3907.61.00 - Having a viscosity number of 78 ml/g or higher

This HTS category, 3907.61.00, specifically covers poly(ethylene terephthalate) (PET) that possesses a viscosity number of 78 milliliters per gram (ml/g) or higher. This designation is critical for distinguishing between different forms and grades of PET, impacting its suitability for various manufacturing processes and end-use applications, particularly where higher molecular weight is a requirement for enhanced material properties.

Within the broader classification of poly(ethylene terephthalate) (3907.6), this subcategory is differentiated from its sibling, 3907.69.00 ("Other"), by the specific viscosity threshold. While 3907.69.00 would encompass PET with viscosity numbers below 78 ml/g or those exceeding the range specified in 3907.61.00, this node focuses exclusively on PET with the defined higher viscosity.

The principal subcategory under 3907.61.00 is 3907.61.00.10, which further refines the classification by establishing an upper limit on the viscosity number, ranging from 78 ml/g to 88 ml/g. This granular subdivision allows for precise classification of PET resins intended for applications demanding a specific, controlled molecular weight and rheological behavior, such as certain types of fibers, films, or specialized packaging.