PPG-8 is the INCI name of a chemical substance being a polyoxypropylenodiol-type polyol. The group it comes from (polyols) is a result of its structure that consists of characteristic multivalence alcohols which have at least two hydroxyl groups per molecule. These specialised compounds are industrially used as reactants in the manufacturing of polyurethane (PUR) foams. Polyoxypropylene diol, also called propoxylated propylene glycol or polypropylene oxide (PPG), is a common elastic reactant. Due to its structure, PPG-8 is an example of a surface active compound with non-ionic features. The global CAS number of PPG-8 is 25322-69-4.
Due to its polymeric structure, the average mass of PPG-8 is relatively high, around 450 g/mol. The structure of this chemical compound is bi-functional given the presence of as many as two hydrophilic groups per molecule. It is them that determine its non-ionic properties as a surface active agent. PPG-8 is a component which, amongst many other desirable features, shows anti-foaming properties which are required in many formulations used in industrial processes. In normal conditions, at room temperature, PPG-8 is a colourless, odourless, high-clarity liquid with a relatively high viscosity. It shows a low freezing point of below -20oC, so it does not have the cloud point characteristic of surfactants. PPG-8 perfectly dissolves in cold water, but its solubility decreases along with increasing temperature. Compared to other popular organic solvents, it is mixable in any proportion, the only exception being long-chain aliphatic hydrocarbons. Its good mixability refers not only to liquids but also to organic solids. Other properties interesting to the manufacturers of industry formulations include excellent spreadability and low vapour pressure of PPG-8. At an extremely high temperature, during pyrolysis, it does not produce coke or lacquer. The products of such thermal decompositions are chemical compounds with a low boiling point.
Many chemical formulations, mostly those used in industry, want their ingredients to show features such as PPG-8. In the paper industry, food processing (e.g. in sugar production), during the production of emulsion paints and fermentation tanks, they search for such ingredients that are capable to prevent the formation of foam. PPG-8, as a defoaming ingredient, perfectly proves itself in each such process. That polyol also plays a great role in synthesizing other anti-foaming agents. PPG-8 is thus a commonly applied reactant, a debonding plasticizer used for further chemical modification of more structurally diversified defoaming agents with the use of fatty acids. As a debonding agent, it reduces the adhesion of surfaces to other bodies. As a plasticizer, it plays many roles beneficial during reactions, for example it enhances elasticity, workability and solidity of mixtures, reduces water, improves resistance to moisture and low temperature, and positively contributes to the increase of cohesion. PPG-8 is also a raw material for the production of resins, lubricants and metal working fluids. It can also be used as a solvent or coupling agent in the production of printing inks, where it also serves as a solvent for fountain solutions, which are wetting agents applied in offset printing. Owing to such a factor as high wetting properties, it is also an excellent raw material for the production of dying pastes for polyurethane foams and pesticide preparations. In cosmetics, PPG-8 is applied as an emolient and a softening agent. Ingredients with such features allow for restoring and keeping the appropriate level of moisture, lubrication and flexibility of skin and hair. PPG-8 thus facilitates the protection against an excessive loss of water and safeguards the surface by forming a thin protective layer. It is often used in such cosmetics as shower gels, creams, shampoos or balsams. The possibility to combine PPG-8 with other chemicals also supports the formation of a specific foam which, given the nature of the process, is desired in the flotation of carbon as well as copper, iron, lead and nickel ores.
