Unaxial tensile strength of polymer fluids

Third Europ. Rheol. Conf., Edinburg, Elsevier Applied Science, London, Cand, New York, 1990.

Abstract

     In dependance of the volume concentration of a filler there are two different rupture mechanisms that are realising for dispersion-filled high polymer melts.

Introduction

     At high deformation rates polymer fluids may loos their ability to flow as long as necessery and can break according to cured rubber long-term durability mechanism. In [1] for the first time the condition of fluid "high polymers" rupture at unixial extention was determined as follows:

/( - *) = cost > 0; > *           (1)

where: - the true break stress, * - the rupture recoverable deformation (Hencky measure), * - the critical recoverable deformation, below which the rupture probability is equal to zero. The rupture of cured high polymers may occur at any value of deformation and thus for them * = 0 [2], but in case of "high polymer melts" rupture * 0 and it does not depend on loading conditions and temperature [1, 3].

Materials and Methods

     On Fig 1-3 there are represented the results of investigation of dispersion-filled "high polymer melts" rupture. In a regime of constant rate of unixial deformation at temperature 293 K series of experiments were carried on the base of 1,2-polybutadien (PB) with MM = 1.8 x 10⁵ and M_w/M_n = 1.3. It contained 84% 1,2-units , its glass temperature was equal to 256 K. As despersed fillers were used shale-ash and radiation-cured up to the glass and then milled 1,2-PB. An average size of particles in both cases was equal to 20 mkm.

Results

     As shown in Fig. 1 the conditions of durability (1) stays the same, but the value * falls linearity with the increase of filler concentration _vol and does not depend on type or nature of filler. There is a critical concentration of a filler _cr = 25%_vol - such, that at > _cr  * = 0 (Fig. 2).
     At > _cr the filled polymer melts may break at any recoverable deformation, but in such cases the kind of the dependance 
- changeg qualitatively (Fig. 3). As shown in Fig. 3 there are limited maximally achievable rupture stresses and recoverable deformations at unixial  extention for highly-filled polymer melts. 

 Figure 1. Rupture stress * versus rupture recoverable deformation . 1. - PB; 2. - (PB + 10%_vol of shale-ash); 3. - (PB + 15%_vol of cured PB); 4. - (PB + 20%_vol of shale-ash). 

 Figure 2. Critical recoverable deformation * versus volume concentration of a filler .

Figure 3. Rupture stress * versus rupture recoverable deformation . 1. - PB; 2. - (PB + 25%_vol of cured PB); 3. - (PB + 30%_vol of shale-ash).

References

1. E.K. Borisenkova, O.Yu. Sabsai, M.K. Kurbanaliev, V.E. Dreval, G.V. Vinogradov, Polymer, 1978, Vol. 19, December, p. 1473.
2. Smith T., in Rheology (ed. F.R. Eirich), Acad. Press, N.-Y., 1969, 5, p. 143.
3. Chalaya N.M., Sabsai O.Yu, Abramov V.V. Progressing of filled composit materials, Moscow, NPO Plastic, 1982, p. 80.