Monolithic agricultural chemical storage tanks produced from Braskem LMDPE MR 435 UV are evaluated under ASTM D1693 Condition C after continuous exposure to 10% nonylphenol ethoxylate emulsifier and 30% aqueous urea at 50 °C. The resin’s nominal density of 0.940 g/cm³ and melt flow rate of 4.0 g/10 min at 190 °C/2.16 kg under ASTM D1238 define a linear medium-density polyethylene with slow-crack-growth resistance superior to lower-density MDPE powders but with the low-shear coalescence needed in biaxial rotation moulding. Outdoor storage tanks are further assessed for weather resistance under ISO 4892-2, where the UV-stabilised shell is expected to retain tensile elongation after 3,000 h of xenon-arc exposure; the specific lot value should be verified from the supplier’s certificate because published data for this exact stabiliser package is limited outside Braskem’s internal bulletins. Static tank structures above 450 L are commonly designed to EN 13575 for aerial storage of agricultural liquids, while smaller transport vessels may adopt UN 1H1 drum certification when suitable closures and wall thickness are matched.

The addition ratio for continuous-contact agrochemical service is set at 100 wt% virgin powder when the stored liquid is an emulsifiable concentrate or an acidifying fertiliser solution. Clean dry regrind from the same grade can be included up to 15 wt% only after a bend-strip ESCR trial on a welded wall section clears the supplier’s internal threshold; higher regrind fractions reduce the slow-crack resistance at the inner surface because prior thermal history shortens the high-molecular-weight fraction. A 1.5 wt% dose of a compatible carbon black masterbatch is used only for tanks intended for hot-air repair welding; otherwise no additional UV masterbatch is added, since the grade already carries the UV package. Rotational moulding is performed on carousel-type independent-arm machines with steel moulds rotating at 4:1 primary-to-secondary ratio. Oven setpoints of 270–300 °C and peak internal air temperatures of 200–210 °C produce fully fused walls of 6–12 mm for volumes from 500 L to 10,000 L. After oven dwell, forced-air cooling to 90 °C followed by a water mist to 40 °C minimises warpage at the lid flange. Terminal finished products include stationary sprayer nurse tanks, fertigation dosing tanks, portable ATV spray tanks, and cone-bottom chemical storage vessels.

What Limits Regrind Inclusion in UV-Stabilised Water Tank Shells?

Potable water tank shells rotationally moulded from Braskem LMDPE MR 435 UV are produced without post-mould interior linings, so the inner skin composition must satisfy the olefin polymer extraction limits in FDA 21 CFR 177.1520 and the relevant mechanical and chemical requirements of NSF/ANSI 61 Annex G. Because the UV stabiliser is already fused into the powder, no separate hindered amine light stabiliser masterbatch is dosed; this reduces the total number of low-molecular-weight species available to migrate into standing water during 60 °C stagnation testing. The grade’s nominal melt flow rate of 4.0 g/10 min under ASTM D1238 at 190 °C/2.16 kg is sufficiently low to prevent pinholes in 5–7 mm wall shells, provided the peak internal air temperature is held above 190 °C for at least 8–10 minutes. Where EU food-contact declarations are required, the final moulded tank must also satisfy EU Regulation 10/2011 migration testing; published data for this exact UV-stabilised grade under all three schemes is limited, so the rotomoulder must request a lot-specific certificate before first article approval.

The formulation addition ratio is 98–100 wt% virgin powder, with clean same-grade regrind capped at 20 wt%. Regrind above 20 wt% increases the melt viscosity and shifts the powder coalescence window upward, which can create porosity along the airside surface when moulding thin potable water tanks at PIAT below 200 °C. A 1 wt% blue or white organic pigment masterbatch is used for light transmission control; carbon black is excluded from potable water interiors to prevent plate-out on the mould surface and to avoid additive adsorption. Production uses a three-axis independent-arm rotomoulding machine with a primary rotation of 6 rpm and secondary rotation of 1.5 rpm, oven setpoint 260–285 °C, and a peak internal air temperature of 190–205 °C. Cooling is forced air to 90 °C, then mist to 45 °C, to retain flange flatness on potable water lids. Terminal finished goods include 100 L caravan fresh-water tanks, 500 L modular drinking-water storage tanks, and 2,000 L mobile water delivery tanks for rural distribution.

For monolayer buoyancy shells exposed to 5,000 h of accelerated weathering under ISO 4892-2 and intermittent salt fog under ISO 9227, Braskem LMDPE MR 435 UV is specified when the part must retain impact strength after prolonged outdoor storage without painting or post-mould fluorination. The density of 0.940 g/cm³ reduces shell mass relative to a 0.945–0.955 g/cm³ HDPE rotomoulding grade, while the melt flow rate of 4.0 g/10 min under ASTM D1238 allows complete coalescence in complex buoy shapes with internal bulkheads. Tensile elongation after 1,000 h salt spray is measured under ASTM D638 at 50 mm/min; values below 70% retention indicate that the pigment masterbatch or regrind source introduced a contaminant or that the oven dwell was insufficient. Published data for this specific configuration is limited, so first article moulding should include destructive sectioning of the foam-filled mould to confirm wall thickness at the mooring eye locations.

The foam-filled buoy recipe uses 80 wt% virgin MR 435 UV powder and 20 wt% closed-loop regrind screened through 35 mesh / 500 µm. The regrind particle size must remain below 500 µm because oversize particles reduce surface smoothness and can create voids at the foam interface. A 2–3 wt% loading of phthalocyanine blue or safety orange masterbatch is used for visibility, with the upper limit set at 3 wt% to avoid lowering low-temperature impact under ASTM D256 at -20 °C. Rotational moulding of the hollow shell is performed in a cast aluminium mould at an oven setpoint of 250–290 °C and a peak internal air temperature of 200–210 °C; slow air cooling to 80 °C is followed by demoulding and insertion of a 25 mm vent plug. After a surface flame treatment on the inner skin, a two-component polyurethane foam formulation is injected to achieve a core density of 30–50 kg/m³. Terminal products include cylindrical mooring buoys from 300 mm to 1,200 mm diameter, floating dock pontoons, and impact fender shells for coastal and inland water structures.

When Hollow Rotomoulded Play Structures Are Specified Without Post-Mould Painting

When outdoor play structures are specified without post-mould paint, the colour must be integrated into the polymer and the shell must meet structural and migration requirements simultaneously. Braskem LMDPE MR 435 UV is used for rotomoulded slide beds, tunnel sections, and climbing shells because the UV package reduces colour fade and surface chalking under ASTM G154 Cycle 1 for 2,000 h. In the European market, finished components are tested under EN 1176-1 for load-bearing geometry and under EN 71-3 for elemental migration from pigmented surfaces. In North America, structural drawings are checked against ASTM F1487 for play equipment; the material itself does not carry a playground safety certificate, so the moulder must control wall thickness at entrapment points and hand-grip locations.

The formulation addition ratio is 98 wt% virgin powder with 2 wt% high-tin oxide yellow or red masterbatch for high-visibility colour. Cosmetic-surface regrind is held to 10–15 wt% and screened through 35 mesh / 500 µm; higher regrind fractions produce surface specking on slide flutes and tunnel ribs. Components are moulded in fabricated steel or cast aluminium tools at oven setpoints of 260–290 °C. Complex ribbed sections require a peak internal air temperature of 205–210 °C to coalesce powder in deep recesses, while flat slide beds are moulded at 195–205 °C to avoid internal voiding. Cooling is air-only to 70 °C, then water mist from 70 °C to 40 °C to reduce warpage in unsupported spans. Terminal finished goods include straight slide beds of 1.5–2.5 m, curved tunnel sections, climbing rock shells, and perforated play panels.

Bulk Solids Handling Liners and Abrasion-Exposed Discharge Hoppers

Dry granular material handling applications use the same rotomoulding grade to replace mild steel hoppers in fertiliser, salt, and aggregate transfer stations. In silo discharge cones handling ammonium nitrate granules or potash, the material is tested for surface degradation in a rotating drum containing 20 kg of crystalline material; published data for this specific configuration is limited, so plant trials are used to compare mass loss against standard rotomoulding HDPE. The 0.940 g/cm³ density and 4.0 g/10 min melt flow rate of MR 435 UV allow 8–15 mm thick walls to be moulded without sagging in vertical tooling, while the UV package prevents embrittlement of outdoor hoppers. Structural integrity of the moulded cone is verified under ASTM D638 at 50 mm/min for yield stress and ASTM D256 at -20 °C for impact on conditioned wall sections cut perpendicular to the weld line.

The formulation addition ratio is 100 wt% virgin powder for hoppers handling hygroscopic fertiliser salts, where the inner surface cannot accept porosity from regrind. For inert quartz sand or rock salt, 20 wt% clean regrind is permissible if the pulverised powder is screened through 35 mesh / 500 µm and the melt flow rate after blending remains within ±10% of the virgin value under ISO 1133. Pigment loading is limited to 1 wt% because higher masterbatch doses reduce low-temperature Izod impact and can generate stress concentration at the cone-to-flange transition. Rotational moulding is performed at 280–300 °C oven setpoint with a peak internal air temperature of 205–215 °C for 12 mm walls. The demoulded cone is cooled in air to 80 °C before a 2 mm polyurethane wear coat is spray-applied at the discharge throat. Terminal finished goods include 200–1,000 L tote liners, 45° silo discharge cones, dust collection hoppers, and salt-sand spreader bins.