Seiichi Kawahara

• Nagaoka University of Technology

Natural rubber (NR) with structural integrity was prepared by Fast Rubber Sheet-Forming (FRSF) method for the first time, using NR latex derived from Para rubber tree (Hevea brasiliensis). NR was prepared by spraying the NR latex onto preheated metallic surfaces at various drying temperatures of 140, 150, 160, and 170 °C for short times, a minute o...

Island-nanomatrix structure, discovered as a nanostructure inherent to natural rubber, is one of the essential key-factors in elucidating the reason why natural rubber possesses better balanced mechanical properties required for a raw rubber. It is important to understand how the island-nanomatrix structure is formed, what roles it plays, and how i...

Latex consisting of a NR/polyaniline (NR/PAni) blend is used in the preparation of thin elastic films. In this study, NR/PAni latex blends with different amounts of doped PAni and surfactants (sodium dodecylbenzene sulfonate [SDBS] and sodium dodecyl sulfate [SDS]) were prepared through prevulcanization. The films were prepared from prevulcanized l...

In the present scenario, the world is concerned about producing more environmentally friendly and sustainable products by reducing the carbon footprint, especially in elastomer products. Therefore, the incorporation of maximum naturally produced white fillers like silica into a naturally originated elastomer, i.e., natural rubber (NR), is the ultim...

Modification of graphene oxide (GO) by vinyltriethoxysilane (VTES) was investigated to study the effect of silanized GO on radical graft copolymerization of GO onto deproteinized natural rubber (DPNR). The modified GO, GO-VTES (a and b), was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, contact angle, thermal gr...

This study describes the preparation and characterization of a green and safe membrane based on a natural polymer for metal adsorption. Natural rubber-grafted-(2-hydroxyethyl methacrylate) with a special nanostructure was synthesized by graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of natural rubber (NR) particles us...

This study aims to prepare and characterize a composite of graphene oxide (GO) and deproteinized natural rubber (DPNR/GO). The GO was synthesized using the modified Hummer method, and characterized with XRD, Raman, TEM, and water contact angle measurements. The results showed that GO was succesfully exfoliated from graphite with XRD diffraction pea...

A novel and simple approach was developed in the present work to prepare vulcanized natural rubber with high tensile strength and self-healing capability. Solid rubber from high ammonia natural rubber (HANR) was vulcanized using various contents (1.0, 1.5, 2.0, 2.5, and 3.0 phr) of tetramethylthiuram disulfide (TMTD). The vulcanized HANR samples we...

Effect of zinc oxide (ZnO) nanoparticles on vulcanization mechanism of natural rubber and crosslinking structure of its vulcanizate was investigated by rubber‐state NMR spectroscopy. Natural rubber was compounded with various ZnO nanoparticles (c‐ZnO, NC105, NC205, NC23, NC234(STA), and AZ12N), stearic acid, N ‐ tert ‐butyl‐2‐benzothiazole sulfonam...

The self‐healing performance of epoxidized deproteinized natural rubber (EDPNR) and EDPNR/graphene oxide (GO) composites was investigated. Composites of EDPNR25 and EDPNR50 with GO contents of 0.5 and 1.0 phr were prepared by adding a GO dispersion into a EDPNR latex and the product was subsequently cast into films. Tensile strengths of the origina...

Water present in natural rubber was found to play a role in forming carbon-carbon crosslinking junctions before forming carbon-sulfur crosslinking junctions when its effect on the accelerated sulfur vulcanization was investigated by analyzing low–molecular weight products through various instrumental analytical techniques. Samples were prepared by...

In this article, a newly discovered nanostructure, that is, island‐nanomatrix structure, of natural rubber is introduced after reviewing previous studies on the structure of natural rubber. The reason why the structures of ω‐ and α‐terminal groups of natural rubber have not been elucidated, yet, is described in relation to the island‐nanomatrix str...

The defects of polyester films used for glass curtain walls, such as discoloration, peeling, and wrinkling, are thought to be caused by degradation. This occurs in a short period (approximately 1/10) of the conventional service lifetime. A comprehensive investigation demonstrated that extremely low ultraviolet (UV) absorber (2,2’,4,4’-tetrahydroxyb...

Our work aims to investigate the morphology and properties of natural rubber (NR) dispersed in a polystyrene/silica hybrid nanomatrix. The hybrid nanomatrix structure was formed by the graft copolymerization of vinyltriethoxysilane onto NR grafted with styrene. This hybrid nanomatrix structure was composed of nanosilica with a size of less than 100...

Green Resources Chemistry Laboratory of Nagaoka University of Technology conducts an educational program for the science of technology (Gigaku) which is produced to create a new industry by studying technology scientifically, aiming to establish a new chemistry with natural rubber as a resource biosynthesized by various plants, i.e., natural rubber...

Colloidal silica-filled deproteinized natural rubber (DPNR) grafted with poly(methyl methacrylate) (PMMA) (DPNR-graft-PMMA/silica) was prepared and characterized. DPNR-graft-PMMA/silica was prepared by graft copolymerization of NR latex with MMA and tert-butyl hydroperoxide/tetraethylenepentamine as initiators, followed by the addition of silica pr...

Degradation of unsaturated polyester and aggregate, both of which are constituents of artificial stones, was investigated in terms of temperature and alkaline solution based on the environmental condition in the construction site, to elucidate the cause of yellowing of artificial stone under light-shielded and sealed conditions. The artificial ston...

This work presents insights into how naturally occurring proteins affect the graft copolymerization of vinyltriethoxysilane (VTES) on natural rubber (NR) latex. Four NR latexes with different protein contents were subjected to graft copolymerization catalyzed by tert-butyl hydroperoxide (TBHP)/tetraethylene pentamine (TEPA) initiators. The four NR...

In this study, a composite of a natural rubber (NR) discontinuous phase (dispersoid) and a graphene continuous phase (matrix) was prepared and characterized. Graphene was prepared and grafted onto NR particles in the latex stage in the presence of the redox initiators tert-butylhydroperoxide and tetraethylene pentaamine. The structure and morpholog...

Effect of accelerators on the vulcanization of natural rubber was investigated by analyzing structure of the crosslinking junctions through rubber state NMR spectroscopy. The accelerated sulfur vulcanization of natural rubber was carried out with one of the three accelerators, i.e., Zinc diethyldithiocarbamate (ZDEC), Zinc dibutyldithiocarbamate (Z...

The effect of co-polymer, i.e. poly(methyl methacrylate) (PMMA), and doping salt, i.e. lithium trifluoromethanesulfonate (LiCF3SO3) inthe epoxidized rubber-polymer blends preparation was evaluated. The electrolyte membrane was developed through solution castingmethod in the presence of 0-50wt.% of LiCF3SO3. The influence of LiCF3SO3 on chemical int...

In this study, electrically conductive membrane based on natural rubber was prepared through graft‐copolymerization of aniline on natural rubber, and epoxidation in latex stage. The structural characterization of the resulting material through NMR spectroscopy confirmed that polyaniline and epoxy group were successfully introduced to natural rubber...

The mechanism of bromination of NR was studied by solution-state 1H-NMR spectroscopy. The bromination of NR was carried out at 20–50 °C with N-bromosuccinimide as the brominating agent, and the kinetic study of bromination was conducted under nitrogen atmosphere at 30–50 °C for various reaction times. The influence of bromine atom substituent on th...

Vulcanized natural rubber with outstanding mechanical properties due to the rapid strain-induced crystallization was prepared by controlling stereoregularity, based on structural analysis of the vulcanized rubbers. The vulcanized rubbers were prepared at 110, 130, 150 and 170 °C for t90 from natural rubber compounded with sulfur, ZnO, stearic acid...

The temperature glass behavior of epoxy deproteinized natural rubber/polymethylmethacrylate/lithium trifluoromethanesulfonate (EDPNR/PMMA/LiCF 3 SO 3 ) and the conductivity behavior of EDPNR in the ternary blends were studied by DSC and multichannel potentiostat. The DSC result revealed the temperature glass of the EDPNR was shifted to the right wi...

Epoxidized jackfruit gum (EJG) was prepared and characterized. An attempt to prepare a solid polymer electrolyte from EJG was made. The characterizations of epoxidized jackfruit gum were carried out through FT-IR spectroscopy, NMR spectroscopy, gel permeation chromatography, nitrogen content determination, water uptake determination and ion exchang...

The relationship between structural characteristics and some physico-chemical properties of ma-funori and fukuro-funori was elucidated. Ma-funori and fukuro-funori were extracted from red seaweeds which was harvested in Japan. The structure of ma-funori and fukuro-funori extracted from Gloiopeltis tenax and Gloiopeltis furcata, respectively, was ch...

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...

This work presents two different paths of graft-copolymerization of methyl methacrylate (MMA) and vinyltriethoxysilane (VTES) binary monomers onto natural rubber (NR) to prepare NR/PMMA/silica hybrid materials and investigates their properties. The first path was performed by adding VTES during graft copolymerization of MMA onto NR initiated by TBH...

The origin of energetic elasticity in conjunction with the entropic elasticity for natural rubber with a nanodiamond nanomatrix structure was investigated in terms of bound rubber formed between nanodiamonds, based on the interaction between natural rubber and nanodiamonds inside the nanomatrix. The natural rubber with a nanodiamond nanomatrix stru...

Protein effect on vulcanization of NR, obtained from Hevea brasiliensis, was investigated by analyzing the crosslinking structure of the resulting vulcanizates prepared from untreated NR, deproteinized natural rubber (DPNR), and protein-free natural rubber (PFNR) by swelling methods and rubber-state NMR spectroscopy. The proteins present in NR were...

Atom transfer radical polymerization with an activator regenerated by electron transfer (ATRP-ARGET) was performed for graft copolymerization of styrene onto natural rubber in the latex stage as a heterogeneous system. Deproteinized and subsequently brominated natural rubber particles in the latex stage were subjected to graft copolymerization of s...

Expanded graphite (EG) and hydrogenated natural rubber (HNR) latexes with the hydrogenation conversion of 60 and 95 mol% (HNR60 and HNR95, respectively) were prepared according to our proposed procedure, and they were blended in the latex stage. The characterization of EG was determined through BET surface area determination, XRD, and SEM. The inve...

Rubber-state nuclear magnetic resonance (NMR) spectroscopy, a novel analytical method, was applied to quantitative analyses of crosslinking junctions and uncrosslinked pendant sulfidic groups for natural rubber (NR) vulcanizates. NR was vulcanized with two formulations: i.e., one including sulfur, ZnO, stearic acid and N-tert-butylbenzothiazole-2-s...

Vulcanization, tensile strength and water-resistance of protein-free natural rubber (PFNR) were investigated in a viewpoint of application to a seal-product. The PFNR was prepared by incubation of high ammonia natural rubber (HANR) latex with urea, sodium dodecyl sulfate and acetone followed by washing with a centrifuge, twice. It was vulcanized wi...

The presence of protein in the natural rubber latex for the medical device manufacture seems to be the most considered compound due to its allergic effect. Magnetic coated alumina (Fe3O4@Al2O3) has been known as an adsorbent for organic substrates due to its performance through physical and/or chemical interaction. In the current study, we tried to...

Natural rubber-grafted polyaniline with a nanomatrix structure was prepared and characterized. The graft copolymerization of aniline on natural rubber was performed in the latex stage. Factorial experimental design and univariate experiments were used to evaluate the effect of the factors on the conversion of aniline in the graft copolymerization....

The entropic and energetic elasticities of natural rubber with a nanomatrix structure are investigated by measuring the viscoelastic properties of deproteinized natural rubber (DPNR)-graft-polystyrene (PS). A nanomatrix structure is formed by graft-copolymerization of styrene onto the surface of natural rubber particles followed by coagulation. The...

In this study, natural rubber-based electromagnetic shielding materials for coating application were made. Expanded graphite was prepared using our method and dispersed in the polyaniline/natural rubber matrix. The effect of PAni and expanded graphite on the properties of resulting materials was evaluated. The characterization of properties that ar...

Nanodiamond glass is an amorphous solid consisting of nanodiamond as a nanoparticle. The several‐nm‐space between the nanodiamonds is filled with a medium that reversibly deforms and recovers. Hence, nanodiamonds linked in the medium are arranged in several‐nm intervals. To prepare the nanodiamond glass, nanodiamonds are dispersed as inorganic nano...

NR/Na ⁺ -montmorillonite (NR/Na ⁺ -MMT) nanocomposites were prepared through mixing in the latex stage. NR/Na ⁺ -MMT nanocomposites with various amounts of Na ⁺ -MMT were fabricated using three types of NR latexes: fresh NR (FNR), high ammonia NR, and deproteinized NR latex. The Na ⁺ -MMT and NR latexes were characterized by particle size distribut...

Hydrogenated deproteinized natural rubber (HDPNR) with nanomatrix structure was prepared through graft‐copolymerization of acrylonitrile and styrene onto HDPNR particle in latex stage. Structural characterization of the resulting materials through nuclear magnetic resonance and Fourier‐transform infrared spectroscopy confirmed that acrylonitrile an...

Vulcanized rubbers, i.e., vulcanized natural rubber and vulcanized chloroprene rubber, were characterized by rubber-state NMR spectroscopy. High resolution ¹H and ¹³C-NMR spectra were accomplished for the vulcanized rubbers due to fast magic angle spinning. The correlation between ¹H and ¹³C of the vulcanized rubbers was investigated by one- and tw...

Phenyl‐modified natural rubber was prepared in latex stage by bromination of deproteinized natural rubber followed by Suzuki‐Miyaura cross‐coupling reaction. First, the bromination of natural rubber was carried out using N‐bromosuccinimide in latex stage. The bromine atom content increased as amount of N‐bromosuccinimide increased. Second, the ally...

The resolution and the relaxation time of poly(butyl acrylate) in latex-state 13C-NMR spectroscopy are associated with local motions of the polymer in a dispersoid. Latexes were prepared by emulsion polymerization of butyl acrylate with ammonium persulfate. The latex-state 13C-NMR spectra were measured at 323–353 K with a spectrometer operating at...

Protein-free natural rubber was prepared by incubation of high ammonia natural rubber latex with urea, sodium dodecyl sulfate and polar solvent at room temperature followed by centrifugation. Total nitrogen content and extractable protein content of natural rubber were reduced from about 0.4 w/w% and 100 μg/ml to 0.00 w/w% and 0.0 μg/ml, respective...

Graft copolymerization of vinyltriethoxysilane (VTES) onto NR particles in the latex stage is a unique reaction, since it occurs together with hydrolysis and condensation of the triethoxysilane group of VTES to form a colloidal silica linking to the rubber particles. These reactions may contribute to the formation of a silica nanomatrix structure t...

Detection of isomerization in commercial natural rubber (NR) was performed through Nuclear Magnetic Resonance (NMR) spectroscopy in conjunction with structural analysis of pure NR. Three similar grades of commercial NR, which are technically specified rubbers from Vietnam (SVR10), India (SIR10) and Indonesia (ISNR10) and the pure NR, which is prepa...

Natural rubber is a naturally occurring nano-composite, which possesses a complicated hierarchal structure. A primary structure of natural rubber is ω'-(trans)2-(cis)n-α' : that is, modified dimethylallyl group, 2 trans-1,4-isoprene units, about 5,000 cis-1,4-isoprene units and modified prenol group, aligned in this order. The ω'-terminal unit and...

Thermal degradation of deproteinized natural rubber (DPNR) was investigated by heating at 70 °C and 150 °C for 24 h, which was compared with thermal oxidative degradation of natural rubber (NR). The DPNR was prepared by incubation of the NR latex with urea and sodium dodecyl sulfate at room temperature for an hour followed by centrifugation. FT-IR,...

The factors influencing the green strength of commercial solid rubbers were investigated in the present study through characterization of commercial natural rubber (NR). Various solid commercial rubbers such as standard Vietnam rubber (SVR10), standard Indonesia rubber (SIR10), India standard natural rubber (ISNR10), ribbed smoked sheets (RSS3), an...

Degradation of natural rubber (NR) during processing was investigated through NMR spectroscopy. Various commercial rubbers were used in the present study such as Pale Crepe (PC), Rubber Smoked Sheet (RSS 3), Technically Specific Sheet (TSS 8®), Standard Thai Rubber (STR 5L), Standard Vietnamese Rubber (SVR 10) and Standard Malaysian Rubber (SMR 20)...

Degradation of natural rubber and deproteinized natural rubber (DPNR) at 70 °C and 150 °C for 24 hours was investigated. Natural rubber was degraded at 150 °C to produce blown viscous liquid, whereas pale yellow rubber was covered with black brittle rind after degradation of DPNR at 150 °C. FT-IR, ¹H-NMR and ¹³C-NMR measurements of degraded natural...

The distribution of nanodiamond inside a nanomatrix, which is related to the mechanical and viscoelastic properties, is investigated for a natural rubber-nanodiamond composite. The composite is prepared by reacting nanodiamond with deproteinized natural rubber (NR-ND) in the presence of a tert-butylhydroperoxide (TBHPO) / tetraethylenepentamine (TE...

Natural rubber is an excellent material in elasticity and abrasion resistance. However, the detailed structure of natural rubber is still unclear. We aimed to conduct conformational search and structural analysis using computational chemistry and to elucidate the biosynthetic process of natural rubber. From the calculation results, it was found tha...

Liquid deproteinized natural rubber with an epoxy group (LEDPNR) / Poly(lactic acid) (PLA) blend was prepared by mixing and subsequent annealing at 200°C for 20 min. The conversion of LEDPNR on the reaction between LEDPNR and PLA is 23.4%, whereas that between ENR and PLA is 5.8%. The crystallization behavior of PLA was observed with polarization m...

Natural rubber is an excellent material in elasticity and abrasion resistance. However, the detailed structure and the reason for excellent physical properties of natural rubber are still unclear. We aimed to conduct a conformational search and structural analysis using computational chemistry and to elucidate the biosynthetic process of natural ru...

The dynamic mechanical behavior of modified deproteinized natural rubber (DPNR) prepared by graft-copolymerization with various styrene contents was investigated at a wide range of temperatures. Graft copolymerization of styrene onto DPNR was performed in latex stage using tert-butyl hydroperoxide (TBHPO) and tetraethylene pentamine (TEPA) as redox...

Relationship between morphology and mechanical properties of vulcanized rubber samples filled with carbon black was investigated. Samples of natural rubber (NR), isoprene rubber (IR) and deproteinized natural rubber (DPNR) were prepared using an internal mixer with a pair of 6-inch or 8-inch rolls. Dispersion of carbon black was evaluated by transm...

Effect of wax on ozone degradation of vulcanized rubber was investigated at temperatures between -30 °C and 40 °C. The vulcanized rubber was prepared by mixing synthetic isoprene rubber with CB, sulfur, ZnO, stearic acid, accelerator and wax, followed by heating at 160 °C for 8 min. It was further heated at 23 °C, 40 °C and melting temperature of e...

Nanodiamond nanomatrix structure can be formed into deproteinized natural rubber (DPNR-ND) with tert-butylhydroperoxide / tetraethylenepentamine initiator at 303 K under N2 saturated environment. The TEM images of DPNR-ND showed that the natural rubber particles are well dispersed in a nanodiamond nanomatrix structure. Formation of nanodiamond nano...

Method of quantitative analysis through latex-state 13C NMR spectroscopy was established for in situ determination of epoxy group content of epoxidized natural rubber in latex stage. The epoxidized natural rubber latex was prepared by epoxidation of deproteinized natural rubber with freshly prepared peracetic acid in latex stage. The resulting epox...

A nanodiamond nanomatrix structure is formed into natural rubber, generating not only entropic elasticity but also energetic elasticity. The radical reaction with tert-butylhydroperoxide (TBHP) / tetraethylenepentamine (TEPA) in the latex stage forms a chemical linkage between the nanodiamond and natural rubber particles after removing proteins fro...

Ozone degradation of vulcanized isoprene rubber was investigated by changing atmospheric humidity. Ozone exposure test of the vulcanized isoprene rubber was carried out with 50 pphm ozone at 40 °C, for 48 h under relative humidity (RH) between 20 and 90%, after a strain of 0.2 stretching. The degradation of the rubber was assessed by morphology obs...

Strain-induced crystallization of natural rubber (NR) can greatly influence the mechanical properties of NR blends. In this study, we investigated the effect of strain-induced crystallization on the tear energy (G) of NR/styrene butadiene rubber (SBR) blends with different compositions and cross-link densities. Using a shift factor, we could superi...

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Graft copolymerization of styrene onto deproteinized natural rubber (DPNR) using tert‑butyl hydroperoxide (TBHPO) and tetraethylene pentamine (TEPA) as redox initiator have been investigated. The effects of initiator and monomer concentration on conversion and grafting efficiency were studied. The dynamic mechanical and thermal properties of the gr...

Bromination of natural rubber was analyzed through nuclear magnetic resonance (NMR) spectroscopy, in which small ¹H and ¹³C NMR signals, appearing after bromination of natural rubber, were positively assigned by 1D and 2D NMR measurements. The brominated natural rubber (BrDPNR) was prepared by bromination of deproteinized natural rubber (DPNR) with...

Heterogeneous hydrogenation of natural rubber (NR) present in dispersoids in latex is studied by latex-state ¹³C-NMR spectroscopy in order to elucidate its mechanism. The hydrogenation is carried out with palladium catalyst under hydrogen gas atmosphere at 297 to 353 K for various reaction times. The conversion of hydrogenation is found to be depen...

The classification of diamond-like carbon (DLC) films is imperative in guiding large-scale industrial productions. However, it is not easy to classify this issue based on the structural composition and obtained properties, especially, when the film contains a certain amount of hydrogen. In the present study, two types of hydrogenated DLC films were...

Graft-copolymerization of vinyl monomer containing silica precursor, p-styryltrimethoxysilane, onto natural rubber microparticles was performed in latex stage to form three-dimensional networks of nanosilica. After the latex was cast into a film, morphology observation by transmission electron microscopy showed that the natural rubber microparticle...

The effect of the naturally occurring crosslinking junctions on green strength of natural rubber, isolated from Hevea brasiliensis, was investigated by using rubber extracted from Parthenium argentatum Gray (Guayule) as a model. Guayule rubber and natural rubber were characterized through nuclear magnetic resonance spectroscopy and size exclusion c...

Effect of ozone-charged water on degradation of silicone rubber, i.e., crosslinked polydimethylsiloxane/silica composite, was investigated by various analytical techniques, in which active species including active oxygen were generated by self-decomposition of ozone in water. The composite was less swollen with good solvent after degradation with o...

Crosslinking junction as a constituent may play an important role in mechanical properties of rubbers and gels. This may be analyzed by field gradient-fast- magic angle spinning (FG-FMAS) NMR spectroscopy, which is developed to eliminate effect of dipole-dipole interaction for the rubbers and gels. The FG-FMAS NMR spectroscopy enabled to apply vari...

Cell adhesion behaviors on thin of synthetic and natural rubbers supported on solid substrates were examined. When the film was thinner than 60 nm, the adhesion of L929 fibroblasts was clearly promoted. This can be explained in terms of the manifestation of mechanical response from the hard solid substrate. Protein-free natural rubber exhibited bet...

An attempt to prepare graft copolymer of natural rubber, NR and poly(stearyl methacrylate), PSMA, was made to improve mechanical properties of NR, since the grafted PSMA was composed of crystallizable stearyl groups as a nucleating agent and methacrylate units. The graft-copolymerization of stearyl methacrylate (SMA) onto deproteinized natural rubb...

Graft copolymerization of styrene onto deproteinized natural rubber (DPNR) using tert-butyl hydroperoxide (TBHPO) and tetraethylene pentamine (TEPA) as redox initiator have been investigated. The effects of initiator and monomer concentration on conversion and grafting efficiency were studied. The dynamic mechanical and thermal properties of the gr...

Highly purified commercial natural rubbers were prepared and characterized to elucidate the effect of processing condition on structure characteristic of the rubbers. In the present study, various commercial rubbers, i.e. Pale Crepe (PC), Ribbed Smoked Sheet (RSS3), Technically Specified Sheet (TSS8 ®), Standard Thailand Rubber (STR5L) and Standard...

Effect of wax on the ozone resistance of vulcanized natural rubber (NR) and vulcanized isoprene rubber (IR) was investigated by exposing to ozone at 40 °C and -30 °C. The vulcanized rubbers were prepared by sulfur vulcanization of NR and IR with sulfur, ZnO, stearic acid, accelerator and wax in the presence of carbon black and they were heated at 4...

Assignments of small signals appearing in H-1- and C-13-NMR-spectra were made for naturally occurring cis-1,4-polyisoprene isolated from Lactarius Volemus (LV rubber) based on the correlations measured by 2D-NMR spectroscopy. The LV rubber was collected as a latex by tapping mushroom basidiocarp followed by purification. The resulting LV rubber was...

Controlled scrambling reactions of polybutadiene and olefin-containing polyurethane prepared by step-growth or chain-growth polymerization were accomplished via macromolecular olefin cross-metathesis in the presence of Grubbs' second-generation catalyst to yield scrambled copolymers with different thermal and mechanical properties. In addition, nat...

Natural rubber is an excellent material in elasticity and abrasion resistance, so that it is used for tires of airplanes and heavy automobiles, such as a bus. It is impossible to make a synthetic rubber having the same physical properties as the natural rubber, even with the latest synthesis technology. However, the detailed structure of a natural...

Hydroxyapatite (HAp) has a potential to be an excellent photocatalyst because of its strong adsorption ability for organic substances. However, the HAp has a poor photocatalytic ability without modification. We firstly revealed that after substitution of a part of Ca ions by V ions in HAp lattice (V:HAp), visible light driven photocatalytic activit...

Effect of frozen non-equilibrium structure for anisotropically deformed natural rubber with the nanomatrix structure on mechanical properties was investigated with respect to morphology analysis through 3D observation. Natural rubber with the nanomatrix structure was prepared by graft copolymerization of styrene onto natural rubber particles in lat...

An attempt to prepare hydrogenated natural rubber with hydroxyl groups was made by hydrogenation of epoxidized natural rubber (ENR) in latex stage after removal of proteins. The hydrogenation was carried out by reaction of deproteinized ENR (EDPNR) with hydrogen gas in latex stage with palladium black as the catalyst, in which EDPNR was prepared by...

Natural rubber with filler nanomatrix structure was prepared by forming chemical linkages between natural rubber particles and filler nanoparticles. The filler nanomatrix structure was formed by graft copolymerization of vinyltriethoxysilane (VTES) onto natural rubber particles in the latex stage followed by casting of the latex to prepare an as-ca...

Prevulcanization of isoprene rubber (IR) latex was investigated by latex-state 13C-NMR spectroscopy to understand its mechanism in latex stage. The prevulcanization was carried out at 50 to 90 °C with sulfur (S) and zinc-dibutyldithiocarbamate (ZDBC) as vulcanizing agents. The prevulcanized IR latex was subjected to latex-state 13C-NMR spectroscopy...