Key Engineering Materials VI

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Authors: Zhao Chen, Yu Guang Li, She Sheng Zhang
Abstract: Excellent material can improve the function of water lubricated stern bearing. According to the material properties and the theory of operational research, the mathematical model of the optimal selection material of water lubricated rubber bearing is established. The condition of selecting materials is discussed. The expression of the maximum value is obtained by using software. The influence of material properties on the objective function is discussed.
Authors: Clare L. Garing, Bryan B. Pajarito
Abstract: The effect of carbon black (CB) substitution with raw (BNT) and modified (M-BNT) bentonite on the thermal aging resistance of natural rubber (NR) composites was investigated in this study. NR composites were prepared at varied proportions of CB, M-BNT, and BNT using a three-component, third degree simplex lattice mixture design of experiment (DOE). M-BNT was produced by modifying sodium-activated bentonite with tetradecyldimethylamine (TDA) salt and cocamide diethanolamine (CDEA). Thermal aging was performed at 70 and 100°C for 168 and 336 h. Substitution of CB with 5 phr M-BNT gave the highest values of tensile properties (modulus and strength) for both unaged and aged samples. This is attributed to the synergistic effect of CB and M-BNT fillers on the tensile properties of NR composites. In terms of property retention (%), composites filled with M-BNT and BNT clay fillers attained the highest values which signified their excellent thermal aging resistance. This observation proves the barrier effect of clay platelet structure which hinders oxygen diffusion in the rubber. Reduced hierarchical models as function of CB, M-BNT, and BNT proportions were used to generate contour plots for tensile properties of NR composites after 168 h of aging at 70 and 100°C.
Authors: Mark Rigel R. Ali, Bryan B. Pajarito
Abstract: Modified bentonite (M-BNT) was prepared by treating raw bentonite (BNT) with NaCl, tetradecyldimethylamine chloride salt and coco diethanolamide. X-ray diffraction (XRD) analysis and attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy showed intercalation of the organic modifiers into the layers of M-BNT. The effect of partially replacing silica with BNT and M-BNT on the tensile properties of natural rubber (NR) composites was investigated. Results showed that 15 phr M-BNT, as well as 10/5 phr silica/BNT mixture filler, imparted great improvement in the tensile modulus and stresses at 100, 200 and 300% strain of NR composites. Moreover, 10/2.5/2.5 and 2.5/10/2.5 phr silica/M-BNT/BNT mixture filler gave the NR composites high tensile strength and elongation at break relative to unfilled NR. Contour plots showed that tensile properties of NR composites decreased with increasing amount of BNT.
Authors: Nathapong Sukhawipat, Nitinart Saetung, Anuwat Saetung
Abstract: The novel natural rubber based cationic waterborne polyurethanes (cWPUs) with having quaternary amine as an emulsifier were successfully synthesized by additional polymerization. These polyurethanes were synthesized by the reaction of hydroxyl the method of telechelic natural rubber. Molecular weight approximately of hydroxyl telechelic natural rubber (HTNR) for 3000 g.mole-1, toluene-2,4-diisocyanate (TDI), and N-methyl diethanol amine (NMDEA) (used as an emulsifier) were prepared for cWPU. The concentrations of NMDEA were examined in range of 0 – 2.0 moles. From the results under the isocyanate index of 100, the study revealed that cWPU with well-distributing had to consist of emulsion concentration more than 1.50 moles. Zetasizer nanorange was used to identify the prepared cWPU particle size distribution. The results showed that the particle size of cWPU was decreased from 86.6 to 78 nm with increasing of NMDEA concentration. The smallest particle size was 2 moles with non-acetic acid odor, and very soft film. In addition, cWPU would be well-dispersed more than 4 months. The 1H NMR spectroscopy and FT-IR confirmed that the cWPU has been successfully synthesized from natural rubber.
Authors: Karl C. Ondoy, Bryan B. Pajarito
Abstract: This study reports the results of investigation on the main and interaction effects of grit type, aging temperature, and aging time on particle size of ground natural rubber/zeolite (GNR/Z) composite powder using general factorial design of experiment. GNR/Z composite powder produced by mechanical grinding is porous, like an aggregated chain structure. These aggregates exist in clusters of irregular shape. Analysis of variance (ANOVA) shows that the effects of aging temperature and aging time depend on the particle size range. GNR/Z composite powder with large particle size is produced when aging is done at low temperature and short time due to high resistance of rubber to oxidation. On the other hand, GNR/Z composite powder with small particle size is produced when aging is done at low or high temperature and longer aging time. Low temperature condition offers high O2 concentration available to oxidize rubber while high temperature condition leads to more chain scissions due to higher oxidation rate.
Authors: Abhel Y. Ananoria, Bryan B. Pajarito
Abstract: The effect of compounding ingredients to swelling and mechanical properties of vulcanized natural rubber (NR) in deionized water at 80°C was investigated. Rubber sheets are compounded according to a fractional factorial design of experiment, where ingredients are treated as factors varied at two levels of loading. Results show that sulfur, used oil, calcium carbonate (CaCO3), reclaimed rubber, asphalt, diphenyl guanidine (DPG), mercaptobenzothiazole (MBT), and mercaptobenzothiazole disulfide (MBTS) are some of the significant ingredients of the formulation affecting the material properties of vulcanized NR. Among the compounding ingredients, sulfur and used oil are the most influential and consistent factors which affect the swelling and tensile properties of vulcanized NR during water diffusion.
Authors: Bryan B. Pajarito, Jimyl Arabit
Abstract: Tensile properties of surfactant-loaded natural rubber (NR) vulcanizates are investigated in correlation with blooming. Rubber sheets are compounded using an L12 orthogonal array of Taguchi design of experiment, where ingredients are treated as factors varied at low and high loadings. Blooming experiments are carried out by placing NR sheets in a natural convection oven set at 50 °C for 20 days. The amount of bloom on the surface is removed using adhesive tape and is monitored with time. Tensile properties of rubber dogbone samples are also measured with time. Results show that 5 out of 12 formulations show blooming to be significantly related to tensile modulus (0.005 < p < 0.039). It is observed that the tensile modulus increases with blooming (0.898 < r < 0.973). Three formulations indicate significant correlation of blooming with tensile strength (0.022 < p < 0.047). As observed, tensile strength decreases with blooming (-0.884 < r < -0.930). Five formulations signify blooming to have significant correlation with maximum tensile strain (0.000 < p < 0.011), which decreases with blooming (-0.957 < r < -0.995). Two formulations imply significant negative (-0.960 < r < -0.963) correlation between blooming and tensile set (p= 0.009).
Authors: Chaiwute Vudjung
Abstract: Natural rubber (NR) containing the nata de coco fiber or Bacterial cellulose (BC) was prepared by co-coagulation of BC and concentrated NR latex with CaCl2 and compounded by two roll mill. The effect of BC content was the important factor in this study. It was that found tensile strength and elongation at break of NR filled BC (NR/BC) decreased with increasing BC content. The addition of BC into NR affect Mooney viscosity of NR/BC masterbatch, with increasing BC content, scorch time and cure time of their compound decreased.
Authors: Sarawut Prasertsri, Pranee Nuinu, Sansanee Srichan, Siriwat Radabutra, Chaiwute Vudjung, Saowaluk Boonyod
Abstract: This research aims to investigate the efficiency of polybutadiene-grafted maleic anhydride (PB-g-MAH) as the compatibilizer for ethylene-propylene diene rubber and epoxidized natural rubber (EPDM/ENR) blends. PB-g-MAH was varied from 0-10 parts per hundred parts of rubber (phr), and the cure characteristics, mechanical and dynamic properties of 70/30 EPDM/ENR blends with and without compatibilizer were evaluated. It was found that the minimum torque, maximum torque, scorch and cure times of the blends increased after adding PB-g-MAH, whereas cure rate decreased. The morphology of the blend is improved by the addition of PB-g-MAH in small amounts, owing to an improved compatibility of these rubbers confirmed by dynamic mechanical property. The hardness and oil resistance increased with increasing PB-g-MAH content. Of all blends investigated, the blend compatibilized with 2-4 phr of PB-g-MAH shows the optimum mechanical properties and thermal resistance.

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