Rubber Science Research Articles

Sustainable composites with self‐healing capability: Epoxidized natural rubber and cellulose propionate reinforced with cellulose fibers

AbstractAligned with the UN's Sustainable Development Goals (SDGs), self‐healing elastomers stand out as a cutting‐edge field in Rubber Science and Technology. These materials have the potential to reduce resource consumption, prolong the lifespan of infrastructure and products, and contribute to the Circular Economy. This study presents the development of bio‐based self‐healing elastomeric composites prepared from blends of epoxidized natural rubber (ENR) and cellulose propionate (CP) reinforced with cellulose fibers (CFs). The ENR/CP ratio was optimized, with a 70/30 ratio enhancing the tensile strength (TS) of the base rubber and slightly reducing the elongation at break. This blend demonstrated a TS healing efficiency of 75% after a temperature‐driven healing protocol (200 bar at 150°C during 12 h). Then, the CF content was varied to enhance both mechanical performance and self‐healing capabilities. Remarkably, from medium‐high (5 phr to 15 phr) CF content, healing efficiencies higher than 85% were observed with important improvements in the mechanical performance. The self‐healing process was attributed to the synergistic interplay between the polymeric chain mobility and the formation of hydrogen bonds. This innovative approach promises materials with extended lifespans, mechanical robustness, and repairability, underscoring the commitment to SDGs 9, 11, 12, 13, 14, and 15.Highlights Matrix of epoxidized natural rubber (ENR) and cellulose propionate (CP) blends. Cellulose fibers (CFs) reinforced the ENR/CP 70/30 optimized blend. CF addition increases tensile strength (TS) by up to 60%. Healing efficiency over 85% achieved with 5 phr to 15 phr CFs content. Self‐healing attributed to polymeric chain mobility and hydrogen bonds.

Microscopic Origins of the Nonlinear Behavior of Particle-Filled Rubber Probed with Dynamic Strain XPCS.

The underlying microscopic response of filler networks in reinforced rubber to dynamic strain is not well understood due to the experimental difficulty of directly measuring filler network behavior in samples undergoing dynamic strain. This difficulty can be overcome with in situ X-ray photon correlation spectroscopy (XPCS) measurements. The contrast between the silica filler and the rubber matrix for X-ray scattering allows us to isolate the filler network behavior from the overall response of the rubber. This in situ XPCS technique probes the microscopic breakdown and reforming of the filler network structure, which are responsible for the nonlinear dependence of modulus on strain, known in the rubber science community as the Payne effect. These microscopic changes in the filler network structure have consequences for the macroscopic material performance, especially for the fuel efficiency of tire tread compounds. Here, we elucidate the behavior with in situ dynamic strain XPCS experiments on industrially relevant, vulcanized rubbers filled (13 vol %) with novel air-milled silica of ultrahigh-surface area (UHSA) (250 m2/g). The addition of a silane coupling agent to rubber containing this silica causes an unexpected and counterintuitive increase in the Payne effect and decrease in energy dissipation. For this rubber, we observe a nearly two-fold enhancement of the storage modulus and virtually equivalent loss tangent compared to a rubber containing a coupling agent and conventional silica. Interpretation of our in situ XPCS results simultaneously with interpretation of traditional dynamic mechanical analysis (DMA) strain sweep experiments reveals that the debonding or yielding of bridged bound rubber layers is key to understanding the behavior of rubber formulations containing the silane coupling agent and high-surface area silica. These results demonstrate that the combination of XPCS and DMA is a powerful method for unraveling the microscale filler response to strain which dictates the dynamic mechanical properties of reinforced soft matter composites. With this combination of techniques, we have elucidated the great promise of UHSA silica when used in concert with a silane coupling agent in filled rubber. Such composites simultaneously exhibit large moduli and low hysteresis under dynamic strain.

Influence of Sulfur-Curing Conditions on the Dynamics and Crosslinking of Rubber Networks: A Time-Domain NMR Study.

The characterization of the structural and dynamic properties of rubber networks is of fundamental importance in rubber science and technology to design materials with optimized mechanical properties. In this work, natural and isoprene rubber networks obtained by curing at three different temperatures (140, 150, and 170 °C) and three different sulfur contents (1, 2, and 3 phr) in the presence of a 3 phr accelerator were studied using a combination of low-field time-domain NMR (TD-NMR) techniques, including 1H multiple-quantum experiments for the measurement of residual dipolar couplings (Dres), the application of the Carr–Purcell–Meiboom–Gill pulse sequence for the measurement of the transverse magnetization decay and the extraction of 1H T2 relaxation times, and the use of field cycling NMR relaxometry for the determination of T1 relaxation times. The microscopic properties determined by TD-NMR experiments were discussed in comparison with the macroscopic properties obtained using equilibrium swelling, moving die rheometer, and calorimetric techniques. The obtained correlations between NMR observables, crosslink density values, maximum torque values, and glass transition temperatures provided insights into the effects of the vulcanization temperature and accelerator/sulfur ratio on the structure of the polymer networks, as well as on the effects of crosslinking on the segmental dynamics of elastomers. Dres and T2 were found to show linear correlations with the crosslink density determined by equilibrium swelling, while T1 depends on the local dynamics of polymer segments related to the glass transition, which is also affected by chemical modifications of the polymer chains occurring during vulcanization.

Rubber-reinforced rubbers toward the combination of high reinforcement and low energy loss

Reinforcement is a fundamental issue in rubber science and engineering. Traditionally, rubber reinforcement relies on the incorporation of rigid particles into rubber network or creation of the rubber network with dual-crosslink. However, all these methods inevitably sacrifice the unique elasticity of rubber, which is a shackle toward some crucial applications such as energy-saving tires. In this contribution, a novel strategy of rubber-reinforced rubber (3R) with the combination of significant reinforcement and high elasticity is proposed. With experimental/simulating integrated method, a brand-new reinforcing mechanism for rubber is disclosed, called soft matrix-induced large extensionability of hard rubber (“SMILE-HR”). The soft matrix endows the highly-crosslinked rubber particles (HPs) with the capacity of large extensionablity, so the molecular chains in HPs can be highly oriented and thus obtain high strength during stretching, which are primarily responsible for the dramatic reinforcement of 3R. This skillful combination of these two elastic constituents conquers the stubborn contradiction between reinforcement and elasticity, which is very promising for the engineering rubbers served in dynamic environment.

Polymer Materials Research at CMSE

Polymer Materials Research at CMSE

Concluding Cooperation Agreement between The Society of Rubber Science and Technology, Japan, Local Chapter in The Kyushu Area and National Institute of Technology, Kurume College.

Concluding Cooperation Agreement between The Society of Rubber Science and Technology, Japan, Local Chapter in The Kyushu Area and National Institute of Technology, Kurume College.

ゴムの科学研究と私の人生：パタニから京都、そして、今、バンコクで

ゴムの科学研究と私の人生：パタニから京都、そして、今、バンコクで

University Polymer Education in Thailand

SummaryThe scope in Thailand of education in Polymer Science and Technology is reviewed. Five technical colleges offer a diploma in rubber science and technology. Several universities offer a bachelor degree in Polymer or Rubber Science and Technology or Engineering. Others offer degrees in Industrial Chemistry or Materials Science which emphasize polymer technology. A number of universities in Thailand are registered to offer postgraduate degree courses in polymer science/technology/engineering. Of course many universities are authorized to teach polymer science or engineering in their degree courses, or are engaged in polymer research, but do not offer degrees specific to Polymer Science and Technology. Masters degrees have been offered for several decades and now a number of doctoral programs are authorized. Instruction is mainly in reasonably equipped university Chemistry Departments, although there is some in Materials Science programs. Most lecturers have a doctoral degree from a developed country, although Thai PhD graduates are now entering employment. In the instructional process attention has to be paid to problems arising from the nature of teaching in Thai schools. Postgraduate instruction must realize the limited coverage of the first degree as well as certain cultural factors. The majority of the Polymer Bachelor graduates move into industry each year. 80% of Master graduates enter industry. Of the PhD graduates, each year 30% work in industry, about 50% become university lecturers particularly at new universities in the provinces and about 20% work in government research institutes.

A model filler network in nanocomposites prepared by in situ silica filling and peroxide cross-linking in natural rubber latex

Preparation and characteristics of model filler networks in nanocomposites are reported for development of rubber science. The nanocomposites were prepared via a sol–gel reaction in natural rubber (NR) latex using tetraethoxysilane followed by a peroxide cross-linking reaction in the liquid state employing a casting method. The filler network structure was formed in the NR matrix, even though the silica content was only 10 and 17 parts per one hundred rubber by weight. One of the important factors for the formation of the filler network was utilization of rubber particles in the latex as a template. Dynamic mechanical analysis revealed the significant characteristics of the filler network of silica particles in the rubber matrix: Higher and longer plateau regions of storage modulus and dissipation loss modulus in the low frequency region were observed in the in situ silica-filled nanocomposites compared with conventionally prepared nanocomposites. This was mainly ascribed to a strong filler–filler interaction.

Dinuclear Bridging Bidentate Zinc/Stearate Complex in Sulfur Cross-Linking of Rubber

An essential structure of the intermediate generated from zinc oxide and stearic acid during sulfur cross-linking reaction of isoprene rubber is proposed using time-resolved zinc K-edge X-ray absorption fine structure and infrared spectroscopies in situ. The structure is dominantly a bridging bidentate zinc/stearate complex, the molar ratio of the zinc ion to stearate and the coordination number of which are unexpectedly 1:1 and 4, respectively. Combination with a density functional calculation for identifying the intermediate predominantly suggests that its most possible structure is (Zn2(μ-O2CC17H35)2)2+(OH–)2·XY, where X and Y are water and/or a rubber segment. This intermediate has been unknown despite the long history of rubber science and technology. The newly observed zinc/stearate complex may play a role to accelerate the sulfur cross-linking reaction of rubber like an enzyme because of the high Lewis activity of the zinc ion.

金型研究分科会の歩み －発足から14年－

金型研究分科会の歩み －発足から14年－

分析研究分科会の歩み

分析研究分科会の歩み

ナノフィラー充塡架橋ゴムにおけるナノフィラーの構造と物性

Advantages of 3D-TEM/electron tomography are described for development of rubber science and technology. The first result of visualization of carbon black (CB) network is shown, which was obtained by combining 3D TEM/electron tomography and electric characteristic measurements. A novel analysis for characterization of the CB network is proposed on the basis of gelation mechanism of polymer network, where structural parameters of crosslined and branched chains of CB aggregates are determined by 3D-TEM/electron tomography and are utilized. Good relationships between the CB network structures and electrolytic properties are also shown in this review paper.

Influence of Fillers Surface Characteristics on Bound Rubber Properties of Filled Natural Rubber Compounds

One of the most important phenomena in rubber science is the reinforcement by rigid entities, such as carbon black, clays, silicates and calcium carbonate. Thus, these fillers are added to rubber formulations to optimise properties that meet a given service application or set of performance parameters. Fillers can be divided into three categories reinforcing, semi-reinforcing and non-reinforcing. For a given elastomer and state of mix, bound rubber can be considered as a measurement of a surface activity of a filler and is considered as one of major factors in reinforcement. A strong rubber: filler interaction results in a large bound rubber content. Good dispersions and distribution of filler aggregates is also important for the full reinforcing potential of fillers to be reached. In this study, the influence of fillers on bound rubber content of Natural Rubber compounds were determined and compared. Results showed that the bound rubber content followed the trend of Carbon Black>Silica>Carbon Black>Starch. The two main filler characteristics that affect the bound rubber properties are the filler particle size and surface activity. The specific activity of the filler is determined by the physical and chemical nature of the filler surface in relation to that of elastomer. Keywords: reinforcement, surface energy

ELASTOMERIC COMPOSITES BASED ON NANOSPHERICAL PARTICLES AND CARBON NANOTUBES: A COMPARATIVE STUDY

ABSTRACT The reinforcement of elastomeric materials by addition of mineral fillers represents one of the most important aspects in the field of rubber science and technology. The improvement in mechanical properties arises from hydrodynamic effects depending mainly on the amount of filler and the aspect ratio of the particles and also on polymer–filler interactions depending on the surface characteristics of the filler particles and the chemical nature of the polymer. The past few years have seen the extensive use of nanometer-scale particles of different morphologies on account of the small size of the filler and the corresponding increase in the surface area that allow a considerable increase in mechanical properties even at very low filler loading. Among these nanoparticles, spherical particles (such as silica or titania) generated in situ by the sol-gel process and carbon nanotubes are typical examples of materials used as a nanosize reinforcing additive. Specific features of filled elastomers are discussed through the existing literature and through results of the author's research based on poly(dimethylsiloxane) filled with spherical silica or titania particles and on styrene–butadiene rubber filled with multiwall carbon nanotubes. The reinforcing ability of each type of filler is discussed in terms of morphology, state of dispersion (investigated by transmission electron microscopy, atomic force microscopy, small-angle neutron scattering), and mechanical and electrical properties. In addition, the use of molecular spectroscopies provides valuable information on the polymer–filler interface. Spherical silica and titania spherical particles are shown to exhibit two distinct morphologies, two different polymer–filler interfaces that influence the mechanical properties of the resulting materials. The superiority of carbon nanotubes over carbon black for mechanical reinforcement and electrical conduction is mainly attributed to their large aspect ratio rather than to strong polymer–filler interactions. The use of hybrid fillers (carbon nanotubes in addition to carbon black or silica, for example) has been shown to give promising results by promoting an enhancement of mechanical and electrical properties with regard to each single filler.

History of Compounding Technology Subcommittee in the Society of Rubber Science and Technology Japan

History of Compounding Technology Subcommittee in the Society of Rubber Science and Technology Japan

MICROSTRUCTURE AND MOLECULAR DYNAMICS OF ELASTOMERS AS STUDIED BY ADVANCED LOW-RESOLUTION NUCLEAR MAGNETIC RESONANCE METHODS

ABSTRACTNuclear magnetic resonance (NMR) certainly belongs to the most powerful spectroscopic tools in rubber science. Yet the often high level of experimental and in particular instrumental sophistication represents a barrier to its widespread use. Recent advances in low-resolution, often low-field, proton NMR characterization methods of elastomeric materials are reviewed. Chemical detail, as normally provided by chemical shifts in high-resolution NMR spectra, is often not needed when just the (average) molecular motions of the rubber components are of interest. Knowledge of the molecular-level dynamics enables the quantification and investigation of coexisting rigid and soft regions, as often found in filled elastomers, and is further the basis of a detailed analysis of the local density of cross-links and the content of nonelastic material, all of which sensitively affect the rheological behavior. In fact, specific static proton NMR spectroscopy techniques can be thought of as molecular rheology, and they open new avenues toward the investigation of inhomogeneities in elastomers, the knowledge of which is key to improving our theoretical understanding and creating new rational-design principles of novel elastomeric materials. The methodological advances related to the possibility of studying not only the cross-link density on a molecular scale but also its distribution and the option to quantitatively detect the fractions of polymer in different states of molecular mobility and estimate the size and arrangement of such regions are illustrated with different examples from the rubber field. This concerns, among others, the influence of the vulcanization system and the amount and type of filler particles on the spatial (in)homogeneity of the cross-link density, the amount of nonelastic network defects, and the relevance of glassy regions in filled elastomers.

X-RAY COMPUTED MICROTOMOGRAPHY OF RUBBER

ABSTRACT In rubber science, X-ray computed microtomography (micro CT) is becoming an increasingly used technique to characterize 3D microstructures. As a first step, experimental methods, limitations, and data analysis are described. A review of published micro CT studies for rubber is reported. Examples of our recent works are presented, including investigations on samples or complex structures, for compact or foam rubbers. Micro CT is used to describe the evolution of microstructures relative to different processing steps, to environmental interaction, and to adaptation to a mechanical deformation. New insights and better understanding of damage mechanisms due to quasistatic, creep, and fatigue solicitations are presented from in situ micro CT experiments. Perspective studies are outlined.

The Scientist, the Governor, and the Planter: The Political Economy of Agricultural Knowledge in Indochina During the Creation of a “Science of Rubber,” 1900–1940

From the turn of the twentieth century until shortly before the Second World War, private business collaborated with the colonial government in Indochina in the formative development of colonial agricultural science. This article focuses on that development with a particular eye to how research was conducted and influenced by the changing politics of French colonization, what was chosen as worthy of research, and how agricultural science projects were defined, structured, and funded.

The Scientist, the Governor, and the Planter: The Political Economy of Agricultural Knowledge in Indochina During the Creation of a “Science of Rubber,” 1900–1940

From the turn of the twentieth century until shortly before the Second World War, private business collaborated with the colonial government in Indochina in the formative development of colonial agricultural science. This article focuses on that development with a particular eye to how research was conducted and influenced by the changing politics of French colonization, what was chosen as worthy of research, and how agricultural science projects were defined, structured, and funded.