4. The expression "copolymers" covers all polymers in which no single monomer contributes 95 percent or more by weight to the total polymer content.
For the purposes of this chapter, except where the context otherwise requires, copolymers (including co-polycondensates, co-polyaddition products, block copolymers and graft copolymers) and polymer blends are to be classified in the heading covering polymers of that comonomer unit which predominates by weight over every other single comonomer unit. For the purposes of this note, constituent comonomer units of polymers falling in the same heading shall be taken together.
If no single comonomer predominates, copolymers or polymer blends, as the case may be, are to be classified in the heading which occurs last in numerical order among those which equally merit consideration.