Combined effect of epoxy functionalized graphene and organomontmorillonites on the morphology, rheological and thermal properties of poly (butylenes adipate-co-terephtalate) with or without a compatibilizer

International audienceIn this work, clay polymer nanocomposites(CPN) with simultaneous dispersion of graphene and organomontmorillonites (OMt) in a poly (butylene adipate-co-terephthalate) (PBAT) biodegradable matrix were prepared, using the melt-blending technique. Two different OMt were used non polar Cloisite15A and polar Cloisite30B with a composition of 3 mass% as well as epoxy functionalized graphene (EFG) with different compositions (1, 3, 5 mass%). The morphology and thermal properties of OMt/PBAT, EFG/PBAT and OMt-EFG/PBAT nanocomposites were studied. A compatibilizing agent (PBATgMA) was elaborated by grafting maleic anhydride on PBAT chains. The effect of incorporation of this compatibilizer on the different nanofillers dispersion in PBAT matrix was studied. The structure of the nanofillers/PBAT nanocomposites was examined using X-ray diffraction analysis and transmission electron microscopy (TEM). The co-addition of EFG with OMt allowed a better dispersion of these nanofillers and more intercalated structures were obtained. The rheological results showed an increase of the storage modulus G' in the different nanofillers/PBAT nanocomposites, particularly after the co-addition of OMt and EFG. The thermal properties evaluated by TGA were sensibly improved by the association of these nanofillers. From all these results, it can be speculated that a synergism phenomenon between graphene and OMt was produced in the PBAT matrix. However, this phenomenon was reduced after the addition of PBATgMA compatibilizer, probably because of repulsive interactions were produced between this compatibilizing agent and the epoxy functionalized graphene

Synergistic effects in epoxy functionalized graphene and modified organo-montmorillonite PLA/PBAT blends

In this work, the organo-montmorillonites (OMt) non polar Cloisite15A and polar Cloiste30B, epoxy functionalized graphene (EFG) and OMt/EFG mixture were adopted as property enhancers for a blend based on poly (lactic acid) (PLA) and poly(butylenes adipate-co-terephthalate) (PBAT). Blends of PLA/PBAT, OMt-PLA/PBAT, EFG-PLA/PBAT and OMt/EFG-PLA/PBAT were prepared, through the melt-blending technique. The morphological, interfacial, rheological and mechanical properties of the different systems were studied. A synergistic reinforcement was achieved by the combined incorporation of OMt with EFG in the PLA/PBAT blend, leading to improve rheological and mechanical properties. The storage modulus (G') increased because of formation stronger percolated networks by the dispersed nanofillers at low frequencies. Concerning tensile tests, an increase in elastic modulus and elongation at the break were observed. This synergistic reinforcement resulted from co-dispersion and interfacial interactions as shown by X-ray diffraction, TEM analysis and interfacial properties

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed