Shipping LLDPE: container loading, moisture protection and weight limits are controlled by the polymer’s bulk density, packaging format, container maximum gross mass, and the IMO/ILO/UNECE Code of Practice for Packing of Cargo Transport Units (CTU Code). Linear low-density polyethylene pellets exhibit a density of 0.915–0.940 g/cm³ under ASTM D1505 or ISO 1183-1:2019. Film grades typically show a melt mass-flow rate of 0.5–2.0 g/10 min at 190 °C/2.16 kg per ISO 1133-1:2022. The polymer is non-hygroscopic; equilibrium moisture uptake remains below 0.01 wt% at 23 °C/50% RH under ISO 62:2008. Common transport packages include 25 kg multi-wall paper or woven polypropylene sacks, 500–1250 kg flexible intermediate bulk containers, and 1.0–1.5 t octabins. The shipment is not classified as dangerous goods under the IMDG Code, but spillage of pellets is covered by MARPOL Annex V discharge restrictions and port waste procedures.

What Governs Container Loading Practices for Pelletized LLDPE?

Container loading must satisfy the CTU Code requirements for packing, blocking, and securing. For bagged LLDPE, pallets are interlocked from the front wall to the door, with heavy FIBC units placed over the gooseneck and lighter sacks in the door area to reduce lashing loads. The Code assumes horizontal acceleration of 0.8 g forward and 0.5 g sideways and rearward; therefore, cargo must be secured to withstand these forces rather than only vertical static weight. Dunnage strips of high-density polyethylene or corrugated fiberboard are installed between pallet rows and side walls. Anti-slip sheeting with a coefficient of friction above 0.4 reduces motion between sack layers. Standard 1200 mm × 1000 mm pallets load in a 20 ft container as 10–11 single-stack units; double stacking of 25 kg sacks is generally refused for moisture-sensitive film grades because bottom sacks creep and split after multi-day vibration.

For bulk shipments, loading through pneumatic or conveyor systems is limited by container internal volume and achievable fill factor. The effective bulk density of pelletized LLDPE is 480–560 kg/m³. A 20 ft GP container with an internal volume near 33.2 m³ can receive only 15.9–18.6 t of bulk pellets before the volume is exhausted; mass limits are usually not reached. In contrast, the same pellets in compacted FIBCs can present an effective stowage factor below 1.5 m³/t, making 20 ft loads mass-limited in some port operations.

Representative container data for LLDPE logistics are summarized below. Individual tare masses and allowable payloads must be verified against the container Safety Approval Plate under the International Convention for Safe Containers (CSC); published data for specific container series can vary by manufacturer.

Road transit imposes stricter payload limits than container ratings in many corridors. In the European Union, Council Directive 96/53/EC sets a 40 t gross combination mass for standard five-axle articulated vehicles; this commonly constrains a 40 ft container cargo mass to 24–26 t after subtracting tractor unit and chassis tare. In the United States, the federal Interstate limit is 80000 lb gross combination weight under 23 CFR 658.17, with 20000 lb single-axle and 34000 lb tandem-axle limits. Export loads optimized at container maximum gross mass may therefore be non-compliant for road moves unless the shipper confirms the complete vehicle tare and axle spacing.

When Ocean Freight Condensation Reaches the Pellet Surface

Moisture damage in LLDPE shipping is primarily a packaging-surface phenomenon. Although the pellet itself absorbs below 0.01 wt% water, ocean container walls undergo daily temperature cycles; when wall temperature falls below the dew point of trapped air, condensation forms on the roof and upper side walls and can drip onto top sacks. Cargo loaded at 35 °C/70% RH contains approximately 25 g/m³ water vapor, which condenses when the container shell cools. Because LLDPE film production is sensitive to surface moisture in the feed throat, processors increasingly reject sacks with visible wet surfaces or water staining.

Moisture protection uses passive desiccant units and controlled ventilation. Calcium chloride or silica gel desiccant bags are placed at floor level and suspended from lashing rings; dosage for ocean passages exceeding 7 days commonly ranges from 100–250 g/m³ of container internal volume. Active desiccant rotor units may be specified for fractional-melt film grades or moisture-sensitive additive masterbatches. The container should not be stuffed during rain or when internal relative humidity exceeds 70%, and roof panels and door gaskets should be inspected before loading.

Humidity data loggers calibrated under ISO 17025 record internal dew point and temperature at intervals of 30 min or less. Upon arrival, the recorded profile is compared with the voyage route; intervals with dew point above 30 °C or internal relative humidity above 80% trigger a pallet-by-pallet inspection. Bagged film-grade LLDPE with surface moisture above the converter’s specification should be segregated, dried in a desiccant dryer at a maximum hot-air temperature of 80 °C, or returned to the shipper depending on the certificate of analysis and the nature of the moisture exposure.

Container loading should sequence palletized LLDPE from the front wall to the door without leaving center voids. For a 20 ft unit, the cargo center of gravity should remain within the middle 60% of the container length and below 1.8 m above the floor. When FIBCs are loaded over pallets, the bottom layer should be rated for at least 2000 kg static stack load, and the top layer should be secured with cross-strapping to door lashing rings. Weighbridge records at the port are compared with the shipper’s declared net weight; deviations above ±0.5% typically require rehandling or reweighing before the container is released for vessel loading.

Container Payload, Axle Weight and Regulatory Limits

Mass distribution inside the container determines road axle loads after discharge. A 40 ft GP container with a cargo mass of 25000 kg loaded unevenly can shift the rear axle group by more than 2000 kg. Load planners use stowage plans to keep the cargo center of gravity within the middle 60% of the container floor and below 1.8 m. For a 20 ft container on a two-axle trailer, the kingpin mass should remain at 15–25% of gross combination weight to avoid trailer sway. The Safety Approval Plate under the CSC lists maximum operating gross mass, racking strength, and stacking test values; shippers should use the rated mass on the plate rather than the ISO series default because some containers carry reduced operating ratings.

Marine and road weight documents must align. The packing list, bill of lading, verified gross mass declaration under the International Convention for the Safety of Life at Sea (SOLAS) Chapter VI, Part A, and the certificate of analysis should show the same net and gross masses. For LLDPE packaged in 25 kg sacks, the total tare mass of pallets, sacks, and dunnage adds approximately 3–5% to the net polymer mass. For 1250 kg FIBCs, the FIBC tare mass is typically 2.5–4.0 kg per unit, and the wooden pallet adds 15–25 kg; these components must be included in the verified gross mass calculation. In Europe, REACH Regulation (EC No 1907/2006) applies to monomer registration and safety data sheet communication, while LLDPE as a polymer is exempt from registration under Article 2(9).

Upon arrival, the consignee should inspect the container seal, floor dryness, and the humidity logger before unloading. Wet sacks from condensation should be isolated from dry inventory and sampled for surface moisture using ASTM D7191-18 or ISO 15512:2019. Containers that show evidence of wall dripping, rust-colored water staining, or door gasket failure may require claim documentation including the CTU Code stuffing check, the humidity record, and the weighbridge ticket. Published data for specific LLDPE grade performance after prolonged container condensation exposure is limited; therefore, converter trials are required when surface moisture remains above the receiving specification.