1518.00 - Animal, vegetable or microbial fats and oils and their fractions, boiled, oxidized, dehydrated, sulfurized, blown, polymerized by heat in vacuum or in inert gas or otherwise chemically modified, excluding those of heading 1516; inedible mixtures or preparations of animal, vegetable or microbial fats or oils or of fractions of different fats or oils of this chapter, not elsewhere specified or included:

Heading 1518.00 encompasses a range of animal, vegetable, or microbial fats and oils that have undergone significant chemical modification. This includes processes such as boiling, oxidation, dehydration, sulfurization, blowing, polymerization, or other treatments that alter their original properties. Importantly, this heading excludes fats and oils classified under heading 1516, which are typically partially or wholly hydrogenated, inter-esterified, re-esterified, or fractionated but not otherwise chemically modified. It also covers inedible mixtures or preparations derived from these modified fats and oils or their fractions, provided they are not specified elsewhere in Chapter 15.

This classification differs from other categories within Chapter 15 which typically deal with raw, processed, or edible fats and oils without these extensive chemical modifications. For example, headings concerning refined edible oils or animal fats not subjected to the processes described here would fall under different HTS codes. Heading 1518.00 is specifically for those fats and oils whose fundamental characteristics have been intentionally altered for various industrial or technical applications, rather than for direct consumption.

The subcategories within 1518.00.00 differentiate based on the source of the modified fats and oils. Subheading 1518.00.20.00 specifically addresses products derived from linseed or flaxseed oil, highlighting a particular origin for these chemically modified substances. The residual category, 1518.00.40.00, captures all other modified animal, vegetable, or microbial fats and oils and their inedible mixtures or preparations that do not fall under the more specific linseed or flaxseed oil classification. This hierarchical structure allows for precise classification based on both the modification process and the source material.