Nonionic surfactants
As non-ionic surfactants or nonionic surfactants are called surfactants , which no dissociable functional groups contained and, therefore, not in the water in ion separate. Like every surfactant, nonionic surfactants are also made up of a non-polar and a polar part. As a non-polar part is mostly a fatty alcohol (C 12 -C 18 ) or octyl or nonyl phenols . The polar groups here are the hydroxyl group and the ether group . These groups are found in polyethylene glycol or monosaccharides .
Typical representatives
| class | general molecular formula |
Examples |
|---|---|---|
|
Polyalkylene glycol ethers (fatty alcohol ethoxylates (FAEO)) |
CH 3 - (CH 2 ) 10-16 - (OC 2 H 4 ) 1-25 -OH | |
| Fatty alcohol propoxylates (FAPO) | CH 3 - (CH 2 ) 10-16 - (OC 3 H 6 ) 1-25 -OH | |
| Alkyl glucosides | Polysorbate 20 (Tween 20), octyl-β-glucoside , N-octyl-β-D-1-thioglucopyranoside | |
| Alkyl polyglucosides (APG) | CH 3 - (CH 2 ) 10-16 - (O-glycoside) 1-3 -OH | |
| Octylphenol ethoxylates | C 8 H 17 - (C 6 H 4 ) - (OC 2 H 4 ) 1-25 -OH | Octoxinol-9 (Triton X-100) |
| Nonylphenol ethoxylates | C 9 H 19 - (C 6 H 4 ) - (OC 2 H 4 ) 1-25 -OH | Nonoxinol-9 |
There are also other nonionic surfactants of different classes of substances, e.g. B. 3,5-dimethyl-1-hexyn-3-ol (Surfynol 61),
Manufacturing
The ethoxylate types are obtained by reacting fatty alcohol or phenol with ethylene oxide .
important terms
HLB value
The HLB value (hydrophile-lipophile balance) indicates the mass ratio between the polar and the non-polar part. Surfactants with a low HLB value have good fat-dissolving properties, a high HLB value results in good wetting of hydrophilic surfaces. Due to different HLB values, stable emulsions - O / W to W / O systems can be built up.
Cloud point
The cloud point is the temperature at which a non-ionic surfactant solution (1 g / 100 ml) becomes cloudy. The higher the HLB value, the higher this temperature is. The cloud point is therefore a quality feature. Depending on the method, the cloud point is determined in water, 1% NaCl solution or 25% butyl diglycol solution. The cloud point is also dependent on the surfactant concentration.
ecology
Nonylphenol ethoxylates are ecologically questionable, they are in part readily degradable , but the degradation products (especially nonylphenol) are suspected of having a hormone-active ( estrogenic ) effect. This is why the chemical industry has voluntarily refrained from using them for a long time.
Fatty alcohol ethoxylates are degradable to different degrees. Fatty alcohol ethoxylates that are based on linear (unbranched) fatty alcohols that have only been reacted with ethylene oxide and the terminal -OH group left in place are the most degradable. Reactions of the alcohol with ethylene oxide / propylene oxide (EO / PO) are less biodegradable. The degradability is also detrimental if the terminal alcohol group is converted to the ether (end group-capped).
Alkyl polyglucosides are the “model boys” among surfactants. They are easily degradable and can be made entirely from renewable raw materials .
See also
Individual evidence
- ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, pp. 503-504.