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INFLUENCE OF PLASTIFIERS CONCENTRATION ON THE RELATIVE CHANGING OF SURFACE TENSION ON THE BONDERY SOLID – LIQUID

УДК 541.18.182

Abstract

There have been measured the surface tension on border «a plastifier solution - air» (δs-g) and limiting corners of moistening (θ) on the polished surface of a marble (СаСО3), having similar to chalk a chemical composition and using in this investigation as modeling system. СаСО3 surface has been polished, washed out by Na2CO3 solution and then the distilled water for determination of the limiting corner of moistening.

Keywords: plastifier, hydrophilization, viscosity, electro conductivity, reological data for this suspension, electro kinetic potential

Intensive development of many branches of industry connected with processes of obtain and application of mineral dispersion systems, raising of articles quality, improvement of their physical-technical characteristics, modernization of production and using of new modern technologies at production of materials and articles on their base aren’t possible without fundamental and applied investigations in different fields of science including chemistry of dispersion systems and surface phenomena’s. Regulation of processes of structure forming, increasing of aggregated stability and achievement of maximal fluidity of concentrated dispersion systems in dynamical and static conditions are actual problems in colloidal chemistry and physical-chemical mechanics.

At present time the direct methods of measuring of the surface tension on the boundary solid-liquid are absence and by this reason a changing of δs-l at formation of absorbed layer from molecules of surface-active compounds on the surface of hydrophilic particles of chalk was valued indirectly by changing of the work of moistening (Wm):

Wm=δs-g – δt-l = δl-g • cos θ

were: δs-g, δt-l and δl-g – surface tension correspondently on the boundary solid-gas; solid-liquid; liquid-gas;

θ – limiting corner of moistening.

The surface tension on the boundary plastifier solution – air (δs-g) and limiting corner of moistening (θ) on polished surface of marble (CaCO3), having similar to chalk a chemical composition and using in this investigation as model system, have been measured.

For determination of the limiting corner of moistening on the surface of CaCO3 the it’s sample was polished, than was washed by Na2CO3 solution and distilled water. Drop of solution was polished surface of marble by micro syringe and the limited corner of moistening was determined by method [1]. An average values obtained on the base of 5-7 parallel measuring is presented in Table 1.

Table 1. Influence of plastifiers concentration on the limiting corner of moistening of CaCO3 and surface tension on the boundary solution-air

Type of plastifier

Measured parameter

Plastifier concentration, kg/m3

0

0,0625

0,125

0,25

0,5

1

WSSASFC

Corner, degree

54,5

50,5

49,7

48,3

47,8

46,0

cos θ

0,5807

0,6361

0,6468

0,6652

0,6717

0,6947

δl-g • 103, J/m2

71,9

71,85

71,8

71,75

71,73

71,7

Wm • 103, J/m2

41,75

45,5

46,74

47,73

48,6

49,61

SB-5

Corner, degree

54,5

52,5

50,5

49

48,5

47,5

cos θ

0,5807

0,6088

0,6157

0,6428

0,6626

0,6756

δl-g • 103, J/m2

71,9

71,7

71,6

71,3

71,2

70,5

Wm • 103, J/m2

41,75

43,65

44,6

45,8

46,8

47,6

The work of moistening was determined as product of values of the limiting cornе of moistening and the surface tension on the boundary solution-air. The character of concentration influence of the investigated plastifiers on the value of the work of moistening is presented on Figure 1.

Figure 1. Influence of the plastifiers concentration on the work of moistening CaCO3: 1-WSSASFC; 2 – SB-5.

As far as the surface tension on the boundary solid-gas (σs-g) was constant the fact that increasing of the work of moistening has testified about decreasing of the surface tension on the boundary solid-solution (σs-l) at plastifiers introduction. Decreasing of values of σs-l has testified about hydrophilization of CaCO3 surface. In more degree σs-l has decreased at introduction of WSSASFC that can be explaining by greater content of oxy-groups in aromatic rings of WSSASFC molecules than in molecules of SB-5.

Investigations by influence of plastifiers on the electro-kinetic potential of particles of chalk, alumina
(Al2O3) and silica (SiO2) were carried out with using of method of the potential proceed [2]. The plastifiers additives were introduced in amount 0,1-0,3 % from mass of dispersion phase.

Calculation of the electro-kinetic potential was carried out by formula:

η • ǽ • ΔΕ

ζ = ε • ε0 • ΔР

were: ζ – electro-kinetic potential, mV;

η – viscosity of dispersing medium Pa•s;

ε – relative dielectrical of medium, F/m; ε0 = 8,85 • 10-12 F/m;

ǽ - specific electro conductivity, om-1 • m-1.

Specific electro conductivity was determined by formula:

KCl W

ǽ = ǽ WKCl

were: ǽKCl – specific electro conductivity of the standard solution of KCl;

W – electro conductivity of cell with dispersing medium, Om;

WKCl – electro conductivity of cell, filled by standard solution of KCl.

The results of investigation are presented in Table 2 and on Figures 2, 3.

Table 2. Influence of WSSASFC concentration on the value of ζ – potential

Type of dispersion phase

C, %

0

0,1

0,2

0,3

Chalk

P•10-4, Pa

- E, mV

0.00

17.2

63.0

70.3

69.8

1.568

18.8

66.0

72.9

72.1

3.136

19.7

69.1

75.5

74.6

4.704

21.0

71.9

77.8

76.6

6.272

22.5

75.0

80.1

78.7

7.840

23.8

78.0

82.3

80.5

9.406

25.1

81.2

84.3

82.1

W, mS

0.140

0.227

0.314

0.453

WKCl, mS

1.177

1.177

1.177

1.177

T, 0C

20

20

20

20

-ζ, mV

15.7

59.0

65.5

66.0

Alumina

P•10-4, Pa

- E, mV

0.00

8.5

41.3

60.5

65.4

1.568

8.7

41.9

61.2

66.1

3.136

8.8

42.7

62.2

66.9

4.704

8.9

43.5

63.1

67.7

6.272

9.0

44.1

63.9

68.2

7.840

9.1

44.7

64.5

69.0

9.406

9.2

45.1

65.0

69.7

W, mS

0.555

0.622

0.682

0.741

WKCl, mS

1.114

1.114

1.114

1.114

T, 0C

18.5

18.5

18.5

18.5

-ζ, mV

5.8

34.6

47.0

52.0

Silice

P•10-4, Pa

- E, mV

0.00

24.0

39.8

55.5

62.1

1.568

24.7

40.7

56.3

63.1

3.136

25.3

41.7

57.4

64.0

4.704

25.9

42.9

58.3

65.0

6.272

26.5

43.8

59.4

65.9

7.840

27.0

44.8

60.6

66.9

9.406

27.6

46.0

61.9

67.7

W, mS

0.220

0.371

0.497

0.647

WKCl, mS

1.147

1.147

1.147

1.147

T, 0C

19

19

19

19

-ζ, mV

10.5

29.5

40.1

46.0

Change of ζ – potential is coursed by two factors. Firstly anion active oligomeric additives owing to adsorption on surface of dispersion phase will increase an absolute value of the negative potential of surface. On the other hand as bar as forming of adsorption layer the boundary of sliding will move aside in depth of solution that decreased an absolute value of potential on the boundary of sliding.

Figure 2. Influence of additives concentration on the electro-kinetic potential of chalk particles: 1-WSSASFC; 2 – SB-5; С-3.

Figure 3. Influence of additives concentration on the electro-kinetic potential of alumina particles: 1-WSSASFC; 2 – SB-5; С-3.

The second factor has explain for example decreasing of ζ – potential by adsorption of uncharged high molecular compounds both on hydrophilic and both on hydrophobic surfaces; and it has been considered in detail in articles [3,4].

Comparison of values of the ζ – potential and reological parameters has shown that in general case the correlation between trend of changing of the electro kinetic potential and reological parameters of investigated systems was observed. Thus for chalk suspensions an addition of plastifiers WSSASFC and SB-5 in amount 0,15% has caused an decreasing τ0 nouth; the plastical viscosity has approached to it’s minimum value. At the same concentrations of oligomers the ζ – potential has increased to its maximal value (from 15 mV to 70 and 65 mV correspondently).

Definite correspondence of dependence of value τ0 and ζ – potential for SiO2 and Al2O3 suspensions was observed. At additives concentrations decreasing value of τ0 practically to nought the ζ – potential of suspensions has a maximal value by module.

WSSASFC in more degree has increased the absolute value of the ζ – potential that also is correlated with reological data for these suspensions.

Equilibrium value of pH for investigated suspensions has changed negligibly (from 7,5 to 8,0) at introduction of plastifiers at 0,3%.

Было измерено поверхностное натяжение на границе «раствор пластификатора–воздух» (σт-г) и краевые углы смачивания (θ) на отполированной поверхности мрамора (СаСО3), используемого в качестве модельной системы, имеющего близкий к мелу химический состав.

Бордың химиялық құрамына жақын келетін, модельді жүйе ретінде қолданылатын «пластификатор ерітіндісі - ауа» шекарасындағы беттік керіліс және тегістелген мәрмәр (СаСО3) бетіндегі аймақтық сулау бұрыштары өлшенді.

References

1. Savina V.A., Sherbak Y.V. High strong concretes with additives of superplastifiers // Investigation and using of concretes with superplastifiers. – M., 1982. – P.28-32.

2. Kosukhin M.M. Regulation of properties of concrete mixtures and concretes by complex additives with different hydrophilic groups: thesis; cand. techn. scienses:05.23.05 / Belgorod, 1995.-173p.

3. Bedenko V.G. Additive’s carbon-alkali reagent and reological properties of the raw shlam // Concrete, 1989. -№11. P.17-18.

4. Saviskay T.S. Influence of water soluble polymers on stability of reological properties of suspensions of biberous activated carbon. // Colloid Journal. – 2006. – V.68, №1. – P.93-99.