9 - Surfactants (Book)

surfactants

• surface and interfacial phenomena

• formation of aggregates

• wetting agents; enables the optimum spread of an active substance on the entire surface of a plant

• can remove oil, fat and grease

• dispersion of pollutants from oil and gas activities into water and enhance their biodegradation

Surfactants

main functions are:

• skin cleansing (by removing the lipid surface layer)

• modification of the skin surface

• enhancement of the penetration of active ingredients

• often the ‘heart’ of a cosmetic formulation

surfactant

a substance that has the property of adsorbing onto the surfaces or interfaces of a given system, and remarkably alter the surface or interfacial free energies of those surfaces or interfaces

interface

a boundary between any two immiscible phases

surface

indicates an interface, represented by a gas (or usually air) in contact with a liquid or a solid

interfacial free energy

minimum amount of work required to create a unit area of the interface or to expand it by a unit area

interfacial free energy per unit area

what we measure when we determine the interfacial tension between two phases and is a measure of the difference in nature of two dissimilar phases

surfactant

• amphiphilic substances; have groups with antagonistic characteristics in their molecular structure

• reduce the amount of work required to expand them and mitigate the application of a cosmetic

• alkyl aryl sulphonates

• sulphated alcohols

At the end of World War II, _____ were mainly used for cleaning, while ______ were preferably used in shampoo

• propylene tetramer (TP)

• benzene

After World War II, an adduct of ______ and ______ became a predominant feedstock for the surfactant industry. Recognized as pollutants due to their persistent foam in rivers and lakes

Non-polar groups

mainly derived from petrochemical or oleochemical raw materials

Petrochemical raw materials

materials derived exclusively from petroleum

oleochemicals

• derived from vegetable or animal sources

• greater market acceptance than those of petrochemical origin

product specification

set of characteristics that meet legal, quality, toxicological, environmental, safety, sensory, market and, above all, functional requirements

Ethoxylation

• This reaction is regarded as a polyaddition, but it is a nucleophilic substitution, where the weak nucleophilic agent has increased its nucleophilicity by a previous reaction with a strong base

• introduces a polyether moiety into the molecule, which is responsible for its solubility in water

• used to create non-ionic surfactants

Propoxylation

same process as ethoxylation but with the use of propylene oxide as an electrophile

Alkoxylation

generic name of ethoxylation and alkoxylation

Hydrogenation

Unsaturated fatty chains are prone to undergo oxidation and form oxides and peroxides, which cause rancidity and yellowing.

Sulphation

A reaction that introduces a sulphate group into an organic molecule, making the surfactant anionic.

Sulphonation

A reaction that introduces a sulphonate group into an organic molecule, making the surfactant anionic

Esterification

• Functionalization reaction of the molecule, making it an ester of variable solubility in water

• used to make non-ionic biodegradable surfactants, normally used as emulsifiers and emollients

• Functionalization reaction of the molecule. The amide bond is strong and resists better to hydrolysis when compared to ester bonds

• used to make non-ionic surfactants

Quaternization

Reaction of a tertiary amine with sodium monochloroacetate, methyl chloride

Clarification

• Chemical process that employs oxidizing agents to ‘decompose’ coloured by-products

• used to improve the colour of surfactants

Deodorization

Removal of volatile products that cause odour or other normally unwanted effects on products (dioxane, for example).

Filtration

Removal of dust or any other particulate that may affect product appearance.

Distillation

• Physical separation of products of different boiling points by means of temperature and/or pressure gradients

• helps to improve product odour and toxicity

Blending

• Operation to incorporate additives to surfactants or to blend surfactants to form dispersed, emulsified concentrates or simple solutions

• makes it possible to handle viscous materials and enhances productivity

Drying

this process using spray driers or vacuum to allow for preparation of powder surfactants

Pelletizing

Obtaining products in the form of pellets, which facilitate handling and fractionation by cosmetic producers

Preservation

• Addition of preservatives to avoid microbial contamination of surfactants and finished products

• placed in surfactants with more than 30% water

based on structure

most common way to classify surfactants

gemini surfactants

Surfactants containing two or more non-polar chains and two or more polar heads

Anionic surfactants

• possess a negative charge in their hydrophilic portion when dissolved in water