Role of additives in fabrication of soy-based rigid polyurethane foam for structural and thermal insulation applications

Environmental concerns continue to pose the challenge to replace petroleum-based products with renewable ones completely or at least partially while maintaining comparable properties. Herein, rigid polyurethane (PU) foams were prepared using soy-based polyol for structural and thermal insulation applications. Cell size, density, thermal resistivity, and compression force deflection (CFD) values were evaluated and compared with that of petroleum-based PU foam Baydur 683. The roles of different additives, that is, catalyst, blowing agent, surfactants, and different functionalities of polyol on the properties of fabricated foam were also investigated. For this study, dibutyltin dilaurate was employed as catalyst and water as environment friendly blowing agent. Their competitive effect on density and cell size of the PU foams were evaluated. Five different silicone-based surfactants were employed to study the effect of surface tension on cell size of foam. It was also found that 5 g of surfactant per 100 g of polyol produced a foam with minimum surface tension and highest thermal resistivity (R value: 26.11 m²·K/W). However, CFD values were compromised for higher surfactant loading. Additionally, blending of 5 g of higher functionality soy-based polyol improved the CFD values to 328.19 kPa, which was comparable to that of petroleum-based foam Baydur 683.     

Torsional statics of two-dimensionally functionally graded microtubes

A size-dependent governing equation is derived to investigate the torsional static behaviors of two-dimensionally functionally graded microtubes based on the modified couple stress theory. The shear modulus is assumed to vary along the tube’s length direction according to an exponential distribute function, and varies along the tube’s radius direction according to a power-law function. A generalized differential quadrature method is developed to determine the rotational angle and shear stresses. Some illustrative examples are given to investigate the effects of applied torques, the length scale parameter and various material compositions on the torsional angle and shear stresses.     

Skeletal Muscle Health and Cognitive Function: A Narrative Review

Sarcopenia is the loss of skeletal muscle mass and function with advancing age. It involves both complex genetic and modifiable risk factors, such as lack of exercise, malnutrition and reduced neurological drive. Cognitive decline refers to diminished or impaired mental and/or intellectual functioning. Contracting skeletal muscle is a major source of neurotrophic factors, including brain-derived neurotrophic factor, which regulate synapses in the brain. Furthermore, skeletal muscle activity has important immune and redox effects that modify brain function and reduce muscle catabolism. The identification of common risk factors and underlying mechanisms for sarcopenia and cognition may allow the development of targeted interventions that slow or reverse sarcopenia and also certain forms of cognitive decline. However, the links between cognition and skeletal muscle have not been elucidated fully. This review provides a critical appraisal of the literature on the relationship between skeletal muscle health and cognition. The literature suggests that sarcopenia and cognitive decline share pathophysiological pathways. Ageing plays a role in both skeletal muscle deterioration and cognitive decline. Furthermore, lifestyle risk factors, such as physical inactivity, poor diet and smoking, are common to both disorders, so their potential role in the muscle–brain relationship warrants investigation.     

Quasi-static compressive behaviour of aluminium cenosphere syntactic foams

In this paper, cenosphere particles embedded in AA2014 aluminium matrix are used to fabricate syntactic foam by stir casting method. The particle size is about 100?µm and foam density is about 1990?kg?m^?3. Compression tests at strain rate 0.001/s are performed on foam samples to characterise their mechanical properties which are then used in numerical analysis on commercial finite element analysis software ABAQUS/CAE with isotropic elastic-plastic material model. Experimental and numerical results show good conformity in deformation behaviour with elastic and plateau zones showing average deviations less than 5% and 20%, respectively. Foams showed high yield stress and energy absorption capabilities that can be useful in making blast and impact resistant structures.     

The overall crystallization behavior of polyethylene/wax blends as phase change materials for thermal energy storage: A mini review

This review paper deals with the overall crystallization behavior of polyethylene/wax blends as phase change materials (PCMs) for thermal energy storage with the determination of their thermal properties. The addition of molten wax to the polyethylenes decreases the crystallization and melting temperatures of the blends. However, incorporating fillers to the polyethylene/wax blends can either decrease or increase the crystallization and melting temperatures of the composites depending on the filler type. The normalized enthalpy values of linear low-density polyethylene showed no significant change when increasing the wax content. On the contrary, the normalized enthalpy values of the wax in the blends were lesser than that of pure wax and increased with increasing wax content. Since the wax in the blend had a lower crystallinity compared to pure wax, this influences its effectiveness as a PCM for thermal energy storage. The effect of different polyethylenes on the wax morphology gave rise to enhance phase separation when wax was blended to high-density polyethylene as compared to the other polyethylenes. On the contrary, the effect of various waxes on the morphology of polyethylene resulted in different morphologies due to the molecular weight of the wax used and the structure of the polyethylene chain. The addition of fillers to the polyethylene (PE)/wax samples resulted in enhanced phase separation. The overall isothermal crystallization rate and the equilibrium melting temperature of PEs in the PEs/wax blends were depressed by wax addition due to the wax dilution effect.     

The biological mechanisms of butanol tolerance and the application of solvent-tolerant bacteria for environmental protection

Toxicity caused by the accumulation of butanol in fermentation media is an important factor limiting the concentration of butanol. There is currently no systematic research in place investigating the butanol tolerance mechanism of bacteria such as Clostridium acetobutylicum, which adapts to butanol stress and regulates its growth and metabolism. Here, research results related to the butanol tolerance of C. acetobutylicum are reviewed to understand the molecular basis of changes in butanol-tolerant strains. Organic solvent-tolerant bacteria play an important role in the fields of biofuel production, enzyme preparation and bioremediation. An analysis of limitations of the application of organic solvent-tolerant bacteria has revealed that future research should focus on combining the microbial tolerance phenotype with specific utilization to achieve an optimal balance between organic solvent tolerance and production. This review serves as a reference for the improvement and engineering of strains that tolerate organic solvents. © 2019 Society of Chemical Industry     

Fabrication and performances of high lithium-ion conducting solid electrolytes based on NASICON Li1.3Al0.3Ti1.7-xZrx(PO4)3 (0≤ x≤ 0.2)

Solid electrolytes are the key component in designing all-solid-state batteries. The Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) structure and its derivatives obtained by doping various elements at Ti and Al site acts as good solid electrolytes. However, there is still scope for enhancing the ionic conductivity using simple precursors and preparation methods. In this study, the Li superionic conductors Li_1.3Al_0.3Ti_1.7-xZr_x(PO₄)₃ (LATZP) with 0 ≤ x ≤ 0.2 have been successfully prepared by the solid-state reaction route. The structural, morphological, and ionic transport properties were analyzed using several experimental techniques including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and impedance spectroscopy (IS). The presence of two relaxation processes corresponding to grain and grain boundary was studied using various formalisms. We have observed that grain effects dominate at lower temperatures (<100 °C) while the grain boundary at higher temperatures (> 200 °C) on ionic conductivity. The relaxation mechanisms of grain and grain boundaries were investigated by the Summerfield scaling of AC conductivity. The highest total ionic conductivity of 2.48 × 10^-4 S/cm at 150 °C and 5.50 × 10^-3 S/cm at 250 °C was obtained for x = 0.1 in Li_1.3Al_0.3Ti_1.6Zr_0.1(PO₄)₃ sintered at 950 °C/6 h in the air. The ionic conductivity value was found to be higher than the ionic conductivity reported for LATP prepared via solid-state reaction mechanism using the same precursors and conditions.