Issue 41

E. Nurullaev et alii, Frattura ed Integrità Strutturale, 41 (2017) 369-377; DOI: 10.3221/IGF-ESIS.41.48 370 Structural and mechanical dependence of conventional stress  ( ) from relative elongation degree  ( ) in case of no lamination between filler particles and polymer binder, for example in road asphalt covering, was proved in previous work [1]. Nowadays it is important to develop polymer composite material [2] as a covering for roofs of residential and industrial buildings, sports grounds, and road asphalt with advanced service life in comparison with commonly used PCM. To accelerate development of mentioned polymer composites, it is necessary first of all to investigate relation between molecular structure of polymer binder, effective extent of volume filling, mechanical characteristics and mechanical fracture energy of PCM [3]. Previously we have shown that effective mole concentration of transverse chemical and intermolecular bonds is key structural parameter of 3D-linked elastomers filled with solids and based on low-molecular rubbers with terminal functional groups [4]. Unfortunately mechanical characteristics of 3D-linked rubbers are usually evaluated without construction of envelopes of sample rupture points according to T. L. Smith at uniaxial tension and different temperatures and deformation rates [3, 5]. The latter enable to predict service life of advanced PCM in different coverings. This work is intended to investigate numerically the dependence of conventional rupturing stress and mechanical fracture energy at uniaxial tension from fractional composition of dispersed filler, plasticizer volume fraction in polymer binder, effective density of transverse bonds, applied to development of covering for different purposes and with advanced service life in temperature range from 223 to 323 K. O BJECT OF NUMERICAL EXPERIMENT bject of numerical experiment is 3D-linked polymer composite material based on mixture of high-molecular rubbers: isoprene of grade IR and butadiene of grade BR. [6, 7]. Linking agent – sulfur; vulcanization accelerator – tetralkyltiuramdisulfide (“tiuram-D”); catalyst of cross-linking reaction – zinc oxide [6]. Plasticizing oil is used as a plasticizer [7]. Dispersed filler – silica (silicon dioxide, silica sand) with different fractional compositions. T HEORETICAL PART omputer prediction (calculation) for diagram of uniaxial tension of filled elastomer sample is based on description of its structural and mechanical behavior [1]. At that dependence of conventional (related to initial cross-section of the sample) stress (σ) from relative elongation (α), which is related to deformation (ε) by the expression: α = 1+ε/100%, comprises following basic structural parameters and deformation conditions:    M c ch , where  is polymer density, M c – average internodal molecular weight of the polymer binder; φ r = 1- φ sw – polymer volume fraction in the composite binder,  sw – plasticizer volume fraction in the binder; R – universal gas constant; T ∞ – equilibrium temperature, at which concentration of “physical” (intermolecular) bonds (ν ph ) is negligible; T g – glass transition temperature of the polymer binder; T – sample test temperature (of numerical experiment);    1 a – velocity shift coefficient,    1 a = 1 at standard relative extension rate      1 , c accepted for science and industry; φ – filler volume fraction; φ m – maximum filler volume fraction, depending on fractional composition, particle shape and physicochemical interaction on the filler – binder interface. Basic equation is as follows:                                                                   1 2 3 1 1 3 2 2 2 1 1 1 29exp 0.225 10 1 1 1.25 1 exp 0.5 2 1 ch r g n m i i i m i RT T T a t dt O C