The constant need of the rubber industry to improve quality and expand the assortment of products entails the development of new types of elastomeric blends with innovative compositions. It often involves the replacement of a commonly used filler in the recipe of an industrial elastomer blend with new types of alternative fillers, especially based on wastes
[1, 2]. In the past, many of them did not occur in sufficient volume for industrial use, but today they form an economically cheaper and often more ecological variant. In the case of replacing a commonly used filler with an alternative one, it is necessary to carefully study not only the properties of the new final elastomeric product, but also the process of mixing the elastomeric blend. Alternative fillers also affect important measurable parameters of this process. Changing the filler in the elastomer blend recipe can negatively affect e.g. the real temperature of the blend during the mixing process, which has a significant effect on the viscosity of the elastomeric matrix, as well as on the filler dispersion and distribution. The advantage of commonly used fillers is their positive effect on the mechanical properties of blends, which, however, cannot be achieved when using alternative fillers without additional adjustment of the elastomeric blend recipe [3, 4]. This study deals with the impact of replacing the commonly used filler carbon black type N339 in a recipe containing energo-gypsum filler based on an industrial by-product, with an alternative carbon-based filler emerging as waste from another industry. The study results provide an overview of the content influence of these two types of alternative fillers on the mixing process and vulcanization characteristics of the new elastomeric blend, as well as on the final vulcanizates properties. This research work was created within the project „Development of a new elastomeric composite system with specific properties containing two types of alternative fillers based on industrial waste as a complete replacement for the standard carbon black filler - modification of the patented formula (PP 50073-2018)“, code of the project MVP05_2024, based on the financial support from the Internal Grant Scheme of the Alexander Dubček University of Trenčín (Call for proposals: Early Stage Grants), it has been also supported by the Operational Program Integrated Infrastructure, co-financed by the European Regional Development Fund by the project: Advancement and support of R&D for "Centre for diagnostics and quality testing of materials" in the domains of the RIS3 SK specialization, Acronym: CEDITEK II., ITMS2014+ code 313011W442 and by Scientific Grant Agency VEGA 1/0265/24 and KEGA 001TnUAD-4/2022.

[1] Yangthong H, Buaksuntear K, Suethao S, Chworos A, Smitthipong W. Waste material fly ash as an alternative filler for elastomers. Polym Eng Sci. 2023; 63(8): 2624-2644. doi:10.1002/pen.26400.

[2] Ondrušová D, Labaj I, Vršková J, Pajtášová M, Mezencevová VZ. Application of alternative additives in the polymer composite systems used in automotive industry. InIOP conference series: materials science and engineering 2020 Feb 1 (Vol. 776, No. 1, p. 012101). IOP Publishing.

[3] Lee S-H, Park G-W, Kim H-J, Chung K, Jang K-S. Effects of Filler Functionalization on Filler-Embedded Natural Rubber/Ethylene-Propylene-Diene Monomer Composites. Polymers. 2022; 14(17):3502. https://doi.org/10.3390/polym14173502.

[4] Masa A, Krem-ae A, Ismail H, Hayeemasae N. Possible use of sepiolite as alternative filler for natural rubber. Materials Research. 2020 Sep 23;23:e20200100.