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Growing environmental concerns have increased the need to reduce zinc oxide (ZnO) in sulfur vulcanization without compromising rubber performance. This study investigates MICro‐naNO structured ZnO (MicNo‐ZnO), a hierarchically structured zinc oxide consisting of micrometer‐sized platelets built from ZnO nanoparticles, as an alternative activator for natural rubber. MicNo‐ZnO loadings between 5 and 0.5 phr were compared with a conventional 5 phr ZnO formulation. Rheometric analysis showed higher cure extent and effective crosslink density even at significantly reduced ZnO levels. Despite up to 90% ZnO reduction, MicNo‐ZnO compounds exhibited comparable scorch safety, high cure extent, and retained mechanical performance along with improved resistance against thermal aging. Cyclic compression tests confirmed lower hysteresis and reduced stress softening under limited cyclic loading. SEM–EDX mapping indicated a more homogeneous spatial distribution of zinc‐ and sulfur‐containing regions in the MicNo‐ZnO compounds than in the conventional ZnO formulation. XRD results confirmed the presence of crystalline ZnO domains, with decreasing peak intensity as the ZnO loading was reduced. This work presents the investigation of MicNo‐ZnO, a hierarchically structured zinc oxide consisting of micron‐sized platelets assembled from chemically bonded nanoparticles, as a vulcanization activator for natural rubber compounds.

Epoxy‐based materials have low erosion resistance due to their brittle nature, and toughness modification stands out for enhancing it. At this stage, the use of waste rubber as a reinforcement component in the composite system is of interest due to its role in providing toughness and making recycling possible. This study aims to improve erosion resistance through recycled rubber reinforcement while also determining the effect of the rubber phase. For this purpose, waste rubber particles with different types and characteristics were evaluated. The rubber particles were characterized using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and rubber process analyzer (RPA). Rubber/epoxy composites were produced by the open‐mold method. Erosion tests were performed and erosion rates were measured. Neat epoxy exhibited the lowest erosion resistance, and all recycled rubber particle reinforcements increased it. The reductions in erosion rate were 5.3%–46.8%, depending on the waste composition. Natural rubber‐based waste particles with a relatively high modulus demonstrated superior performance among all. The morphological observations further supported the enhanced erosion resistance observed in the rubber/epoxy composites. It has been concluded that the appropriate selection of recycled rubber particles provides a significant contribution to the overall performance of epoxy along with to environmental sustainability.

In this study, a combination of Plackett–Burman and Box–Behnken designs is applied to discover the relationships between the components of rubber compounds and technical specifications. Optimization of rubber compound formulation is realized by support vector regression integrated genetic algorithm to minimize compound cost. Twelve components potentially affecting the technical specifications of rubber compound, which are natural rubber, carbon black, white filler, stearic acid, zinc oxide, antiozonant, antioxidant, process oil, curing retarder, curing agent, and accelerator, are screened through Plackett–Burman design to decide the significant variables. Afterwards, four significant parameters, including carbon black, process oil, curing agent, and accelerator are analyzed using Box–Behnken design to minimize the number of experiments while obtaining the correlation between formulation and specifications. Lastly, a support vector regression integrated genetic algorithm is implemented to predict optimum compound formulation at minimum cost.Highlights: Optimization of rubber compound to reduce the mixture and curing cost. Combination of Plackett–Burman and Box–Behnken designs. Integration of support vector regression to genetic algorithm. Correlations between the amounts of components and technical specifications.

Using biological/renewable resources as filler or modifier in both thermoplastics and rubbers has been of a great interest in order to reduce negative effects of traditional petroleum/natural gas based fillers. In this study, the main goal was the use of spent (waste) coffee grounds as a natural alternative filler to carbon black in acrylonitrile butadiene rubber (NBR) based compounds. Carbon black (CB) was partially replaced with fresh as well as spent coffee grounds (SCG) in NBR compound formulation. Stabilization effect of fresh coffee grounds was also investigated. Cure characteristics, physico‐mechanical, thermal, morphological, and dielectric properties of the bio‐based composites were tested and compared with the control (reference) compounds. Processability has been affected positively in the case of using coffee grounds thanks to the presence of triacyl groups in coffee. Up to 20% higher elongation at break values were measured when coffee is partially replaced with CB. Abrasion loss and oil resistance could be retained for coffee containing compounds. In conclusion, SCG were found to be a good natural alternative filler for bio‐based NBR composites without a significant change in material properties.Highlights: Spent coffee grounds ‐ a sustainable filler in bio‐based NBR composites Both fresh and spent coffee grounds are successful stabilizers Physico‐mechanical, thermal, and dielectric properties are comparable

Ethylene propylene diene rubber (EPDM) is a common raw material for weather resistant rubber products used in lots of areas such as cable, automotive, marine industry and aviation applications. Superior processing behaviour, electrical properties and moderate high temperature resistance also make EPDM an attractive raw material for a wide range of further industrial performance requirements. As well as the other general purpose rubbers, EPDM needs to be protected against thermo-oxidative aging. Short and long term aging behaviour of both sulphur and peroxide cured EPDM has been studied in literature. However, to the authors’ best knowledge, there is not any study in literature systematically evaluating a common rubber antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) for investigating theoretical life-time of EPDM based materials that were vulcanized with different crosslinking systems. In this study, effects of TMQ on the thermo-oxidative resistance of EPDM has been studied for conven-tional and efficient sulphur vulcanization systems as well as peroxide vulcanization system. Aging mechanism for different cases has been investigated by using structural, rheological and mechanical tests. Thermo-oxidative aging has been monitored by carbonyl index and activation energy. Arrhenius based life-time estimation methodology has also been employed to evaluate aging behaviour of the reference and TMQ containing (-T) compounds. TMQ was found to exhibit different levels of protection against thermo-oxidative aging for all the curing systems and at all aging conditions. Higher aging activation energy for -T compounds has been attributed to extended service life of the material in the presence of TMQ.

The effect of octaisobutyl-polyhedral oligomeric silsesquioxane (OIB-POSS) as a nanosized reinforcement on the cure kinetics, crosslinking density, and mechanical properties of styrene-butadiene rubber (SBR) nanocomposites was examined in this study. For this purpose, SBR compounds with various OIB-POSS nanoparticle loadings at 1, 3, and 5 phr were prepared and their results were compared with a reference compound without OIB-POSS. When 1 phr of OIB-POSS was added to the rubber matrix, the elongation at break values and tensile strength of the corresponding nanocomposite increased by 24.1% and 29.2% compared to the reference sample, respectively. The presence of OIB-POSS nanoparticles and their random distribution in the SBR matrix was confirmed by transmission electron microscopy. The crosslinking density of nanocomposites was calculated by the Flory-Rehner method and a decrease was observed with the addition of OIB-POSS nanoparticles. In addition, thermal aging process as 70 °C for 70 h was applied to vulcanized samples. It was noted that the mechanical properties of SBR/OIB-POSS nanocomposites remarkably improved, whereas their crosslinking densities gradually decreased after thermal aging.

Phenolic resins are useful additives that provide various functions for rubber compounds during compounding and vulcanization, as well as after cure. Natural resins are considered as strong alternatives to synthetic ones due to environmental concern. Liquidambar Orientalis Mills is an endemic plant and grows in many different geographies including Turkey. In this study, the phenolic resin obtained from Liquidambar Orientalis Mills has been studied regarding its functions in a generic natural rubber compound. It was incorporated into the rubber compound with and without selected gum and phenolic resins so that mainly obtaining competitive adhesion properties. Both individual and collaborative effects of the natural resin were evaluated. Rheological, thermal, morphological, mechanical and adhesion properties of the compounds were studied comparatively along with the non-linear cure kinetics. Liquidambar Orientalis Mills has been found to be a good alternative to both gum and phenolic resins in rubber compounds. Besides, significant improvement could be achieved for particularly rubber–steel adhesion.

Unsaturated chain structure of natural rubber makes it a poor defense against thermo-oxidative aging. Synthetic antioxidants are commonly used in rubber compound recipes to prevent/retard aging of the rubber material during its service life. However, synthetic antioxidants cause some negative effects on human and environmental health; they tend to be replaced by natural alternatives. In this study, the short- and long-term antioxidant effects of henna and its basic active components, lawsone and gallic acid, have been investigated individually for natural rubber cured with semi-efficient sulfur vulcanization system. The composition of henna was determined by gas chromatography-mass spectrometry (GC-MS) analysis. Qualitative and quantitative analysis were performed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to highlight structural changes on aged vulcanizates. The authors attempted to correlate the suggested aging mechanism with rheological, mechanical, and morphological properties. Results showed that both lawsone and gallic acid were impressively successful regarding their anti-oxidation activity. In addition, henna, which contains a sufficient amount of lawsone and gallic acid, has been suggested as a competitive natural alternative to the common synthetic stabilization system for natural rubber, considering its sustainable commercial abundancy.

Vulcanization at lower temperatures can be considered as a good alternative to reduce both investment and operation costs for cable insulation sheat and special purpose hose production lines. In this study, silane vulcanization of chlorinated polyethylene and chloroprene rubber blends at lower temperature was investigated. Rubber compounds were prepared by using internal mixer instead of an extrusion system which is widespread used for projected applications. Rheological and dynamic properties of the rubber compounds were studied. After vulcanization, physico‐mechanical, thermal, morphological and temperature scanning stress‐relaxation properties were investigated before and after thermal aging. Structural analysis was performed by using Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy so as to identify vulcanization reaction mechanism. All the compound compositions could be vulcanized at 110°C in the presence of water. Amino silane was found to be more effective than epoxy silane.

Since they arises in many stages of manufacturing as well as at the end of their lifetime, glass fiber reinforced polymers‐based wastes are one of the biggest problem for the composite industry. There are many waste disposal methods available, but these are low value‐added and usually imply additional cost to the manufacturers. In this study, composite wastes have been ground into three different grain sizes and used as filler in the production of new glass fiber reinforced composites. Composites were examined regarding their rheological, thermal, mechanical, dynamic‐mechanical, and morphological properties. High thixotropy a resin could be obtained by waste incorporation ensuring easier gel‐coat application in hand lay‐up molding technique. A remarkable reduction in linear shrinkage of the resulting composite was also considered as a benefit. Although there was tolerable loss in their mechanical properties, higher grain size of waste particles shifted glass transition temperature up to 50°C higher due to restricted chain mobility. Fibers from both the waste matrix and fresh glass fiber content exhibited quite similar interphase with the unsaturated polyester. In summary, using composite waste in their own composition has been found to be a good solution to recover the wastes in both economic and environmental concern.