What Is Diglycerin?
Diglycerin, or diglycerol, is a polyhydric alcohol formed by the dimerization of two glycerol molecules, resulting in a compound with four hydroxyl groups. Classified under the Fire Service Law as both a “Class 4 Hazardous Substance” and “Class 3 Petroleum,” it presents as a colorless, odorless, viscous liquid. Produced through the dehydration-condensation of glycerin, diglycerin is purified from a mix that includes triglycerin via distillation.
Its hygroscopic nature and excellent moisture retention make it a favored moisturizer in cosmetics, alongside various industrial applications such as raw materials for urethane and surfactants, and as a plasticizer for water-soluble polymers.
Uses of Diglycerin
In cosmetics, diglycerin is prized for its skin compatibility, enhancing hydration without irritation, and is found in lotions, facial cleansers, and massage gels. Industrially, it serves as a versatile raw material in polyurethane production, surfactant synthesis, and as a highly polar stationary phase in gas chromatography due to its four reactive hydroxyl groups.
Properties of Diglycerin
Water and ethanol soluble but ether insoluble, diglycerin boasts a flash point of 190-202°C and a specific gravity of 1.29. Comparatively, it offers a lighter skin feel than glycerin and poses a lower risk of promoting acne-causing bacteria.
Structure of Diglycerin
The molecular essence of diglycerin involves the condensation of two glycerol units, retaining four hydroxyl groups, which contribute to its hydrophilic nature. Its chemical formula is O [CH2CH (OH) CH2OH]2, indicating its capacity for forming derivatives like diglycerin fatty acid ester when an ester bond is introduced.
Other Information on Diglycerin
Surfactants With Diglycerin Structure
Diglycerin-based surfactants, such as diglycerol fatty acid esters, exhibit hydrophilic and hydrophobic properties determined by the fatty acid types esterified to the diglycerin backbone. These include variants like diglycerin laureate, stearate, and olate, with surfactant performance varying based on the fatty acid chain length. However, full esterification of all hydroxyl groups eliminates its surfactant functionality by removing the hydrophilic group.