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The addition of six different clays (laponite, montmorillonite, halloysite, and their organomodified counterparts) to poly(methyl methacrylate), polystyrene, and their blends was studied. The morphologies of the obtained composites were studied using transmission electron microscopy and scanning electron microscopy. Small angle oscillatory shear experiments, as well as shear induced coalescence tests, were carried out to evaluate the role of the clay as a coalescence inhibitor. Using the six different clays enabled the evaluation of the effect of the clay location and the clay platelet size for a given location (matrix, dispersed phase, interphase) on the coalescence phenomenon. A decrease of the dispersed phase of the blend was generally observed upon the addition of the clay. Clays located exclusively in the matrix (laponite, montmorillonite, halloysite, and modified halloysite) were shown to migrate to the interface during coalescence tests, inducing a decrease of coalescence at a certain extent of migration. Modified montmorillonite, located at the interface, was the most efficient clay at inhibiting coalescence, due to relaxation of Marangoni stresses with an important barrier effect. Overall, it was shown that having a certain size of a nanoparticle is essential for it to locate at the interface and inhibit coalescence. Nanoparticles with a larger size than the droplets are not able to locate at the interface and, therefore, do not have an effect on coalescence. Conversely, nanoparticles whose size is 10% or less of the droplet were found to be well dispersed in the whole blend. These particles did not have a preferred location nor had an effect on coalescence.

The compatibilization mechanism of poly(methylmethacrylate) (PMMA)/polystyrene (PS) blends induced by PMMA-b-PS block copolymers of different molar masses (30 and 104 kg/mol) was studied. The blend morphologies with and without copolymers were observed by scanning electron microscopy. The rheological behavior was studied performing small amplitude oscillatory shear experiments. The experimental results were compared to Palierne's model predictions. Shear induced coalescence tests were also conducted. Contrary to what was expected, adding block copolymers did not result in a refinement of the droplet size. However, it induced Marangoni stresses, a decrease in interfacial tension and an inhibition of coalescence of the dispersed phase. During coalescence tests, a decrease in the relaxation time due to Marangoni stresses with time was revealed. This interesting behavior contradicts previous works on the subject, and is believed to be due to a migration of block copolymers to the interface during the tests rather than droplets' coalescence. As such, the morphology was explained by the fact that block copolymers are not entirely at the interface initially. Also, the block copolymer with a higher molecular mass was shown more efficient at inhibiting coalescence, indicating that the compatibilization mechanism is a combination of Marangoni stresses and steric hindrance.

Poly(butylene succinate) (PBS) and poly-[(butylene succinate)-co-(butylene adipate)] (PBSA)-based composite films loaded with 5 wt % of fillers (native or organomodified montmorillonites) were extruded using a standard protocol or assisted by water injection. In the resulting composite films, the filler morphology was altered, as evidenced by TEM images. The CNa aggregates were broken with the help of water injection, and the exfoliation/dispersion levels of C30B were dependent on the matrix. By considering the degree of crystallinity of the polymer matrix, the nature of the fillers, and also the processing conditions, the film (micro)structure was successfully correlated to the water (liquid and vapor) behavior of the PBSand PBSA-based films, studied by means of sorption and permeation measurements. The water permeability and diffusivity were significantly reduced even with an increased water sorption, depending on the matrix and the clay morphology or nature. Specifically, concomitant effects such as tortuosity and trapping but also preferential diffusion pathways as well as free volumes in matrix strikingly were responsible for the barrier performances evolution.

In this work, the effect of adding organoclay (Cloisite 20A) to a poly(methyl metacrylate) (PMMA)/polystyrene (PS) blend was evaluated in order to understand the compatibilization mechanism taking place. The blend morphology was quantified using micrographs obtained by scanning electron microscopy and observed by transmission electron microscopy. The state of dispersion of the clay was studied using small angle X-ray scattering and wide angle X-ray scattering and by applying the Carreau-Yasuda with a yield stress model to small amplitude oscillatory shear (SAOS) data. Morphological analyses revealed that the clay was intercalated, that its addition resulted in a decrease in the size of the dispersed phase and that it was preferentially located at the interface, except in the case of saturated interfaces, in which case the remaining clay was dispersed in PMMA. By applying the simplified Palierne model to SAOS experiments, the interfacial tension between the polymers forming the blend was inferred and shown to decrease upon addition of clay. The relaxation spectra inferred from the SAOS data, using the Honerkamp and Weese method, revealed four relaxation times: Relaxation of PMMA and PS chains, relaxation of the droplet shape, as well as an additional relaxation phenomenon attributed to the Marangoni stress. Although Marangoni stresses have already been studied in the case of blends compatibilized by block copolymers, this is the first time that it has been evidenced in the case of a clay as compatibilizer.

Composite films composed of a biodegradable poly[(butylene succinate)-co-(butylene adipate)] (PBSA) matrix with several contents (2.5; 5; 7.5; 10 wt %) of native (MMT) or organo-modified montmorillonite (OMMT) were successfully extruded using an innovative water-assisted extrusion process. As expected, better dispersion and exfoliation levels of nanofillers were obtained in PBSA+OMMT than in PBSA+MMT composite films, whatever the nanofiller content. Otherwise, the water-assisted extrusion process has also clearly enhanced the dispersion and exfoliation levels of native montmorillonite. This process was particularly efficient to delaminate and to disperse high amounts (≥5 wt %) of MMT in the PBSA matrix, which has highly increased tortuosity effects in the resulting composite films. The films prepared via the water-assisted extrusion have consequently exhibited better barrier properties to water and to gases than the films classically extruded and as the nanofiller content increases.

Bio-based polyamide 11 (PA11) and water-soluble polyethylene oxide (PEO) (80/20 wt/wt) were used to prepare an immiscible polymer blend. Ternary systems containing 1 wt% hydrophilic clay (organomodified or native clay) were elaborated using extrusion with and without injection of water. The cryoscopic effect on PA11 and PEO observed by high pressure differential scanning calorimetry indicated that they were both miscible with water under conditions of water-assisted extrusion. Transmission electron microscopy revealed a selective localization of both types of clay in the matrix (PA11). However, with water-assisted extrusion a part of the organomodified clay platelets was localized into the dispersed phase (PEO). Under rheological tests, the unmodified clay exhibited a different effect compared with the organomodified clay on the modulus and viscosity of the blend. The van Gurp–Palmen plot indicated that clay potentially decreased the interfacial tension between PA11 and PEO, while the weighted relaxation spectra confirmed that water improved the dispersion state of the clay and limited the polymer degradation. Thermogravimetric analyses showed that the presence of clay and water improved the thermal stability of PA11/PEO blends. Our work is the first one which has realized water-assisted extrusion of a clay-filled ternary blend.

Hybrid membranes made of a biopolymer matrix poly(butylene succinate) (PBS) or poly(butylene succinate-co-butylene adipate) (PBSA) loaded with 5 wt% of native (CNa) or organo-modified (C30B) montmorillonites were successfully extruded using new extrusion conditions where liquid water was introduced into the extruder barrel to improve the nanofiller dispersion and exfoliation levels. The C30B incorporation in both matrices leads to the degradation of polymer chains and the reduction of the thermal stability while the CNa introduction combined with the water injection presents no effect on the polymer molecular weight and the thermal stability. The water-assisted extrusion process enables the increase in CNa dispersion and exfoliation levels in both matrices, which improves barrier properties to gases and water by tortuosity effects. In the case of C30B, the positive effect of dispersion induced by water injection was much less pronounced since C30B particles were already well dispersed and exfoliated in both matrices. The use of the water injection at high pressure during the extrusion process was found really efficient for native montmorillonite and so appears as a promising process for dispersing hydrophilic particles in polymers having a low hydrophilic character, without preliminary chemical modification of the fillers.

Cellulose is one of the structural elements of wood, cotton, flax… It has a so-called “microfibrillar” structure made from a meticulous assembly of parallel chains resulting from the biosynthesis of cellulose. Microfibrils have a section of nanoscopic dimension combined with a high length conferring them a high aspect ratio (=length/diameter). They exhibit also interesting mechanical properties (Young’s modulus around 150 GPa), a low density, biodegradability, wide availability, etc. making them quite attractive filler compared to a glass fibre. The objective was to investigate the dispersion of cellulose microfibrils in polymers using melt processing technique. Microfibrils were envisaged to be released from cellulose fibres either during extrusion assisted by water injection under pressure or in suspension via homogenization (producing microfibrillated cellulose or MFC) before extrusion. Limiting cellulose thermal degradation under melt processing conditions was another challenge. The impact of the good specific properties and the gel effect of microfibrillated cellulose on the composite properties were also aimed. In-situ defibrillation during extrusion step was not reasonably reached. However it was shown that high shearing forces improved the dispersion of cellulose fibres in polyolefins. The most spectacular effects came from the water injection under pressure during extrusion. The dispersion of the fibres was enhanced whatever the shear applied. The yellowing of the composites resulting from the thermal degradation of cellulose during processing was reduced. The incorporation of microfibrils in polymers was realized by first defibrillating cellulose by homogenization and then by introducing the dried MFC in the polymer using melt compounding. Addition of surfactant, suspension of polypropylene grafted on maleic anhydride (PP-g-MA) or polyethylene glycol (PEG) to the MFC gel was necessary for preserving microfibrils from agglomeration during drying. Thermal pr, (FSA 3) -- UCL, 2010