Hydrocarbon Tolerance - Dilution Ratio

A hydrocarbon, non solvent is added normally to a solution of nitrocellulose for achieving economy and dilution. In this addition a point is eventually reached when the nitrocellulose no longer remains in solution and is precipitated out. The volume ratio of hydrocarbon non solvent or diluent to solvent at this point is called dilution ratio. Hydrocarbon tolerance of any given Nitrocellulose varies with the solvent used and the type of diluent. For a given solvent mixture it depends on

  • The grade of nitrocellulose
  • Purity of solvents
  • Ratio of active solvents to alcohol
  • Concentration of nitrocellulose (the dilution ratio diminishes with increasing concentration)
  • Temperature (the dilution ratio diminishes with increasing temperature)

Variation of dilution ratio with type of solvent and dilution is illustrated in Table 1. In this table the value of dilution ratio is shown to vary with type of solvent i.e. butylacetate or MIBK or ethyl alcohol and the type of diluent i.e. toluene, SBP petroleum solvents and n-butanol for the same concentration and grade of HX 30/50. In Table 2 the value of dilution ratio has been shown to be varying for different grades of nitrocellulose in the same solvent

Dilution Ratio (HX 30/50)
Active Solvent Toulene/Xylene SBP/Petroleum Solvents N - Butanol
Butyl acetate 2.7 1.5 10
MIBK 3.6 0.8 -
Ethyl glycol 4.7 1.1 -

Table 1 : Dilution ratio of common lacquer solvents (Nitrocellulose conc. 8%)

Nitrocellulose Grade Dilution Ratio Final conc of Nitrocellulose
HX 2.7 8.0
HL 3.0 3.5
LX 2.0 10.0

Table 2 : Variation of toluene dilution ratio with grade of industrial nitrocellulose (solvent butyl acetate)

Dilution Ratio is useful as a guide to the quantity of one diluent that may be used as a substitute for another in an established formulation. The actual ratio of diluent / hydrocarbon non-solvent to active solvent in practice should always be appreciably less than quoted dilution ratio for two reasons.

  • Dilution ratios are referred to at 8% concentration while in most formulation nitrocellulose concentrations are higher than 8%.
  • Most lacquers contain resins and plasticizers which adversely effect dilution ratios i.e. they reduce hydrocarbon tolerance.