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The special mechanical properties of natural rubber originate from the stretching of the network chains (i.e., cis‐1,4‐polyisoprene chains) in the rubber network. The chains with various lengths exhibit various relative extensions, leading to various normalized energy contributions to the mechanical properties of rubber. However, the stretching behaviors of cis‐1,4‐polyisoprene chains with different lengths are not studied clearly. Here, the stretching behavior, which is the basis for analyzing the normalized energy contribution, is obtained by the modified freely jointed chain model. Next, using a new statistical model, i.e., the two‐component quantum‐mechanics Gaussian (TCQMG) model, the relative extension–length relationship of network chains is determined. Combining the above results, the energy contributions of network chains with different lengths are analyzed. The results show that long and short chains show different stretching states. The following can be explained by these results: short chains play an important role in the mechanical properties of rubber. As the network chain density increases, the average length of the chains decreases, leading to the variation of the normalized extensions. It is found that the variation of the normalized extensions is responsible for both the effects of the network chain density and network chain length on the mechanical properties of rubber. [ABSTRACT FROM AUTHOR]

Soft, stretchable, conductive thin films have propelled to the forefront of applications in stretchable sensors for on-skin health monitoring. Stretchable conductive films require high conformability, stretchability, and mechanical/chemical stability when integrated into the skin. Here, we present a highly stretchable, conductive, and transparent natural rubber/silver nanowire (AgNW)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite film. Overcoating the PEDOT:PSS layer results in outstanding mechanical robustness and chemical stability by suppressing the mechanical and chemical degradation of the nanowire networks. Moreover, the introduction of the organic surface modifier enhances the bonding strength between the natural rubber substrate and AgNW at the interface. The highly conformable composite films are integrated into multifunctional on-skin sensors for monitoring various human motions and biological signals with low-power consumption. We believe that the highly stretchable, robust, and conformable natural rubber/AgNW/PEDOT:PSS composite film can offer new opportunities for next-generation wearable sensors for body motion and physiological monitoring.

Soft, stretchable, conductive thin films have propelled to the forefront of applications in stretchable sensors for on-skin health monitoring. Stretchable conductive films require high conformability, stretchability, and mechanical/chemical stability when integrated into the skin. Here, we present a highly stretchable, conductive, and transparent natural rubber/silver nanowire (AgNW)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite film. Overcoating the PEDOT:PSS layer results in outstanding mechanical robustness and chemical stability by suppressing the mechanical and chemical degradation of the nanowire networks. Moreover, the introduction of the organic surface modifier enhances the bonding strength between the natural rubber substrate and AgNW at the interface. The highly conformable composite films are integrated into multifunctional on-skin sensors for monitoring various human motions and biological signals with low-power consumption. We believe that the highly stretchable, robust, and conformable natural rubber/AgNW/PEDOT:PSS composite film can offer new opportunities for next-generation wearable sensors for body motion and physiological monitoring. [ABSTRACT FROM AUTHOR]

The ability of Lactobacillus plantarum to degrade different mixtures of styrene–butadiene and natural rubbers was investigated. In experiments, 12 various compositions of rubber waste mixtures were investigated. Lactobacillus plantarum cultivation was carried out in a medium with the addition of individual mixtures at the temperature of 30 °C for 14 days. The presence of cellulose on the surface of bioreactors indicated the activity of bacteria. After cultivation, the rubber mixtures were tested again. Analyses of the elemental composition and mass balance of waste were carried out. The experiments showed that the culture media supplemented by various natural rubber mixtures allowed bacteria to produce bacterial cellulose. The mean thickness of bacterial cellulose was 3–6 mm after 14 days of culturing. In samples where the cellulose appeared, about 4% average mass loss was observed. The average carbon content in the rubber material used as the carbon source for bacteria, before the culture process, was about 89.07–95.40%. After 14 days of culturing, the carbon content was reduced from 31.15% to 56.45–65.7%. [ABSTRACT FROM AUTHOR]

In the tire industry, the incorporation of natural origin oils in the development of elastomeric formulations has been one of the alternatives to reduce the use of petroleum derivatives, with a high content of toxic compounds. In this work, soybean vegetable oil was investigated as a lubricant and co-activator in sulfur-vulcanized natural rubber compounds. The soybean oil was used in its natural state and chemically modified by the epoxy ring's introduction in its structure. In an internal mixer a standard formulation of natural rubber, five formulations replacing a conventional aromatic oil and stearic acid by vegetable oil, and a formulation without an activation system were prepared. The natural and epoxidized soybean oil was characterized chemically, and the elastomeric compositions were evaluated by mechanical and rheological analysis. The mechanical properties showed satisfactory results when vegetable soybean oil was used as a lubricant and could be a substitute for conventional aromatic oils, thus guaranteeing reduction of aromatic polycyclic content in the formulations. The crosslink degree and the rheological characteristics of the samples prepared with vegetable soybean oil were similar to the natural rubber standard sample. The formulations without the zinc oxide and stearic acid evidenced the need for activators in the vulcanization reaction, as they presented properties below standard. We verified that the epoxidized soybean oil, even when promoting better dispersion of the fillers, interfered in the crosslink formation, and consequently there was a decrease in the mechanical properties of these formulations. Finally, we indicated vegetable soybean oil as a substitute for aromatic oil and stearic acid, in the elastomeric compositions used to manufacture treads. [ABSTRACT FROM AUTHOR]

The use of a surfactant derived from the degradation of natural rubber gloves via cross‐metathesis with methyl acrylate and subsequent saponification of the ester group for the stabilization of water in dicyclopentadiene high internal phase emulsions is described. The versatility of the resulting high internal phase emulsion is demonstrated by polymerizing the continuous dicyclopentadiene phase via ring‐opening metathesis polymerization yielding macroporous poly(dicyclopentadiene) foams with a porosity of 82%. The use of the ionic surfactant allows for the preparation of foams, which are resistant to absorb water. This property is hitherto not accessible with protocols involving the use of nonionic surfactants commonly employed in emulsion templating of polymers. [ABSTRACT FROM AUTHOR]

The ability of Lactobacillus plantarum to degrade different mixtures of styrene–butadiene and natural rubbers was investigated. In experiments, 12 various compositions of rubber waste mixtures were investigated. Lactobacillus plantarum cultivation was carried out in a medium with the addition of individual mixtures at the temperature of 30 °C for 14 days. The presence of cellulose on the surface of bioreactors indicated the activity of bacteria. After cultivation, the rubber mixtures were tested again. Analyses of the elemental composition and mass balance of waste were carried out. The experiments showed that the culture media supplemented by various natural rubber mixtures allowed bacteria to produce bacterial cellulose. The mean thickness of bacterial cellulose was 3–6 mm after 14 days of culturing. In samples where the cellulose appeared, about 4% average mass loss was observed. The average carbon content in the rubber material used as the carbon source for bacteria, before the culture process, was about 89.07–95.40%. After 14 days of culturing, the carbon content was reduced from 31.15% to 56.45–65.7%.

Superhydrophobicity is vital to natural rubber‐based materials and can endow materials with intriguing features, such as self‐cleaning. Normally, low surface energy and surfacial micro/nanostructure are the two premises of superhydrophobicity. However, the fragility of micro/nanostructures in natural rubber (NR) composite surfaces makes the maintenance of durable superhydrophobicity under external forces difficult. Thus, the application of NR composite elastomers is limited in industrial fields. In this work, a novel NR‐based elastomer is prepared by uniquely dispersing perfluorooctytriethoxysilane‐modified leather collagen fibers (M‐LCF) with multiscale structures into rubber matrix. The as‐prepared NR composite with 40% M‐LCF content displays excellent superhydrophobicity with a water contact angle of 156°, and the endowed superhydrophobicity is ultradurable and can be retained after 2000 cycles of mechanical abrasion under a pressure of 100 kPa. Moreover, the prepared material features superior self‐cleaning performance and mechanical properties. The reported work may serve as a basic for fabricating materials with durable superhydrophobicity. [ABSTRACT FROM AUTHOR]

Bitumen, a vital component in asphalt mixtures for road construction, confronts persistent challenges stemming from traffic loads and temperature fluctuations, leading to issues such as permanent deformation, fatigue, and thermal cracking, ultimately jeopardizing road safety. A promising solution involves enhancing asphalt mixture performance through asphalt binder modifiers, including biopolymer materials. Among these, non-petroleum-based biodegradable polymers, such as natural rubber and natural oil, stand out as viable options in highway engineering. This comprehensive review commences by introducing various biopolymeric materials, delving into their types, sources, and processing methods. Their interaction mechanism with bitumen is also discussed. Subsequently, it summarizes the production of bio-advantaged polymer-modified bitumens and mixtures. The study meticulously analyzes the rheological and chemo-mechanical properties of biopolymer-modified bitumens and underscores their mixture performances. Finally, the economic and environmental sustainability of the biopolymer-based bitumens was also evaluated. Natural rubbers enhance rutting, fatigue, thermal cracking, aging resistance, and moisture resistance in bitumen or mixtures, but do increase viscosity, which reduces workability. Natural oils improve fatigue, thermal cracking, and aging resistance without impacting rutting or moisture susceptibility in bitumen or mixtures. Biopolymer-modified asphalt presents the potential to reduce annual maintenance expenses while promoting sustainable road construction. To satisfy road pavement applications, cup lump rubber and extraction oil can be utilized. To further advance this field, future research should focus on utilizing more advanced biopolymers through innovative optimization and interaction mechanisms with other modifiers (e.g., epoxidation and polymerization) to render asphalt mixtures both economical and environmentally friendly without compromising their performance. [ABSTRACT FROM AUTHOR]

The transient response of elastomeric polymers is dependent on polymer composition, temperature and the loading history. In particular, hysteresis, dissipation and creep are significant in the choice of material for elastomer membrane wave energy converters. Natural rubber is a good candidate when looking for material for a wave energy harvester since it has an excellent stretchability, is almost resistant to the environment in which the harvester will be used and has good fatigue properties. The mechanical behaviour of the natural rubber used in this work has been deeply characterised: the material resulted to have a very little hysteretical behaviour (that is a very low energy dissipation during stretching) but also to show a strain-dependency, stress softening, and relaxation at constant stretch. Low dissipation represents the best case scenario for energy harvesting; in reality reinforcement of the material is required which adds to the dissipative behaviour. Afterwards, an extended finite strain viscoelastic constitutive model is proposed that is calibrated analytically to the experimental data to identify the relevant material parameters resulting in non-linear viscosity functions in the evolution equations of the constitutive model. The model was able to capture the minimal dissipation behaviour with good degrees of accuracy. Results are shown for a flexible membrane wave energy converter under creep and cyclic loading. A parametric study is made comparing the experimentally characterised polymer with different amounts of viscous dissipation. The response of the wave energy converter shows that even minimal amounts of dissipation manifests itself into changes in the pressure–volume function and reduction in energy capture through hysteresis. The new material model shows, for the first time, that the control of internal pressure in wave energy membranes must take into account transient material effects. • Experimental study on a low dissipative natural rubber is performed. • Non-linear viscosity functions are derived using experimental data. • A novel numerical scheme is developed to numerically calculate highly non-linear viscosity functions. • A flexible membrane energy converter is simulated with viscoelastic constitutive model. [ABSTRACT FROM AUTHOR]

Application of renewable fuels and changes in fuel composition often create many trouble in gaskets, seals, elastomers and O-rings in the engine fuel system. In a CI engine fuel system, fuel comes in touch with different elastomeric components. The compatibility of automotive fuel system components like seals, gaskets and hose materials using conventional fossil based diesel has long been recognized and documented but there is concern over the use of elastomeric materials with biodiesel. Based on these concerns, a study of compatibility of Natural rubber, Nylon and EPDM (Ethylene Propylene Diene Monomer) with biodiesel and diesel was carried out. High FFA oil, which is a byproduct of edible and non-edible oil refineries, is available at low price and in considerable quantities at vegetable oil refinery sites. In the current study, high FFA oil is synthesized into biodiesel by two step process i.e. esterification followed by transesterification. The methyl ester content of biodiesel is determined by GCMS. The fuel properties of the produced biodiesel were found to be comparable with that of biodiesel specifications. Static immersion test in biodiesel and diesel has been carried out as per SAE J1748 standards. This paper aims to characterize the compatibility of Natural rubber, Nylon and EPDM, commonly encountered in the automotive fuel system in diesel engines. Static immersion test in B100 and diesel fuel was carried out at 55±2 °C (SAE J1748 para 5.2) for 500 hours. Fuels were replaced weekly as suggested in SAE standard. Before the immersion test, mass measurements and visual inspection were recorded. Before and after immersion, comparative behavior was investigated by weight loss, volume change, hardness; tensile strength measurements. Changes in surface morphology were studied by Scanning Electron Microscopy. It was found that natural rubber showed less detrimental effects while significant detrimental effect on EPDM and Nylon was observed. [ABSTRACT FROM AUTHOR]

Abstract: This review aims to cover the state of the art of renewable feedstock use in materials production using photopolymerization processes. This area of investigation is an emerging field of research, and it combines biosourced molecules with a cheap and rapid radiative processing method that avoids any emission of volatile organic compounds. The main classes of naturally occurring molecules and macromolecules such as lipids, amino acids, carbohydrates, polyenes, etc. are detailed. The way they are used or integrated in photopolymerizable systems are described in relation to their applications: coatings, biomaterials, biodegradable drug delivery systems, microelectronics or optoelectronics. This critical review takes into account the reactivity of the various compounds as well as their cytotoxicity, biodegradability and finally their end uses. [Copyright &y& Elsevier]

Abstract: Synthetic and natural polyisoprenes (PI) films were exposed to different UV light sources and then analyzed by Fourier transform infrared (FTIR) and UV spectroscopy, before and after exposure to the UV source. Films of PI standards were separately irradiated by UV sources of different wavelengths: 253, 300, and 350nm. The photo-oxidation was monitored by looking at the dependence of the IR absorbances of the Clyph name="dbnd" />O, and O–H stretching and the H wagging modes of cis- and trans-PI. Irradiation at 253nm leads to cross-linking and polymer reticulation avoiding the complete oxidation of the polymer film. Under 300nm irradiation, the chain-scission reactions occur preferentially leading to the complete oxidation of the film. Irradiation at 350nm leads to photo-oxidation only for exposure times larger than 12h. The natural PI rubbers, Hevea brasilienses (HB), Hancornia speciosa (HS), and Mimusops globosa (MG) were characterized by DSC and FTIR as being high cis-1,4-PI (HB and HS) and high α-trans-1,4-PI (MG). The photo-oxidation of NR presented different kinetics, with induction times smaller than those observed for the cis- and trans-PI standards. The faster photo-degradation process observed for NR films was assigned to the presence of impurities characterized by the presence of O–H and Cds in the FTIR spectra, even before UV irradiation. [Copyright &y& Elsevier]