Unusual types of gramophone records vinyl colors became too high, but the different colored labels were continued, at least for popular music (black) and classical (red, as in "Red Seal"). In October 1945, RCA Victor put on the market its first "non-breakable" phonograph records. Made of a ruby-red, translucent vinyl resin plastic, they cost twice as much ($2 per disc) as the 12-inch Victor Red Seal. In the 1960s, a distinction was made in label colors of promotional copies of 45 RPM records as well, with pop music being issued on yellow labels and country on light green. In the 1970s, such gimmicks started to
IUPAC polymer nomenclature written in italic font. Non-linear polymers and copolymers, and polymer assemblies are named using the italicized qualifiers in Table 2. The qualifier, such as "branch", is used as a prefix (P) when naming a (co)polymer, or as a connective (C), e.g., "comb", between two polymer names. In place of the monomer name used in source-based nomenclature, structure-based nomenclature uses that of the "preferred constitutional repeating unit" (CRU). It can be determined as follows: Polymers that are not made up of regular repetitions of a single CRU are called irregular polymers. For these, each constitutional unit (CU) is separated by a