
Introduction to binder and plasticizer
Published:
2022-03-25
Source:
In order to separate from the substrate material and facilitate handling, the cast film must have certain strength, toughness and ductility. Therefore, the binder and plasticizer must be added into the slurry.
In order to separate from the substrate material and facilitate handling, the cast film must have certain strength, toughness and ductility. Therefore, the binder and plasticizer must be added into the slurry.
Factors to be considered when selecting the binder include:
(1) The thickness of the prime embryo membrane;
(2) The type and matching of the selected solvent are conducive to solvent volatilization and no bubbles;
(3) It shall be easy to burn off without residue;
(4) It can stabilize the sedimentation of slurry and particles;
(5) A lower plastic transition temperature is required to ensure that no condensation occurs at room temperature;
(6) The properties of the substrate materials used shall be considered to avoid bonding and easy separation.
Binders can be divided into three categories: non-ionic, anionic and cationic according to the functional group type. Anionic and non-ionic binders are mostly used in tape casting process, mainly including vinyl and propylene. The commonly used binders in non-aqueous slurry are PVB, polyacrylate methyl ester and ethyl cellulose. The commonly used binders in water-based media are polyvinyl alcohol, acrylic acid emulsion, polyacrylate amine salt, etc.
The main function of the plasticizer in the slurry is to reduce the plastic limit temperature Tg of the binder, so that Tg can reach room temperature or below, so as to ensure that the binder has good fluidity at room temperature and does not coagulate. In addition, the plasticizer can also lubricate and bridge the powder particles, which is conducive to the dispersion and stability of the slurry, but the addition of the plasticizer will reduce the strength of the plain embryo film. The commonly used plasticizers are polyethylene glycol, phthalate, ethylene glycol, etc. They have different effects on the rheological properties of slurry. Phthalate grease can lubricate powder particles and reduce slurry viscosity, while polyethylene glycol can form an organic bridge between powder particles and increase slurry viscosity.
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