Structure and preparation of polyalkylene glycol (PAG)
Polyalkylene glycols (PAGs) are polymers obtained by reaction of alkyl oxides, such as ethylene, propylene or butylene oxide, with compounds containing active hydrogen. Most often they are mono- or polyhydric alcohols and organic acids. The most popular polyalkylene glycols are homopolymers of ethylene and propylene oxide as well as block and statistical copolymers EO / PO.
What are the properties of compounds from the PAG group?
PAGs are divided into soluble and insoluble in water. The higher the content of propylene oxide in the chain, the lower the solubility of these compounds in water. Depending on the structure and length of the chain, substances with very different properties are obtained. One of the most important parameters describing this group of compounds is the kinematic viscosity, which increases with the increase of molecular weight of the polymer. The parameter closely connected to this is the viscosity index, calculated on the basis of the kinematic viscosity determined at 40°C and 100°C. The viscosity index indicates the stability of the kinematic viscosity under varying temperature conditions.
Polyalkylene glycols are characterized by excellent lubricating properties. Due to which, they protect machines and devices from wear, extending their life. They are distinguished by temperature-stable properties, which is indicated by the value of the viscosity index. Polymers belonging to the PAG group are also characterized by thermal stability – depolymerization occurs at temperatures above 200°C.
Where are the polyalkylene glycols used?
Polyalkylene glycols are used, inter alia, as synthetic base oils for lubricants and as functional additives for lubricants and for formulation of metalworking fluids.
Polyalkylene glycols are used in hydraulic fluid formulations, metalworking fluids, gear oils, turbine oils, compressor oils and liquid heat carriers. They are also used for packaging of flame-retardant hydraulic fluids, runway de-icing liquids or circulating fluids in cooling systems. PAGs are also used as anti-foaming agents and additives that improve lubricating properties of synthetic processing fluids.
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