" " wisno wood furniture finishing: Nitrocellulose coating

Monday, October 12, 2009

Nitrocellulose coating

Nitrocellulose is coating that uses nitrocellulose resin as the main ingredient. Nitrocellulose resin is made from cellulose (wood fibers) that was cooked and processed with nitric acid and sulfuric acid. Pure nitrocellulose resin (when it is dry is bulk state) is very easy to explode. Since the safety reason, then it is usually stored in a solution in a liquid condition. Pure nitrocellulose is hard and brittle (very easy to crack), then to make nitrocellulose lacquer he needs plasticizers to make the lacquer becomes more plastic and flexible. Plasticizers is a chemical that is very difficult to dry or need very long time to dry. There are many plasticizers materials that are suitable for nitrocellulose, for example: vegetable oil or ester monomers and polymers. Then to develop the character of the resulting film at the finish, into the nitrocellulose lacquer mixture is also added the hard resin materials. There are a lot of hard resins that can be mixed with nitrocellulose, such as: Castor oil, coconut resins, resin, acrylic resin, vinyl resins, etc.
The resin mixture is still need some additive materials such as: surfactants, bubble breaker, flattening powder, etc. An additive material is a material that is needed to make up the performance of the coating. Surfactant is a material to reduce surface tension, make the lacquer flow evenly and make the smooth film. Bubble breaker is a material that allows the film wet longer so that the trapped air in the film formed can be release. Flattening powder is a substance that uses to reduce and adjust the gloss of the resulting film. Finally the lacquer thinner is added into the mixture of nitrocellulose resin, hard resin, plasticizers, and additive to reduce the viscosity and make the nitrocellulose lacquer is in the liquid form. The lacquer thinner is mixture of solvent to reduce the viscosity of the mixture. The special composition of the lacquer thinner is also made according to the lacquer formula and to develop some special properties and character of the lacquer. The thinner mix can be used to do minor adjustment to the lacquer such as: the drying time, the flow, the viscosity.

Nitrocellulose sealer

Nitrocellulose sealer is the same material with the nitrocellulose lacquer, but with different additive. The nitrocellulose sealer doesn’t need flattening powder and lacquer retarder, because the sealer is designed to be sanded and layered with other coating, not as the final coat. Sanding agent the material to help sanding is added to the sealer to reduce the heat arisen by the friction form the sandpaper and the coating. The sanding agent for nitrocellulose sealer is usually zinc stearate or aluminum stearate. This material is the same material used in the sandpaper to reduce the heat during sanding, and reduce the coating material clogged to the sandpaper.

The nitrocellulose coating is very popular in furniture finishing and is still one of the most widely used in furniture finishing industry. The ease in application and the great look resulted make this material is favored by many people in furniture finishing industry. 

The advantages of nitrocellulose clear coating
  •   Nitrocellulose is 1 component, very easy to be handled and applied.
Nitrocellulose clear coating is dry by the evaporation of his solvent without any chemical reaction. The film coating formed is easily resolved with his solvent. The film result can be re coated with the same material many times easily. If there any mistake in the finishing, the dry finish is very ease to be washed off and refinish. The drying time is fast at the room temperature, without need a special oven. The touch dry is very fast make his wet coat is not too sensitive to dust or dirt. It can be applied in he simple spraying room and drying room.
  • The resulting film layer is very clear, thin and looks natural.
This nitrocellulose coating when applied to wood or veneer surface will always down and become a thin film layer after dry for few days. Therefore, the resulting appearance will look natural and give the natural beauty of the wood. The nitrocellulose clear coating produce the clear film finish with the best clarity, compared with the other types of coatings. Therefore this type of clear coating is the most widely used for high-end furniture products when the appearance and beauty is considered as the most important point.
  • The resulting film layer does not emit toxic gases.
Nitrocellulose clear coating will be dry with evaporation of his solvent without any chemical reactions. This clear coating does not need catalyst for drying. Therefore, in his drying process this material depend on how he releases his solvent. It drying times depends to the environment condition. The drying time is very fast, the releases of his solvent takes about 30 minutes in the normal condition. And after it dry, the coating film has no more gas emissions. Therefore, the nitrocellulose coating is quite friendly to the environment. The main ingredient of paint is nitrocellulose, a wood product which is safe for the environment. Of course in the paint mixture is still needed to mix with some certain additives and solvents which may be the pollutant materials, but with the development and the strict regulation the present additive and solvents used is more friendly materials for health and environment.

nc finish for wood
NC finish for furniture

While the disadvantages of nitrocellulose clear coating
  • Relatively low strength.
This clear coating has a relatively low strength to withstand scratches, heat or chemicals. This material is not suitable to finish product which need maximum protection and strength of his finishing. To finish on top dining table, kitchen cabinets or furniture for hotels or cafe, or for outdoor furniture that requires maximum protection and strength for his finishing this material is not suitable.
  • The coating film will turn yellow after a certain time
The resulting film layer of nitrocellulose clear coating has a low resistance to ultraviolet light. The film will turn yellow after a certain time, this process is called yellowing. For the dark or brown colors the yellowing is not so obvious, but for light color or white color, the yellowing of the film will affect the final color.The yellowing on the light or white color will change the color and the final look of the finishing. For the light or white finish when the yellowing is not acceptable, usually we need the non yellowing clear coating such as acrylic or butyrate.See our previous article : butyrate coating

2 comments:

  1. Dear Sir,
    I am Ricky Tan, I just start to learning the furniture coating, like NC, PU and other.
    I have not ideas of the all chemical and additives for my coating, I hope you can help me to improve my coating, special the coating formulation.
    I hope can get the answer from you.

    Thank you very much
    Ricky Tan

    ReplyDelete
    Replies
    1. Dear Ricky

      I am sorry but i don,t know much about the coating formulation.
      But anywhere, if you have any question you can send email to me.

      Delete