**3.3 Determining filler activity by cohesive strength of the pitch matrix film on the filler surface**

Another way to determine the activity of the filler is determining the cohesive strength of the pitch composite in the film state on the filler surface. The more active the filler with respect to the pitch binder, the more IFL is structured on the surface of the filler and, correspondingly, the higher its strength.

We solved the problem of determining the strength of the matrix in the film as follows.

In the filling region, which is characterized by the falling section of the curve of the dependence of the strength of the composite on the degree of its filling (**Figure 4**), the strength of the pitch matrix does not change, despite the reduction in the overall strength of the pitch composite. The loss of strength curve in this descending section is approximated by a straight line:

$$\mathbf{y} = \mathbf{b} - a\mathbf{x} \tag{6}$$

**27**

ing in works [27, 28].

**Figure 6.**

*straight line.*

low modulus filler.

addition of a filler when x = 0.

*Determining the Filler Activity in the Sintering of Pitch Composites*

anthracite. By the way, anthracite, as a standard, is used to estimate coal by sinter-

*Approximation of the falling branch of the dependence of the strength of the pitch composite with the coke by a* 

Testing the strength of a semicoke from pitch without filler cannot give an estimate of the pitch sintering. The reason is that when the pitch is heated and sintered during solidification, the solids are formed, which in fact play the role of the filler, which is unevenly distributed in volume. Therefore, such a semicoke is heterogeneous in terms of physical and mechanical properties [29]. In addition, the sintered material contains an uncontrolled amount of pores, which are, in essence, a

Monitoring of the quality of the B1 (softening point 72°C) and V (softening point 86°C) at the factory (**Tables 4** and **5**) showed that the sinterability (σ0) of the pitches was significantly higher than the other indicators' quality for these pitches. This means that it is more sensitive than the rest (the error in determining σ0 is 5%). As a coefficient of measure, free term of the equation (**Table 4** of Eqs. (1)–(6) and **Table 5** of Eqs. (1)–(7)) is adopted. The physical meaning of the free term of these equations is the strength of the semicoke of the pitch film in the absence of the

**3.4 Determining filler activity by work of destruction of pitch composite**

The area under the dependence curve of the strength of semicoke samples from composites is an integral characteristic—the work of destruction. The term "work of destruction" is used in the physics of polymers [30, 31]. The work of destruction, in fact, is the energy used to overcome the forces of grip (in our case, the sintering) between the pitch matrix and the filler, so this figure can be taken as a measure

*DOI: http://dx.doi.org/10.5772/intechopen.82012*

where *y* is the strength of the composite and x is the filler content. One can estimate the strength of the "film" pitch matrix by extrapolating this linear dependence on the ordinate axis, which gives the value of the strength of the semicoke of the pitch matrix (film) without the filler (for x = 0). The extrapolation value obtained by extrapolation at zero fill (σ0) (**Figure 6**) is simultaneously a measure of the activity of the filler and at the same time can serve as a measure of the sinter ability of the pitch.

The sintering thus determined is an indicator of the peculiarity of the pitch to a specific filler. The same pitch with another filler will have a different sintering, because the sintering process depends on the nature of the filler and its physical–chemical interactions with the binder. **Figure 6** shows the variant of approximation of the falling part of the curve of the strength of the pitch composite on the content of coke in it.

In order to compare the pitch with each other, you can enter the parameters of sintering and sinter ability with respect to the filler standard, for example,

*Determining the Filler Activity in the Sintering of Pitch Composites DOI: http://dx.doi.org/10.5772/intechopen.82012*

*Fillers - Synthesis, Characterization and Industrial Application*

**3.3 Determining filler activity by cohesive strength of the pitch matrix film on** 

*The microstructure model of the pitch composite: a – a binder in the film on the surface of the filler; b – with* 

Another way to determine the activity of the filler is determining the cohesive strength of the pitch composite in the film state on the filler surface. The more active the filler with respect to the pitch binder, the more IFL is structured on the

We solved the problem of determining the strength of the matrix in the film as

In the filling region, which is characterized by the falling section of the curve of the dependence of the strength of the composite on the degree of its filling (**Figure 4**), the strength of the pitch matrix does not change, despite the reduction in the overall strength of the pitch composite. The loss of strength curve in this descending section is

*y* = *b* − *ax* (6)

where *y* is the strength of the composite and x is the filler content. One can estimate the strength of the "film" pitch matrix by extrapolating this linear dependence on the ordinate axis, which gives the value of the strength of the semicoke of the pitch matrix (film) without the filler (for x = 0). The extrapolation value obtained by extrapolation at zero fill (σ0) (**Figure 6**) is simultaneously a measure of the activity of the filler and at the same time can serve as a measure of the sinter

The sintering thus determined is an indicator of the peculiarity of the pitch to a specific filler. The same pitch with another filler will have a different sintering, because the sintering process depends on the nature of the filler and its physical–chemical interactions with the binder. **Figure 6** shows the variant of approximation of the falling part of the curve of the strength of the pitch composite on the content of coke in it. In order to compare the pitch with each other, you can enter the parameters of sintering and sinter ability with respect to the filler standard, for example,

surface of the filler and, correspondingly, the higher its strength.

**26**

**the filler surface**

*pitch deficit: 1 – filler particles, 2 – semi-coke of the matrix.*

approximated by a straight line:

ability of the pitch.

follows.

**Figure 5.**

**Figure 6.** *Approximation of the falling branch of the dependence of the strength of the pitch composite with the coke by a straight line.*

anthracite. By the way, anthracite, as a standard, is used to estimate coal by sintering in works [27, 28].

Testing the strength of a semicoke from pitch without filler cannot give an estimate of the pitch sintering. The reason is that when the pitch is heated and sintered during solidification, the solids are formed, which in fact play the role of the filler, which is unevenly distributed in volume. Therefore, such a semicoke is heterogeneous in terms of physical and mechanical properties [29]. In addition, the sintered material contains an uncontrolled amount of pores, which are, in essence, a low modulus filler.

Monitoring of the quality of the B1 (softening point 72°C) and V (softening point 86°C) at the factory (**Tables 4** and **5**) showed that the sinterability (σ0) of the pitches was significantly higher than the other indicators' quality for these pitches. This means that it is more sensitive than the rest (the error in determining σ0 is 5%). As a coefficient of measure, free term of the equation (**Table 4** of Eqs. (1)–(6) and **Table 5** of Eqs. (1)–(7)) is adopted. The physical meaning of the free term of these equations is the strength of the semicoke of the pitch film in the absence of the addition of a filler when x = 0.
