Harmonized Tariff Chief Weight Adjustments under Variable Regain Rates
Harmonized tariff chief weight declarations require converting oven-dry fibre masses into commercial mass using statutory regain allowances to prevent reclassification.
Polyester Regain Rate
Absorption Standard
A fixed percentage value represents the amount of water a specific synthetic polymer absorbs from the atmosphere under standard conditions. The polyester regain rate is notably low compared to natural fibres, typically settled at 0.4 percent for commercial transactions. This figure allows buyers and sellers to calculate the dry weight of a shipment from its invoiced mass.
Moisture Resistance
Hydrophobic properties of the material ensure that it maintains its dimensions and strength even in high humidity. Because the polyester regain rate is minimal, fabrics made from this fibre dry quickly after washing or exposure to rain. The characteristic makes it suitable for outerwear and technical applications where water weight is a disadvantage.
Laboratory Verification
Technicians determine the actual moisture content by heating a sample in an oven until the weight stops decreasing. They compare the loss of mass to the dry weight to see if it aligns with the official polyester regain rate. If the value is higher, it may indicate the presence of finishes or contaminants on the fibre surface.
Processing Behavior
Static electricity buildup occurs frequently in environments with low humidity due to the lack of internal water. Since the polyester regain rate is so low, the fibre cannot easily dissipate electrical charges. Mills must apply antistatic agents to ensure smooth running through spinning and weaving machinery.
Sparks or clinging fabric can disrupt the automation in a high-speed garment factory if the moisture levels are not managed correctly. Proper application of these finishes compensates for the dry nature of the polymer.