Cross-linked polyfuran networks with elastomeric behaviour based on humins biorefinery by-products

International audienc

Synthesis of Resins Using Epoxies and Humins as Building Blocks: A Mechanistic Study Based on In-Situ FT-IR and NMR Spectroscopies

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Shear induced structuration of liquid crystalline epoxy thermosets

International audienceLow-molecular weight liquid crystals (LC) have wide technological applications due to their self-assembly in the mesophase. An azomethine nematic monomer based on diglycidyl functionalized mesogenic core and without spacers has been cured with a diamine. The great affinity of LC epoxy to the formation of ordered structures introduces a spatial driving force into the process of curing. Thermal and LC behaviors were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The nature of the LC phases was confirmed by X-ray diffraction. Rheological experiments were conducted during crosslinking at different shear stresses. The viscosity of the mixture is strongly decreasing by three orders of magnitude when the solid epoxy is melting into a LC phase, and is increasing again due to the curing. Unexpected results were found. Applying a stress during curing had a profound influence on the ordering of the structure. The material becomes isotropic if a small shear stress is applied. Then, the higher the stress is, more ordered the final material is. For the highest stresses, the final material is in a highly ordered, quasi-crystalline, smectic structure

Sustainable access to fully biobased epoxidized vegetable oil thermoset materials prepared by thermal or UV-cationic processes

Beyond the need to find a non-toxic alternative to DiGlycidyl Ether of Bisphenol-A (DGEBA), the serious subject of non-epichlorohydrin epoxy resins production remains a crucial challenge that must be solved for the next epoxy resin generations. In this context, this study focuses on the valorization of vegetable oils (VOs) into thermoset materials by using (i) epoxidation of the VOs through the “double bonds to epoxy” synthetic route and (ii) synthesis of crosslinked homopolymers by UV or hardener-free thermal curing processes. A thorough identification, selection and physico-chemical characterization of non-edible or non-valuated natural vegetable oils were performed. Selected VOs, characterized by a large range of double bond contents, were then chemically modified into epoxides thanks to an optimized, robust and sustainable method based on the use of acetic acid, hydrogen peroxide and Amberlite® IR-120 at 55 °C in toluene or cyclopentyl methyl ether (CMPE) as a non-hazardous and green alternative solvent. The developed environmentally friendly epoxidation process allows reaching almost complete double bond conversion with an epoxy selectivity above 94% for the 12 studied VOs. Finally, obtained epoxidized vegetable oils (EVOs), characterized by an epoxy index from 2.77 to 6.77 m(eq.) g(−1) were cured using either UV or hardener-free thermal curing. Both methods enable the synthesis of 100% biobased EVO thermoset materials whose thermomechanical performances were proved to linearly increase with the EVOs' epoxy content. This paper highlights that tunable thermomechanical performances (T(α) from −19 to 50 °C and T(g) from −34 to 36 °C) of EVO based thermoset materials can be reached by well selecting the starting VO raw materials

Politics of Care and Reverberations of Trauma: Syrian Refugees in Izmir, Turkey

For Syrians in Turkey, displacement produces new relationships to governance and forms of care. This dissertation explores a broad framework of international, national, and local institutions—including care and assistance sectors (health care and humanitarian aid), the labor market, and urban settlement—that are part of the interface between Syrians and the Turkish state. Displacement also causes new anxieties, fears, and shocks—from war trauma in Syria to refugee camps and homelessness in Turkey, from housing scarcity and income precarity to attempts at irregular migration by boat to Europe, from medicalized violence in giving birth and fears of dismemberment to local xenophobia and violence and ad hoc strategies for survival in the everyday. The broad question asked is: Why did Syrians experience Izmir as such a dangerous, necropolitical space, even though the government provided many services to enhance their lives, and even though they were supported by the dominant ruling government party? In answering this question, this dissertation studies the following fields: humanitarian programming, a history of migration in Izmir and contemporary gentrification practices, the unregulated labor sector, gender politics, health care services, the processing of refugee bodies, forensic medical practices, and cemeteries on the Aegean. Most importantly, this dissertation connects Syrian affects and emotions to the institutions that regulate their everyday lives through multiple interventions. Specifically, I ask: How can history, politics, and displacement be read in the feelings encoded in narratives of displacement and trauma? This historical timeline is related to four central dynamics: (1) The 2016 attempted coup and resulting state of emergency in Turkey; (2) the 2016 Turkey-EU deal; (3) the violence and policies of military incursions on the Turkey-Syria borderlands; and (4) necropolitics on the Turkey-Greece (EU) borderlands. All four dynamics limited Syrian movement within Turkey and along its increasingly securitized borders. In relation to examining those dynamics, this work takes inventory of Syrian politics and historicizes the experiences of Syrian refugees in Turkey. Population management and emerging biopolitical projects feature in this study as elements that organize Syrian lives in particular ways. Among other affects, shock or trauma, articulated in Arabic as sadma, is an important node of analysis for Syrian experiences of migration. Here, Syrian experiences of trauma become part of an “archive of feelings” (Cvetkovich, 2003) about the politics of displacement, connecting systemic structures of exploitation and oppression to the fears and dangers one feels and associates with everyday living in displacement. Emotional reverberations of fear are political, and Syrian affects in Turkey tell us about the politics of displacement in important ways

Polymers Keratin Associations with Synthetic, Biosynthetic and Natural Polymers: An Extensive Review

International audienceAmong the biopolymers from animal sources, keratin is one the most abundant, with a major contribution from side stream products from cattle, ovine and poultry industry, offering many opportunities to produce cost-effective and sustainable advanced materials. Although many reviews have discussed the application of keratin in polymer-based biomaterials, little attention has been paid to its potential in association with other polymer matrices. Thus, herein, we present an extensive literature review summarizing keratin's compatibility with other synthetic, biosynthetic and natural polymers, and its effect on the materials' final properties in a myriad of applications. First, we revise the historical context of keratin use, describe its structure, chemical toolset and methods of extraction, overview and differentiate keratins obtained from different sources, highlight the main areas where keratin associations have been applied, and describe the possibilities offered by its chemical toolset. Finally, we contextualize keratin's potential for addressing current issues in materials sciences, focusing on the effect of keratin when associated to other polymers' matrices from biomedical to engineering applications, and beyond

Influence of the Presence of Disulphide Bonds in Aromatic or Aliphatic Dicarboxylic Acid Hardeners Used to Produce Reprocessable Epoxidized Thermosets

The design of polymers from renewable resources with recycling potential comes from economic and environmental problems. This work focused on the impact of disulphide bonds in the dicarboxylic acids reactions with three epoxidized vegetable oils (EVOs). For the first time, the comparison between aromatic vs. aliphatic dicarboxylic acids, containing or not S–S bonds with EVOs was discussed and evaluated by dynamic scanning calorimetry. The obtained thermosets showed reprocessability, by the dual dynamic exchange mechanism. The virgin and reprocessed materials were characterized and the thermomechanical properties were compared. The thermosets derived from EVOs with high epoxy content combined with aromatic diacids containing disulphide bridges showed high glass transition values (~111 °C), high crosslink densities and good solvent stability

Biorefinery by-products and epoxy biorenewable monomers: a structural elucidation of humins and triglycidyl ether of phloroglucinol crosslinking

International audienceTThe need for thermosets from renewable resources is permanently increasing in order to find eco-friendly alternatives to petroleum-derived materials. Products obtained from biomass have shown to play an important role in this challenge. Here we present the structural characterization of new bio-based thermosets made by humins, a by-product of lignocellulosic biorefinery, and glycidylated phloroglucinol coming from biomass phenolic fraction. By employing ATR-FTIR and NMR spectroscopies, we elucidated the connections between these two systems contributing to clarify their molecular structure and their reactivity. We demonstrated that the resin curing takes place through ether bond formation between humins hydroxyl functions and phloroglucinol epoxides. Besides crosslinking, humins show a complex rearrangement of their furanic structure through different concomitant chemical pathways depending on the reaction conditions

Design of Sustainable Materials by Cross-linking a Biobased Epoxide with Keratin and Lignin

Awareness of the environmental impact of using polymeric materials obtained from petroleum is causing increased interest in sustainable materials manufacturing. Here, we present the elaboration of fully biobased materials using an aromatic epoxy resin matrix coming from wood biomass and two natural by-products, namely, keratin from chicken feathers and lignin. In situ FTIR kinetic studies show that the two natural fillers increase the conversion of the epoxide during cross-linking. This result, together with DSC studies, proves the chemical interactions between the keratin or lignin and the epoxide network. Up to 30% of these natural components could be reacted and incorporated into the epoxide with good compatibility. The thermomechanical properties of the elaborated materials are comparable to those of commercial ones

RESINES EPOXYDES MESOMORPHES

PARIS-MINES ParisTech (751062310) / SudocSudocFranceF