Powder-free natural rubber gloves for chemical migration resistance of food-contact grade are prepared using a variety of fillers, including ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), aluminum silicate (AS), and barium sulfate (BS)-filled natural rubber (NR), respectively. The properties of NR gloves, including mechanical, dynamic mechanical, and thermal properties, were investigated. Furthermore, the overall migration test of NR gloves was conducted according to the regulations for food contact gloves (EU Regulation No. 10/2011), using 3% acetic acid as the simulant. Among the fillers studied, the plate-like particles of AS facilitated the most effective filler-rubber interactions and reinforcement in AS-filled natural rubber (NR/AS). Consequently, the highest crosslink density, force at break, and damping properties of NR gloves were achieved by applying AS in the NR matrix. Moreover, the lowest overall migration level was observed for NR/AS with a value of 5.35 mg/dm², which complies with EU Regulation (overall migration of food simulants shall not exceed 10 mg/dm²). Therefore, NR gloves filled with AS are suitable for food-contacting NR gloves.

Cyclized natural rubber (CNR) was synthesized through the acid-catalyzed reaction of natural rubber (NR) latex using sulfuric acid as a catalyst and stabilized with a non-ionic surfactant. Cyclization was evaluated by iodine numbers under varying reaction times, temperatures, and NR-to-acid ratios. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (¹H-NMR) confirmed the formation of cyclic structures in CNR molecules. Differential scanning calorimetry (DSC) showed that the glass transition temperature (T_g) of CNR increased with cyclization, indicating greater rigidity and less chain flexibility. CNR was then blended with NR and used as a compatibilizer in NR/acrylonitrile butadiene rubber (NBR)blends. It increased blend viscosity, hardness, and dimensional stability but reduced tensile strength and elongation due to its rigid cyclic domains. In NR/NBR blends, CNR outperformed a commercial homogenizer in enhancing interfacial interactions, leading to superior shear flow properties, curing behavior, and mechanical performance. This is attributed to the polar groups in CNR, which enhance intermolecular interactions and phase compatibility, resulting in finer phase morphology. This study highlights the potential of CNR as a versatile material for enhancing the performance of rubber compounds, with promising applications in advanced industrial formulations.

An antibacterial natural rubber (NR) latex film was successfully prepared in this study. This was done by coating silver (Ag) nanoparticles onto the surface of the NR latex film. The Ag nanoparticles were synthesized using green tea (GT) extract as a bio-reducing agent. The corresponding Ag nanoparticles were then deposited onto the NR latex film. Before synthesis, the phenolic compounds were identified using high-performance liquid chromatography (HPLC). The Ag nanoparticles were found to be smaller than 25 nm in size. Subsequently, an experimental evaluation was conducted to determine the influence of deposition time, namely 1 to 20 min, on the film’s overall performance. Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (SEM-EDX) confirmed that the Ag content was higher over the deposition time. The surface roughness of the samples was also screened by atomic force microscopy (AFM), where the films became rougher over the deposition time, confirming that Ag nanoparticles dispersed over the surface. As for the antibacterial activities, both qualitative and quantitative tests showed significant outputs. The clear zones of S. aureus and E. coli increased over the deposition time, and a shorter contact time was used to kill the bacteria. This study offers a scientific foundation that supports the development of future rubber products utilizing these findings.

Natural rubber (NR) composites filled with silica and crosslinked with phenolic resin were prepared in this study. The influence of a small sepiolite addition (1–5 part(s) per hundred parts of rubber, phr) on the properties of NR composites was studied. It was found that sepiolite reduced silica aggregate size, allowing improved dispersion in the NR matrix. Sepiolite facilitates silica dispersion by locating at the silica surfaces and acting as a barrier that prevents agglomeration of silica filler. The swelling resistance, crosslink density, tensile strength, and strain-induced crystallization were all strengthened by incorporating sepiolite because of the improved silica dispersion. The greatest tensile strength was achieved at a 2 phr sepiolite addition level. The improvement was about 18% over the reference composite due to the greatest filler-rubber interactions and the finest filler dispersion. The results clearly indicate that sepiolite clay can be applied as a dispersing agent in silica-containing rubber composites.

This paper extends previous studies by the authors that aimed to describe the effect of apparent cross-link density (CLD) of the rubber polymer networks on the fracture mechanism caused by cut and chip (CC) wear of natural rubber (NR), demonstrating the positive effect of conventional vulcanization (CV). This work is focused on the determination of the effect of CLD while keeping constant the accelerator-to-sulfur ratio A/S = 0.2, typical for CV systems. For this ratio, different sulfur quantities were chosen, and the concentration of the accelerator N-tert-butyl-benzothiazole sulphonamide (TBBS) was calculated to achieve CLDs in a range from 35 to 524 μmol・cm^–3. Standard analyses such as tensile tests, hardness, rebound resilience and DIN abrasion were performed. From these analyses, the optimum physical properties of the NR-based rubber were estimated to be in the CLD range of approximately 60 to 160 μmol・cm^–3. A CC wear analysis was performed with an Instrumented cut and chip analyzer (ICCA) and it was found that the highest CC wear resistance of the NR is in the CLD range of 35 to 100 μmol・cm^–3. Furthermore, the effect of straininduced crystallization (SIC) of NR on CC wear and its dependence on the CLD region was discussed. For the first time, we determine a CLD range for a CV system in which the material achieves both optimal mechanical properties and CC wear resistance.