Stearic acid st a

Natural rubber (NR), i.e., cis-1,4-polyisoprene of RSS1 type, was provided by Torimex Chemicals (Lodz, Poland) and applied as an elastomer matrix. It had a density of 0.930 g/cm³ and content of volatile matter of 0.56 wt%. NR composites were vulcanized using sulfur (Siarkopol, Tarnobrzeg, Poland) as a curing agent, zinc oxide (ZnO) with a specific surface area of 10 m²/g (Huta Bedzin, Bedzin, Poland) along with stearic acid (St.A.) (Sigma-Aldrich, Poznan, Poland) as vulcanization activators and 2-mercaptobenzothiazole (MBT) (Brenntag Polska, Kędzierzyn-Koźle, Poland) as an accelerator. Ground tea waste (GT) made from black leaf tea (country of origin: Sri Lanka, supplier: KOL-POL, Stasiowka, Poland) was applied as a waste biofiller. Additionally, ionic liquids (ILs), i.e., 1-ethyl-3-methylimidazolium lactate (EmiLa) and 1-benzyl-3-methylimidazolium chloride (BenmiCl) (Sigma-Aldrich, Poznan, Poland), were used to improve the dispersion of the waste biofiller in the elastomer matrix.

NR, cis-1,4-polyisoprene (RSS1 type) was supplied by Torimex Chemicals (Lodz, Poland). It was characterized by a density of 0.930 g/cm³, with the contents as follows: volatile matter—0.56%wt., ash—0.33%wt., nitrogen—0.47%wt., and dirt—0.004%wt. A conventional curing system containing sulfur (Siarkopol, Tarnobrzeg, Poland) used as a curing agent was employed to vulcanize NR rubber compounds. A microsized zinc oxide (ZnO) demonstrated a specific surface area of 10 m²/g (Huta Bedzin, Bedzin, Poland) along with stearic acid (St. A.) (Sigma-Aldrich, Poznan, Poland) was applied to activate the vulcanization process, whereas 2-mercaptobenzothiazole (MBT) (Brenntag Polska, Kędzierzyn-Koźle, Poland) was used as an accelerator. Natural bio-waste such as ground chicken eggshells (ES) (Pokusa for Health, Sygneczów, Poland) was applied as a biofiller for NR compounds. Additionally, silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPTS); ionic liquids, i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr); and a surfactant, cetyltrimethylammonium bromide (CTAB), were employed to improve the dispersion degree of the biocomponent added in the elastomer matrix. All mentioned compounds were supplied by Sigma-Aldrich (Poznan, Poland). The structure of additives used is presented in Figure 1.

Natural rubber (NR, RSS1 type, cis-1,4-polyisoprene) with a density of 0.93–0.988 g/cm³ was obtained from Torimex Chemicals, Lodz, Poland. A conventional crosslinking system containing sulfur as a crosslinker (Siarkopol, Tarnobrzeg, Poland) in the presence of a vulcanization accelerator, i.e., 2-mercaptobenzothiazole (MBT), purchased from Sigma-Aldrich, Schelldorf, Germany, was applied. Zinc oxide (ZnO) with a specific surface area of 10 m²·g⁻¹ (Huta Bedzin, Bedzin, Poland) together with stearic acid (St.A, Sigma-Aldrich, Schelldorf, Germany) were used to activate the vulcanization. Silica AEROSIL^® 380 (A380) supplied by Evonik Industries (Essen, Germany) was used as a filler. Additionally, eight ionic liquids (ILs) with characteristics given in Table 1 were applied to enhance the vulcanization and properties of NR composites. ILs were provided by IoLiTec Ionic Liquids Technologies GmbH, Heilbronn, Germany. These ILs consist of bromide or chloride anion and different cations with butyl or decyl substituents. The general structures of ILs cations are given in Figure 1.