LyondellBasell Icorene 3550-1732G Target WHT is a linear low density polyethylene powder manufactured for rotational molding. The product model couples the Icorene 3550 base resin with a 1732G target white pigmentation package. It is supplied as a dry-flow powder rather than as a pelletized injection molding or film extrusion feedstock. The material is intended for sintering against a heated mold surface under biaxial rotation in shuttle, clamshell, and carousel equipment. Typical applications include chemical storage tanks, agricultural hoppers, playground structures, kayak hulls, and equipment enclosures. The base resin is specified by a density of 0.935 g/cm³ under ISO 1183-1 and by a melt mass-flow rate of 5.5 g/10 min under ISO 1133-1 at 190 °C and 2.16 kg. The 1732G target white pigment package modifies melt rheology, heat transfer, and mechanical property retention relative to natural Icorene 3550. Batch certificates and pigmented-grade trial data are therefore required before transferring an existing rotational molding cycle. Selection between this product, natural Icorene 3550, higher-flow LLDPE rotomolding powders, and HDPE rotomolding grades is normally based on environmental stress crack resistance under ASTM D1693-B, low-temperature impact behavior under ISO 6603-2, stiffness, and color stability.

What nominal properties define the base Icorene 3550 resin?

Typical properties in the following table are derived from published base-resin data and laboratory compression-molded plaques. The values are not specification limits and do not automatically transfer to the 1732G Target WHT configuration. Grade-specific release limits must be read from the certificate of analysis.

The 0.935 g/cm³ density places the grade below HDPE rotomolding resins and above LLDPE film grades. The 5.5 g/10 min melt flow rate balances long-flow mold filling against melt strength. Compared with a high-flow LLDPE rotomolding powder having a melt flow rate near 8 g/10 min, Icorene 3550 typically retains a higher molecular weight fraction, which correlates with environmental stress crack resistance above 1000 h under ASTM D1693-B and with a lower tendency for thin-wall melt fracture. Rotational molding is a low-shear process; melt flow index is a relative ranking rather than a direct process model. A grade with the same melt flow rate but a broader molecular weight distribution can sinter differently. Powder densification trials on laboratory plaques should therefore be supplemented by rotomolded part tear-down on production-representative tooling.

Powder Flow, Particle Size Distribution, and Dry-Flow Consistency

Dry-flow consistency governs wall thickness uniformity before coalescence. On shuttle machines operating at biaxial rotation ratios of 4:1 and arm speeds from 4 rpm to 8 rpm, the powder must distribute into complex mold recesses without bridging. Rotomolding powders are commonly controlled across the 150–500 µm size range, although the certificate of analysis for this specific 1732G white configuration may define tighter internal bands. Excess fines below 150 µm can promote surface porosity because fine particles may sinter prematurely at the hot mold surface; excessively coarse particles above 500 µm can produce pinholes at narrow ribs and sharp returns. Bulk density and pourability are measured by ISO 6186 or an equivalent internal funnel method. For a free-flowing rotomolding powder, bulk density typically lies between 0.35 g/cm³ and 0.45 g/cm³. A significant shift in dry-flow time or bulk density between lots should trigger re-validation of the oven cycle and cooling schedule, because particle geometry directly affects the powder-to-melt transition.

Sintering densification follows melt flow under capillary pressure. The rate of bubble collapse is proportional to surface tension and inversely proportional to particle radius and melt viscosity. A larger particle size fraction requires longer time at peak internal air temperature to eliminate voids. Therefore, shifts in particle size distribution above 500 µm have a disproportionate effect on pinhole frequency. A thermocouple or infrared probe inside the mold cavity is the primary control signal. For LLDPE rotational molding, the peak internal air temperature is typically held between 190 °C and 210 °C. A hold above 180 °C for 4–6 min is commonly required to collapse bubbles and densify the melt. When the peak internal air temperature exceeds 220 °C, antioxidant consumption accelerates and the 1732G white surface can shift toward yellowing before visual inspection detects it. Cooling must permit crystallization before demolding; forced-air cooling followed by water mist after the part cools below 80 °C is used to reduce cycle time. Abrupt quenching below the crystallization point increases residual stress and lowers impact toughness in thick sections.

Wall thickness variation is influenced by particle size distribution, mold release, and arm speed. For complex asymmetric parts, the rotational speed ratio may be adjusted from 2:1 to 5:1 rather than fixed at 4:1. An arm speed above 10 rpm can generate centrifugal force high enough to pack powder in outer sections; below 2 rpm can cause sliding and poor distribution. These boundaries are determined by mold diameter and must be validated with the specific powder dry-flow. Mold surface preparation also influences nucleation and release. Aluminum molds with textured cavity surfaces are used to control gloss and hide flow lines. A semi-permanent release coating rated for 280–320 °C is applied to maintain clean ejection. Surface treatment for bonding or coating requires oxidation to a wetting tension of 40–50 mN/m, measured by ISO 8296; without such treatment, the nonpolar LLDPE surface resists adhesives and paints.

When the 1732G Target White Pigmentation Alters Oven Cycle Settings

Processors cannot directly copy oven dwell, oven temperature, and cooling curves from natural Icorene 3550 when the 1732G white package is introduced. White pigmentation based on titanium dioxide alters opacity and radiative heat transfer; depending on mold geometry and oven emitter type, the pigmented powder may reach peak internal air temperature earlier, later, or at a different interior gradient than natural powder. On a three-station carousel machine with gas-fired oven setpoints in the 260–316 °C range, changes in oven dwell should be made in increments no larger than 5–10 % while maintaining the same peak internal air temperature target. Early degradation of white-pigmented LLDPE can be subtler than in natural material, so molders should measure melt flow retention on scrap samples. A shift in melt flow rate of more than 10 % relative to the powder certificate of analysis after molding suggests antioxidant depletion or pigment dispersion failure.

Storage conditions below 50 °C and below 70 % relative humidity prevent condensation on cold powder surfaces. Although polyethylene is not hygroscopic, surface moisture can form steam during sintering and generate voids. Chemical incompatibility limits follow LLDPE behavior. Stressed parts exposed to strong oxidizing acids, chlorinated solvents, or aromatic hydrocarbons may crack; environmental stress crack resistance testing under ASTM D1693-B does not replicate all chemical environments. Sustained load-bearing applications above 80 °C should be avoided because creep modulus falls with increasing temperature. White color consistency can be evaluated using CIE L*a*b* coordinates under ISO 11664-4. For outdoor applications, color shift and chalking are assessed by ISO 4892-2 xenon-arc weathering. Oxidative stability is monitored by oxidative induction time under ISO 11357-6; a decrease below the established lower control limit indicates antioxidant depletion and predicts early embrittlement.

Direct replacement of natural Icorene 3550 by 1732G Target WHT requires re-qualification because pigmented LLDPE differs in stiffness, elongation at break, and heat absorption despite sharing the same base resin identification. The rigid pigment phase may produce a modest increase in flexural modulus and a measurable reduction in elongation at break. Relative to high-flow LLDPE rotomolding powders with melt flow rates in the 7–9 g/10 min range, Icorene 3550-1732G prioritizes stress crack resistance and low-temperature ductility over rapid thin-wall mold fill. Relative to HDPE rotomolding grades at 0.940–0.945 g/cm³, the lower density and linear low-density structure reduce flexural modulus and heat deflection temperature while increasing environmental stress crack resistance. For a chemical tank under intermittent hydrostatic loading, the selection between an HDPE grade and this LLDPE product is usually driven by failure history at weld lines and sharp corners, where ASTM D1693-B performance and low-temperature impact measured under ISO 6603-2 or ARM specimen geometries provide more relevant ranking than tensile yield. Compared with crosslinkable HDPE rotomolding grades, Icorene 3550-1732G is thermoplastic and can be reprocessed as regrind within controlled limits. Typical rotomolding practice limits regrind addition to 30 % or less because ground powder changes particle shape, lowers dry-flow consistency, and may reduce low-temperature impact toughness.

Compliance statements must be confirmed against the current Safety Data Sheet and product stewardship bulletin. Olefin polymers of this type may be evaluated under FDA 21 CFR 177.1520 for food-contact applications, subject to extractive limits and end-use restrictions. In the European Union, polyethylene materials fall under EU Regulation (EU) No 10/2011 when used in food-contact plastics; overall migration and specific migration limits are determined by food simulant testing. The 1732G white pigment package requires separate heavy-metal and specific migration evaluation. Potable water tanks require NSF/ANSI 61 certification; the product should be explicitly listed under the manufacturer’s certification before use in municipal water systems. Electrical and electronic enclosures must satisfy RoHS Directive 2011/65/EU substance restrictions and IEC 62321 screening methods. REACH obligations for SVHC content are governed by the current candidate list and must be verified by the producer or importer.

Production-scale experience shows that batch-to-batch variance in pigmented rotomolding powders is best detected through dry-flow retention, melt flow retention after molding, and visual color measured against a controlled white plaque. On shuttle lines with independent arm rotation, a lot that passes bulk density inspection can still deposit unevenly if the fine particle fraction shifts; molders should therefore record house air temperature and powder conditioning time before charging. A powder conditioned to the production hall for 4 h minimizes condensation risk when moving from unheated storage. These process-control checks are more predictive of wall thickness consistency than color difference alone. A 5 °C reduction in peak internal air temperature below the established lower control limit can cause incomplete densification at wall sections adjacent to the parting line, while a 15 °C overshoot above the upper control limit accelerates yellowing.

Rotomolded agricultural hoppers and chemical tanks produced from this grade are typically specified for impact resistance under cold conditions. Cold-arm impact testing at -40 °C using ISO 6603-2 or equivalent ARM methods provides a rank-order measure of toughness; published data for this specific 1732G Target WHT configuration is limited and must be generated on production-representative wall sections. Automotive fluid reservoirs and equipment enclosures require additional OEM-specific chemical resistance and fogging protocols such as SAE J1681 for hydrocarbon permeation. When these requirements are present, the grade should not be qualified on density and melt flow rate alone.