No abstract

No abstract

Low density polyethylene (LDPE) and agar were blended by using the former as an internal mixer and varying the amount of agar. Resulting blends were hot pressed and characterized with regard to their torque‐rheological, mechanical, dynamic‐mechanical, thermal, and morphological properties. The torque rheological properties were determined using classical power law model. Tensile properties of LDPE‐agar biocomposites showed that agar improves the tensile modulus (stiffness), but compromise the tensile strength and elongation at break. Viscoelastic behavior of the matrix is clearly influenced by the presence of agar biofiller as shown by the dynamic mechanical analysis (DMA). Thermal behavior of the biocomposites was also investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Morphological observations by scanning electron microscopy (SEM) show the ductile to brittle fracture of LDPE‐agar biocomposites subjected to tensile test. This work is an initial reference to identify potential applications of biocomposites based‐on agar as a biofiller. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

We have examined a water-dominated multicomponent system after irradiation in the multimegarad dose range with gamma rays from a 60Co source at both 77 and 310 K. The constituents were simple organic compounds in the proportions in which they appear in a dense interstellar cloud: HCN/CH3OH/CH3CN/C2H5CN/HCOOH = 1:0.6:0.2:0.1:0.05. The total amounts were adjusted to correspond to a carbon to nitrogen ratio of 1.8 and a water content of about 50% in a cometary nucleus where the dust to volatiles ratio is 1; the total amount of CN-bearing compounds was taken to correspond to 0.4% of the cometary mass. In experiments at 310 K about 40 radiolytic products are identified, among them aldehydes and amino and carboxylic acids. Abundant polymeric material (Mw up to 80,000 daltons) is formed. The basic aspects of radiolysis of the liquid system are present also at 77 K, although at radiation-chemical yields that are lower by one to two orders of magnitude. We have considered the relevance of the present findings to the chemistry of a liquid-water core and the icy layers of a cometary nucleus.

Single-walled carbon nanotubes (SWNTs) have many interesting properties; they may be metallic or semiconducting depending on their diameter and helicity of the graphene sheet. Hydrostatic or quasi-hydrostatic high pressures can probe many electronic features. Resistance -temperature measurements in SWNTs from normal condition and under 0.4 GPa of quasi-hydrostatic pressures reveal a semiconducting-like behavior. From 0.5 to about 2.0 GPa the resistance changes to a Kondo-like feature due to magnetic impurities used to catalyse the nanotube formation. Above 2.0 GPa, they become metallic and at about 2.4 GPa the resistance decreases dramatically around 3 K suggesting a superconducting transition. 71.30.+h, 74.10.+v, 75.20.Hr, 74.62.Fj Two unique characteristics of carbon nanotubes are their different electronic behavior depending on diameter and helicity [1,2]. Electronic and transport properties of singlewalled carbon nanotubes (SWNTs) also differ depending on chirality [3][4][5]. Many theoretical studies indicate that the local density of electronic states changes if the graphene sheet is wrapped in a zigzag or an armchair configuration. Armchair