Plasticizers

They are mainly used for film flexibility of the finish and as plate releasing agent. Varying amounts of plasticizing substances should be added to the finishing floats depending upon the flexibility of the leathers, the film hardness of the binders used and the thickness of the finish coats. They are employed to increase the stretchiness and elasticity of the respective binder coats and prevent embrittlement of the entire finish during storage and during use of the final leather products. Different types of plasticizers are required for aqueous or solvent-soluble finishing agents.
Ester plasticizers serve as plasticizers, softeners, extenders, and lubricants, esters play a significant role in rubber manufacturing. The basic function of an ester plasticizer is to modify a polymer or resin enhancing its utility. Ester plasticizers make it possible to achieve improved compound processing characteristics, while also providing flexibility in the end-use product. Ester plasticizers are selected based upon cost-performance evaluation. The rubber compounder must evaluate ester plasticizers for compatibility, processibility, permanence and other performance properties. The wide variety of ester chemistries that are in production include sebacates, adipates, gluterates, phthalates, azelates, and other specialty blends. This broad product line provides an array of performance benefits required for the many elastomer applications such as tubing and hose products, seals and gaskets, belts, wire and cable and print rolls. Low to high polarity esters provide utility in a wide range of elastomers including nitrile, polychloroprene, EPDM, chlorinated polyethylene, and epichlorohydrin. Plasticizer-elastomer interaction is governed by many factors such as solubility parameter, molecular weight and chemical structure. Compatibility and performance attributes are key factors in developing a rubber formulation for a particular application

Product of water-soluble finishing agents
Sulphated castor oil
This is also called Turkey red oil. As it has additional wetting properties excessive amounts should be avoided to prevent impaired fastness properties of the finish.
Higher molecular alcohols Wax emulsion
The derivatives of polyglycols, glycol ether, glycerol or their esters are the mainly used products.
Castor wax is used in polishes, cosmetics, electrical capacitors, carbon paper, lubrication, and coatings and greases where resistance to moisture, oils and other petrochemical products is required. Castor wax is also useful in polyurethane coating formulation, as it contains three secondary hydroxyl group.These coating compositions are useful as a top coat varnish for leather, wood & rubber.

Wax emulsions

These give the films additional fullness and elasticity and reduce tackiness during plating. They should not be used in large amounts as otherwise the coats become extremely water repellent ( may result in impaired adhesion)

Products for solvent finish (none gelatinizing)
Vegetable oils
The most commonly used product is castor oil, less frequently rape oil. They are only loosely deposited in nitrocellulose films. Therefore it is advisable to apply them in combination with synthetic plasticizer.

Castor oil is a vegetable oil obtained from the castor bean (technically castor seed as the castor plant, Ricinus communis, is not a member of the bean family). Castor oil (CAS number 8001-79-4) is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is 313 °C (595 °F) and its density is 961 kg/m3.[1] It is a triglyceride in which approximately ninety percent of fatty acid chains are ricinoleic acid. Oleic and linoleic acids are the other significant components.[2]
Products for solvent finish (gelatinizing)
Synthetic plasticizer oils
These are mainly esterification products of the phthalic and adipic acid. They have a solubilizing effect on nitrocellulose and polymers.
Camphor
This is a ketone in a crystallized form. Besides having a plasticizing effect it improves the glazing properties of nitrocellulose lacquers.