Calculating turbulent nonisothermal jets

Experimental and calculated data concerned with the propagation of turbulent nonisothermal jets are compared.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 4, pp. 653–656, April, 1976.     

Reusable and durable electrostatic air filter based on hybrid metallized microfibers decorated with metal-organic-framework nanocrystals

As global air pollution becomes increasingly severe,various types of fibrous filters have been devel-oped to improve air filter performance.However,fibrous filters have limitations such as high packing density that generally causes high-pressure drop and ultimately deterioration in the filtration effi-ciency.High-pressure particulate matter precipitators are limited in terms of scope for commercialization because they require high voltage supplies and ozone generators.In this study,we develop fibrous fil-ters with enhanced durability and improved performance using metallized microfibers decorated with metal-organic-framework(MOF)nanocrystals.Not only does the efficiency of the developed filters remain at or above 97％for 0.50-1.5 μm PMs but the durability also significantly increases.In addi-tion,using the water purification ability of the MOF,we explore the dye degradation effect of the hybrid microfibers by immersing them into Rhodamine B aqueous solution.In such an experiment the Rho-damine B aqueous solution is completely purified by the presence of the hybrid microfibers under the UV irradiation.     

Polymer adhesion in heat‐treated nonwovens

Polymer adhesion and sintering in compound nonwovens was studied. Nonwovens containing a mixture of binding bi‐component (BICO) fibers embedded in a fibrous matrix were heated to melt the outer shell of BICO fibers and interlock the matrix to create stiff load‐bearing surfaces. It was found that stiffness depends on heat‐treatment regimes. In low‐temperature regimes, BICO fibers melt, but do not fully flow and encase the surrounding filler matrix. At sufficiently high temperatures, the shells of BICO fibers melt and flow which results in encasing the neighboring filler fibers. This results in an abrupt increase in the nonwoven stiffness which is independent of heat‐treatment temperature. At significantly high temperatures, the filler matrix fibers sinter to each other leading to a further increase in stiffness. The experiments were conducted with co‐polymers frequently used in the shells of BICO to demonstrate the interlocking mechanism characteristic of these compound nonwovens. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46165.     

Shear and extensional rheological investigations in solutions of grafted and ungrafted polysaccharides

Many polysaccharides with varying shear stability have been grafted with polyacrylamide branches to enhance their turbulent drag‐reducing and flocculating characteristics. Their aqueous solutions have been studied by shear and extensional rheometric techniques. All the solutions of grafted carboxymethyl cellulose, guar gum, starch, and sodium alginate exhibit shear‐thinning non‐Newtonian behavior. The viscosities are higher than those of ungrafted polysaccharides. The solutions of grafted carboxymethyl cellulose, guar gum and sodium alginate are spinnable. When subjected to uniaxial stretching in a stretching device, the formation of a thread and reduction of the thread diameter with time were observed. The stretching device was used to measure the relaxation time, which was found to be the largest (∼26 ms), on the order of flexible polyacrylamide, for the grafted carboxymethyl cellulose. Though a polyacrylamide solution degrades through nozzle flow and completely loses its extensional properties, a solution of grafted carboxymethyl cellulose retains about half its relaxation time because of the shear stability of polysaccharide chains and their structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3200–3209, 2000     

Recent progress in interfacial toughening and damage self‐healing of polymer composites based on electrospun and solution‐blown nanofibers: An overview

In this article, we provide an overview of recent progress in toughening and damage self‐healing of polymer–matrix composites (PMCs) reinforced with electrospun or solution‐blown nanofibers at interfaces with an emphasis on the innovative processing techniques and toughening and damage self‐healing characterization. Because of their in‐plane fiber architecture and layered structure, high‐performance laminated PMCs typically carry low interfacial strengths and interlaminar fracture toughnesses in contrast to their very high in‐plane mechanical properties. Delamination is commonly observed in these composite structures. Continuous polymer and polymer‐derived carbon nanofibers produced by electrospinning, solution blowing, and other recently developed techniques can be incorporated into the ultrathin resin‐rich interlayers (with thicknesses of a few to dozens of micrometers) of these high‐performance PMCs to form nanofiber‐reinforced interlayers with enhanced interlaminar fracture toughnesses. When incorporated with core–shell healing‐agent‐loaded nanofibers, these nanofiber‐richened interlayers can yield unique interfacial damage self‐healing. Recent experimental investigations in these topics are reviewed and compared, and recently developed techniques for the scalable, continuous fabrication of advanced nanofibers for interfacial toughening and damage self‐healing of PMCs are discussed. Developments in the near future in this field are foreseen. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2225–2237, 2013