Antioxidant 552 (3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide)
Antioxidant 552 is the commercial grade of 3,9-dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide, a non-halogenated organo-phosphorus stabilizer for polymers. It falls under HTS 2931.48.00.00 due to its specific spiro phosphonate structure with P-C bonds, as defined in Chapter 29 heading 2931.
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Alternative Classifications
This product could be classified differently depending on its characteristics or intended use.
If for retail-packaged formulations with added carriers
If put up for retail sale with non-qualifying additives, it becomes a chemical mixture under Chapter 38 rather than a pure compound.
If reclassified as organo-sulfur due to trace sulfur impurities
Chapter notes specify organo-sulfur precedence in 2930, but non-halogenated P-C dominant stays in 2931.
If the diol-derived structure emphasizes oxygen function
Oxygen functions take precedence in earlier headings per Chapter 29 notes if not clearly organo-inorganic.
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Import Tips & Compliance
• Label with commercial name and CAS number (CAS 65481-32-7) for easy verification
• Test for stabilizer additives to ensure they qualify under Chapter 29 note (f) without changing classification
• Avoid bulk mixtures to prevent reclassification as preparations
Related Products under HTS 2931.48.00.00
3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide
This is a specific non-halogenated organo-phosphorus compound featuring a spirocyclic structure with two phosphonate groups, classified under HTS 2931.48.00.00 as an organo-inorganic compound where phosphorus is directly linked to carbon. It is used primarily as a synthetic intermediate in pharmaceutical and agrochemical production.
DOPO Derivative 3,9-Dimethylspiro Phosphonate
A DOPO-based derivative, this compound is precisely 3,9-dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide, used in flame-retardant synthesis for electronics. Classified in HTS 2931.48.00.00 as a non-halogenated organo-phosphorus compound per Chapter 29 definitions.
Spiro Phosphonate Monomer for Polymer Synthesis
This research-grade spiro phosphonate monomer, chemically 3,9-dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide, is used in copolymer production. It qualifies under HTS 2931.48.00.00 for its organo-inorganic phosphorus structure excluding halogens.
CAS 65481-32-7 3,9-Dimethylspiro[5.5]undecane Phosphonate Dioxide
Identified by CAS 65481-32-7, this is pure 3,9-dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide, a building block for organophosphorus ligands. HTS 2931.48.00.00 covers it as a non-halogenated organo-phosphorus derivative.