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This work addresses the large strain behaviors of thermoplastic polyurethanes (TPUs) spanning a range of fractions of hard and soft contents in both experiment and theoretical modeling. The key mechanical features involve a combination of elasticity and inelasticity, and are quantified experimentally under a broad variety of loading scenarios. A finite deformation constitutive model is then presented...
We report molecular simulation, at the atomistic level, of crystalline 4,4′-diphenylmethane diisocyanate (MDI) with n-butanediol (BDO) as chain extender, henceforth denoted as MDI/BDO, which is one of the most important components of thermoplastic polyurethanes. This work studies the structure and properties of crystalline MDI/BDO at equilibrium and under deformation. An atomistic molecular model...
The mechanical and tribological properties of electrospun fiber mats are of paramount importance to their utility as components in a large number of applications. Although some mechanical properties of these mats have been reported previously, reports of their tribological properties are essentially nonexistent. In this work, electrospun nanofiber mats of poly(trimethyl hexamethylene terephthalamide)...
Adequate mechanical integrity of nonwoven fabrics is generally a prerequisite for their practical usage. Nonwoven fiber mats of poly(trimethyl hexamethylene terephthalamide) (PA 6(3)T) with average fiber diameters from 0.1 to 3.6 microns were electrospun from solutions in dimethylformamide and formic acid and their in-plane mechanical response characterized. Two quantitative microstructure-based models...
Young’s modulus and yield strength of individual electrospun fibers of poly(trimethyl hexamethylene terephthalamide) (PA 6(3)T) have been obtained in uniaxial extension. The Young’s modulus is found to exhibit values in excess of the isotropic bulk value, and to increase with decreasing fiber diameter for fibers with diameter less than roughly 500 nm. The yield stress is also found to increase with...
Submicron fibers with bactericidal properties were prepared from electrospinning of blends containing cellulose acetate (CA) as a polymer base, chlorhexidine (CHX) as a bactericidal agent, and organic titanate Tyzor ® TE (TTE) as a cross-linker. A small amount of high molecular weight poly(ethylene oxide) (PEO) was incorporated into the blends to facilitate the electrospinning, and its effect...
Mechanical properties of processed polymers depend sensitively on their microstructure. In order to understand how different processing conditions affect the mechanical properties of polymers, one needs a means to describe the process-induced microstructure. Because the characteristic relaxation times of processed polymer chains often span several orders of magnitude, it is commonly the case that...
Modification of polyacrylonitrile (PAN) by hydroxylamine resulted in polyacrylamidoxime (PANOx), the oxime groups of which are nucleophilic and capable of hydrolyzing esters. PANOx fiber mats with submicrometer fiber diameters ranging from tens to 300nm were produced by electrospinning a suspension of PANOx blended with PAN (1:1 by weight) in a mixture of N,N-dimethyl formamide (DMF) and dimethyl...
We describe a method to determine the mechanical and thermodynamic properties of the interface between a polyethylene crystal and melt by united-atom Monte Carlo simulations. In particular, the {201} fold surface is studied in the temperature range 380–450K. The interface properties are defined by using the concept of a sharp Gibbs dividing surface, which in turn is used to define the interface internal...
The role of fluid elasticity in the formation of fibers from polymer solution by electrospinning is investigated. Model solutions with different degrees of elasticity were prepared by blending small amounts of high molecular weight polyethylene oxide (PEO) with concentrated aqueous solutions of low molecular weight polyethylene glycol (PEG). The elastic properties of these solutions, such as extensional...
The behavior of a glassy polyethylene-like polymer undergoing active compressive deformation was investigated via molecular dynamics simulation. Several important features can be identified within the stress-strain response of the system. Namely, the system deforms elastically, yields, softens, and then at large strains exhibits strain hardening. Simulations reveal that the actively deforming polymer...
Molecular dynamics simulations of realistic, united atom models of polyethylene undergoing uniaxial extension are described. Systems composed of chains ranging from 25 to 400 carbons have been studied, under a variety of processing histories, including isothermal deformation at constant applied stress below the melt temperature T m , isothermal deformation below T m followed by annealing,...
Detailed calculations of the elastic, piezoelectric and pyroelectric properties of the β phase of poly(vinylidene fluoride) are reported. The calculations are based on an empirical atomistic force field that uses the shell model of electronic polarization. Quasi-harmonic lattice dynamics is used to include the vibrational entropy in the calculation of the crystal free energy. The equilibrium crystal...
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