To expand the range of properties and the range of types of thermoplastic elastomer (TPE), materials based on ternary blends of polypropylene and polar and non-polar rubbers were produced and investigated. To obtain blended and dynamically vulcanised materials, one- and two-stage methods were tested. It was established that the best properties are possessed by composites produced using master batches (rubber mixes) based on a thermoplastic vulcanisate (TPV) rubber phase, and to improve the combination of polymers of different polarity, functionalised additives modifying the polypropylene are necessary. Optical microscopy was used to study the influence of compounding factors (the ratio of components of the polymer phase, the presence or absence of compatibilisers) and technological factors (the production method) on the structure and properties both of blended and of dynamically vulcanised TPEs. A study of the morphology of blended and vulcanised TPEs showed that, in all cases, in the polypropylene, which is the dispersion medium, there are areas rich in rubber to different degrees. Here, fragments of polar rubber are found both in the polypropylene and in zones rich in non-polar rubber, and the range of particle sizes of the disperse phase depends on the production method. The introduction of a compatibiliser leads to a considerable increase in the homogeneity of distribution of the components throughout the material, and to a reduction in the size range of the disperse phase and in the thickness of the polypropylene-rich surface layer of the extrudate (strand). In the surface layer of the strands, anisotropy of the polypropylene fibrils is observed in the direction of extrusion.
Optical microscopy and dielectric relaxation spectroscopy (DRS) were used to study the structure of dynamically vulcanised mixes based on polypropylene, ethylenepropylenediene rubber, and copolymers of ethylene and vinyl acetate (Levapren 400, 600, 700). For the microscopic investigations, we used a complex consisting of a Leica DM-2500 optical microscope, a DFC 420C cooling chamber, and a special computer desk. DRS data were obtained on a BDS 89 instrument (NovoControl) at temperatures ranging from −150 to +100°C at a heating rate of 2°C/min and a frequency of 110 Hz. The influence of the content of Levapren and the proportion of vinyl acetate in its composition on the morphology and processing properties of olefinic thermoplastic vulcanisates (TPVs) was investigated. The combination of the discovered changes in the fine structure and DRS data indicate the preferential interaction of Levapren with the rubber component. The evolution of the morphology of the TPVs with increase in the volume fraction of vinyl acetate is not monotonic, which is consistent with the nature of change in the physicomechanical properties of the TPVs. Combined analysis of the morphological characteristics and processing properties of TPVs showed that, to achieve high values of the deformation and strength properties, a uniform distribution and high polydispersity of the ingredients are necessary. Increase in the elastic properties of the material is ensured by modification of the polypropylene phase to form fibrillar structures, while the flow of TPEs that is necessary for processing is facilitated by modification of the rubber phase.
Commercial nitril-butadiene rubbers were comprehensively studied by GPC, DSC, TGA, phase contrast microscopy and surface free energy determination via Owens-Wendt-Rabel-Kiellble method. Specific features were found for molecular mass distribution, phase transitions in negative and positive temperature intervals, the character of supramolecular assembly and microblock distribution of functional groups in BNKS-18AN and BNKS-18AMN rubber brands. A set of differences in initial rubbers macromolecular characteristics was shown, as well as the evolution of the latter during mechanical activaction of BNKS-18AN and BNKS-18AMN rubber brands
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