VNIINP-235 grease (TC 38.101297-78 rev. 1-4) is an organic liquid solidified with an organic thickener.
VNIINP-235 grease of black-violet color, has soft structure. This is a semi-structured grease. It has low tensile strength, slightly improving with increased temperatures from 20 to 80 ° C. At high temperatures, VNIINP-235 grease retains a sufficient tensile strength. The viscosity of the grease depends only weakly on the strain rate. The oil is highly compressible. The grease prevents scuffing and welding of balls when tested on a four ball machine up to peak load of 10000 N, (1000 kgf). However, the diameter of the wear scar in such tests reaches 0.6–0.8 mm even at low loads.
Thermal stability of the dispersion medium and a thickener, small change in tensile strength when heating allows to apply greasing in the wide range of temperatures from —60 to + 250 ° C. Recommended for shallow vacuum of about 4 kPa (30 mm Hg). Heat-resistant grease VNIINP-235 is used in low-speed rolling bearings in aircraft control systems. Other characteristics are similar to conventional soap greases.
Physical and chemical indicators of VNII NP-235 grease (TC 38.101297-78 rev. 1-4)
|Name of the indicator||Norm GOST (TC)|
|Appearance||Homogeneous ointment with a smooth structure of black color|
|Effective viscosity at -40°C and mean gradient of strain rate 10 s-1||126 Pa-s|
|Effective viscosity at -50°C and mean gradient of strain rate 1000 s-1||1,3 Pa-s|
|Content of mechanical impurities, %||-|
|Content of water||-|
|Acid number, mg КОН||-|
|Content of free alkali calculated as NaOH, %||-|
|Content of water-soluble acids and alkalis||-|
|Evaporability at 200°C, 1h, %||0,8|
|Colloidal stability of allocated oil, %||6,5|
|Tensile strength at 80°C||290 Pa|
|Corrosion test on metal plates|