Dynamic mechanical spectroscopy is a common analysis for polymers. Rectangular specimens are usually used for measurement in the solid state due to their easy designing. However, in reason of the non-symmetric shape of sample, rectangular specimens do not experience linear stress on their all body, leading to overestimation of shear modulus. Corrections are required to determine the right shear modulus. In this present work, straight shear modulus determination is carried out using specimens with a cylindrical shape. The reliability of the technique is described on a biosourced polymer materials made of thermoplastic starch, plasticized by glycerol, choline chloride/urea mixture (ChCl/U), 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) and 1-ethyl-3-imidazolium acetate ([EMIM]Ac). The technique is shown to be particularly interesting to avoid any additional shaping of the specimens prior to measurements, that can be detrimental to their properties (evaporation, degradation). A comparison between cylinder and rectangular specimen has also been made to illustrate the interest of cylinder clamping on biosourced polymer material. A cylindrical geometry is designed to improve dynamic mechanical spectroscopy measurements on biobased materials. This geometry allows to make measurement directly on extruded strands, avoiding any molding step that may lead to a modification of the material. This is interesting to determine the thermomechanical behavior of water containing biobased polymers. Examples on thermoplastic starch using various plasticizers are shown. image

The morphology of blends of reclaimed rubber of ethylene, propene and diene monomers (EPDM) with poly(propylene) (PP), elaborated by melt mixing in an internal mixer or by twin screw extrusion, was investigated. A poor dispersion was observed by microscopy in the case of dispersed phase morphology of EPDM in the PP matrix. Because this technique became difficult when the EPDM content increased, dynamic mechanical spectroscopy was used instead and, combined with modeling, was shown to be of powerful help. The model developed by Veenstra for mechanical properties of blends was extended to the case of the dynamic rheology of viscoelastic melts. The analysis and modeling of the frequency dependence of the dynamic moduli enabled to distinguish the various morphologies of PP-reclaimed EPDM blends. In particular, in the medium composition range, reclaimed rubber and PP formed co-continuous phases and the morphology turned to a dispersion of PP in EPDM at high rubber content. The same trend was noted whether the blends were obtained in the mixer or in the extruder.

The carbonatation of semi-crystalline [ethylene–glycidyl methacrylate] copolymers was achieved in batch and solvent-free reactive extrusion processes. Using CO2as reagent and ammonium salts as catalysts, we turn the epoxides into cyclic carbonates.

This work focuses on reactive extrusion to design polypropylene (PP) chains with long and short branching to obtain non-linear behavior for the synthesis of low-density foams (<100 kg m(-3)) using a batch supercritical carbon dioxide (scCO(2)) foaming process. From a maleic anhydride (MA) grafted PP (PP-g-MA), the long-branched chains are performed using [MA]/ [OH] reaction (with Sorbitol alcohol). On the other hand, short branched chains are made from the hydrolysis/condensation of amino-alkoxysilane (3-Aminopropyl-triethoxysilane, APTES) in situ grafted onto PP chains through the ([MA]/NH2] reaction). The results show the need to combine both systems to reach the optimum of the rheological behavior (linear and non-linear) to obtain a low-density foam. On the other hand, the foaming behavior of polypropylene/polyamide 6 (PP/PA6) polymer blends at T = 180 degrees C is also investigated as another way to control the rheology and foamy behavior. At this temperature, T = 180 degrees C, the PA6 phase behaves as solid dispersed particles in a viscoelastic liquid PP matrix. Finally, this study shows the influence of PA6 concentration on the foaming and foam morphology correlated to a rheological study (shear and extensional) and mechanical compressive properties.

The objective of this study is to investigate the ability of thermoplastic vulcanizates (TPVs) (materials based on PP/EPDM blend) to foam under CO2 batch conditions. The EPDM phase, which is dispersed into the PP phase, was dynamically crosslinked either by a phenolic resin (Resol) or by a radical peroxide (dicumyl peroxide). The results show an influence of the crosslinking chemistry on the extensional viscosity of the TPV. Regarding radical chemistry, the peroxide induces polypropylene degradation by β-scission reaction during the dynamic crosslinking process. As a result, the ability of the TPV to deform under extensional flow (Hencky deformation at break <0.5) is greatly reduced. On the contrary, the Resol-based TPV has demonstrated a non-linear viscosity behaviour (strain hardening) and a great ability to deform (Hencky deformation at break >1.5). This unexpected result for a non-homogeneous system can be explained by the confinement of the PP phase between EPDM nodules which gives to the PP chains a gel rheological behaviour. In addition, the influence of the addition of carbon black filler has also been studied. Finally, the relationship between extensional viscosity and physical foaming has been investigated. As for a homogeneous polymer, the extensional viscosity has been proved to be a key factor to estimate the foaming behaviour of complex systems like TPV. Hence, the importance of non-linear viscosity for a multi-phasic polymer to ensure foaming ability has been demonstrated.

The geopolymerization process necessitates the activation of an aluminosilicate source by an alkaline solution. Its kinetics is followed by rheology. The storage modulus (G') and loss modulus (G'') are monitored through oscillatory rheological measurements from the early stage, geopolymer paste, to the gel point with the formation of a geopolymer network. The results show that the temperature increase shortens the reaction time. The principle of Reaction Time-Temperature Superposition (RTTS) is introduced to predict this phenomenon. Furthermore, it is pointed out that using metakaolin blends with different reactivities allows modifying and controlling the reaction time. A critical weight fraction of reactive metakaolin is identified as necessary for the formation of the geopolymer network. The reaction times of the different formulations are linked to the temperature and the weight fraction of metakaolin by the Arrhenius law. A model is established to predict the reaction time according to the temperature and the weight fraction between the two metakaolins used.

This work focuses on the extrusion foaming under CO2 of commercial TPV and how the process influences the final morphology of the foam. Moreover, numerical modelling of the cell growth of the extrusion foaming is developed. The results show how a precise control on the saturation pressure, die geometry, temperature and nucleation can provide a homogeneous foam having a low density (<500 kg/m(3)). This work demonstrates that an optimum of CO2 content must be determined to control the coalescence phenomenon that appears for high levels of CO2. This is explained by longer residence times in the die (time of growth under confinement) and an early nucleation (expansion on the die destabilizes the polymer flow). Finally, this work proposes a model to predict the influence of CO2 on the flow (plasticizing effect) and a global model to simulate the extrusion process and foaming inside and outside the die. For well-chosen nucleation parameters, the model predicts the final mean radius of the cell foam as well as final foam density.

The objective of this work was to study the development of polypropylene (PP) foams with low density (<100 kg m(-3)) using a CO2 batch process. To carry out this study, we used a PP-g-MA that was chemically modified by reactive extrusion to obtain polymer branched structures. Two reagent systems were selected on the basis of chemical reactions with maleic anhydride-the first one is based on the reaction between maleic anhydride and primary amines (MA/NH2, triamine, Jeffamine T-403), and the second one is based on ionic interactions from Zn neutralization. Both of these systems have shown that it is possible to obtain branched PP structures favorable to CO2 foaming and were compared to a commercial, high-melt-strength PP. We have shown that the branched structure of polymer chains can be defined on the basis of a rheological criterion. It defines the notion of fractal behavior (coupling of relaxation modes), which polymer chains must have for nonlinear behavior (strain hardening). This criterion has been defined by analogy with the sol-gel transition, tan delta = 1. Finally, in terms of modeling and simulation, the plasticizing effect of CO2 was modeled from the experimental rheological behavior of the PP plasticized with synthetic oil. A theoretical power law was derived and was then introduced in the mass balance equations to predict the cell growth during depressurization.

This work brings together thermo-mechanical and structural information for plasticized cellulose acetate (CA) by lactates and octanoic acid. CA are processed with plasticizer due to their high Tg and their strong H-bonding network. We prepared CA / plasticizer blends by corotative twin screw extruder and by solvent casting methods. The study of the different relaxations and of the glassy zone modulus was performed by dynamic mechanical analysis (DMA). The miscibility range of cellulose acetate blends were identified by the analysis of the tan delta. Depending on the composition of the system, one or two transitions are noted, this last result indicates the presence of a phase rich in CA and another in plasticizer. To connect this information to crystallinity and molecular organization, X-ray diffraction analyses were carried out. The disappearance of crystallinity allows the plasticization of previously inaccessible zones, causing a glassy modulus drop of more than 1000 MPa.

Volatile organic compounds (VOCs) are mostly toxic and hazardous substances that generally have a strong odor and can cause health and environmental problems. It is thus of upmost importance for the polymer manufacturing industry to eliminate these volatiles from the synthesized polymers. The properties and the application of the polymer, as well as the nature and the concentration of volatiles, govern the choice of the most appropriate elimination technique to avoid any modification or degradation of the polymer. In this review, we take stock of the most suitable purification methods currently used to remove VOCs from polymers in bulk and in emulsion with particular emphasis on the equipment and experimental requirements for each method, as well as the theoretical considerations that motivate the use of the method. In addition to conventional techniques, we are also presenting our efforts to identify potentially promising alternatives for reducing the VOC content from polymers.

The reported work aimed at the modeling of the supercritical CO2 (SCCO2) extraction of contaminants covering a wide range of molecular weights from post-consumer polypropylene. A theoretical model taking into account the combined effects of the two essential phenomena involved in the extraction process (diffusion through the matrix and solubility in SCCO2) is applied to experimental results in order to analyze extraction and disclose relevant kinetics limitations affecting extraction process. From fitting the model to the experimental data obtained at varying pressure and temperature conditions, information on diffusion coefficients of contaminants through polypropylene swollen by SCCO2, activation energies for diffusion and solubilities in the supercritical fluid at temperatures of 50, 70 and 90 °C, and pressures of 100, 200 and 300 bar were obtained. Good agreement between the theoretical model and our experimental measurements was observed. Diffusion coefficients of contaminants through swollen polypropylene have an order of magnitude of 10−11–10−10 m2/s, which are much more important than those through virgin polypropylene due to the swelling effects. Finally, the effects of pressure and temperature on diffusion coefficients and solubilities were examined and discussed in order to understand the effects of these two chief parameters on the SCCO2 extraction rate.

Supercritical CO2 (SCCO2) extraction has been employed to remove model molecules (surrogates) which simulate the real and potential contaminants which can be present into recycled post-consumer polypropylene, limiting the recyclability for food contact applications. Different substances covering a wide range of molecular weights were extracted and evaluated. The effects of contaminant molecular structure and several processing parameters (pressure, temperature, extraction time, solvent flow rate, and matrix shape and size) upon extraction rate were investigated. The operating conditions studied were: pressure ranges of 100-300 bar, temperature ranges of 50-90 degrees C, indicating CO2 densities varying from 0.20 to 0.87 g/mL, and solvent flow rate ranges of 60-160 mL/min. Two shapes of contaminated material were studied: pellets and films (thickness ranges of 100-300 mu m). Quantitative results for extraction kinetics have been obtained by gas chromatography. High extraction yields (100%) were achieved with films at restricted extraction times and, likewise, with pellets at reasonable extraction times. Operating conditions of 200 bar, 90 degrees C and 7.5 h of extraction were sufficient to achieve a complete extraction from pellet matrix (2.5 mm of diameter), even for the heaviest contaminant (807 g/mol). (C) 2015 Elsevier B.V. All rights reserved.

Throughout their lifecycle or first use, polyolefins can be exposed to contaminating media which limit their recyclability, especially in food industry, such as packaging. Supercritical carbon dioxide (SCCO2) extraction in dynamic mode is studied as a possible method to purify post-consumer polyolefins. As a first approach, the strategy was to remove the well-known conventional additives (i.e., antioxidant) which are already present in food grade polypropylene (PP) and linear low density polyethylene (LLDPE). The extraction yields and kinetics have been obtained by gas chromatography. A systematic study of the influence of the shape (pellets or films) and the thickness of the materials shows that it is possible to increase the speed of extraction with a thinner material: high yields (100%) are obtained with films at 300 bar, 50 degrees C and 5 min of extraction. Finally, the potential of SCCO2 extraction was compared to that of traditional liquid extraction with methylene chloride. (C) 2015 Elsevier B.V. All rights reserved.

Recently, ionic liquids have been proposed as a promising plasticizing agents of starch. In this work, starch was treated with ionic liquid to obtain thermoplastic starch (TPS). The effects of supercritical carbon dioxide (ScCO2) on the processing of starch with 1-butyl-3-methylimidazolium chloride (BMIMCI) were also studied. For this purpose, the effects of different operating parameters such as temperature, pressure and processing time on the structural and thermal properties of TPS were evaluated.The results suggest that carbon dioxide leads to a low change of crystalline structure and this change is primarily influenced by temperature processing. Furthermore, the use of supercritical CO2 with different pressures and temperatures induces a decrease of the glass transition compared to formulations without it. This result can be interpreted as the plasticizing effect of CO2 and the preferred interaction between CO2 and starch plasticized with ionic liquid compared to glycerol-starch samples. (C) 2014 Elsevier Ltd. All rights reserved.

Cellulose acetate (CA) plasticized by 1-butyl-3-methylimidazolium chloride (BMIMCl) and with diethylphtalate (DEP) was obtained by melt processing at 150 °C. The effect and the interaction of ionic liquid with the cellulose acetate and their influence on structural, thermo-mechanical, rheological and tensile properties of CA materials were investigated. Ionic liquid (BMIMCl) has shown a good plasticization and more efficient destruction of the crystalline structure of cellulose acetate than the DEP plasticized CA. BMIMCl interacts intensively with CA molecules due to the pronounced van der Waals interactions, hydrogen bonding and electrostatic nature of ionic liquid. The tensile test and the low Young's modulus for plasticized CA suggest a strong reduction of the interaction between the CA chains due to the presence of the ionic liquid.

A one-step process is reported to directly synthesize blends of poly(trimethylene carbonate) (PTMC) with a modified granular starch. Trimethylene Carbonate (TMC) ring-opening polymerization is performed in the presence of native starch particles in bulk conditions at 150 °C and the efficiency of metal-free organic catalysts (TBD and phosphazene superbases P1-t-Oct, P2-t-bu, and P4-t-bu) are investigated to replace the organo-metallic stannous octanoate initiator. TMC monomer is successively converted into PTMC and the robustness of organic catalysts is highlighted with significant activities at very low concentrations (<100 ppm), where stannous octanoate is inefficient. Reactivity of starch toward TMC ROP is deeply investigated by NMR techniques and a starch-graft-PTMC is indirectly evidenced. Starch substitution degree reaches 0.9% indicating that PTMC grafting only occurs at the surface of swollen granular starch. PTMC graft length from the starch surface remained low in the range 2–12 and model ROP reactions highlight the role of TMC hydrolysis on PTMC graft length. Despite low PTMC grafts, a fine dispersion of intact starch particles into the PTMC matrix is evidenced. Consequently, metal-free organic catalysts at low concentrations are promising candidates for synthesizing blends of PTMC with high loadings of surface-modified starch (32% by weight) in 2 min within a one-step process. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 493–503

The purpose of the present work was to investigate the relationship between the glass transition temperature of the materials produced by the melting method and the water content, as well as the nature and concentration of the plasticizer used. Native starch was successfully treated with ionic liquid to obtain thermoplastic starch (TPS). Ionic liquids have shown a better plasticization, and low absorption of water compared to glycerol, which means a better interaction of starch with ionic liquids. The water binding properties of TPS were studied by commenting the water absorption for the plasticized starch at different % RH and with different ratios of plasticizers. An amount of 22.5 wt% AMIMCl is the maximum that can act as a plasticizer. Above this composition, an increase in the wt% water and wt% AMIMCl induces a phase separation. This value corresponds to a chemical interpretation, which corresponds to a ratio of 1:3 AMIMCl/anhydro-glucose. A schematic representation of the different binding between starch, plasticizer and water has been proposed.

This paper deals with immiscible blends of poly(ethylene terephthalate) with polycarbonate obtained by melt mixing. Miscibility of the polyester blends is influenced by transesterification reactions, that are catalyzed either by catalyst residues in the polyesters or by catalysts added on purpose in the blend. These reactions convert the initial homopolymers into block and even random copolymers and affect both the miscibility of the system and the adhesion between the phases. The effect of catalysts and stabilizers on the morphology of PET/PC 50/50 blends was investigated using dynamic mechanical thermal analysis, rheology, microscopy and tensile tests. PET/PC 50/50 containing 0.05 wt.% of lanthanide acetyl acetonate exhibit a irreversible transition occurring at temperature higher than the glass transitions of PET and PC. This transition induces a large increase of the shear modulus and it was attributed to the formation of a third phase in the blend. (c) 2012 Elsevier Ltd. All rights reserved.

The preparation of functional nanocomposites by dispersion of a synthetic lamellar a-ZrP within a styrene/butadiene random copolymer during melt compounding is described. It is shown how the physical and chemical incompatibility of filler and polymer can be overcome, and problems arising from the low viscosity ratio between slurry and polymer matrix are discussed. The aqueous phase can easily be eliminated at the end of the process. The dispersion of the ZrP requires the use of intercalants, and alkylamines were used for this purpose. XRD and TEM are used to characterize the degree of organization of ZrP in the slurries and in the matrix. DMA helps to understand the origin of the limited reinforcing effect.