An attempt was made to prepare purified natural rubber by removal of proteins to achieve a low extractable protein content. The removal of the proteins were performed by leaching natural rubber gloves possessing high extractable protein content and high nitrogen content and by deproteinization of high ammonia natural rubber latex with urea, sodium dodecyl sulfate (SDS) and acetone. The extractable protein content and nitrogen content of the purified natural rubber were measured by the modified Lowry method and the Kjeldahl method. The extractable protein content of the natural rubber glove was reduced from 692 µg/g to 86 µg/g by leaching, while the nitrogen content decreased a little. The nanomatrix of non-rubber content of the natural rubber glove disappeared after leaching at 60, 80 and 100°C, as observed with a focused ion beam / scanning electron microscope. In contrast, the extractable protein content and the nitrogen content of natural rubber were reduced to 0.0 µg/g and 0.000 w/w%, after deproteinization with urea, SDS and acetone.

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Trifunctional polyacetal polyols with various main-chain structures were synthesized by polyaddition of hydroxyl-modified vinyl ethers (HBVE, HEVE, DEGV, CHMVE) in the presence of glycerine with an acid catalyst in tetrahydrofuran (THF) at 0°C for 4 h. Crosslinked polyacetal polyurethane elastomers were synthesized by the reaction of polyacetal polyols with 2,4-tolylene diisocyanate at 120°C for 15 h. The obtained polyacetal polyurethane elastomers had glass-transition temperatures depending on their main-chain structure (−58~10°C) and high thermal stability (274~312°C). The polyacetal polyurethane elastomers underwent smooth hydrolysis by treating them with aqueous acid in THF at room temperature to give the corresponding diol compounds for chemical recycling.

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For the first time, sulfur K-edge X-ray absorption near-edge structure (S K-edge XANES) measurement was conducted at room temperature to evaluate a kind of the sulfidic linkage in solvent-extracted sulfur cross-linked isoprene rubbers. The vulcanizates were prepared by heat-pressing of the rubber compounds containing zinc oxide, stearic acid, N-cyclohexyl-2-benzothiazole sulfonamide and sulfur. The sulfidic linkage varied from a polysulfide type to a disulfide type with increasing of the torque during curing. A monosulfide type was also suggested to be generated from the disulfidic linkage. The S K-edge XANES measurement will be of use for evaluating a characteristic of the sulfidic linkages in the sulfur cross-linked rubber by combining the solvent extraction technique.

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Resolution and relaxation time of latex-state nuclear magnetic resonance (NMR) spectroscopy were investigated with respect to not only the mobility of the polymer but also to the movement of the dispersoid in the latex. The latex was prepared by emulsion polymerization and soap-free polymerization of butyl acrylate with peroxodisulfate. The latex-state ¹³C NMR spectra were measured with various pulse sequences that were known to be useful for the solution state ¹³C NMR spectroscopy. The high resolution latex state NMR was achieved at a temperature of more than 78 K.

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We prepared segmented poly(urethane-urea)s (SPUUs) from a lysine-based diisocyanate (LDI) and an aliphatic polyester poly(ε-caprolactone) diol (PCL-diol), and 1,4-butanediamine (BDA). We also investigated the molecular aggregation structure, mechanical performance and biodegradability. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements indicated that the LDI-based hard segment (HS) shows weak segregation because of the bulky asymmetric chemical structure of the LDI. The stress-strain curve of PCL(1250)-LDI-BDA exhibits a yielding point and less mechanical strength than PCL(1250)-BDI-BDA because of the plastic deformation of the HS domains. PCL(1250)-LDI-BDA shows adequate biodegradability due to weak aggregation capacity of LDI-based components.

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