University of Akron

About: University of Akron is a education organization based out in Akron, Ohio, United States. It is known for research contribution in the topics: Polymer & Polymerization. The organization has 17401 authors who have published 29127 publications receiving 702386 citations. The organization is also known as: The University of Akron.

A taxonomic structure for the concept comfort.

Abstract: The concept of comfort is an important one for nursing, but because of its complexity, it has not been analyzed, operationalized or structured for nursing science. In this paper, three technical senses of the term are derived from: (a) contemporary and archaic lexical entries; (b) analysis of how the concept is used in contemporary and historical nursing literature; and (c) theoretical support found in the disciplines of nursing and ergonomics. Next, the contexts of patients' needs are explored and four contexts are derived from the nursing literature on holism. When the three senses and the four contexts of needs are juxtaposed, a 3 x 4 grid with 12 elements emerges that encompasses the total domain of patient comfort. Each element describes an aspect of comfort from which empirical indicators, antecedents, consequents and test items can be developed. The grid represents a taxonomic structure of the concept that organizes the meanings of this complex concept. The structure can be used to develop comfort pretests as the nurse assesses possible needs in a given situation and to develop comfort post tests, to assess the effectiveness of comfort measures.

High‐Strength Mats from Electrospun Poly(p‐Phenylene Biphenyltetracarboximide) Nanofibers

Abstract: Electrospinning has proven to be a very effective method for producing polymer nanofibers. However, the mechanical properties of electrospun polymer nanofibers can be quite different from textile fibers made from the same polymer since the polymer molecules are not optimally aligned in electrospun nanofibers. Many reports have shown that the tensile strength of electrospun mats of non-aligned nanofibers is lower than 40 MPa. Stretching can be an effective method for making high-performance conventional fibers with high degrees of molecular orientation within the fibers. However, stretching is not a practical process for making high-strength nanofibers by electrospinning due to 1) the very small diameters of electrospun fibers and 2) the complicated coiled path of the jet during the electrospinning process. These factors make it very difficult to stretch the electrospun nanofibers enough to produce high degrees of molecular orientation in the fiber. Multiwalled carbon nanotubes (MCNTs) are commercially available at a competitive price and possess a very high tensile strength of 150 GPa with an elastic modulus of about 1.8 TPa. MCNTs are ideal materials for use in high-performance polymer nanocomposites. There have been several reports on using carbon nanotubes (CNTs) to reinforce fibers or nanofibers. However, the expected degree of reinforcement has not yet been achieved. Many factors, such as adhesion between the polymer matrix and the fillers, and purity and dispersion of CNTs, may be responsible for the observed results; additionally, the geometry of the MCNTs is important for nanofibers reinforced by MCNTs. The MCNTs used to make high-strength nanofibers should be totally straight, since bent, coiled, or spiral-shaped MCNTs cannot be embedded uniformly inside a 300 nm diameter nanofiber, as we have shown previously. In order to make high-strength composite nanofibers, pure, straight MCNTs with no bent, coiled, or spiral-shaped impurities are desired. Although pure rod-like MCNTs are difficult to obtain and quite expensive, rod-like macromolecules can be oriented along the fiber axis to make high-strength electrospun polymer nanofibers. Poly(p-phenylene biphenyltetracarboximide) (BPDA/PDA) is a rigid-rod-like polyimide (PI) formed from its precursor poly(p-phenylene biphenyl tetracarboxamide acid) (BP-PAA), which is flexible and soluble in common organic solvents. The tensile strength of BPDA-PDA PI has been reported to be as high as 1.25 GPa for conventional fibers and 600 MPa for films. X-ray diffraction (XRD) has shown that, in high-temperature-cured BPDA/PDA PI films, the molecular chains are highly ordered and parallel to each other, even in an unstretched film. The high-temperature heat treatment tends to align the rigid-rod-like molecules, which is expected to be useful for making high-performance electrospun nanofibers containing highly oriented polymer molecules. Here, we present a new strategy for using rod-like macromolecules like BPDA-PDA PI to make high-strength electrospun nanofibers. Non-woven fabric mats composed of these nanofibers show a tensile strength of more than 650 MPa and a tensile modulus of more than 15 GPa. These are the first results demonstrating that mats of electrospun polymer nanofibers can possess such high values of tensile strength and tensile modulus, which are much higher than previously reported values. Figure 1 illustrates the chemical and physical conversion of flexible BP-PAA into rigid-rod-like BPDAPDA PI inside a small diameter nanofiber. BPDA-PDA PI is insoluble in all organic and inorganic solvents except for sulfuric acid. The BPDA-PDA PI nanofibers have been made by electrospinning a solution of the PI precursor, BP-PAA, in dimethyl acetamide (DMAc). The BP-PAA precursor used in this experiment was synthesized by a three-day-long condensation of highly pure monomers at a temperature of –5 °C. The inherent viscosity of the assynthesized BP-PAA is 5.17 dL g in DMAc at 25 °C, and the absolute viscosity of a 7.77 wt.-% solution in DMAc is 1170 poise (No. 4 rotor (3.20 mm diameter) at 3 rpm), much higher than the viscosity of commercially available BPPAA (1 poise = 0.1 Pa s). The inherent viscosity of commercially available BP-PAA (Aldrich) is 1.43 dL g in DMAc at 25 °C, and the absolute viscosity is 30 poise (No. 4 rotor at 60 rpm), measured using a commercially available solution C O M M U N IC A TI O N S