View the Material Safety Data Sheet (MSDS) for product WB4101

WB4101 is a fully preformulated, liquid water based acrylic binder for tape casting ceramic powders. It is designed to act like solvent based binders in terms of slurry processing, tape properties and tape processing into multilayered components. The binder concentrate contains all defoamers, plasticizers, and resins to produce tape. A family of modifiers is available to tailor properties such as flexibility, steel belt release, special defoamers or other additives for a particular application.

WB4101 consists of a water solution of an acrylic polymer with copolymerized dielectric affinic functional groups. The base resin has a Tg of approximately 40C but is plasticized to a much lower level to allow typical tough cast tape properties. The resin is soluble in water when the pH is adjusted to be alkaline. WB4101 achieves this pH by the addition of a small percentage of ammonia hydroxide. When the binder is dried, this ammonia hydroxide also evaporates off with the water. Thus, the resin, although initially dissolved in the binder solution, does not redissolve when in the presence of water. This change in solubility and subsequent water resistance is similar to a typical latex. However, unlike the typical latex system, this tape can be cleaned and potentially redissolved by adding water and again adjusting the pH with added base.

WB4101 in many ways acts like a solvent based binder system without the solvents. Unlike many latex systems which are destabilized by milling, this binder is unaffected. Many latex systems require unusually high lamination properties; however, WB4101 again can typically be laminated and processed the same as conventional solvent based binder systems. This is because that, from a physical and chemical standpoint, it is very similar to the resins used in commercial solvent based binders.

Most water based binder systems cannot achieve the tape green density (packing density) of a solvent based binder system. These other systems also require the use of strong dispersants to help achieve dense green tapes and frequently foaming problems result. WB4101, due to the copolymerized dielectric affinic groups, is a natural dispersant all on its own. WB4101 matches and typically exceeds the tape green density of a solvent based binder. This allows the use of even higher ceramic loadings in the tape while maintaining lower porosity levels compared to other systems.

WB4101 was designed to be as universal as possible and easy to use. Most water based systems do not have a low enough surface energy to wet to silicone treated polyester tape (siPET) the way a solvent based system can. Due to the use of strong wetting agents, WB4101 can readily wet low energy substrates including siPET. It also casts acceptably and can be removed from polypropylene and steel belts.

WB4101 was designed to be a system with many advantages over current binders. The lists below show how it compares to other binder groups:

• Binder can be milled without excessive foam or slurry destabilization.

• Binder can be used in one- or two-stage milled slurry systems.

• Slurry viscosity and casting properties are similar to solvent based systems.

• Tape strength and lamination characteristics are typical of solvent based systems.

• Tape is water resistant when dried but is potentially redispersible under proper conditions.

• Clean up can be with water when wet or Windex (trademark of S. C. Johnson and Son, Inc.) and solvents when dry.

• Material can be cast on a variety of casting substrates such as PP or even siPET.

• Achieves denser, more continuous films without coalescing solvents.

• Freeze stable.

• More uniform green tape with less binder segregation.

• Can handle boron containing ceramics.

• Is more resistant to water and humidity.

• Allows higher ceramic loading in the slurry.

• Slurry viscosity and dispersion are more stable.

• Wider lamination and production processing window.

• Not flammable.

• Low toxicity and environmental hazard.

• Easier shipping and disposal.

• Easier, safer, clean up.

• Hazardous cleaning solvents and resulting waste stream avoided.

• Due to dispersing nature of polymer and polarity of water higher tape densities are possible.

• Wet ceramic powders can be utilized.

• Ceramic tends to settle less and is easier to redisperse.

WB4101 has dispersant properties to help deagglomerate the ceramic powder. Therefore, it is desirable to have at least some WB4101 present during the milling step as outlined in the basic steps below (more detailed examples are attached):

Simply batch the whole slurry formula in a ball mill, mill the desired time and drain the mill.

It is important there be some WB4101 in the first stage. The first stage should consist of about 10 - 50% of the total amount of binder to be used in the total formulation, as well as the ceramic powder, and enough water to achieve the approximate milling consistency desired. A typical recipe is given at the end of this section. After the first stage milling is complete, the mill is opened, the balance of the WB4101 added, the mill closed and milled typically for several hours to allow complete mixing of all the ingredients.

De-airing of slurry:

WB4101 has defoaming characteristics which will keep the amount of bubbles generated to a minimum. Typically, all that is required to remove any remaining bubbles is to allow the slurry to sit an hour, or slow roll without media overnight before casting. The slurry does not have to be cast quickly. With typical ceramics, it will hold near fresh slurry characteristics for weeks as long as it is slow rolled to avoid ceramic settling.

WB4101 Typical Characteristics:

Viscosity (HBT SC4 21/13R @ 100 rpm and 25C) ~1,000 cps
Solids (1 gram sample 125C for 1 hour) 35%
Density (25C) 1.03 g/cc
Ash (550C for 1 hour) .10% max.
pH ~ 6.5

If a fairly typical formulated barium titanate of about 2-6 m²/g is used, this formula will load the final dry tape at about 58 volume percent ceramic and result in a slurry viscosity of about 200cps, which typically will give good casting and tape performance.

*Slurry viscosity can be adjusted without changing final tape composition by using either more or less water.