A series of new waterborne polyurethanes (WPUs) was successfully prepared by prepolymer process from renewable source, hydroxytelechelic natural rubber (HTNR), with different amounts of DMPA (1.6-8.4 wt %), different molecular weights (1000-4000 g mol À1 ), and different levels of epoxide (0%-20%) of HTNR. It was found that the urethane conversions of prepolymer were over 80% as calculated by FTIR technique. The resulting HTNR2000-based WPUs exhibit a uniform particle size, which decreases from 420-to 83-nm diameters with an increase in the amount of DMPA from 2.9 to 6.6 wt %. The particle size also decreases with an increase of soft segment or with an increase of epoxide content. They are well stable more over 6 months and without a significant difference in particle size compared with starting of them. Chemical structure of WPU films was confirmed by FTIR, 1 H-NMR, and 13 C-NMR. Molecular weight and polydispersity were determined by SEC. In addition, thermal and water uptake properties were investigated. The experimental results reveal that the DMPA content, molecular weight of HTNR, and epoxide content play an important key role in water uptake and thermal properties.

Novel flexible polyurethane foams were successfully prepared from a renewable source, hydroxytelechelic natural rubber (HTNR) having different molecular weights (1000-3400 g mol À1 ) and variation of epoxide contents (EHTNR, 0-35% epoxidation) by a one-shot technique. The chemical and cell structures as well as physico-mechanical, thermal, and acoustic properties were characterized and compared with commercial polyol analogs. The obtained HTNR based foams are open cell structures with cell dimensions between 0.38 and 0.47 mm. The HTNR1000 based foam exhibits better mechanical properties but lower elongation at break than those of commercial polyol analog.However, the HTNR3400 based foam shows the best elastic properties. In a series of EHTNR based foams, the tensile and compressive strengths show a tendency to increase with increasing epoxide content and amount of 1,4-butanediol (BD). The HTNR based foams demonstrate better low temperature flexibility than that of the foam based on commercial polyol. Moreover, the HTNR based polyurethane foams was found to be an excellent absorber of acoustics.

Telechelic oligoisoprenes were successfully prepared by the selective controlled degradation of natural rubber, a renewable source, via epoxidation and cleavage reactions. The molar mass of the oligoisoprene product obtained depends on the degree of epoxidation of the starting materials. The chemically modified structures obtained via epoxidation, hydrogenation, and ring opening of epoxide groups were also studied, and the chemical structures and thermal properties of the oligoisoprene products were determined. Moreover, the preliminary study of preparation of hydroxytelechelic natural rubber (HTNR)-based polyurethane foam was performed. A novel HTNR-based polyurethane foam was successfully prepared and its thermal properties were investigated and the results indicated that the HTNR-based polyurethane foam has a good low temperature flexibility.

Graft copolymers of natural rubber (NR) and methyl methacrylate (MMA) were prepared using cumene hydroperoxide and tetraethylene pentamine as redox initiators via the semibatch emulsion polymerization technique. Various molar percentage ratios of NR/MMA were studied in the grafting reaction (i.e., 95/5, 90/10, 80/20, 70/30, and 60/40). The graft copolymer with a 70/30 molar ratio was selected and used to prepare rubber blends with cassava starch. The starch was used at levels of 0, 20, 40, and 60 phr. Another set of rubber blends was prepared for comparison purposes. The NR-g-poly(MMA) (PMMA, 75 phr) was blended with 25 phr of NR air dried sheets (ADS) and a given level of the cassava starch. We found that the Mooney viscosity, shear stress, and shear viscosity increased with an increasing concentration of cassava starch. This may be attributed to the chemical interactions between the polar groups of the NR-g-PMMA and the cassava starch. The blends were later compounded using a compounding formulation according to ASTM D 3184-89. A similar short delay onset of vulcanization (i.e., approximately 1 min) was observed for the whole set of compounds under study. However, different curing characteristics were observed for the blends of NR-g-PMMA-cassava starch and NR-g-PMMA-ADS-cassava starch. The NR-g-PMMA-cassava starch compounds exhibited two-stage curing characteristics. The curing curve had a slight reversion at a testing time of approximately 8 min. The shear modulus then abruptly increased with an increasing testing time in the range of 20 -60 min. The curing curves for NR-g-PMMA-ADS-cassava starch blends exhibited a single curing stage with a shear modulus that increased slightly with the testing time was increased from 20 to 60 min.

A series of new waterborne polyurethanes (WPUs) was successfully prepared by the prepolymer process from the bio-renewable sources hydroxytelechelic natural rubber (HTNR with MW 3000 g mol −1 ) and hydroxylated rubber seed oil (HRSO), with DMPA fixed at 5.6 wt%. The effects of ratio of HTNR and HRSO (ranging from 1.00/0 to 0.10/ 0.90) and of hydroxyl value (OHV) of HRSO (200 or 270 mgKOH/g) on final properties were studied. It was found that the particle size of WPU increased significantly with both HRSO/HTNR ratio and OHV of HRSO. Chemical structure of the WPU films was confirmed by FT-IR. The water uptake, mechanical, dynamic mechanical properties and thermal stability of WPU film improved with both HRSO content and OHV of HRSO, while swelling in THF decreased. All these WPU films had similar Tg. This article reports novel green biobased WPU with promising applications as adhesive for shoe industries.

Creaming process with a novel creaming agent, hydroxyl ethyl cellulose, and ammonium laurate soap is performed. It has been found that the total solid content and dry rubber content of creamed latex are 64.33% and 63.31%, respectively. Latex properties of the creamed latex are examined and compared with that of centrifuged latex. It has been found that most properties are similar, except that extractable protein content, mechanical stability time, and viscosity of the creamed latex are higher than that of the centrifuged latex. Furthermore, the creamed latex exhibits larger particle size with broader particle size distribution than that of the centrifuged latex.

Waterborne polyurethane (WPU) has its main applications in coatings and adhesives. Compared with the competing PU products from solvent-based processes, it has a more environmentally friendly manufacturing process. Its economic competitiveness could also be improved by the use of aromatic isocyanates that are widely available and cheaper than the currently used aliphatic isocyanates. We report on the synthesis and properties of WPU, based on natural rubber (NR) whose molecular structure has been altered, in combination with an aromatic isocyanate. The NR modification is by hydroxyl termination, with experiments using two chain lengths (HT600 and HT1000, named after molecular weight). The aromatic isocyanates used are 4,4’-Methylene bis (phenyl isocyanate) (MDI) and polymethylene polyphenyl polyisocyanate (p-MDI). The synthesized chemical structure is characterized using ATR-FTIR, while the key material properties reported here are the pH value, mean particle size and size distribution, and glass transition temperature. The WPU achieved suitable material properties, with small particles sizes and good dispersion, for applications in coatings.

Fresh field natural rubber was coagulated by acetic acid, soaked in water at room temperature (WRT) or 70°C (W70) for 1 hr, and then dried in an oven at 40°C. Non-soaked natural rubber samples (NoW) served as a control. Two grades of natural rubber, namely air-dry sheet (ADS) and ribbed smoked sheet No.3 (RSS3) derived from the same latex, were also investigated. All dry rubber samples were characterized with Lovibond colorimeter according to ASTM D3157, as well as with a HunterLab spectrophotometer. Furthermore, all the dry rubber samples were dissolved in a chloroform:methanol mixture (4:1 v:v). The rubber was then precipitated out of the solution with methanol, and the remaining solution was quantitatively analyzed for total phenolic content (TPC). The plasticity retention index (PRI) was determined for all the dried rubber samples according to ASTM D3194. It was found that WRT, W70 and ADS were similar in lightness L*, while RSS3 had the lowest L*. W70 had the lowest redness a*, which increased in the order WRT, NoW, RSS3 and ADS. W70 also had the lowest yellowness b*, which increased in the order RSS3, NoW and WRT and ADS. Moreover, TPC was the lowest for the W70 sample, increasing in the order ADS, WRT, NoW and RSS3. The PRI was highest for W70, and decreased in the order WRT, RSS3, NoW and ADS. All of the PRI values observed were comparatively high relative to blocked standard Thai rubber 20 (STR20).