Ask the Expert Question-and-Answer Archive

by Ron Joseph

April, 2007

Viscosity of Nitrocellulose Lacquer

Q: Let me know whether, viscosity of nirtocellulose solution changes for diffrent conc. of nitrocellulose?

There are many literatures available for viscosity of nitrocellulose in solution for a given conc. of nitrocellulose in diffrent solvent or mixture of solvent. Eg. 10 % solution of nitrocellulose in acetone, cellosolve, esters etc. is different for diffrent solvents.

But I want to know whether viscosity of nitrocellulose changes for diffrent conc. of nitrocellulose in the same solvent?

I am using a solvent mixture of 66% N - Propanol and 34 % cellsolve. Now will the viscosity of solution be different for 6% solution of nitrocellulose and 8 % solution of nitrocellulose. Will the viscosity increase if conc. of same grade of nitrocellulose is increased. i.e ( 6%, 8 %, 10 %, 12 % ). Or will the the viscosity remain same, no matter what the % solid content of nitrocellulose is.

A: First let me admit that I am no expert on nitrocellulose; however for a solution that is made of a mixture of resin and solvents, the viscosity will change depending on the concentration of the ingredients and their respective viscosities.

I don't know what method you intend to use to measure viscosity, but if you use an instrument that is sensitive to small viscosity increases or decreases, you will find that by increasing the weight solids (or molar mass) of the resin the viscosity should be expected to increase accordingly. I am not suggesting that the relationship between viscosity and solids content is linear, but if a concentrated solution of nitrocellulose has a high viscosity, then by adding solvents you can lower the viscosity.

With regard to nitrocellulose lacquers, painters tend to add large volumes of solvents to the lacquer before applying them. This is done to decrease the viscosity of the solution to a value that is more appropriate for spray application.

Regards,

Ron Joseph