| HS Code | 915550 |
| Product | SK LLDPE RG500U |
| Density | 0.935 g/cm³ |
| Melt Flow Index | 4.0 g/10min (190°C/2.16kg) |
| Tensile Strength At Yield | 15 MPa |
| Elongation At Break | 800% |
| Flexural Modulus | 700 MPa |
| Impact Strength Izod | 600 J/m |
| Environmental Stress Crack Resistance | >1000 hours |
| Vicat Softening Point | 108 °C |
| Melting Point | 124 °C |
| Brittleness Temperature | <-70 °C |
As an accredited SK LLDPE RG500U factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | SK LLDPE RG500U is supplied in 25 kg moisture-proof bags, palletized and wrapped for safe transport and storage. |
| Container Loading (20′ FCL) | Container Loading (20′ FCL): SK LLDPE RG500U is packed and shipped in a 20-foot full container load, ensuring secure, efficient transport. |
| Shipping | SK LLDPE RG500U is a non-hazardous linear low-density polyethylene resin, shipped as free-flowing pellets. It is typically transported in polyethylene-lined jumbo bags, bulk bags, or railcars/trucks. Keep dry and protected from moisture, direct heat, and contamination during transit. No IMDG/DOT hazardous classification required. |
| Storage | Store SK LLDPE RG500U in a cool, dry, well-ventilated area away from direct sunlight, heat, and ignition sources. Keep containers tightly sealed to prevent moisture contamination and dust accumulation. Avoid exposure to strong oxidizers. Maintain good housekeeping to reduce slipping hazards from spilled pellets. No special temperature control is required under normal conditions. |
| Shelf Life | Store in a cool, dry place away from direct sunlight. Shelf life is indefinite if kept in original sealed packaging. |
| Check item | Reference standard | Condition or clause |
|---|---|---|
| Potable water compliance | 21 CFR 177.1520(c) | Olefin polymer clearances for food-contact use |
| Upright tank structural minimum wall | ASTM D1998-21 | Design stress and bottom-sidewall joint coverage |
| Melt mass-flow index | ISO 1133-1:2022 | 190 °C / 2.16 kg |
| Density | ISO 1183-1:2019 | Method A, gradient column |
| Tensile yield | ISO 527-1:2019 / ISO 527-2:2012 | Type 5A dumbbell, 50 mm/min |
| Environmental stress crack resistance | ASTM D1693-21 | Condition A, 100% Igepal CO-630, 50 °C |
RG500U is used for rotationally moulded agricultural sprayer tanks and induction hoppers that sit on tractor-mounted and self-propelled spray rigs. The resin’s non-polar semicrystalline matrix resists hydrolysis by aqueous pesticide formulations, dilute phosphoric acid, urea ammonium nitrate solutions, and most micronutrient chelates. Resistance is not universal: concentrated aromatic solvents, cyclohexanone, and certain chlorinated solvents cause measurable swelling and must be screened before production. The standard screening method is ASTM D543-21, in which coupons of 5 mm wall thickness are immersed for 7 days at 40 °C and mass change is recorded. A mass change above 1.0% after drying does not automatically disqualify the tank, but it indicates that fitting inserts and welded joints may separate under cyclic pressurisation. Tanks for emulsifiable concentrate dosing are therefore rotationally moulded with a wall thickness of 6 mm to 8 mm and are fitted with fluoropolymer seal rings rather than EPDM at chemical outlet points. In service, the most common failure is environmental stress cracking at the base of rotationally moulded inserts; this is accelerated by amine-neutralised surfactants and high-ionic-strength formulations. Production controls include preheating metallic inserts to 120 °C to 140 °C before the powder charge, maintaining a minimum insert boss diameter-to-wall-thickness ratio of 3:1, and post-mould annealing for 30 min at 80 °C to reduce residual stress. The powder should be dried at 60 °C for 2 h when ambient relative humidity exceeds 70%, because surface moisture creates pinholes in areas of slow powder flow. Published RG500U-specific long-term chemical resistance data for complex co-formulated products is limited; for tanks intended to store oxidising agents above 5% active chlorine, post-mould fluorination or an alternative resin system should be evaluated.
Rotational moulding of mobile refuelling tanks and generator day tanks in RG500U requires a lower peak internal air temperature than potable water tooling, typically 185 °C to 195 °C, to minimise oxidative degradation of the polymer chain during long oven dwell. The wall is built to 8 mm to 12 mm at the bottom shell, and the oven cycle is between 28 min and 40 min depending on tool mass. Slow crack growth is the governing failure mode at the brass or stainless steel inserts used for fuel fittings, outlet flanges, and level sensors. The insert knurling depth should not exceed 0.5 mm, and the mould cycle is programmed to rotate the boss through the powder pool for 15 s to 20 s to ensure full melt penetration around the knurled surface. After demoulding, insert zones are stress-relieved by holding the tank at 60 °C for 2 h, which reduces frozen-in orientation. Because polyethylene is intrinsically non-conductive, surface resistivity is above 10¹⁴ Ω; fuel tank assemblies must be fitted with external grounding straps and anti-static filler necks. Permeation compliance for permanently installed small craft fuel tanks is validated under EN ISO 21487:2012 and similar regional codes; the tank wall must show no softening or permeability after 1,000 h exposure to diesel fuel at 40 °C. Published RG500U-specific data for biodiesel blends above B7 is limited, so storage tests with representative fuels should be conducted when the application includes fatty acid methyl esters.
Outdoor cabinets, antenna radomes, and telecommunication enclosures are rotationally moulded with RG500U where a one-piece shell eliminates the seam leaks observed in fabricated HDPE sheet enclosures. The presence of a hindered amine light stabiliser package and a UV absorber allows the grade to retain surface integrity in non-black colours for moderate exterior exposure, though black and dark grey pigmentation provide the longest hot-humid ageing life. The minimum wall thickness for a floor-standing enclosure of 1.8 m height is 5 mm at the side walls and 7 mm at the roof to prevent wind-load deflection. Because the linear coefficient of thermal expansion for LLDPE is approximately 1.7 × 10⁻⁴ K⁻¹, a 1.0 m vertical panel subjected to a 40 K temperature rise expands by 6.8 mm, which must be absorbed by slotted mounting holes and resilient gasket interfaces. The powder is dry-blended with carbon black masterbatch up to 2.0 wt%; higher loadings reduce melt flow and create pinholes at the inner wall because the pigment particles nucleate crystallisation unevenly. The mould is run with a peak internal air temperature of 195 °C and a total oven cycle of 22 min to 30 min for a 5 mm wall. Warpage is controlled by using symmetrical cooling air on the roof and base; asymmetric water mist cooling of the door opening can produce a permanent twist in the frame. Weathering acceptance is specified under ISO 4892-3:2021 for condensation-based UV exposure, with no surface cracking after 2,000 h and a change in tensile elongation at break of less than 25% when tested per ISO 527-1:2019. Published RG500U-specific colour-hold data for outdoor exposure beyond 3 years is limited and should be generated for the intended pigment blend.
Dry granular media transfer hoppers are lined with rotationally moulded RG500U when mild abrasion resistance and freedom from welded seams are required. The liner is moulded as a single-wall shell with a 10 mm base and 6 mm side wall by applying an insulating pad to the outside of the mould base during the oven cycle; this raises local wall thickness without extending the overall cycle beyond 40 min. After demoulding, the conical outlet is machined flat and a slide gate flange is rotationally moulded in place from the same powder, eliminating a welded joint. The liner is then attached to the steel support frame with flexible mounting bolts and rubber washers to accommodate differential thermal movement between the LLDPE shell and the steel structure. In continuous flow of granular urea or ammonium sulphate at 25 °C, the surface develops a polished wear track, but sharp-edged angular aggregates cause local gouging. If the hopper handles quartz-containing mineral sand, a replaceable polyurethane sheet of 10 mm thickness is installed over the impact zone because the LLDPE wall loses thickness at a rate that is not acceptable for long campaigns. The abrasion resistance boundary is therefore defined by the media angularity, not by the polymer’s Shore D hardness. Moisture absorption of the liner is below 0.01% after 24 h immersion in water, which avoids hydrate crust formation on the outlet. The liner must be electrically grounded if the process stream contains combustible organic dust; surface resistivity above 10¹⁴ Ω requires an external copper bond wire embedded in the flange.In foam-filled marine fenders, aquaculture floats, and buoyancy modules, RG500U shells are rotationally moulded with a wall thickness of 4 mm to 6 mm, and the foam is injected after the shell has cooled to room temperature. Because LLDPE has a low surface energy, adhesion between the moulded shell and a closed-cell polyurethane core is negligible; the design must rely on internal ribs, undercuts, or annular grooves rather than chemical bonding. The foam formulation is selected with an exotherm below 120 °C to avoid softening and sagging of the LLDPE wall during the rise. The moulding itself is carried out with a peak internal air temperature of 190 °C to 200 °C; after demoulding, any residual surface release agent is removed with a neutral detergent wash before the foam-in-place step. The shell is then pressure-tested at 30 kPa for pinholes and fitted with a vent plug to release gas generated by foam curing. In service, the main failure mode is fatigue cracking at the vent plug when the module is repeatedly compressed under wave load; the plug mounting area is therefore thickened to 8 mm and provided with a rounded root radius of 3 mm. Impact resistance at −20 °C is verified by a falling dart test on a 2 kg striker according to ISO 6603-1:2021. Published RG500U-specific cyclic fatigue data for water-exposed shell-to-foam interfaces is limited; long-term qualification for submerged load-bearing modules should include accelerated salt-spray and cyclic compression tests on production-scale samples.
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SK LLDPE RG500U is a pelletized linear low-density polyethylene resin supplied by SK Geo Centric for rotational molding applications. The grade is defined by a nominal density of 0.935 g/cm³ when measured according to ASTM D1505 and a melt flow rate of 5.0 g/10 min at 190 °C under a 2.16 kg piston load per ASTM D1238. The density position places the material at the upper end of the linear low-density class and the lower end of the medium-density polyethylene range, which directly affects stiffness, chemical resistance, and low-temperature ductility in rotomolded parts. The resin is an ethylene/α-olefin copolymer in which short-chain branching distribution controls the crystalline fraction, slow crack growth resistance, and the final melt coalescence behavior.
In rotational molding, RG500U is ordinarily ground to a powder with a top size near 35 mesh (500 µm) to obtain suitable dry flow, bulk density, and particle fusion during biaxial mold rotation. The nominal melt flow rate of 5.0 g/10 min reduces melt viscosity enough to promote bubble release and particle sintering, but it does not eliminate the need for precise peak internal air temperature control. The grade is specified for applications in which a balance between moderate stiffness, good environmental stress crack resistance, and practical cycle time is required, such as chemical storage tanks, agricultural water tanks, and general industrial containers. Manufacturer-published typical values should be confirmed against the current certificate of analysis because lot-to-lot variation in melt flow, density, and additive loading is controlled within the agreed specification window rather than held at a single point value.
For linear low-density polyethylene with a density of 0.935 g/cm³ and melt flow rate of 5.0 g/10 min, the practical processing window is defined by oven residence time, oven temperature, mold rotation ratio, and internal air temperature. In carousel and shuttle rotational molding machines, oven temperatures for this class are commonly set between 280 °C and 310 °C. The target internal air temperature is generally in the range of 190 °C to 210 °C, depending on wall thickness and mold thermal mass. Peak internal air temperature is a more reliable process indicator than oven setpoint alone because it records the actual thermal history inside the mold cavity.
During heating, the ground resin first densifies and sinters, then coalesces into a continuous melt layer. Bubble removal occurs when the melt layer reaches sufficiently low viscosity and the mold remains at temperature long enough for gas diffusion and buoyancy-driven bubble migration. If the internal air temperature is terminated below approximately 190 °C, residual bubbles and incomplete sintering can appear at weld lines or inside thick bosses. If the oven residence time is excessive, oxidative degradation produces surface yellowing, reduced impact strength, and the formation of carbonyl species detectable by infrared spectroscopy. On production-scale carousel machines with swing diameters up to 2.5 m, the major bottlenecks are typically uneven oven heat flux across large side walls, overcure at thin floating-cast edges, and undercure at thick insert regions.
Mold rotation ratio for this density class is commonly maintained between 3.5:1 and 4.5:1, with primary-axis speeds near 4–6 rpm and secondary-axis speeds adjusted to produce uniform wall coverage. Cooling is usually carried out with forced air followed by water mist or controlled water spray. The cooling curve affects shrinkage, warpage, and crystallinity. Polyethylene of this type is non-hygroscopic, so pre-drying is not required for normal warehouse storage, but surface condensation should be avoided when moving powder from cold storage into a warm processing hall. Clean in-house regrind may be incorporated only after validation of low-temperature impact and ESCR on the finished part.
Published typical values for the grade include a tensile yield stress near 17 MPa and a tensile strength at break near 21 MPa when tested on compression-molded specimens according to ASTM D638. Elongation at break is reported above 800%, indicating a high level of chain extension before failure in slow tensile loading. Flexural modulus is approximately 700 MPa under ASTM D790, which supplies moderate stiffness without the brittle fracture risk associated with higher-density rotomolding grades. Shore D hardness is near 58 under ASTM D2240, and Vicat softening temperature is approximately 118 °C under ASTM D1525 with a 10 N load.
Environmental stress crack resistance is a critical property for rotomolded tanks and containers that hold surfactants, agricultural chemicals, or polar liquids. The grade is reported with an F50 value greater than 1000 h under ASTM D1693 Condition B when tested in a 10% Igepal CO-630 solution. Low-temperature brittleness test results under ASTM D746 are commonly below -70 °C. These values are typical and are not upper or lower specification limits. Because rotational molding produces a different morphology than compression molding, the values should be used as material-selection data rather than as a direct prediction of molded-part performance.
| Property / test method | SK LLDPE RG500U | Lower-density butene LLDPE rotomolding grade | HDPE rotomolding grade |
|---|---|---|---|
| Density, ASTM D1505 | 0.935 g/cm³ | 0.925 g/cm³ | 0.950 g/cm³ |
| Melt flow rate, ASTM D1238 | 5.0 g/10 min | 3.5 g/10 min | 6.0 g/10 min |
| Flexural modulus, ASTM D790 | 700 MPa | 480 MPa | 1000 MPa |
| Tensile yield stress, ASTM D638 | 17 MPa | 13 MPa | 24 MPa |
| Elongation at break, ASTM D638 | 800% | 900% | 600% |
| ESCR F50, ASTM D1693 Condition B | >1000 h | >1000 h | 40–100 h |
The comparative values for the lower-density butene LLDPE and HDPE rotational molding grades are representative of publicly reported class data and are not manufacturer specifications for those materials. Compared with the lower-density butene copolymer, RG500U provides higher flexural modulus and tensile yield stress, which permits thinner nominal walls in moderate-section parts where deflection controls the design. Compared with the HDPE rotomolding grade, RG500U sacrifices approximately 300 MPa of flexural modulus but gains a substantially longer ESCR F50. That difference is significant when the end-use environment includes wetting agents, mineral oils, or slow-loading structural stresses.
In rotomolded parts with nominal wall thickness above 6 mm, the inside and outside surfaces cool at different rates, establishing a non-uniform crystallinity gradient through the wall. The skin that contacts the mold surface solidifies and contracts first, while the inner surface remains molten and constrained. This gradient becomes the dominant cause of warpage, dimensional instability, and residual stress in large flat panels, tank lids, and double-wall structures. With RG500U, forced-air cooling rates of 2–5 °C/min in the crystallization range are often used to reduce warpage, but the exact cooling profile must be matched to mold geometry, ribbing, and localized part restraint.
Slow cooling allows more time for stress relaxation and reduces residual stress, but it also increases cycle time and can lower tensile yield strength through isothermal crystal thickening. Water-mist cooling shortens the cycle but can generate differential shrinkage around inserts, kiss-off features, and mold parting lines. The practical limit for a given tool is reached when the part develops measurable sink marks over thick regions or exceeds the dimensional tolerance specified on the drawing. For this material, published data for warpage after specific water-mist cooling histories is limited; therefore, tool trials on production-scale machines remain necessary to qualify a cooling protocol.
Comparative assessment against other rotational molding polyethylenes indicates that RG500U is selected when end-use service conditions require a combination of moderate stiffness and resistance to environmental stress cracking rather than maximum rigidity or maximum low-temperature impact. The higher melt flow rate, relative to lower-density rotomolding grades with melt flow rates near 3.0 g/10 min, improves mold-filling detail in complex geometries but can also increase air-bubble entrapment if the peak internal air temperature is not maintained long enough. Compared with hexene-based LLDPE rotomolding resins, the grade may show lower instrumented dart impact under identical wall thickness; therefore, low-temperature impact-critical parts should be evaluated by a falling weight test such as ASTM D5628 or the ARM impact method rather than by tensile elongation alone.
Regulatory documentation for the grade should be obtained from the supplier because food-contact status depends on formulation, colorants, and the conditions of use. Polyethylene olefin polymers may be permitted under 21 CFR §177.1520 when the final article meets the migration and end-use limitations stated in the regulation. Heavy metals are not intentionally added, and the material is normally within the scope of the European Union REACH registration dossier for polyethylene. For articles sold in the European Union, documentation against RoHS 2011/65/EU recast should be confirmed for the specific lot and packaging configuration. Outdoor service requires an adequately compounded UV-stabilization package, because the natural resin has limited resistance to extended ultraviolet exposure. Published data for the UV-stabilized variant after 5,000 h of xenon-arc weathering is limited; outdoor parts therefore require separate weathering validation under the relevant application standard.
