LyondellBasell Icorene 3550-8423G Yellow 35 Mesh GT Polyethylene, Linear Low Density is a pre-colored, ground linear low-density polyethylene powder supplied primarily for dry-feed rotational molding and related powder-consuming processes. The “35 Mesh GT” designation identifies a ground thermoplastic form with a nominal top particle size controlled at a 35-mesh sieve opening of 500 µm under ASTM E11. The yellow pigmentation is dispersed within the powder rather than supplied as a separate colorant concentrate. The full designation contains the base resin identifier 3550 and the colored ground suffix 8423G. Published data for this exact yellow grind configuration is limited; however, the base resin class is typically characterized by density under ISO 1183-1:2019 and melt flow rate under ISO 1133-1:2022 at 190 °C/2.16 kg. Commercial 35-mesh LLDPE rotational-molding powders in this family commonly fall within a melt flow rate range of 3.0–6.0 g/10 min and a density range of 0.932–0.939 g/cm³. The Icorene 3550 base grade is commonly associated with a nominal density near 0.935 g/cm³ and a nominal melt flow rate near 5.0 g/10 min; the yellow 8423G formulation may shift values within the production specification window. End-use specifications should be confirmed against lot-specific certificates of analysis rather than representative class data.

The physical form of the powder has direct implications for dry-feed equipment. Positive-displacement powder pumps, vibratory tray feeders, and rotary airlock valves are used in rotational molding, with selection dependent on bulk density, fines content, and electrostatic behavior. A 35-mesh top-size powder with a broad particle-size distribution can compact in hoppers and create “rathole” flow channels. Production lines often install pneumatic vibrators or fluidizing pads on hopper cones to maintain flow. Ground polyethylene powders can accumulate static charge during pneumatic conveying; grounding straps with resistance below 10⁶ ohms are recommended, and maintaining relative humidity above 40% reduces charge buildup. The product should not be exposed to open flame, uncontrolled dust suspension, or temperatures above 40 °C during prolonged storage.

What operational boundaries arise from a 35-mesh ground LLDPE in dry-feed rotational molding?

The ground powder form is more sensitive to hopper bridging and electrostatic charging than pelletized feedstock. Production-scale dry-feed systems can experience inconsistent feed when the powder contains excessive fines below 75 µm or when storage temperature falls below 10 °C. Under such conditions, surface moisture can condense on cold powder and generate steam pinholes during the sintering stage. Process engineers typically maintain powder conveying lines at a dew point below 10 °C and limit free-fall heights above 2 m to reduce particle segregation. The 35-mesh top size provides a balance between bulk density and dust generation, but it is generally too coarse for thin-wall sections below approximately 2 mm because the largest particles may not fully consolidate before the inner wall solidifies. The powder should not be dry blended with high-density polyethylene or polypropylene powders unless a full melt-phase compatibility study has been performed; differences in crystallization temperature and melt viscosity can produce interlayer delamination, weld-line splitting, or inconsistent color distribution.

Particle-size distribution and bulk density under ASTM D1895 define dry-feed behavior.

Because published lot-specific values for Icorene 3550-8423G Yellow 35 Mesh GT are not uniformly available, the following ranges are representative of commercial 35-mesh LLDPE rotational-molding powders. They are provided as a screening reference and do not replace the producer’s certificate of analysis.

The dry-flow behavior of the powder depends on particle shape, bulk density, and fines content. Ground powder with a broad particle-size distribution can compact in storage silos and produce rathole flow. Sieve analysis under ASTM D1921-18 should be performed on each incoming lot, particularly when the material is blended with regrind. Electrostatic charging can be reduced by maintaining relative humidity between 40% and 60% in the powder handling area, although dry conditions may be required for moisture-sensitive mold surfaces. Any significant shift in fine fraction below 75 µm should trigger a feed calibration check because fines can alter bulk density and packing in volumetric feeders.

On carousel and shuttle rotational molding machines, LLDPE powders of this class are processed with oven air temperatures commonly between 260 °C and 315 °C. Peak internal air temperature is a more reliable control parameter than oven temperature; many commercial processors hold peak internal air temperature at approximately 190–205 °C for full particle coalescence. Tooling mass, wall thickness, and the infrared absorption behavior of the yellow pigment can alter oven residence time by several minutes. A pre-colored yellow powder may read differently on an infrared pyrometer than natural powder even when the internal air thermocouple records the same temperature; emissivity correction and shielded thermocouple verification are therefore required. Cooling after demolding is also critical. Rapid water quench can reduce cycle time but may increase warpage in flat or asymmetric parts; many production lines use forced-air cooling to approximately 90 °C before water mist or secondary cooling. The linear low-density structure provides lower flexural modulus and higher environmental stress-crack resistance than high-density rotomolding grades, but exact mechanical values must be determined on rotomolded test plaques using ISO 527-2:2012 for tensile properties and ISO 179-1:2010 for Charpy impact.

The sintering behavior of linear low-density polyethylene is governed by the melting peak and the zero-shear viscosity. A powder with nominal melt flow rate near 5.0 g/10 min typically has sufficient melt strength to avoid sagging on vertical mold walls, but not so high that air bubbles remain trapped. Vacuum venting can reduce pinholing when part geometry creates enclosed volumes; mold vent holes of 0.5–1.5 mm are common in production tooling. However, vent hole size must be balanced against the risk of powder loss and flash formation. If the yellow pigment shifts the crystallization temperature, cooling time may require adjustment to avoid warpage.

Mechanical property evaluation for rotomolding powders is highly sensitive to specimen preparation. Rotomolded test plaques should be produced on the same machine and with the same peak internal air temperature profile as production parts. Compression-molded specimens may not capture the residual stress state or crystalline morphology of rotomolded parts. Tensile properties are commonly measured under ISO 527-2:2012 at 5 mm/min or 50 mm/min depending on the specification; the selected rate should be reported with the data. Impact strength is evaluated under ISO 179-1:2010 Charpy or ISO 180:2019 Izod using notched specimens machined from rotomolded plaques. Because rotomolded parts often show uneven wall thickness, specimen thickness variation should be held below 10% to maintain comparability.

Regulatory boundary conditions, pigment chemistry, and food-contact status

The polyolefin backbone of Icorene 3550-8423G may be covered by FDA 21 CFR 177.1520 for olefin polymers and EU Regulation 10/2011 when the base resin and additives meet the relevant migration and extraction limits. However, pre-colored grades are not automatically compliant for food-contact or toy end uses. The yellow pigment package must be evaluated separately under 21 CFR 178.3297 for colorants in polymers and, for toys, under EU Directive 2009/48/EC. Heavy-metal restrictions from RoHS 2011/65/EU may apply to electrical and electronic applications; cadmium-based yellow pigments are not acceptable under many global specifications. Potable water contact may require additional approvals under NSF/ANSI/CAN 61 or local equivalent. Users should request a material-specific compliance statement from LyondellBasell before specifying this pre-colored grade in regulated applications. Storage should avoid direct sunlight, oxidizers, and temperatures above 40 °C, because thermal aging can shift the yellow color and reduce the activity of the antioxidant package.

Application areas for a yellow 35-mesh LLDPE powder include high-visibility covers, material-handling bins, traffic-control devices, agricultural components, chemical-resistant tanks, outdoor recreational parts, and industrial liners where color is used for safety marking or product identification. The pre-colored form eliminates dry color mixing at the rotational molder, but color consistency across production campaigns should be verified using a spectrophotometer with CIE L*a*b* coordinates under D65/10°. Because the material is a linear low-density polyethylene, parts can be expected to exhibit greater puncture resistance than LDPE parts of equivalent thickness, but lower stiffness than HDPE parts. No specific end-use performance claim should be based solely on class data; application testing on rotomolded specimens is required.

Relative to a 60-mesh or 100-mesh LLDPE rotomolding powder, the 35-mesh grade has a coarser particle-size distribution. That coarser distribution can increase bulk density and reduce dust, but it may be less suitable for thin-wall sections below approximately 2 mm. Relative to a 35-mesh HDPE rotomolding powder, the linear low-density class exhibits lower flexural modulus and higher environmental stress-crack resistance. Typical tensile yield values for commercial LLDPE rotomolding grades fall between 13 MPa and 18 MPa, while many HDPE rotomolding grades exceed 20 MPa. Relative to LDPE rotomolding powder, LLDPE offers higher tensile strength and improved puncture resistance because the short-chain branching distributes stress differently in the semi-crystalline structure. Compared with pelletized extrusion grades, the ground thermoplastic form eliminates the need for post-pellet grinding and can be fed directly into rotational molding equipment, but the powder is more susceptible to moisture adsorption on particle surfaces, electrostatic separation, and oxidation because of the increased surface area.

When a pre-colored 35-mesh grade replaces natural LLDPE in multi-layer tooling

Switching from natural or black LLDPE powder to a yellow 35-mesh grade on existing tooling requires more than a color change. The pre-colored powder may absorb radiant heat differently, shifting the required oven dwell time and peak internal air temperature. Process engineers should record peak internal air temperature curves with a shielded thermocouple and compare them to the prior natural-powder baseline under identical oven settings. In multi-layer rotational molding, the yellow outer layer and a natural or foamed inner layer may require different powder charge weights because the colored layer can begin sintering earlier or later depending on pigment chemistry. Dry blending the yellow powder with regrind should be performed in tumbling or ribbon blenders with sieve analysis before and after blending; adding regrind above 20% without particle-size control can create color streaking and wall-thickness variation. Mold vents should be cleaned between color changes because residual yellow pigment can accumulate in vent channels and later contaminate natural or light-colored layers. If the material is to be foamed with azodicarbonamide or other chemical blowing agents, the blowing-agent decomposition temperature must be matched to the yellow grade’s thermal profile. Exact processing conditions should be established using design-of-experiment trials on production-scale machinery rather than laboratory powder tests alone.

Moisture control at the powder surface is a recurring process boundary. If condensation is visible or warehouse relative humidity exceeds 60%, drying at 60 °C for 1–2 h in a dehumidifying tray dryer or hopper is common before molding. Ground polyethylene powder forms combustible dust; conveying equipment should be grounded, and dust collectors should be sized for the fines fraction below 75 µm. The material should not be exposed to aromatic solvents, chlorinated hydrocarbons, or strong oxidizing acids at elevated temperatures because these media can initiate stress cracking or surface oxidation. Continuous load-bearing service for rotomolded LLDPE parts is typically limited to approximately 60 °C, with intermittent exposure depending on the antioxidant package and part design. The yellow 35-mesh grade may exhibit batch-to-batch color drift within producer tolerances; incoming color and particle-size verification are recommended for critical customer applications. Decisions based on representative class data should be limited to screening; only lot-specific certificates of analysis and production-scale tooling trials establish final suitability.