No abstract

Sulfate deposits of the Loei-Wang Saphung (LWS) area, northeastern Thailand, intercalated with carbonate and silicic clastic rock were analyzed for S, O, C, and Sr to determine the depositional environment, as well as the age of formation. Sulfate samples yielded average values of δ 34 S of 14.6‰, while the 87 Sr/ 86 Sr ratio of gypsum was 0.708282 and that of anhydrite was 0.708288. The carbonate layers yielded average δ 18 O PDB , and δ 13 C values of −12.5‰ and −0.1‰, respectively. Our results revealed that the LWS evaporite deposits were originally formed from seawater, and the relatively negative value of δ 18 O was a result of meteoric alteration during subaerial exposure of the sections. Comparing these isotopic values with the nearby Nakon Sawan sulfate deposits, the Sr isotopes showed slightly higher values with very mild variations. These isotopic values suggest that the LWS deposits were not affected by subsequent hydrothermal alteration by younger igneous dikes in this area. Therefore, some of these isotope signatures are considered to be primary features of the deposit, despite the fact that the deposit underwent anchizone to epizone metamorphism. The S and Sr isotope values support the depositional age of the LWS sulfate deposit in the Middle to Late Carboniferous.

Biopolymers of hard, brittle and low flexible polyhydroxyalkanoates (PHAs) and a soft and high elastic natural-latex rubber are blended at room temperature by using a combination technique. Concentrations of the PHAs solution are constituted at 1%, 2% and 3% w/v and mingled with fresh natural latex in different ratios (PHAs : Latex Rubber = 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 and 10:0). After vigorous blending, forming polymeric sheets leave a dried-film pattern. Only the best 3 different ratios (4:6, 5:5 and 6:4) are selected by evaluating morphological-based information. These lead to actually define and characterize for their morphological and mechanical properties. The morphological attributes are exemplified by polarized optical microscopy and X-ray diffractometry (XRD) while the thermal characterization is determined by differential scanning calorimetry (DSC). Morphological analysis for the criterion of blending achievement indicated that there is a significant relationship among porosity, texture and shrinkage. The porosity shows obviously low to high for gradually increasing PHAs and decreasing the latex. Thus, dense texture and shrinkage relate to blending compositions between PHAs and latex. The XRD and DSC reveal certain aspects of decreasing crystallinity arising from enhancing of the latex content. A high degree of crystallinity and melting temperature relates to greater PHAs ratio. The mechanical investigations have revealed complex localization patterns of tensile strength and elastic modulus. The more PHAs concentration at 2% w/v indicates the greater elastic modulus than 3% and 1% w/v. Significant differences are found on polymeric composites of mechanical analyses between PHAs and natural latex. The constituted superiority in the ratio of 5:5 significantly differs in extension to break. Additionally, both tensile strength and elastic modulus of 2% w/v PHAs present the maximum value among them.

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is mixed with natural rubber latex to make better mechanical properties of PHBV. The various ratios between PHBV and natural rubber latex are examined to improve their mechanical properties. The PHBV are solid, easily broken, while natural rubber is excessive elastic materials. Concentrations of the employed PHBV solution are 1, 2, and 3 (%w/v). The mixtures of this solution to natural rubber latex are fabricated the biofilms in three different ratios, 4:6, 5:5, and 6:4, respectively. The films are characterized by electron microscope, universal testing machine, and differential scanning calorimetry (DSC). The electron micrographs of the mixed films and unmixed PHBV yield the lowest void distributions in 3%w/v PHBV. For mechanical properties, the averaged elastic moduli of 1, 2, and 3 (%w/v PHBV) mixed films are 773, 955 and 1,008 kPa, respectively. Their tensile strengths increase with increasing the PHBV concentrations. A similar trend is also found in elastic modulus. The crystallization and melting behavior of pure PHBV and the mixed films are examined by DSC. Melting transition temperatures of pure PHBV exhibit two melting peaks at 154°C and 173°C. In addition, the melting peaks of the mixed films remain in the range of 152-156°C and 168-171°C, respectively. According to their morphology, void distributions reduce twice, compared to the unmixed PHBV. Mechanical properties and thermal analysis indicate that the mixed PHBV can be improved their properties with more resilient and wide range temperature than usual.

Biopolymers of polyhydroxyalkanoates (PHAs) are produced by pure bacterial strain of Alcaligenes eutrophus TISTR 1095 via batch fermentation using sugarcane juice as a carbon source, and yielded up to 21% (w/w) after recovery process. The PHAs are blended with bio-based materials such as tapioca and corn starch including glycerol and methanol to improve their microstructures. The combination of various plasticizers with PHAs is studied in different ratios. The PHAs and starch are mixed for 3% w/v and 30% w/v in hot chloroform, respectively. The varieties of PHAs to starch solution ratios are situated for casting as of films. The PHAs blended films are characterized by polarized light microscopy, differential scanning calorimetry (DSC) and x-ray diffractometry (XRD). The initial PHAs indicate remarkably crystalline structure with cross-polarized light on optical microscope. Macroscopic scales of their films are very brittle and flexible. However, their microscopic scales present small patches of particular components from each starch. Immiscibility of the blends is gradually increased on adding the starch portions. Additional glycerol shows more strongly interfacial adhesion between starch and PHAs, and methanol produces specifically thin films. Melting transition temperatures of blended films are slightly higher than the biosynthesized PHAs as examined by DSC. Corn starch mixture causes highly brittle films than tapioca mixtures, which indicates poor adhesion between corn starch and the PHAs. This result is correspondent to their highly crystallinity from diffractogram. Microstructural evolution of the blended films is increased slightly crystallinity by the solution casting.