12 Questions
What is the primary factor that determines the ability of a liquid to spread on a smooth solid surface?
Polar nature of the solid surface
What is the function of surfactants when used to wet out repellent fabrics?
To penetrate the fabric and remove air
What is the primary function of detergents?
To remove soils from solid surfaces
What is the function of the lyophilic part of an emulsifying agent?
To adsorb onto the oil droplet
What is the primary difference between emulsifying agents and dispersing agents?
The type of material being dispersed
What is the characteristic of anionic surfactants?
They develop a negative charge on the water solubilizing end
What is the origin of the word 'Surfactant'?
From the expression 'surface active agent'
What is the characteristic feature of a surfactant molecule?
Having two ends attached by a covalent bond with diametrically opposed polarities
What is the non-polar end of a surfactant molecule?
Lyophilic (strongly attracted to organic molecules)
What is responsible for molecular interactions with water molecules in a surfactant molecule?
Hydrophilic part
What are the two structural elements of a surfactant molecule?
Hydrophilic and hydrophobic parts
How are surfactants classified?
According to use, ionic charge, and chemical structure
Study Notes
Surfactants in Textile Processing
- Surfactant is a shortened form of "surface active agent", which possesses surface activity due to its chemical structure.
- A surfactant molecule has two ends with diametrically opposed polarities: a non-polar (lyophilic) end and a strongly polar (lyophobic) end that is hydrophilic.
- The duality of polarity causes the molecule to align itself with respect to the polar nature of the surfaces it contacts.
Structure of Surfactants
- Surfactants contain two structural elements:
- A hydrophilic part (polar) that interacts with water molecules, which can bear a positive or negative charge, or contain multiple polar groups.
- A hydrophobic part (non-polar) that exhibits low polarity and does not interact with water molecules, represented by long chain hydrocarbons, perfluoroalkyl groups, and alkylaromates.
Classification of Surfactants
- By Use:
- Wetting Agents: reduce surface tension, enabling liquids to spread on non-polar solid surfaces, and are used to wet out repellent fabrics.
- Detergents: reduce water's surface tension, adsorb onto soil surfaces, and keep soil suspended to prevent redeposition.
- Emulsifying Agents: convert water-insoluble oils into stable, aqueous suspensions, and add a charge-charge repulsion field to keep droplets separated.
- Dispersing Agents: disperse solid particulate matter, similar to emulsifying agents, but with a lyophilic part that adsorbs onto the particle's surface.
Classification by Ionic Charge
- Anionic surfactants: develop a negative charge on the water solubilizing end, and comprise almost 70% of commercial surfactants, with a negatively charged group in their active molecule part.
- Cationic surfactants: develop a positive charge on the water solubilizing end, with a positively charged group in their active molecule part.
Learn about surfactants, their properties and uses in textile processing. Understand the chemical structure and surface activity of surfactant molecules.
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