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
Polymer are composed of four types of nucleotide subunits. A polymer molecule containing ionizable subunits is known as a polyelectrolyte or ionomer. The microstructure of a polymer (sometimes called configuration) relates to the physical arrangement of monomer residues along the backbone of the chain. These are the elements of polymer structure that require the breaking of a covalent bond in order to change. Structure has a strong influence on the other properties of a polymer. For example, two samples of natural rubber may exhibit different durability, even though their molecules comprise the same monomers. An important microstructural feature of a polymer