Characterization of various polymer networks in the presence of isotropic and anisotropic solvents

La caractérisation des réseaux de polymères, obtenus par photopolymérisation radicalaire, a été faite par gonflement en masse du réseau de poly(n-butylacrylate) dans des solvants organiques isotropes. L’étude a montré que le taux de gonflement dépend à la fois de la nature du solvant, de la densité de réticulation ainsi que de la température. Ce dernier paramètre influe seulement sur les réseaux gonflés dans des mauvais solvants, comme par exemple le méthanol. L’étude a été suivie d’une caractérisation par gonflement en volume des réseaux de poly(n-butyl-acrylate) et de poly(2-éthyl-hexyl-acrylate) dans des solvants anisotropes, tels que les cristaux liquides 5CB et E7. L’analyse a été effectuée par microscopie optique dans une grande plage de température. Le E7 présente une meilleure compatibilité avec le PABu qu’avec le PEHA. Le 5CB a une miscibilité supérieure à celle du E7 dans le PABu. L’étude comparative de gonflement dans des solvants isotropes et anisotropes a mis en évidence, qu’en termes de miscibilité, les cristaux liquides E7 et 5CB se situent entre le toluène comme bon solvant isotrope, et le méthanol, comme mauvais solvant isotrope. Le modèle de diffusion de Fick a été appliqué aux résultats expérimentaux de cinétique de gonflement des systèmes « polymères isotropes et solvants isotropes ». Une méthode d’optimisation a été utilisée qui consiste à déterminer les facteurs influant sur le gonflement et la réponse quand ces facteurs varient. A partir d’un minimum d’expériences, on aboutit à une surface de réponse qui couvre toute la gamme de l’étude. La méthode utilisée est le plan d’expériences factoriel 2k.The characterization of polymer networks, obtained by radical photopolymerization, was made by swelling of the network of poly (n-butylacrylate ) in isotropic organic solvents. The study showed that the swelling rate depends on the nature of the solvent, on the density of crosslinking as well as on the temperature. This last parameter influences only networks swollen in bad solvents, such as methanol. The study was followed by a characterization by swelling in volume of the networks of poly (n-butyl-acrylate ) and of poly (2-ethyl-hexyl-acrylate) in anisotropic solvents, such as the liquid crystals 5CB and E7. The analysis was made by optical microscopy on a large range of temperature. E7 presents a better compatibility with the PABu than with the PEHA. 5CB has a higher miscibility to that of E7 in PABu. The comparative study of swelling in isotropic and anisotropic solvents put in evidence, that in terms of miscibility, the liquid crystals E7 and 5CB are situated between the good isotropic solvent toluene and the bad isotropic solvent methanol.The model of diffusion of Fick was applied to the experimental results of swelling kinetics of the systems " isotropic polymers and isotropic solvents ". A method of optimization was used which consists in determining the factors influencing the swelling and the answer when these factors vary. From a minimum of experiments, we end up in a surface of answers which covers the whole range of the study. The used method is the factorial plan of experiments 2k

Application of polyvinylpyrrolidone-iodine complex as corrosion inhibitor for carbon steel using an experimental design method

Corrosion processes are responsible for numerous losses, especially in the industrial sector. Inhibitors are commonly used to prevent corrosion in acidic medium. The aim of this study was to apply an experimental design to optimize the influencing parameters such as inhibitor concentration, temperature and immersion time on the corrosion inhibition of polyvinylpyrrolidone-iodine (PVP-I) complexes on carbon steel using the weight loss technique (WL). The parameters of the corrosion protection process were optimized and predictive mathematical models were developed using the Response Surface Methodology (RSM) using the Central Composite Design (CCD). It was also found that the data predicted by the regression analysis had a good agreement with the data obtained from the experiments, with the values R2 = 0.999 and Adj. R2 = 0.997 for the inhibitory effect. The best efficiencies for experiments that were not performed were determined by experimental design (DOE

Analysis of dynamic mechanical properties of photochemically crosslinked poly(isobornylacrylate-co-isobutylacrylate) applying WLF and Havriliak-Negami models

International audienceChemically crosslinked poly (isobornylacrylate-co-isobutylacrylate) was elaborated by radical photo-copolymerization of isobornylacrylate and isobutylacrylate monomers in a 4:1 mass ratio, by adding a crosslinking agent at low concentration. The obtained copolymer was characterized by Fourier transform infrared spectroscopy for structural analysis, by differential scanning calorimetry for the determination of the glass transition temperature, and by thermogravimetric analysis to investigate thermal degradation effects. Storage modulus, dissipation modulus and tan delta were evaluated by dynamic mechanical analysis and modeled using different physical approaches such as the time-temperature superposition principle and the Havriliak-Negami model. The Cole-Cole curve was fitted with the Havriliak-Negami model yielding five parameters which were used to calculate the dynamic mechanical properties of the copolymer over a large frequency range from 1.03 × 10−4 Hz to 7.58 × 107 Hz. Calculated elastic and dissipative moduli agree well with the experimental data