Ethanaminium, 2-hydroxy-N-(2-hydroxyethyl)-N,N-dimethyl-, esters with C16-18 and C18-unsatd. fatty acids, chlorides

Surface tension

Link to relevant study record(s)

Reference

Endpoint:

surface tension

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25.09.2008 to 09.03.2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

the test system, however, proved to be unsuitable for this kind of substance

Qualifier:

according to guideline

Guideline:

OECD Guideline 115 (Surface Tension of Aqueous Solutions)

Version / remarks:

(1995)

Qualifier:

according to guideline

Guideline:

EU Method A.5 (Surface Tension)

Version / remarks:

(2008)

GLP compliance:

yes (incl. QA statement)

Type of method:

OECD harmonised ring method

Surface tension:

68.3 mN/m

Temp.:

20 °C

Conc.:

15.2 mg/L

Surface tension:

< 40 mN/m

Temp.:

20 °C

Conc.:

15.2 mg/L

The surface tension of MDEA-Esterquat (Rewoquat V 10057) was investigated in a study conducted according to OECD Guideline 115 (Surface Tension of Aqueous Solutions; 1995) and EU Method A.5 (Surface Tension; 2008). A mean surface tension (5 -9 measurements) of 68.3 mN/m at 20°C was determined. The result in this test is not in line with the expected surface tension behaviour of the test substance. Cationic surfactants carrying two C18 alkyl chains, such as MDEA-Esterquat, are designed to possess surface active properties and typically exhibit surface tension values as low as 27 mN/m (depending on the area per molecule) when studied on a Langmuir film balance. Typically, molecules dissolved in water tend to adsorb to the air/water interface in the form of a monolayer, often in the form of aggregates of spherical micelles. As a consequence, the surface tension of water (72 mN/m) is somewhat reduced. Double-chain surfactants, however, cannot form spherical micelles for geometric reasons and tend to form bilayer aggregates such as vesicles (Sperically closed bilayers) at the air/water interface. Another aspect which has to be considered with respect to bilayer aggregates is the presence of a phase transition temperature of the alkyl chains within the bilayer. In the so-called solid-analogue state, the alkyl chains are crystallized, and there is neither flexibility of the bilayer vesicle nor any lateral diffusion of the amphiphiles within the bilayer. Above the transition temperature, the alkyl chains in the bilayer are molten and the quat molecules have some mobility within the layer. For double-chain cationic amphiphiles carrying predominantly saturated C18 alkyl chains, like MDEA-Esterquat, this transition temperature is well above room temperature, typically in the range of 40 -45°C. The presence of crystallized alkyl chains at 20°C has important implications for the determination of surface activity according to the OECD guidelines. When a solid surfactant aggregate reaches the air/water interface, there is no mobility of the (crystallized) surfactant molecules which could allow the formation of a surfactant monolayer. Hence, the surface tension will not be significantly reduced. Therefore, the results obtained in the present study only confirm that surface tension measurements below the melting point of double-chain amphiphiles do not yield meaningful results when using the ring method.

Conclusions:

The surface tension of MDEA-Esterquat C16-18 and C18 unsatd. was investigated in a study conducted according to OECD Guideline 115 (Surface Tension of Aqueous Solutions; 1995) and EU Method A.5 (Surface Tension; 2008). A mean surface tension (5 -9 measurements) of 68.3 mN/m was determined. The result in this test is not in line with the expected surface tension behaviour of the test substance. Cationic surfactants carrying two C18 alkyl chains, such as MDEA-Esterquat C16-18 and C18 unsatd. , are designed to possess surface active properties and typically exhibit surface tension values as low as 27 mN/m (depending on the area per molecule) when studied on a Langmuir film balance. Therefore due to the intrinsic properties (crystallization) of this double-chain cationic amphiphile at temperatures below the melting point no reliable results were obtained using the ring method.

Executive summary:

The surface tension of MDEA-Esterquat C16-18 and C18 unsatd. was investigated in a study conducted according to OECD Guideline 115 (Surface Tension of Aqueous Solutions; 1995) and EU Method A.5 (Surface Tension; 2008). A mean surface tension (5 -9 measurements) of 68.3 mN/m was determined. The result in this test is not in line with the expected surface tension behaviour of the test substance. Cationic surfactants carrying two C18 alkyl chains, such as MDEA-Esterquat C16-18 and C18 unsatd. , are designed to possess surface active properties and typically exhibit surface tension values as low as 27 mN/m (depending on the area per molecule) when studied on a Langmuir film balance. Therefore due to the intrinsic properties (crystallization) of this double-chain cationic amphiphile at temperatures below the melting point no reliable results were obtained using the ring method.

Description of key information

A mean surface tension of 68.3 mN/m at 20°C was determined. 

Additional information

The surface tension of MDEA-Esterquat C16-18 and C18 unsatd. was investigated in a study conducted according to OECD Guideline 115 (Surface Tension of Aqueous Solutions; 1995) and EU Method A.5 (Surface Tension; 2008).

The result in this test is not in line with the expected surface tension behaviour of the test substance (please refer to the discussion on surface tension in the Endpoint summary "Physical and chemical properties").