Aqualon ethylcellulose (EC) is a cellulose ether distinguished by its versatility. As a unique product with wide-ranging solubility and flexibility at low temperatures, ethylcellulose is frequently used in electronics in addition to a variety of other applications. It provides high solution clarity, good thermal stability, even burnout and has very low decomposition temperatures.
Aqualon EC is a key binder for gravure printing inks as well as a thickening binder in flexographic and screen printing inks. In these applications, Aqualon EC polymers provide scuff resistance, adhesion, fast solvent release, film formation and outstanding rheology control.
Aqualon EC is soluble in a wide range of organic solvents. Typically, Aqualon EC is used as a non-swellable, insoluble component in matrix or coating systems.
Aqualon EC can be used to coat one or more active ingredients of a tablet to prevent them from reacting with other materials or with one another. It can prevent discoloration of easily oxidizable substances such as ascorbic acid, allowing granulations for easily compressed tablets and other dosage forms.
Aqualon EC can be used on its own or in combination with water-soluble components to prepare sustained release film coatings that are frequently used for the coating of micro-particles, pellets and tablets. The improved compressible grade, Aqualon T10 EC, was developed with optimized compactibility (high ethoxyl content and low viscosity) and good powder flow. The PHARM grades of Aqualon EC are compliant with the monograph requirements of the National Formulary and the European Pharmacopoeia.
Ethylcellulose is a cellulose ether made by the reaction of ethyl chloride with alkali cellulose, as expressed by the reaction: RONa C2H5CI → ROC2H5 NaCI, where R represents the cellulose radical.
The structure that is most widely accepted for the cellulose molecule is a chain of ß anhydroglucose units joined together by acetal linkages. This is indicated in Figure 1a. These long, oxygen-linked anhydroglucose-unit chains have great strength, which is passed on to cellulose derivatives such as nitrocellulose, cellulose acetate, and ethylcellulose. The properties of flexibility and toughness in these derivatives are directly attributable to this long-chain structure.
From the top figure, it is seen that each anhydroglucose unit has three replaceable OH groups, all or part of which may react as indicated in the reaction cited earlier. Complete substitution of all three groups would give the triethyl ether possessing a substitution value of 3, or 54.88 percent ethoxyl, which is illustrated in the bottom figure. The completely substituted triethylcellulose has no commercial significance, however, because it lacks strength and flexibility, is not thermoplastic, and shows extremely limited compatibility and solubility. The commercial product, which exhibits the remarkable combination of useful properties cited in the introductory paragraphs, has a substitution value between 2.25 and 2.60 ethoxyl groups per anhydroglucose unit, or 44-52 percent ethoxyl content.