An ultrasonic method was applied in this work to measure third-order elastic moduli of polystyrene samples fabricated using different technologies: two commercial samples of a styrene copolymer with ethylene glycol dimethacrylate in different concentrations and two laboratory samples obtained by melt technology in different temperature regimes. It is shown that the dependences of nonlinear elastic moduli on the frequency of ultrasonic waves in the range of 1-3 MHz differ significantly between commercial copolymer samples and laboratory samples. The moduli of laboratory samples obtained using the same technology, but in different temperature regimes, also differ markedly. Thus, the manufacturing technology can affect significantly the nonlinear elastic properties of polymer materials.

Regularities of statistical distributions of a complex of mechanical properties, including the module of elasticity (E), strength () and strain at break (b), high-strength industrial oriented polypropylene (PP) fibers have been analyzed using the Weibull and Gauss models based on large a wide array of measurements (50 identical samples in each series). The values of the statistical Weibull modulus (m) - a parameter characterizing the scatter of the measured values of the data arrays of E,  and b – have been estimated for the PP samples of two types: single fibers (monofilaments) and multifilament fibers consisting from several hundred single fibers. For the PP multifilament fibers, a more correct description of the distributions of E,  and b has been received both in the framework of the normal distribution (Gaussian distribution) and in the framework of the Weibull distribution in comparison with the description of such distributions for the PP monofilaments. The influence of the polymer chain conformation on the regularities of the statistical distributions of E,  and b for the high-strength oriented polymeric materials with different chemical chain structures and the correctness of their descriptions in the framework of the Gauss and Weibull models have been analyzed. For this purpose, the values of m calculated in this work for PP with a helical chain conformation have been compared with the values of m determined by us earlier for ultra-high molecular weight polyethylene and polyamide-6 with the chain conformations in the form of an in-plane trans-zigzag.

The patterns of the statistical distributions of tensile strength of high-strength ultraoriented mono-and multifilament fibers, consisting of several hundred single fibers of ultra-high-molecular-weight polyethylene (UHMWPE), have been analyzed using the Weibull and Gaussian models by considering a large number of measurements (50 identical samples in each series). It has been shown that the strength distribution of the multifilament UHMWPE fibers can be described both within the normal Gaussian distribution and the standard Weibull distribution function. At the same time, the strength distribution of the UHMWPE monofilaments oriented to a final draw ratio of 120 is not subject to the normal distribution. The reasons for the revealed differences in the types of the statistical strength distributions of the mono- and multifilaments of high-strength UHMWPE during fracture are discussed.

AbstractThe influence of the gauge length l _0 of a sample on the modulus E of ultraoriented film filaments of ultra-high-molecular-weight polyethylene (UHMWPE) has been elucidated. The filament samples are obtained by a multistage orientation drawing on a contact heater with achieving extremely high draw ratios as large as λ = 120. Precursors were xerogels prepared by the drying of 1.5% UHMWPE gel solutions in decalin. A noticeable gain in “methodical” quantity E from 100 to 230 GPa at l _0 increasing from 10 to 80 mm with a damping behavior has been established. The E ( l _0) dependence is shown to be described via the empirical equation that allows the E value to be predicted as a function of l _0. According to the prediction, a saturation of the true value E with a yield to a plateau at E = 242 GPa occurs at l _0 = 200 mm.

AbstractSamples of composites based on polystyrene with addition of halloysite nanotubes, mica, and montmorillonite aluminosilicates are obtained and the influence of these fillers on viscoelastic, mechanical, and structural properties of composites is studied. It is shown that an addition of up to 5% of mica can increase the rigidity of composites along with maintaining their strength at the level of pure polystyrene and without considerable embrittlement of samples. The addition of halloysite nanotubes and montmorillonite also increases the material stiffness but reduces its strength and elasticity. A significant (up to 50%) increase in the bending elasticity modulus of the composite was achieved by addition of 15% of halloysite nanotubes or 5% of mica.

A statistical analysis of the distributions of Young's modulus Е and strain at break b of the commercial oriented fibers of polyamide-6 has been carried out in the frameworks of the models of Gauss and Weibull. The duality of the statistical distributions of Е and b revealed earlier for the strength of polyamide-6 has been confirmed. It consists in the validity of the description of the experimental data by using both the normal Gaussian distribution and the standard Weibull distribution function.

AbstractStatistical analysis of distribution of the tensile strength of commercial oriented polyamide-6 (PA-6) fibers has been performed in the framework of the Gaussian and Weibull models using a large data array of the results of measurements for a large number (50) of identical samples. Using the example of PA-6, the dualism of strength distribution in oriented high-strength polymers is demonstrated for the first time, which consists in the validity of both the normal Gaussian distribution (characteristic of viscoelastic and plastic materials) and the Weibull distribution (characteristic of brittle materials).

Механические свойства полимерных композитов с наночастицами диоксида кремния

Получены мононити из смеси двух полимеров: волокнообразующего полиэтилентерефталата и конструкционного термопласта полифениленсульфида. Установлены температуры фазовых переходов как чистых полимеров, так и их смесей. Исследовано влияние концентрации полифениленсульфида на деформационно-прочностные свойства мононитей, полученных из смеси полимеров