Synthesis, Antimicrobial Activity and Micellization of Gemini Anionic Surfactants in a Pure State as Well as Mixed With a Conventional Nonionic Surfactant

New gemini anionic surfactants were prepared from sodium salts of monoalkyl sulfosuccinate esters of ethylene glycol having variably long tails (C₁₂, C₁₆, C₁₈) and dichloroethane. The chemical structures of the prepared surfactants were confirmed using different spectroscopic techniques. The surfaces tension values of the synthesized surfactants were measured at 25 °C individually or mixing at different molar fractions with ethoxylated alkylphenol. In all cases, mixed micellar aggregates were formed and critical micellar concentrations of binary mixtures containing different mole fractions of the surfactants were measured. The micellization processes of the individual and mixed surfactants were investigated. The effect of different alkyl chains of gemini anionic surfactants on properties of binary systems and molar ratio in the mixed aggregates were deduced. The critical micelle concentration of mixed surfactants shifted to lower values compared to those of the single surfactants. Effectiveness values increased with decreases in the mole fraction of gemini anionic surfactants. The negative values of interaction parameter (β) increased with increases in the chain length of anionic surfactants. The activity coefficient (f ₁, f ₂) and total minimum surface area of mixed solution were calculated. Also, the gemini anionic surfactants prepared have moderate antimicrobial activity towards bacteria and not active towards fungi.     

Compatibilization of low‐density polyethylene/plasticized starch blends by reactive compounds and electron beam irradiation

Blends based on various compositions of low‐density polyethylene (LDPE) and plasticized starch (PLST) were prepared by melt extrusion and molding in the form of sheets under hot press. The rheology properties during mixing were studied in terms of torque and temperature against mixing time. The structural properties of LDPE/PLST blends before and after electron beam irradiation was characterized by IR spectroscopy, tensile mechanical testing, and scanning electron microscopy (SEM). The torque‐time curves during the mixing process showed that the values of torque in the first region of mixing for pure LDPE or LDPE/PLST blends are higher in the presence of the compatibilizer PEMA than that in the presence of EVA. In addition, the stability of mixing was attained after a short time in the presence of PEMA. The IR spectroscopy suggests that the compatibilization by EVA and PEMA compounds proceeds through the formation of hydrogen bonding during mixing and this compatibility was improved after electron beam irradiation. The stress–strain curves of pure LDPE and its blends with PLST showed the behavior of tough polymers with yielding properties. The SEM micrographs of the fracture surfaces give supports to the effect of EVA and PEMA as compatibilizers and the effect of electron beam irradiation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Challenges and possibilities for achieving household food security in the Western Sudan region: the role of female farmers

This paper investigates the role of women in achieving household food security in the Western Region of Sudan, an area much affected by the impacts of drought and civil conflicts. The study is based on a quantitative survey and qualitative focus group discussions, supported by personal observations made during fieldwork. Additionally, the study draws upon secondary data that is publicly available. Results demonstrate that women play a major role in producing and providing food for their households in this high-risk climate and conflict area, while men are more likely to migrate seasonally and even permanently. In addition, women are responsible for food preparation, processing, and food preservation and are wholly responsible for attending to household garden plots. They therefore contribute more to household food security than men, though this contribution is not recognized in official statistics. The study findings indicate that the main problems women face as food producers and providers are a lack of access to the full package of improved production methods (improved seeds, fertilizers, modern farming methods, credit services, pesticides, appropriate technologies, and marketing facilities), in addition to gender disparities and gender-biased traditions. The impacts of natural crises and civil conflicts are gendered and therefore the responses to these crises must be gender responsive. Holistic and strategic policies and plans that take gender issues into account are thus needed in order to achieve food security.     

Poly(lactide)/cellulose nanocrystal nanocomposites by high-shear mixing

There is currently considerable interest in developing stiff, strong, tough, and heat resistant poly(lactide) (PLA) based materials with improved melt elasticity in response to the increasing demand for sustainable plastics. However, simultaneous optimization of stiffness, strength, and toughness is a challenge for any material, and commercial PLA is well-known to be inherently brittle and temperature-sensitive and to show poor melt elasticity. In this study, we report that high-shear mixing with cellulose nanocrystals (CNC) leads to significant improvements in the toughness, heat resistance, and melt elasticity of PLA while further enhancing its already outstanding room temperature stiffness and strength. This is evidenced by (i) one-fold increase in the elastic modulus (6.48 GPa), (ii) 43% increase in the tensile strength (87.1 MPa), (iii) one-fold increase in the strain at break (∼6%), (iv) two-fold increase in the impact strength (44.2 kJ/m²), (v) 113-fold increase in the storage modulus at 90°C (787.8 MPa), and (vi) 10³-fold increase in the melt elasticity at 190°C and 1 rad/s (∼10⁵ Pa) via the addition of 30 wt% CNC. It is hence possible to produce industrially viable, stiff, strong, tough, and heat resistant green materials with improved melt elasticity through high-shear mixing.     

Transparent Nanocrystalline Glass-Ceramic System for Organic Pollutants Degradation

Because of the superior photocatalytic activities of nanocrystalline TiO₂ and ZnO under UV irradiation, they were embedded into the glass system (SiO₂, TiO₂, ZnO, B₂O₃, Na₂O, K₂O, P₂O₅, Li₂O and BaO) to provide easy separation from the aqueous system. Different contents of TiO₂ and ZnO have been investigated. Conversion to glass-ceramic materials was carried out by heat treatment at 450 °C, which is the onset of the nucleation peak according to the differential thermal analysis (DTA) result, for different times. This heat treatment regime preserves the transparency of the prepared materials in the visible region and good absorption in the UV region. The high content of TiO₂ or ZnO caused an improvement of microhardness of the prepared materials, though the presence of the two oxides with the same ratio decreased the microhardness values. Photocatalytic activity of the prepared glass-ceramic materials was investigated according to their efficiency for the degradation of humic acid (HA), the major precursor of disinfection by-products (DBPs), from water. All samples were proved to be photoactive with different extents. Four hours heat treatment at 450 °C appears to be the best conditions for the development of TiO₂ and ZnO crystals leading to better photocatalytic activity.