Novel Deproteinized Natural Rubber Latex Adhesive Used in Extraoral Maxillofacial Prostheses

This study aimed to develop an adhesive for silicone maxillofacial prostheses and compared the properties with the Daro adhesive hydrobond (Factor II, Inc, Lakeside, AZ, USA). Two adhesives were developed from non-vulcanized natural rubber-based adhesives (Adhesive A) and deproteinized natural rubber latex (DNRL) products (Adhesive B) and stored at 4 °C. The Control group was the commercial Daro adhesive hydrobond (Factor II, Inc, Lakeside, AZ, USA). The physical properties (appearance, viscosity, spreadability, color, and pH) of the adhesives were measured and every week for 12 weeks after storing at 4 °C. The adhesives were characterized under scanning electron microscopy. Mechanical testing done were peel bond strength and biocompatibility testing was done using MTT assay. Physical, surface, and mechanical properties were compared with the commercial adhesive. Data analysis was done using SPSS version 24. Both adhesives were physically and chemically stable at temperature 4 °C and had suitable peel bond strength adhesives as the commercial adhesive. Hence, the adhesives can be used to adhere to the maxillofacial silicone prostheses.

Preparation of Ionic Conductivity Polymer Electrolyte Film Based on Epoxidized Deproteinized Natural Rubber

Ionic conductivity polymer electrolyte film based on epoxidized deproteinized natural rubber (EDPNR) and lithium salt lithium triflate (LiCF3SO3) were prepared by solution casting technique. The EDPNR was prepared from deproteinized natural rubber latex (DNR) epoxidized in the latex stage with fresh peracetic acid 33%, which was deproteinized by incubation of the latex with 0,1 wt% urea and 1 wt% surfactant. The ionic conductivity of EDPNR mixed with lithium salt was investigated through impedance analysis. The results show that the conductivity of EDPNR/ LiCF3SO3 mixture was dependent on LiCF3SO3 salt concentration and amount of epoxy group. The highest ionic conductivity at room temperature obtained is 1,71 x 10-5 S.cm-1 at 35 wt% LiCF3SO3 and 45 mol% epoxy groups. Fourier transform infrared spectroscopy (FTIR) spectra showed evidence of complexation between EDPNR and LiCF3SO3. Glass transition temperature, Tg displayed an increasing trend in which are the increase in salt concentration and the increase in epoxy group concentration.

Radiation Graft-Copolymerization of Ultrafine Fully Vulcanized Powdered Natural Rubber: Effects of Styrene and Acrylonitrile Contents on Thermal Stability

Graft copolymers, deproteinized natural rubber-graft-polystyrene (DPNR-g-PS) and deproteinized natural rubber-graft-polyacrylonitrile (DPNR-g-PAN), were prepared by the grafting of styrene (St) or acrylonitrile (AN) monomers onto DPNR latex via emulsion copolymerization. Then, ultrafine fully vulcanized powdered natural rubbers (UFPNRs) were produced by electron beam irradiation of the graft copolymers in the presence of di-trimethylolpropane tetra-acrylate (DTMPTA) as a crosslinking agent and, subsequently, a fast spray drying process. The effects of St or AN monomer contents and the radiation doses on the chemical structure, thermal stability, and physical properties of the graft copolymers and UFPNRs were investigated. The results showed that solvent resistance and grafting efficiency of DPNR-g-PS and DPNR-g-PAN were enhanced with increasing monomer content. SEM morphology of the UFPNRs showed separated and much less agglomerated particles with an average size about 6 μm. Therefore, it is possible that the developed UFPNRs grafted copolymers with good solvent resistance and rather high thermal stability can be used easily as toughening modifiers for polymers and their composites.

Temperature glass and conductivity behavior of epoxy deproteinized natural rubber in ternary blend of EDPNR/PMMA/LiCF3SO3

The temperature glass behavior of epoxy deproteinized natural rubber/polymethylmethacrylate/lithium trifluoromethanesulfonate (EDPNR/PMMA/LiCF3SO3) 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 with the increase of lithium salt amount in these binary blends composition. However, in the ternary blends of EDPNR/PMMA/LiCF3SO3 the temperature glass revealed the miscibility of these ternary blends. Two different temperature glass values were obtained when the ratio of EDPNR in EDPNR/PMMA was less than 80 wt.%. The ionic conductivity of EDPNR could be improved by increasing the amount of lithium salt up to 35 wt.%, after this amount the ionic conductivity of EDPNR was significantly decreased. While in the ternary blends, the highest ionic conductivity value was found at the ratio 80/20 of EDPNR/PMMA. Furthermore, the factors influencing the temperature glass and conductivity behavior of EDPNR were systematically studied in this work. The results demonstrated an intimate correlation between temperature glass and conductivity behavior of EDPNR.

PROTEIN INFLUENCE ON THE MECHANICAL PROPERTIES OF NR

ABSTRACT 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 removed by three methods: deproteinization with enzyme, urea, or urea–acetone in the presence of sodium dodecyl sulfate. The amount of proteins present in NR, approximately 0.238 w/w%, was reduced to 0.000 w/w% by urea–acetone deproteinization, whereas it was reduced to approximately 0.003 and 0.019 w/w% by enzyme and urea deproteinizations, respectively. Hardness, swelling degree, and crosslinking structure depended on the amount of proteins. Changes in mechanical properties for the vulcanizates prepared from not only non-filler compounds but also carbon black–filled and silica-filled compounds were attributed to the amount of proteins.

CHANGES OF BACTERIAL CONSORTIA IN ENRICHMENT OF DEPROTEINIZED NATURAL RUBBER WITH SAPA SOIL

The accumulation of rubber waste has become a major environmental issue worldwide due to its adverse effects on ecology. Bioremediation is focused to minimize this problem. In this study, the degradation of deproteinized natural rubber (DPNR) using bacterial consortia enriched from Sapa soil was examined. This soil was not history with rubber. The highest 39.16 ± 1.95 % weight loss of DPNR film was detected in the sixth enrichment consortium after 30 days of incubation. The occurrence of hydroxyl group in the film was observed by Fourier Transform Infrared Spectroscopy analysis. The changes in bacterial community in the consortia were determined by metagenomic analysis using 16S rRNA gene sequencing. The dominant phyla in all consortia were Actinobacteria, Bacteroidetes, and Proteobacteria, while the phylum Actinobacteria was key rubber-degraders in the consortia.

Poly(L-lactic acid)/deproteinized natural rubber blends with enhanced compatibility

PLLA-g-LMWNR (LMWNR – low molecular weight natural rubber) was used as a compatibilizer (1–3 wt %) of poly(L-lactic acid)/deproteinized natural rubber (PLLA/DPNR) blend (95/5 w/w). The LMWNR was prepared using TiO2/ZnO (9 : 1 w/w) and H2O2 as co-catalyst. The obtained LMWNR was grafted with 0–12 wt % maleic anhydride (LMWNR-g-MA) and then with PLLA (PLLA-g-LMWNR). A significant improvement in the mechanical properties of the PLLA/DPNR blend was found in the blend that contained 3 wt % PLLA-g-LMWNR. Scanning electron microscopy showed a decrease in the pore diameter from 5.44 to 1.56 μm. The thermal analysis of PLLA/DPNR blends showed that the Tg value of PLLA phase shifted from 63.1 to 61.4°C. These results confirmed that PLLA-g-LMWNR can enhance the compatibility of the PLLA/DPNR blend.