Calcium-Lignosulfonate-Filled Rubber Compounds Based on NBR with Enhanced Physical–Mechanical Characteristics

Calcium lignosulfonate in the amount 30 phr was incorporated into rubber compounds based on pure NBR and an NBR carbon black batch, in which the content of carbon black was 25 phr. Glycerine, as a cheap and environmentally friendly plasticizer, was applied into both types of rubber formulations in a concentration scale ranging from 5 to 20 phr. For the cross-linking of rubber compounds, a sulfur-based curing system was used. The work was aimed at the investigation of glycerine content on the curing process and rheological properties of rubber compounds, cross-link density, morphology and physical–mechanical properties of vulcanizates. The results show that glycerine influences the shapes of curing isotherms and results in a significant decrease between the maximum and minimum torque. This points to the strong plasticizing effect of glycerine on rubber compounds, which was also confirmed from rheological measurements. The application of glycerine resulted in better homogeneity of the rubber compounds and in the better dispersion and distribution of lignosulfonate within the rubber matrix, which was subsequently reflected in the significant improvement of tensile characteristics of vulcanizates. A higher cross-link density as well as better physical–mechanical properties were exhibited by the vulcanizates based on the carbon black batch due to the presence of a reinforcing filler

Combined Sulfur and Peroxide Vulcanization of Filled and Unfilled EPDM-Based Rubber Compounds

The sulfur curing system, peroxide curing system and their combinations were applied for the cross-linking of unfilled and carbon black-filled rubber formulations based on ethylene-propylenediene-monomer rubber. The results demonstrated that the type of curing system influenced the course and shape of curing isotherms. This resulted in the change of curing kinetics of rubber compounds. The cross-link density of materials cured with combined vulcanization systems was lower than that for vulcanizates cured with the peroxide or sulfur system. Good correlation between the cross-link density as well as the structure of the formed cross-links and physical–mechanical characteristics of the cured materials was established. Both filled and unfilled vulcanizates cured with combined vulcanization systems exhibited a higher tensile strength and elongation at break when compared to their equivalents vulcanized in the presence of the peroxide or sulfur curing system. It can be stated that by proper combination of vulcanization systems, it is possible to modify the tensile behavior of vulcanizates in a targeted manner. On the other side, dynamical–mechanical properties were found not be significantly influenced by the curing system composition

Electromagnetic absorption characteristics of manganese-zinc ferrite and multiwalled carbon nanotube-filled composites based on NBR

Composites based on acrylonitrile-butadiene rubber, carbon nanotubes, and manganese-zinc ferrite were fabricated and tested for electromagnetic interference (EMI) absorption shielding. First, carbon nanotubes and ferrite were solely used for the preparation of rubber composites. Then, carbon nanotubes were combined with magnetic filler and incorporated into the rubber matrix. The results revealed that carbon nanotubes act as reinforcing filler and significantly enhance the physical-mechanical properties of composites. The presence of carbon nanotubes in the rubber matrix also results in an outstanding increase in electrical conductivity and permittivity of composite materials, as a consequence of which the EMI absorption shielding was poor in the tested frequency range of 1 MHz to 3 GHz. On the other hand, ferrite-filled composites are able to efficiently absorb electromagnetic radiation emitted from various electronic and radiation sources. However, the tensile strength of the composites showed a decreasing trend with increasing content of ferrite. The combination of carbon nanotubes with manganese-zinc ferrite resulted in an improvement in the physical-mechanical properties of hybrid composites. As the permittivity of hybrid composites was still much higher in comparison with those filled only with ferrite, only the composite filled with 5 phr of carbon nanotubes and 100 phr of ferrite showed a slight EMI absorption shielding ability over the tested frequency range.Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-19-009

Aplikácia metodiky AEO pri registrácii silanizácie gumárenských zmesí

Existuje celá řada experimentálních metod zaměřených na zkoumání strukturálních transformaci (DTA , X - Ray , TSDC , .. ). Tyto metody se liší od sebe spektrem kvantitativních ukazatelů a jejich použití je omezeno povahou zkoumané struktury a procesu. V jistém smyslu, je také možné uvažovat o silanizaci pryžové směsi jako o strukturální transformaci. Je to proměna nezesítěné struktury na zesítěnou. Nicméně , specifičnost uvedené transformace je , že se vyskytuje postupně, formou chemické reakce . Experimentální sledování proměn neuspořádané pryžové směsi může být docela obtížné . Příspěvek se zabývá teoretickými principy experimentální metodiky , které jsme nazvali AER (analýza elektrické odozvy) . Uvedená metodika identifikaci pryžových směsí v průběhu silanizace . Pozornost je zaměřena na modelování možné elektrické odezvy na chemické reakce v systému, skládající se z několik součástí. Výsledky modelu jsou porovnány s experimentálními daty AER měřenými při silanizaci reakce zejména kaučukových směsí.There are a number of experimental methods aimed at the investigation of structural transformations (DTA, X-Ray, TSDC, ...). These methods differ from each other by a spectrum of quantitative indicators and their application is limited by the nature of investigated structures and processes. In a sense, it is also possible to consider the silanization of rubber mixtures as a structural transformation. This is a transformation from the unlinked to crosslinked structure. However, the specificity of mentioned transformation is, that it occurs gradually, by the form of a chemical reaction. Experimental observation of transformations of disordered rubber mixtures type structures can be quite difficult. The contribution deals with theoretical principles of experimental methodology, which we have called AER (Analysis of the Electrical Response). We analyze mentioned methodology just in connection with its application for the identification of rubber mixtures silanization. Our attention is focused on the modeling of a possible electrical response of a chemical reaction in system consisting of several components. Results of the model are compared with experimental data AER measured during silanization reaction in particular rubber mixtures.