatness specification. Regulatory compliance for the finished road hardware is assessed under AASHTO MASH 2016 for work-zone crash cushions and water-ballast barriers, with material weatherability tested by ISO 4892-2. End products include water-filled lane separators, ballast-type Jersey barrier shells, crash attenuator shells, and sign base covers.

The blue UV-stabilized powder is used for hollow rotomoulded slide bedways, tunnel sections, and roofing shells where child-contact surfaces must retain ductile failure behaviour after extended UV-B exposure. The charge weight for a 5 mm slide bedway is 4.7 kg/m²; for structural connection collars with 8 mm walls, the charge weight is 7.5 kg/m², and the two zones are produced in the same moulding by locally adjusting mould surface temperature rather than changing the bulk powder formulation. Virgin powder is loaded at 100 phr; in-house regrind is capped at 20 wt%; if a colour shift is required, a 70% pigment-loaded PE masterbatch is added at 1.0 ± 0.2 wt%, with total additive loading not exceeding 2.0 wt% to avoid reducing low-temperature impact below the ductile-to-brittle transition. The process uses a shuttle rotational moulder with a 4:1 rotation ratio, oven set point 285°C to 295°C, peak internal air temperature 200°C to 210°C, and cooling by ambient air to 70°C before demoulding; mould surface roughness is specified at VDI 3400 grade 24–27 to balance gloss against release. Compliance for the finished playground articles includes EN 1176-1 for general safety, ASTM F1487 for public playground equipment, and the GS Mark PAH specification AfPS GS 2019:01 PAK for child-contact polymers. Terminal products produced from this grade include modular slide bedways, crawl tunnels, climbing wall panels, and shade roof shells.