Material selection formulation ingredients

Liquid Dosage Forms. Simple aqueous solutions, symps, elixirs, and tinctures are prepared by dissolution of solutes in the appropriate solvent systems. Adjunct formulation ingredients include certified dyes, flavors, sweeteners, and antimicrobial preservatives. These solutions are filtered under pressure, often using selected filtering aid materials. The products are stored in large tanks, ready for filling into containers. QuaUty control analysis is then performed. 

The strength properties more often specified for plastics materials are (1) tensile strength and elongation, (2) flexural strength, (3) Izod and Gardner impact, and (4) heat deflection temperature under load. Our purpose here is not to describe each test in detail but to point out some of the known effects that colorants and other formulation ingredients can have on these properties. Table 22.1 lists the ISO and ASTM test methods for most of the physical properties, and ref. 1 (pp. 7-112) describes each of the methods in detail. Table 22.2 lists typical values of the above cite four properties for selected thermoplastics. 

Preservative protection. This involves selection of raw materials that act against micro-organism proliferation, and/or the selection of chemical preservatives benign to both other formulation ingredients and packaging materials. Furthermore, the concentrations used must be verifiably compatible with the skin and yet provide sufficient protection for the formulation. 

Several typical or starting point solution pressure sensitive adhesive formulations illustrating some of the uses described above are given in Table 4. They are provided for general guidance on materials selection and quantity but likely require modification to suit specific ingredients, manufacturing, and finished property requirements. 

The raw materials used in a particular product may present some challenges to the formulation chemist when selecting the most appropriate preservative. Problem ingredients may act as microbial nutrients, preservative inactivators or preservative adsorbers and careful testing and assessment of the preservative system is necessary in these cases. One notable example of this is the inactivation of parabens esters by certain non-ionic surfactants. 

Gun propellants are manufactured by three different methods (i) solvent method (ii) semi-solvent method and (iii) solventless method. The solvent method is that most commonly used for the manufacture of gun propellants. Selection of the method for manufacture basically depends on the properties of the raw materials and the propellant formulation. While there are limitations for the manufacture of gun propellants by solventless and semi-solvent methods, the solvent method may be applied for almost every gun propellant formulation. The solid-liquid ratio of the ingredients and the type of nitrocellulose used usually decide the feasibility of manufacture by the solventless method. Some characteristics of solid gun propellants are given in Table 4.1. 

All three grades of mannitol showed similar, relatively low BFI values. This low tendency for brittle fracture represents a very significant advantage of mannitol, particularly with direct compression formulations where material properties, and not powder processing, must be used alone to overcome deficiencies of the API and other ingredients. It should be remembered that low BFI is but one consideration of many when selecting excipients for direct compression formulations. 

Liquid products are approximately 50 to 60 percent water, with the remainder being a combination of surfactants, builders, foam regulators, enzymes and enzyme stabilizers, hydrotropes, antiredeposition polymers, optical brighteners, corrosion inhibitors, dye, and perfume. Two-in-one formulations also contain antistatic and fabric softening ingredients. Liquid systems require careful selection and blending of raw materials to achieve a stable product. Special attention is necessary for the following items. 

Formulation scientists usually formulate their product to be used alone in water. The potential of tank mixes or the use of liquid fertilizers as a carrier liquid is considered later in the formulation development process. Obviously, the environment a formulation will encounter in use is very different when it is mixed with one or more agrichemicals as compared to the formulation being mixed in pure water. Rather than having one active ingredient present with surfactants carefully selected to disperse that formulation, two or three active materials with six or eight different surfactants may be present in the spray tank. No wonder there are incompatibilities ... 

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