3903.90.10.00 - Methyl methacrylate-butadiene-styrene (MBS) copolymers

This classification pertains to specific copolymers of styrene, namely Methyl Methacrylate-Butadiene-Styrene (MBS) copolymers, when presented in their primary forms. MBS copolymers are terpolymers known for their impact-modifying properties, commonly used to enhance the toughness of rigid plastics such as PVC. They are characterized by the presence of methyl methacrylate and butadiene monomers in addition to styrene.

Within the broader category of "Other" polymers of styrene, this subheading is distinct from its sibling, 3903.90.50.00, which encompasses all other styrene copolymers not specifically identified. This distinction highlights the specialized nature and specific composition of MBS terpolymers, requiring their separate classification due to their unique properties and applications as impact modifiers.

As this is a leaf node in the HTS structure, there are no further subcategories. Therefore, the classification is definitive for MBS copolymers in primary forms. Examples of products that would fall under this subheading include raw MBS resin pellets or powders intended for subsequent processing into finished goods.