THE PHASE DIAGRAM OF SYSTEM
POLYAMIDE -6 ─ FORMIC ACID ─ WATER
N.A.Kozlov, A.V.Tarasov, J.A.Fedotov
The Vladimir state university,  Russian Federation, Vladimir, Gorki street , 87
E-mail:  tpp_vlgu@mail.ru 

        Phase balance in system polyamide-6 (РА-6) ─ formic acid (FA) ─ water studied in the installation, allowing to support or the set temperature, or to heat up capacity with a solution with the constant speed. Disintegration of a solution on phases observed at continuous hashing on occurrence (disappearance) turbidity. Heating / cooling of a solution spent with different speed, fixed temperature at which phase transition took place, graphically extrapolated straight lines to zero speed of heating / coolings. Phase disintegration found also on a break of a straight line lg η = f (1/T). Viscosity measured on rео-viscosimeter at 20 - 80 °С with accuracy ± 1 %. Both ways gave the temperatures of phase disintegration differing within the limits of ± 2 °С.

 
          
          The phase diagram built by means of a method of factorial planning. Planning of experiments is lead by a method of simplex lattices, the simplex-trellised of plan Sheffe of the third order for research of a local site of the triangle limited by concentration PА-6 from 8,0 up to 28 %, FA from 46,8 up to 62,3 %, Н2О from 20,7 up to 41,4 % is more exact drawing up. The mathematical model of the phase diagram of threefold system is made, the importance of factors and adequacy of model both in pseudo-components, and in natural values of concentration is shown.
The volumetric phase diagram of system in pseudo-components, by the help of model  in natural components is constructed. On the triangular diagram isotherms of system are shown. The surface of phase disintegration represents curved in the original image a plane. The minimal temperature of phase disintegration  + 44 °С is observed for system of structure PA-6 : FA : Н2О = 14 : 59 : 27 mas. %, in area of high concentration of polymer this surface at temperatures 65 - 67 °С leaves the narrow slightly turned tape.
In the field of the minimal temperature the surface of phase disintegration has the form of funnel with a minimum + 44 °С. The funnel  is distinctly allocated on isotherms of the phase diagram. Disconnection of  funnel occurs at 64 °С. Here the surface of disintegration looks like  a turned tape. The amorphous type of phase disintegration inside of funneled area is not excluded.