Ocean Freight Humidity Control: Preventing PET Hydrolysis

In the global plastic recycling and polymer trading industry, the biggest invisible enemy when exporting high-quality post-consumer pet flakes is container rain and moisture-induced hydrolysis.

Shipping pet flakes from Bangladesh to Europe, North America, or the Middle East (multi-week transoceanic transit) often takes between 3 to 6 weeks. During this long journey, intense fluctuations in ocean temperatures and relative humidity levels inside the shipping container cause water vapor to condense into liquid water.

If your imported pet flakes exceed a moisture content of 0.5%, the polymer chains will break down during melt processing in an extruder, a process known as hydrolysis, leading to a drastic drop in Intrinsic Viscosity (IV).

This technical article breaks down the science of how transoceanic moisture induces hydrolysis and explains how Key Mart Limited utilizes advanced packaging technology to deliver 100% dry and protected rPET feedstock to global convertors.

1. The Chemistry of Hydrolysis and Container Rain

The two-step process of how rPET flakes are degraded by multi-week transoceanic moisture:

Step 1: Ocean Transit Humidity ➔ Multi-Week Sealing in Tropical Container ➔ Temperature Drop at Night ➔ Container Rain
Step 2: Extrusion Processing  ➔ Moisture + 270°C Melt Temp ➔ Ester Bond Scission ➔ Intrinsic Viscosity (IV) Drop & Brittle Product

A. What is Container Rain?

Shipping a sealed container from a tropical country like Bangladesh creates a perfect environment for condensation. When the metal container is sealed, tropical moisture is trapped inside. At night, when the ocean temperature drops suddenly, the steel roof and walls of the container cool, causing the internal moisture to condense (dew point) and fall onto the cargo bags—a phenomenon known as Container Rain.

B. Hydrolytic Degradation

PET is hygroscopic, meaning it absorbs moisture from the air. When moisture-laden flakes are fed into an extruder and melted at 250°C – 270°C, the water molecules chemically react with the molten polymer chain. This is hydrolysis: a chemical scission of the ester bonds, instantly reducing the polymer’s molecular weight and its Intrinsic Viscosity (IV) by $0.08 - 0.15 \text{ dL/g}$ . This degradation leads to brittle final products (e.g., yarn or sheet).

Technical Purity and Moisture Control Benchmark Table

Ocean Transit & Packaging Parameter	Standard Industry Packaging	Key Mart Limited Export Standard	Operational Impact on Processing Line
Moisture Content	$> 1.0\%$ (Hydrolysis Risk)	`< 0.5% (Target < 0.3%)`	Prevents hydrolytic scission & IV drop
Liner Bag Protection	Standard Polypropylene Sheet	`100 µm Virgin PE Baffle Liner`	Block container rain from reaching the rPET.
Container Desiccants	Absent or insufficient	`High-Absorption Calcium Chloride Desiccants`	Maintains low relative humidity inside container.
Batch COA (Moisture)	Absent	`Mandatory Pre-Shipment CoA`	Confirms compliance with GRS 4.0 standards.

2. Preventing Hydrolysis: Advanced Ocean Freight Protection

Achieving a Low Moisture benchmark ( $< 0.5\%$ ) in rPET feedstock at the final destination requires three distinct engineering steps at Key Mart Limited’s factory before container sealing:

Precision De-dusting and Air Elutriation: We remove fine dust and label particulates ( $< 500\,\mu\text{m}$ ) before packaging. Dust is highly hygroscopic and accelerates moisture absorption by creating a larger surface area inside the bag.
Heavy-Duty PE Baffle Liners: We use premium Baffle FIBC jumbo bags with integrated, moisture-barrier Virgin PE inner liners (100-micron thick). This is the absolute first defense against container rain.
Container-Wide Desiccant Poles: For transoceanic freight, we hang calcium-chloride-based high-absorption industrial desiccant poles in all four corners of the container to lower internal relative humidity and block the formation of container rain.

3. How Key Mart Limited Fulfills Global Buyer Demand for Certified Dry Feedstock

Global convertors and pet flakes exporter clients cannot afford hydrolytic IV drop when running technical textile or thermoforming lines.

As a premier pet flakes company bangladesh and trusted pet flakes manufacturer dhaka, Key Mart Limited specializes in specialized processing infrastructure to deliver dry, high-purity rPET feedstock tailored for technical melt extrusion:

Automated Processing in Dhaka: Operating as a leading pet flakes manufacturer dhaka, Key Mart Limited utilizes automated multi-stage hot-caustic washing and continuous rotary hot-air dryers to achieve moisture levels below $0.3\%$ at our Dhaka facility.
GRS 4.0 Moisture Seal Guarantee: As an established bangladesh pet flakes manufacturer, every order is sealed with moisture-barrier PE liners and industrial desiccants, providing full batch traceability and GRS 4.0 certification.
Certificate of Analysis (CoA): Serving as a high-volume pet flakes exporter, every shipment includes a batch-specific Certificate of Analysis (CoA) confirming IV values, PVC $< 50 \text{ PPM}$ , color values (L, a, b), and moisture content.
Maximized Palletized Loading: Our 40ft HC containers are optimized to load 25–26 Metric Tons of palletized feedstock with protected packaging. We guarantee shipment from Chittagong port.

Partner with Key Mart Limited Today

Eliminate hydrolysis, protect your extruder’s Intrinsic Viscosity, and secure certified high-purity rPET flakes from Bangladesh. Contact our Dhaka export management team today to request Technical Data Sheets, order commercial samples, or reserve container allocation schedules.

Company Name: Key Mart Limited
Head Office & Factory Address: Plot #31, Road #N-1, Block #K, Eastern Housing, Pallabi 2nd Phase, Rupnagar, Dhaka-1216, Bangladesh.
Official Website: www.keymartbd.com
Corporate Email: keymartltd@gmail.com | info@keymartbd.com
Direct Phone / WhatsApp: +8801760774499, +8801864935478

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Ocean Freight Humidity Control: Preventing Hydrolysis During Multi-Week Transoceanic Transit