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Atsushi Takai
NIPPON GOMU KYOKAISHI, Volume 94, pp 182-186; https://doi.org/10.2324/gomu.94.182

Abstract:
Natural rubber latex is widely used in medical gloves. However, it contains allergen proteins that cause symptoms such as urticaria. This article reviews the quality-control factor of deproteinized natural rubber latex, which is commercially produced by enzyme-centrifugation method.
Koichi Yamaguchi
NIPPON GOMU KYOKAISHI, Volume 94, pp 245-249; https://doi.org/10.2324/gomu.94.245

Abstract:
Many companies use molds to perform vulcanization molding of rubber. The unvulcanized rubber compound, which has been kneaded, mixed, and preformed, is loaded on the mold, and then mold vulcanization molding is applied using a compression molding machines, an injection molding vulcanization machines, and a transfer molding machines. Mold vulcanization molding, which uses a mold, involves vulcanization reaction (cross-linking reaction) and molding under high temperature and high pressure, and the goodness or badness of the resulting molded product is determined by the compound design, the accuracy of the mold, the goodness or badness of the mold, and the vulcanization molding conditions. In this section, this paper discusses the history of rubber molding, the cancellation of the technology of rubber molding and the trends to be discussed.
Yoshihide Fukahori
NIPPON GOMU KYOKAISHI, Volume 94, pp 237-244; https://doi.org/10.2324/gomu.94.237

Abstract:
In this final Part 6, the Author proposes a new theory of rubber wear connected with rubber friction through abrasion pattern formation generated by stick-slip motion. The kinetic interpretation was introduced to explain the close relationship between the wear rate and the distance of abrasion patterns named the wear-abrasion pattern diagram, which showed that two mechanisms work differently at an initial stage and a final stage of the abrasion pattern formation. After the inspection of the theory of rubber wear given by AG. Thomas theoretically and experimentally, the author proposes a new theory of the rubber wear based on the fracture mechanics treatment, where is shown that the stick-slip motion is the direct driving force to promote the rubber wear, and thus the abrasion pattern of the same length as the period of the stick-slip motion is left on the wear surface of the rubber.
Koji Matsuyama
NIPPON GOMU KYOKAISHI, Volume 94, pp 282-286; https://doi.org/10.2324/gomu.94.282

Abstract:
As for the performance evaluation of winter tires, in general, stable evaluation in the room is desired because the vehicle test is affected by the weather and the evaluation period is limited. In addition, since rubber materials and tire characteristics depend on temperature, temperature is one of the very important factors to obtain high reliable results in tire evaluation, and it can be said that it depends on how it can be tested under constant temperature conditions. We will introduce the general ice performance evaluation technology of winter tires by the indoor vehicle test, indoor drum test method, and lab evaluation technology.
Masatoshi Tosaka
NIPPON GOMU KYOKAISHI, Volume 94, pp 130-135; https://doi.org/10.2324/gomu.94.130

Abstract:
Though the inherent elasticity of rubber materials is derived from the amorphous polymer chains, crystals are also an important factor in understanding the physical properties of rubber. For example, in natural rubber, butadiene rubber, chloroprene rubber, and some others, crystallization occurs under high elongation, which is thought to exert a self-reinforcing effect. Also the hard segments of urethane rubbers are sometimes crystalline. Dynamic change of such crystal structures has a significant effect on the physical properties of rubber, and wide angle X-ray diffraction (WAXD) is a powerful tool for analyzing such dynamic structural changes. In this paper, we aim to explain the basic principles of WAXD in as simple words as possible for readers who are not familiar with WAXD measurements.
Hiroki Yamamura, Tetsuo Tominaga, Takumi Adachi, Hirofumi Senga
NIPPON GOMU KYOKAISHI, Volume 94, pp 151-157; https://doi.org/10.2324/gomu.94.151

Abstract:
Recently, we have developed a very high strength rubber by hydrogenation of styrene-butadiene rubber (SBR). Hydrogenated SBR represents the changes of stress-strain curve and viscoelastic property from conventional SBR. The changes seem to be related to an increment of entanglement density with hydrogenation. To analyze mechanical properties of crosslinked rubbers, coarse-grained molecular dynamics (CGMD) simulation has been frequently used. However, Kremer-Grest model, one of the most famous CG models, uniquely determines an entanglement density of polymer melt and isn’t suitable for studying hydrogenated SBR. Therefore, we performed CGMD simulations using KremerGrest model with angle potential in order to confirm whether the stress-strain curves and the tanδ master curves of the simulations fit that of the experiments for SBR. In this study, we made crosslinked rubber models of hydrogenated and non-hydrogenated SBRs with entanglement densities corresponding to experimental values of viscoelastic measurements. The calculated values of the stress-strain curves and the tanδ master curves roughly match the experimental values. Therefore, we conclude that the increment of entanglement density plays an important role in the changes of mechanical properties by hydrogenation of SBR.
Toshikazu Takata
NIPPON GOMU KYOKAISHI, Volume 94, pp 11-17; https://doi.org/10.2324/gomu.94.11

Abstract:
In this review, we would like to discuss on the effect of rotaxane-crosslink on the toughening of crosslinked polymer, which is obtained by copolymerization of two-vinyl group-tethering rotaxane crosslinker (RC) with a typical vinyl monomer such as n-butyl acrylate. Rotaxane-crosslinked polymer (RCP) always showed higher mechanical property than covalently crosslinked polymer (CCP). As for the effect of movable distance of the wheel component along the axle component, RCP obtained from longer axle-possessing RC showed higher toughness than that from shorter one. Meanwhile, rotaxane crosslinkers having thickness-different axle components were prepared to evaluate the effect of actual mobility on the mechanical property. RCPs derived from RC consisting of higher mobile components showed toughness stronger than that derived from RC with lower mobile components. The effect of the rotaxane crosslink on the toughening of crosslinked polymer was accounted for the high mobility and freedom of the rotaxane components, while the toughening mechanism was studied on the basis of timing of the transition from Affine deformation to Non-Affine deformation caused by the rotaxane crosslink.
Ryota Tamate, Masayoshi Watanabe
NIPPON GOMU KYOKAISHI, Volume 94, pp 39-45; https://doi.org/10.2324/gomu.94.39

Abstract:
Ion gels, soft materials that contain ionic liquids (ILs), are promising soft solid electrolytes for use in various electrochemical devices. Due to the recent surge in demand for flexible and wearable devices, highly durable ion gels have attracted much attention. In this context, the introduction of a self-healing ability would significantly improve the longterm durability of ion gels subject to mechanical loading. Nevertheless, compared to hydrogels and organogels, the self-healing of ion gels has barely investigated. In this review, we address recent our development of functional ion gels that can heal themselves when mechanically damaged. Light-induced healing of ion gels are discussed as a stimuli-responsive healing strategy, after which self-healable ion gels based on supramolecular chemistry are addressed. Tough, highly stretchable, and self-healable ion gels can be fabricated through the judicious design of polymer nanostructures in ILs in which polymer chains and IL cations and anions interact.
Shintaro Nakagawa, Naoko Yoshie
NIPPON GOMU KYOKAISHI, Volume 94, pp 58-65; https://doi.org/10.2324/gomu.94.58

Abstract:
Mechanical performances are the most important aspect of elastomers consisting of a three-dimensionally cross-linked polymer network. Dynamic properties such as toughness, self-recoverability, and self-healing ability can be implemented by incorporation of physical crosslinks, which are weak and reversible bonds or interactions, into polymer networks. In this review, we focus on elastomers having hydrogen bonds (H-bonds) as the physical crosslinks and discuss the recent advances and directions in the field. After a general introduction to physical crosslinks and H-bonds in polymeric materials, our study on a tough and self-recoverable elastomer based on bioinspired phase-separated structure is reviewed. Application of this strategy to triblock copolymer-type thermoplastic elastomers is also discussed in the following section. Then, we turn our attention to the chemistry of H-bonds and introduce our recent findings on a tough and self-healable elastomer based on a new class of H-bonds, namely the entropy-driven H-bonds. Finally, the current and future directions of the H-bonded polymeric materials are discussed.
Masao Doi
NIPPON GOMU KYOKAISHI, Volume 93, pp 352-357; https://doi.org/10.2324/gomu.93.352

Abstract:
When a drop of coffee dries on a dish, many non-equilibrium processes are taking place. The water changes into vapor and diffuses out in air. Inside the coffee, liquid flow is induced by the surface tension, and coffee particles are convected to the edge of the droplets, leaving ring-like stains at the edge. This example demonstrates the complexity and the multi-physics nature involved in the phenomena we are seeing in our everyday life. Here as the last part of this series of lectures, I will discuss a few physics involved in evaporation and drying focusing on two problems, how the evaporation rate is determined, and how the structure of the dried material is determined.
Katsuhiko Tsunoda, Yoshihiro Morishita
NIPPON GOMU KYOKAISHI, Volume 94, pp 142-149; https://doi.org/10.2324/gomu.94.142

Abstract:
In this paper, fundamental knowledge for fracture of rubber is summarized. Standardized rubber testing methods and fundamental understanding of fracture mechanics for rubber is briefly discussed. Tensile strength in standardized testing method is also reviewed from fracture mechanics point of view. Throughout this paper, the important role of hysteresis energy for rubber strength is highlighted.
Akihiro Yabuki, Ji Ha Lee
NIPPON GOMU KYOKAISHI, Volume 94, pp 66-71; https://doi.org/10.2324/gomu.94.66

Abstract:
Corrosion protective coatings have been widely applied as a surface treatment to prevent corrosion of various metallic materials, such as carbon steels, aluminum alloys and magnesium alloys. One of the important characteristics which is required in the corrosion protective coatings is the self-healing ability. The self-healing coatings mean that when mechanical damage occurs and corrosive substances in the environment begin to degrade the bare metal surface, the damaged surface is repaired automatically by the chemical composition of the coating. This paper describes recent results which are developed self-healing coatings using the cellulose nanofibers and their network structure.
Kazuaki Sanada, Yasuka Nassho
NIPPON GOMU KYOKAISHI, Volume 94, pp 26-32; https://doi.org/10.2324/gomu.94.26

Abstract:
Microscopic damage such as matrix crack, interlaminar fracture and interfacial debonding generates within carbon fiber reinforced polymers (CFRPs) and causes reduction in mechanical properties of CFRPs. Inspired by biological system, a concept of self-healing was proposed. Self-healing composites are designed to sense damage and repair automatically, thereby improving the reliability of CFRPs. Self-healing is accomplished by containers incorporating healing agents within matrix of CFRP, thus it is important to distribute containers throughout the matrix to obtain sufficient self-healing efficiency. In this paper, we present simply outline of self-healing CFRPs and report recently progress for self-healing spread carbon fiber (SCF)/ epoxy (EP) laminates.
Hideyuki Hideyuki Otsuka, Daisuke Aoki, Yasuhiro Shoda, Katsuhiko Tsunoda
NIPPON GOMU KYOKAISHI, Volume 94, pp 33-38; https://doi.org/10.2324/gomu.94.33

Abstract:
In this review paper, the design of self-healing polymers and urethane-containing rubber materials based on dynamic covalent chemistry is described. This review is mainly divided into two parts. In the former part, the design of self-healing polymer networks with autonomously exchangeable C–C bonds or thermally exchangeable S–S bonds is introduced. The incorporation of such dynamic covalent bonds into polymer networks can endow polymer networks with structurally reorganizable properties. Not only self-healing property, but also reprocessability and adhesion capability were observed for the polymer networks with dynamic covalent bonds under appropriate conditions. In the latter part, the application of cross-metathesis reactions of C=C bonds between polybutadienes and olefin-containing polyurethanes to the synthesis of novel polybutadienes with urethane linkages as a source of hydrogen bonds is described. A series of polybutadienes copolymers with different contents of urethane linkages can be prepared by changing the feed ratios of the polybutadiene and olefin-containing polyurethanes in the cross-metathesis reactions. The aggregation structure of deuterated polybutadienes copolymers with different contents of urethane linkages are characterized by small-angle neutron scattering. Cured rubber materials prepared from polybutadienes copolymers with urethane linkages exhibit large energy dissipation at high strain.
Yosuke Maeda
NIPPON GOMU KYOKAISHI, Volume 94, pp 177-181; https://doi.org/10.2324/gomu.94.177

Abstract:
Rubber products such as gloves and masks are indispensable in a medical workplace etc., where hygienic measures are required. However, rubber products sometimes cause health problems such as allergic disorders. Allergies caused by rubber products include immediate-type latex allergy and delayed-type allergic contact dermatitis. In particular, chemicals deliberately added in working processes of rubbers such as vulcanization accelerator sometimes cause allergic contact dermatitis, so it is very important to evaluate their allergic potentials by skin sensitization tests. Although animal tests have been the mainstream for skin sensitization tests for a long time, non-animal alternative test methods are becoming mainstream for animal welfare reasons. This review describes the latest trends of skin sensitization test methods.
Daisuke Nohara
NIPPON GOMU KYOKAISHI, Volume 94, pp 265-270; https://doi.org/10.2324/gomu.94.265

Abstract:
In this review, technologies of materials development and compound development for winter tire are summarized. Especially, implemented materials and compound technologies, which are used for tire, and relating patents are introduced. Some of those technologies about mechanism of improving grip on ice are also discussed.
Yoshimasa Hashimoto
NIPPON GOMU KYOKAISHI, Volume 94, pp 260-264; https://doi.org/10.2324/gomu.94.260

Abstract:
The history of winter tire development in Japan is described. Studless tires (tires without stud pins) have been developed to replace studded tires whose use has been prohibited due to the dust problem caused by stud pins scraping the road surface. With the spread of studless tires, the icy road surface was polished by the tires and changed to a very slippery and smooth icy road surface. Therefore, the history of development of studless tires is the history of improvement of performance on ice. In order to improve the frictional force of the tire on the icy road surface, it is necessary for the rubber to adhere to the icy surface. For that purpose, adhesive friction, edge effect, and water film removal effect are important as friction mechanisms.
Hiroyuki Minaki
NIPPON GOMU KYOKAISHI, Volume 94, pp 276-281; https://doi.org/10.2324/gomu.94.276

Abstract:
In order to develop a tire that can run safely even on snowy and icy road surface, it is necessary to elucidate the complex friction phenomenon with prediction technologies. This paper introduces prediction technologies for winter tire development. Finite Element Method and Finite Volume Method are used to model tire and snow, respectively. Snow deformation is calculated by the Eulerian formulation to solve the complex interaction between snow and tire tread pattern. In order to represent the shear characteristics of snow, the Mohr-Coulomb plasticity model is used. This prediction technology is used to improve snow traction performance through pattern design. In addition, a crushable foam material and Discrete Element Method are applied to model the mechanism of snow deformation. Thermal fluid-structure interaction analysis considering phase change using particle-based simulation is applied to elucidate the friction characteristics of rubber on ice. Ice and water are modelled using Lagrangian particle-based method, and a phase change model is introduced to consider ice melting. The method predicts that the coefficient of friction decreases due to low drainage performance when the number of sipes is small.
Toshikazu Takata
NIPPON GOMU KYOKAISHI, Volume 94, pp 103-110; https://doi.org/10.2324/gomu.94.103

Abstract:
We discuss on the effect of rotaxane-cross-link on the mechanical property (i.e. toughening) of the cross-linked polymers, in particular on the mobility effect of the rotaxane components, using [2]rotaxane cross-linkers having low molecular weight axles but not high molecular weight one as mentioned in the previous paper, to evaluate the function of the circumrotatory and flipping mobilities in comparison with the translating mobility of the wheel components at the cross-link points. Independent on the length of the axle component, the low molecular weight axle-containing rotaxane cross-linkers showed good power to strengthen the toughness of the cross-linked polymers. Meanwhile, [3]rotaxane cross-linkers having two crown ether wheels with two polymerizable vinyl groups worked as the excellent cross-linkers to contribute to the toughening of the cross-linked polymers, whereas the axle component had no direct bonding to the polymer chain, being different from that of [2]rotaxane cross-linker. In the latter half of this review, we dealt with macrocyclic cross-linkers which can accept polymer chains in their cavity to form rotaxane-type cross-link. 60-Membered macrocycle possessing two Pd(II) complex units in its cavity functioned as a rotaxane-type cross-linker by accepting two polymer chains possessing the coordinating sites to Pd(II). Cross-linker synthesized by linking two 30-membered macrocyclic Pd(II) complex also showed a similar ability to link two polymer chains to cross-linking.
Makiko Kano, Atsuya Higuchi, Hirobumi Ito, Takeshi Kondo, Masaki Kakiage, Takeshi Yamanobe, Hiroki Uehara
NIPPON GOMU KYOKAISHI, Volume 94, pp 87-94; https://doi.org/10.2324/gomu.94.87

Abstract:
Assuming the degradation of styrene-butadiene rubber (SBR) during its practical usage, the accelerated weathering tests were conducted with various pre-strains. Although the isotropic narrower cracks form under no pre-strain (0% strain), the wider crazes orients perpendicular to the pre-strained direction under 20% pre-strain. The larger prestrain of 40% induces the vertical penetration of these crazes vertically from the exposed surface. The cross-sectional observation under 80% pre-strain suggests that the further craze propagation finally tears the sample inside. Correspondingly, both of breaking strength and strain significantly decreased with increasing pre-strain. In contrast, the post-strain applied after the accelerated weathering test under no pre-strain gave only the middle cracks, suggesting that the initial narrower cracks grow into the latter wider crazes during the accelerated weathering tests under prestrained. The origin of such initial narrower cracks is attributable to the pre-strained structure before the accelerated weathering test, which was confined by scanning probe microscopy (SPM) observation. The distribution of carbon black (CB) mixed in the base rubber was biased even at the low strain. The characteristic phase separation of CB domains gave the narrower cracks during the accelerated weathering test, which further grow into the wider crazes and inside tearing.
Taizo Sakaki
NIPPON GOMU KYOKAISHI, Volume 94, pp 217-222; https://doi.org/10.2324/gomu.94.217

Abstract:
3D printer is a manufacturing method which builds layer upon layer and is in contrast to conventional manufacturing methods. This manufacturing method has the potential to significantly change the way of manufacturing and brings various advantages. In the past, since 3D printer was technically at an early stage, it was referred as Rapid Prototyping and was used only for prototype to confirm the shape. However, today, with technical enhancements, the usage is spreading from functional prototype, production tools such as jigs, to end use parts production. This paper includes case studies at Ricoh. Furthermore, this paper describes the possibility that 3D printer can change way of manufacturing and its limitations. The specific examples introduced in this paper focus on polymer.
Shohei Ida
NIPPON GOMU KYOKAISHI, Volume 94, pp 46-51; https://doi.org/10.2324/gomu.94.46

Abstract:
In order to develop highly functional hydrogel materials, elaborate design and precision construction of network structure are required. To this end, we are focusing on controlled/living radical polymerization techniques not only to synthesize defined precursor polymers but also to give a unique function by reversible activation-deactivation reaction mechanism. In this paper, a feature of living radical polymerization for gel synthesis is briefly described, and our recent results are outlined. In particular, the design of self-healable gel utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization mechanism and amphiphilic conetworks with crosslinked domains capable of unique thermoresponsive swelling behavior and mechanical toughening are presented.
Masayoshi Nishiura, Zhaomin Hou
NIPPON GOMU KYOKAISHI, Volume 94, pp 52-57; https://doi.org/10.2324/gomu.94.52

Abstract:
This article describes a new class of self-healing materials formed by the copolymerization of ethylene and anisyl-substituted propylenes using a sterically demanding half-sandwich scandium catalyst. The copolymerization proceeded in a controlled fashion, affording unique multi-block copolymers composed of relatively long alternating ethylene-alt-anisylpropylene sequences and short ethylene−ethylene units. By controlling the molecular weight and varying the anisyl substituents, a series of copolymers that show a wide range of glass-transition temperatures (Tg) and mechanical properties have been obtained. The copolymers with Tg below room temperature showed remarkable self-healability, being able to autonomously self-heal upon mechanical damage not only in a dry environment but also in water and aqueous acid and alkaline solutions, while those with Tg around or above room temperature exhibited excellent shape-memory property. The unique mechanical properties may be ascribed to the phase separation of the crystalline ethylene−ethylene nanodomains from the ethylene-alt-anisylpropylene matrix.
Yoshihide Fukahori
NIPPON GOMU KYOKAISHI, Volume 94, pp 3-10; https://doi.org/10.2324/gomu.94.3

Abstract:
The author proposes a new philosophy and theory for rubber friction that are significantly different from the existing classical theories. The total friction coefficient μall incorporates three factors including an adhesion term μadh, a deformation term μdef and a crack formation term μcrac. This generates an equation μall=μadh+μdef+μcrac≒μadh [1+K2( tanδ/√2+√2 Kεc)E−7/6 W1/6 ] where η is the viscosity of the uncross-linked phase, E the modulus of the cross-linked rubber, V sliding velocity, C crack length, W normal load, K1, K2, Kε are all coefficients. The adhesion term is the most dominant factor during rubber friction, which roughly contributes about 70~80% of the total friction coefficient as the zeroth approximation. The new theory might prepare a quite reasonable interpretation for the velocity and normal load dependence of the friction coefficient of the rubber, which is related closely to the formation of meniscus in the interface between the rubber and the solid.
Yoshihide Fukahori
NIPPON GOMU KYOKAISHI, Volume 94, pp 95-102; https://doi.org/10.2324/gomu.94.95

Abstract:
The author proposes the essential features of wear of rubber, where the rubber wear is related inseparably to abrasion pattern formation generated by stick-slip motion during frictional sliding of the rubber. Initial micro-cracks in this process are induced by the micro-vibration of high frequency, which grow up to the abrasion patterns accelerated by the stick-slip motion. Thus, the wear of the rubber is just understood to be the process of the formation and separation of ridges of the abrasion pattern. The author newly induces “Wear-abrasion pattern diagram”, where the rate of wear V 4 is connected directly to the distance between the abrasion patterns Dab with the equation, V 4 =k(Dab) n, n be - ing 1/3 at an early stage and 3.5 for a final steady stage of the wear, k a constant.
Yoshihiro Morishita, Katsuhiko Tsunoda
NIPPON GOMU KYOKAISHI, Volume 94, pp 116-122; https://doi.org/10.2324/gomu.94.116

Abstract:
Stress-strain relation is one of the most basic mechanical properties of cured rubber, and it has been studied both in academia and industry for many years. It is well known that stress-strain relation of cured rubber depends on various features of rubber compounds, such as type of polymer, type of filler, loading amount of filler, cross-link density and so on. However, there remain several problems to be fully understood for stress-strain relation of filled rubber; e.g., the effect of the structure of filler-network, filler-filler interaction and filler-polymer interaction. In this review, we explain fundamental knowledge for stress-strain relation of cured rubber both for theoretical aspect and methodology for the analysis of experimental data. Firstly, stress-strain relation of unfilled rubber (rubber without filler) is explained, then that of filled rubber (rubber with filler) is explained on the basis of fundamental knowledge for unfilled rubber. Although, various models for stress-strain relation of filled rubber have been proposed and there has not been unified understanding, we explain one of the models, which, we believe, is helpful for engineer/researcher to understand and evaluate stress-strain relations of filled rubber.
Kenji Urayama
NIPPON GOMU KYOKAISHI, Volume 94, pp 123-129; https://doi.org/10.2324/gomu.94.123

Abstract:
This article describes the fundamentals of the measurement and analysis for linear dynamic viscoelasticity of elastomeric materials. We also introduce the linear dynamic viscoelasticity of the two types of high-damping elastomer with different characteristics of network structure.
Katsuhiro Yamamoto
NIPPON GOMU KYOKAISHI, Volume 94, pp 136-141; https://doi.org/10.2324/gomu.94.136

Abstract:
Small-angle X-ray scattering is a method to measure scattered X-ray interference by the spatial scattering length density fluctuation in the sample. One can investigate, for example, the radius of gyration of polymer in solution, size and shape of a protein in aqueous solution, the structure of micelle (size and shape, its distribution), microphase separated structure (period and morphology), crystal lamella, the network structure of gels, nanoparticles. SAXS is a non-destructive method for observing the nanometer-scale structure and is suited for various in-situ measurements. Here, the principle of small-angle X-ray scattering is introduced, and a few examples of SAXS experiments related to the rubber materials will be given.
Seiichi Kawahara
NIPPON GOMU KYOKAISHI, Volume 94, pp 170-176; https://doi.org/10.2324/gomu.94.170

Abstract:
Serious hygiene issues in the field of rubber are summarized in this review article. We look at latex allergy issue and nitrosamine issue that have occurred in the past as serious hygiene issues of rubber products, while keeping in mind that saving a human life is a true proposition as a superordinate concept that must be prioritized above all. We reaffirm that new technologies must be developed based on new concepts to solve these issues and understand a significant importance of developing protein-free natural rubber and nitrosamine-free vulcanization accelerators. We recognize that hygiene issues are usually avoided by laws and regulations such as the positive list system since developments of new technologies based on new concepts are exceedingly difficult. We also look at a progress status of preparation of the “5th edition of the positive list regarding rubber food utensils, containers and packagings”. Consequently, one may understand the activities and importance of the Research Subcommittee on Hygiene Issues of the Society of Rubber Science and Technology, Japan, which conducts research on the hygiene issues in the field of rubber.
Hiroaki Nakano
NIPPON GOMU KYOKAISHI, Volume 94, pp 192-197; https://doi.org/10.2324/gomu.94.192

Abstract:
Rubber materials are frequently used as closures for containers, because of their good sealing properties. As for such closures intended to be used for containers for medical agent, there are regulations regarding protection, compatibility, safety, and functionality. This article briefly describes such regulations of Japanese pharmacopoeia and related information of other pharmacopoeia and ISO standards.
Kazuhiro Takahara
NIPPON GOMU KYOKAISHI, Volume 94, pp 187-191; https://doi.org/10.2324/gomu.94.187

Abstract:
In this review, rubber components for medical devices, especially disposable (single-use) devices, are explained. Synthetic rubbers have been developed since World War II. They are used even in various medical devices. However, its scope of application is limited, most synthetic rubber components are used only for applications that do not come into direct contact with biological tissue, or even come into contact with, only skin and mucous membranes. Disposable medical devices have been also developed rapidly since the 1950s, and adopted a large number of synthetic rubber components that take advantage of their flexibility, elasticity, and resealability after removing the pierced needle. Chemical and biological evaluation should be carried out to prove the safety of medical devices, recently, the demand for E & L (extractable and reachable) testing at the component level is increasing.
Satoshi Hirai
NIPPON GOMU KYOKAISHI, Volume 94, pp 271-275; https://doi.org/10.2324/gomu.94.271

Abstract:
This paper focused on shape design of winter tyres, including Studless tyre, European Winter tyre and Studded tyre. Tread pattern of winter tyres are designed in consideration of tyre grip on ice and snow surface, which consists of four types of friction forces. This paper shows design methods of tread pattern according to the mechanism of the friction forces. Winter tyres are designed with many conflicts in various conditions on ice and snow road.
Yoshihide Fukahori
NIPPON GOMU KYOKAISHI, Volume 94, pp 158-165; https://doi.org/10.2324/gomu.94.158

Abstract:
In the last Part 4, the indivisible relationship between stick-slip motion, abrasion pattern formation and wear of rubber is shown experimentally. However, many questions have been left unanswered concerning the abrasion pattern formation. For example, why is the periodic abrasion patter formed always on the surface of the rubber through the whole wear process? Why does a root (crack) of ridge of the abrasion pattern go ahead along in the sliding direction of slider? In addition, why is the crack deepened only slightly (almost 15 degree) to the surface of the rubber? Here the author discusses about the questions mentioned above from dynamics and fracture mechanics points of view. In the formation of initial microcrack, the geometrical condition shaped between a tip of the slider and a wall of the rubber induced in the front of the slider at a stick stage of stick-slip motion produces the rotary force for the microcrack, which works to change the propagation direction of the microcrack to a lower angle to the rubber surface. In the propagation of abrasion pattern, the rotatory force generated when the slider passes over the ridge bends and opens the root of the ridge, resulting in the steady propagation of the ridge with a low angle to the rubber surface.
Hiroshi Mouri
NIPPON GOMU KYOKAISHI, Volume 94, pp 223-229; https://doi.org/10.2324/gomu.94.223

Abstract:
Para rubber tree, the current source of natural rubber is susceptible to disease and has a history of extinction. To make natural rubber a sustainable product, number of efforts are underway to obtain alternative sources of natural rubber. Guayule and Russian dandelion are currently the two strong candidates. Study on guayule, a bush that grows in an arid area has been on and off for many decades. The prohibitive cost of processing rubber always discouraged continuous effort. In 2014, an environmentally friendly pilot plant using solvent extraction technology was built at the outskirt of Mesa, Arizona, with a nearby 280-acre farm. The new facility will not only significantly improve productivity of rubber manufacturing, but also physical properties are equivalent to the current source, para rubber. Another alternative source of natural rubber, Russian dandelion, a weed that grows in a temperate climate was also discussed.
Kayoko Nohara
NIPPON GOMU KYOKAISHI, Volume 94, pp 230-236; https://doi.org/10.2324/gomu.94.230

Abstract:
It is increasingly difficult to solve social problems using fragmented knowledge when our environment is constantly fluctuating, the future is unpredictable and people have diverse, often contrasting values. When tackling issues, it is desirable to keep an open mind and incorporate the perspectives of others, not bound by the assumptions and traditional culture of each discipline. This review discusses how science and technology can be integrated with other fields to generate more creative questions and solutions, and what theoretical discussions prevail around such transdisciplinary practice. It introduces the notions of science communication, which aims to produce a dialogue between scientists/engineers and the lay public, and STEAM education and thinking, which view scientific and technological knowledge as continuous to that of other disciplines and ways of thinking. The author also discusses the mechanism of science and technology as social symbols from the perspective of semiotics and translation studies, looking at how rubber and latex are interpreted beyond their functions, using the fashion and media scenes as examples.
Luu Thanh Huyen, Chen Ao Ran, Yoshimasa Yamamoto, Seiichi Kawahara
NIPPON GOMU KYOKAISHI, Volume 93, pp 293-299; https://doi.org/10.2324/gomu.93.293

直樹 寺田
NIPPON GOMU KYOKAISHI, Volume 93, pp 337-341; https://doi.org/10.2324/gomu.93.337

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