With the increase in the percentage of plasticizer PVC plastic is reduced, since PVC has = 1015-1016 Ohm km, and plasticizers = 1012-1014 Ohm km. Therefore, the insulating formulation amount of plasticizer should not exceed 40-45%, since it increases PVC plastic will 1 1017Om km, which is less than the required standard. GOST 5960-72 "Plasticized polyvinyl chloride insulation and protective coverings of wires and cables" regulates the basic parameters of the most popular brands of plastic, each of which is assigned the symbol consisting of letters and numbers. The first one (or two) letter grade indicates the scope and type of plastic: I-insulating, O-wrappers (hose), IO-for insulation and sheathing. For insulating plastic two digits following the letters describe the temperature brittleness, and the figures behind them (after the hyphen) is the exponent of the specific bulk electrical resistance of the marks (eg, I40-14). When referring to PVC Hose brittleness temperature indicated by a hyphen after the letter (eg, 0-40). Special properties of compound designated standing next to the letter and or on one or more the initial letters of words that characterize the additional property of this recipe. For example, high thermal plastic compound, called "heat-resistant insulation," denoted by the IT-105 (indicated by a hyphen maximum operating temperature).
In the documentation for the manufacture of cables and wires usually indicate not only the brand, but the number of formulations of PVC plastic. It makes better use of its properties. For example, a well-known formulas 251 and 230 according to GOST 5960-72 are assigned to one brand of insulating plastic and 40-13 and have the same standards for physical, mechanical and electrical characteristics.