Normal stresses in semiflexible polymer hydrogels

Biopolymer gels such as fibrin and collagen networks are known to develop tensile axial stress when subject to torsion. This negative normal stress is opposite to the classical Poynting effect observed for most elastic solids including synthetic polymer gels, where torsion provokes a positive normal stress. As recently shown, this anomalous behavior in fibrin gels depends on the open, porous network structure of biopolymer gels, which facilitates interstitial fluid flow during shear and can be described by a phenomenological two-fluid model with viscous coupling between network and solvent. Here we extend this model and develop a microscopic model for the individual diagonal components of the stress tensor that determine the axial response of semi-flexible polymer hydrogels. This microscopic model predicts that the magnitude of these stress components depends inversely on the characteristic strain for the onset of nonlinear shear stress, which we confirm experimentally by shear rheometry on fibrin gels. Moreover, our model predicts a transient behavior of the normal stress, which is in excellent agreement with the full time-dependent normal stress we measure.Comment: 12 pages, 8 figure

Preliminary investigation on auto-thermal extrusion of ground tire rubber

Ground tire rubber (GTR) was processed using an auto-thermal extrusion as prerequisite to green reclaiming of GTR. The reclaimed GTR underwent a series of tests: thermogravimetric analysis combined with Fourier-transform infrared spectroscopy (TGA-FTIR), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and static headspace and gas chromatography-mass spectrometry (SHS-GC-MS) in order to evaluate the impact of barrel heating solution (with/without external barrel heating) on reclaiming process of GTR. Moreover, samples were cured to assess the impact of reclaiming heating solution on curing characteristics and physico-mechanical properties. Detailed analysis of the results indicated that the heat supplied by the machinery was replaced by energy generated due to the high shearing phenomenon, what significantly influenced energy consumption and hereby lowered processing costPostprint (published version

Porosity governs normal stresses in polymer gels

When sheared, most elastic solids such as metals, rubbers and polymer hydrogels dilate in the direction perpendicular to the shear plane. This well-known behaviour known as the Poynting effect is characterized by a positive normal stress [1]. Surprisingly, biopolymer gels made of fibrous proteins such as fibrin and collagen and many tissues exhibit the opposite effect, contracting under shear and displaying a negative normal stress [2, 3]. Here we show that this anomalous behaviour originates from the open network structure of biopolymer gels, which facilitates interstitial fluid flow during shear. Using fibrin networks with a controllable pore size as a model system, we show that the normal stress response to an applied shear is positive at short times, but decreases to negative values with a characteristic time scale set by pore size. Using a two-fluid model, we develop a quantitative theory that unifies the opposite behaviours encountered in synthetic and biopolymer gels. Synthetic polymer gels are impermeable to solvent flow and thus effectively incompressible at typical experimental time scales, whereas biopolymer gels are effectively compressible. Our findings suggest a new route to tailor elastic instabilities such as the die swell effect that often hamper processing of polymer materials and furthermore show that poroelastic effects play a much more important role in the mechanical properties of cells and tissues than previously anticipated

The Taste of Waste: The Edge of Eggshell Over Calcium Carbonate in Acrylonitrile Butadiene Rubber

Rubber technology experiences a new age by the use of biowaste or natural fillers. In this regard, taking properties of reinforcing agents from biowaste fillers remains as the challenging matter. Chicken eggshell (ES) biowaste has recently been introduced to substitute calcium carbonate (CaCO3) duo to its superior properties and low price. In this work, composites based on acrylonitrile butadiene rubber (NBR) reinforced with ES and CaCO3 microfillers at various loading levels were prepared and characterized. To improve the interactions between fillers and the NBR matrix, ES and CaCO3 were surface-functionalized using a terpolymer, namely poly(vinyl 2-pyrrolidone-co-maleic acid-co-acrylic acid). Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to characterize the modified fillers. The incorporation of the functionalized fillers resulted in a significant rise in the maximum torque according to the rheometric measurements. The Young’s modulus of the ES-based and CaCO3-based compounds showed a mild improvement over a wide range of filler contents. The elongation at break of the NBR composites, however, was dependent on the filler content. This work provides exciting opportunities for the design of novel and innovative coupling agents to be used in rubber applications. © 2019, The Author(s)

Additive Manufacturing of Biopolymers

International audienceAdditive Manufacturing of Biopolymers: Materials, Printing Techniques, and Applications describes various biopolymers that are currently used in additive manufacturing technologies and identifies the challenges/limitations in the materials and printing processes. The book provides basic knowledge and advanced details about 3D printing techniques and the applicable biopolymers as well as the latest updates on materials and techniques for 3D printing of biopolymers. Each chapter dedicates a section to future trends and perspectives in additive manufacturing of biopolymers from the use of biopolymers and new techniques point-of-view

Improvement of flame retardancy of PMMA, combination of nanoparticles and phosphonated compound

Le polyméthacrylate de méthyle (PMMA) est un thermoplastique présentant de nombreux avantages (transparence, légèreté, flexibilité). Cependant, le caractère inflammable du PMMA est un frein pour son utilisation dans de nombreuses applications, connaissant les pertes humaines et matérielles causés par les incendies. Cette thèse avait donc pour but d'améliorer la stabilité thermique et le comportement au feu du PMMA. Dans un premier temps, nous avons étudié l'influence de la dispersion de kaolins purs et traités sur le comportement au feu et la dégradation thermique du PMMA. Nous nous sommes ensuite orientés vers la modification chimique du PMMA par la méthode de copolymérisation du méthacrylate de méthyle (MMA) avec deux co-monomères phosphonés. Enfin, nous nous sommes intéressés à l'incorporation chimique ou physique de deux types de particules de polyhedral oligomeric silsesquioxane (POSS) dans le PMMA ou dans le PMMA modifié (copolymère (MMA – co- monomère monophosphoné)). Cette dernière partie a permis de mettre évidence l'effet bénéfique de la combinaison des particules de POSS et du PMMA modifié sur la dégradation thermique et l'inflammabilité de PMMA. Dans nos travaux, une attention particulière a été portée sur l'effet de phosphore en phase gazeuse et en phase condensée. Dans ce contexte nous avons pu définir, pour le PMMA modifié par les co-monomères phosphonés, un indice d'efficacité du phosphore pour chaque phase.Poly(methylmethacrylate) (PMMA) is an important thermoplastic, widely used in industry. Unfortunately, it is a highly flammable polymer. The aim of this research was to improve the thermal stability and fire behavior of PMMA. First, we studied the influence of the dispersion of pure or treated kaolin on the fire behavior and thermal stability of PMMA. In second part of this work, the chemical modification of PMMA, using copolymerization of methyl methacrylate (MMA) with two phosphonated co-monomers was studied. Finally, we interested in chemical or physical incorporation of two types of polyhedral oligomeric silsesquioxane particles (POSS) in the PMMA or modified PMMA copolymère (MMA – co- monophosphonated monomer)). The effect of the combination of POSS particles and modified PMMA on the thermal degradation and flammability of PMMA was studied. In our work, the effect of phosphorus in the gas and condensed phase was separately studied. This study allowed us to define an efficiency index of phosphorus in each phase

Chapter 11: Flame Retardancy of Recycled Polymer Composites

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Analysis of Flame Retardancy in Polymer Science

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Flame Retardant Epoxy Composites on the Road of Innovation: An Analysis with Flame Retardancy Index for Future Development

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