19 research outputs found

    Recyclable poly(thiourethane) vitrimers with high Tg. Influence of the isocyanate structure

    Get PDF
    Networked poly(thiourethane) materials with Tgs around 130 掳C, derived from two aliphatic isocyanates (isophorone diisocyanate, IPDI and 4,4'-methylene bis(cyclohexyl isocyanate), HMDI) and one aromatic diisocyanate (toluene-2,4-diisocyanate, TDI) have been prepared with the same trithiol as comonomer (trimethylol propane tris(3-mercaptopropionate), S3) in stoichiometric proportions in the presence of dibutyltin dilaurate (DBTDL) as the catalyst. The higher reactivity of TDI allowed the preparation of this material in absence of catalyst. The evolution of the curing process has been followed by FTIR. Thermomechanical studies have been performed to determine their viscoelastic properties and their vitrimeric behaviour. The materials were able to reach a complete relaxation stress state thanks to the exchange process of the thiourethane moiety. Among them, TDI derived material experimented the fastest relaxation. The materials were also characterized by thermogravimetry and tensile tests. The recycled materials obtained by grinding the original thermosets and hot-pressing the powder have been fully characterized by mechanical, thermomechanical and FTIR studies, which allowed to confirm their recyclability without appreciable changes in the network structure. The presence of DBTDL in the materials has been proved to be necessary to reach a good recyclability.Postprint (author's final draft

    Actuator behaviour of tailored poly(Thiourethane) shape memory thermosets

    Get PDF
    n this work, a new family of poly(thiourethane) shape memory thermosetting actuators was developed and characterized. These materials can be easily prepared from mixtures of two different aliphatic diisocyanates and a trithiol in the presence of a latent catalyst, allowing an easy manipulation of the formulation. Rheological studies of the curing process confirm the latent character of the formulations. The glass transition temperatures and the mechanical properties can be modified by varying the proportion of diisocyanates (hexamethylene diisocyanate, HDI, and isophorone diisocyanate, IPDI) with stoichiometric amounts of trimethylolpropane tris(3-mercaptopropionate). The shape-memory behavior was deeply investigated under three different conditions: unconstrained, partially constrained, and fully constrained. Tests were performed in single cantilever bending mode to simulate conditions closer to real complex mechanics of thermomechanical actuators under flexural performances. The complex recovery process in single cantilever bending mode was compared with that obtained using tensile mode. The results evidenced that the amount of recovery force in fully constrained conditions, or energy released during the recovery process in partially constrained, can be modulated by simply changing the proportion of both diisocyanates. A simple model based on Timoshenko beam theory was used for the prediction of the amount of work performed. The reported results are an important guideline to design shape-memory materials based on poly(thiourethane) networks, establishing criteria for the choice of the material depending on the expected applicationPeer ReviewedPostprint (author's final draft

    Preparation of poly(thiourethane) thermosets by controlled thiol-isocyanate click reaction using a latent organocatalyst

    Get PDF
    Different poly(thiourethane) thermosets were prepared by means of a thiol-isocyanate click reaction starting from three diisocyanates with different structure (isophorone diisocyanate, IPDI, 4,4'-methylene bis(cyclohexy isocyanate), HMDI and hexamethylene diisocyanate, HDI, and a tetrathiol, pentaerythritol tetrakis(3-mercap- topropionate), PETMP. The curing process has been catalyzed by basic and acid catalysts. The use of a thermally activated base generator (1-methylimidazolium tetraphenylborate, BG1MI), which is an organocatalyst, allowed a better control on the curing initiation than those traditionally used dibutyltin dilaurate (DBTDL) or tertiary amines. The curing evolution was investigated by DSC and FTIR spectroscopy. The materials obtained were characterized by thermomechanical and mechanical tests. Homogeneous ma- terials were obtained in all cases. The chemical structure of the network was correlated with the thermal and mechanical data determined. T g values in the range of 75 to 150 掳C were obtained. The thermal degradation of these materials has also been investigated and a complex degradation mechanism, with three different steps was observed in all cases. These materials showed a higher thermal stability than their oxygen counterparts did. The thermosets obtained using the latent organocatalyst have similar characteristics to the ones obtained by using the common DBTDLPostprint (author's final draft

    The use of lanthanide triflates in the preparation of poly(thiourethane) covalent adaptable networks

    Get PDF
    Covalent adaptable networks (CANs) are new polymeric materials with the mechanical properties of thermosets and the possibility of being recycled like thermoplastics. Poly(thiourethane) networks have demonstrated vitrimeric-like behavior at high temperatures due to the trans-thiocarbamoylation process, which Lewis acids and bases can accelerate. In this study, we report the use of lanthanide triflates (La, Sm, Dy, Er, and Yb) as Lewis acid catalysts, a greener alternative to other metallic catalysts as dibutyltin dilaurate (DBTDL) widely used in poly (urethane) and poly(thiourethane) networks. Moreover, they are not as reactive as DBTDL, and the curing mixture can be manipulated for a longer time at room temperature. As monomers, trimethylolpropane tris(3- mercapto propionate) (S3), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI) have been used. We have demonstrated that the materials prepared with lanthanum triflate present the lowest relaxation times than those prepared with other lanthanide triflates or DBTDL. Calorimetry (DSC) and infrared spectroscopy (FTIR) were applied to study the curing process. The materials obtained were fully characterized by thermog- ravimetric analysis (TGA) and thermomechanical tests (DMA).This work is part of the R&D projects PID2020-115102RB-C21 and PID2020-115102RB-C22 funded by MCNI/AEI/10.13039/ 501100011033. We acknowledge these grants and to the Generalitat de Catalunya (2021-SGR-00154 and BASE3D). F.G. thanks to MCNI/AEI for the grant PRE2018-084192.Postprint (published version

    Advanced thermosets based on thiol-isocyanate chemistry

    No full text
    En aquest treball, s'ha aprofitat la potencialitat dels termoestables de poli(tiouret脿) (PTUs) partint amb l'estudi de la viabilitat de la reacci贸 "tiol-isocianat" en condicions 脿cides i b脿siques. Utilitzant catalitzadors b脿sics, la reacci贸 茅s massa r脿pida i el sistema dif铆cil de processar. Aix铆, vam proposar l'煤s d'una base latent t猫rmicament activada, per obtenir un control temporal i cin猫tic del proc茅s de curat. A m茅s, vam explorar el seu 煤s com a materials intel路ligents, gr脿cies a llurs transicions t猫rmiques ben definides, que permeten r脿pids moviments i canvis en les seves propietats. Aix铆, suggerim una possible aplicaci贸 dels poli(tiouretans) en la fabricaci贸 de mecanismes intel路ligents per al control aut貌nom, simulant una aplicaci贸 de v脿lvula oberta. Tamb茅 hem implementat un nou procediment de curat dual per adaptar les caracter铆stiques del material i millorar el processament. Es basa en la combinaci贸 de reaccions clic tiol-isocianat i tiol-epoxi, activades seq眉encialment mitjan莽ant temperatura. L鈥檌nter猫s principal de la tesi es va centrar en el desenvolupament de xarxes din脿miques reticulades (CAN)s, que puguin ser remodelades i reciclades eficientment. Primer, vam demostrar la capacitat din脿mica de grup tiouret脿 emprant compostos model. Una vegada v脿rem demostrar que els poli (tiouretans) poden considerar-se com un nou tipus de CANs, aquests materials es van preparar utilitzant un catalitzador d'estanyEn este trabajo se ha aprovechado la potencialidad de los termoestables de poli (tiouretano) (PTU) partiendo del estudio de la viabilidad de la reacci贸n 鈥渢iol-isocianato鈥 en condiciones 谩cidas y b谩sicas. Utilizando catalizadores b谩sicos, la reacci贸n es demasiado r谩pida y el sistema dif铆cil de procesar. As铆, propusimos el uso de una base latente t茅rmicamente activada, para obtener un control temporal y cin茅tico del proceso de curado. Adem谩s, investigamos su uso como materiales inteligentes, gracias a sus transiciones t茅rmicas bien definidas, que permiten movimientos y cambios en sus propiedades r谩pidos. As铆, sugerimos una posible aplicaci贸n del poli (tiouretano) en la fabricaci贸n de mecanismos inteligentes para el control aut贸nomo, simulando una aplicaci贸n de v谩lvula abierta. Tambi茅n hemos implementado un novedoso procedimiento de curado dual para adaptar las caracter铆sticas del material y mejorar el procesamiento. Se basa en la combinaci贸n de reacciones clic tiol-isocianato y tiol-epoxi, activadas secuencialmente mediante temperatura. El enfoque principal de la tesis se centr贸 en el desarrollo de redes din谩micas reticuladas (CAN)s, que puedan ser remodeladas y recicladas eficientemente. Primero, demostramos la capacidad din谩mica del grupo tiouretano mediante el uso de compuestos modeloIn this work, the potentiality of poly(thiourethane) (PTU) thermosets has been exploited, starting from the study of the viability of the 鈥渢hiol-isocyanate鈥 reaction under acidic and basic conditions. Using basic catalyst, the thiol-isocyanate reaction is too fast, and the system is difficult to process. Thus, we proposed the use of a thermally activated latent base, to obtain a temporal and kinetic control of the curing processes. In addition, we investigated their use as smart materials, thanks to their narrow thermal transitions, which allow quick movements and rapid change in their properties. Therefore, we suggested a possible application of poly(thiourethane) in the fabrication of smart mechanisms for autonomous control, simulating an open-valve application. We have also implemented a novel dual-curing procedure to tailor the material characteristics and improve the processing. It is based on the combination of thiol-isocyanate and thiol-epoxy click reactions, activated sequentially by temperature. The main focus of the thesis was centred on the development of dynamic crosslinked networks (CAN)s, which can be efficiently remoulded and recycled. First, we demonstrated the dynamic capacity of the thiourethane group by using model compounds. Once it was shown that poly(thiourethane)s can be considered as a new type of CANs, these materials were prepared using a tin catalys

    Tailor-made thermosets obtained by sequential dual-curing combining isocyanate-thiol and epoxy-thiol click reactions

    Get PDF
    In this work, a new family of thermosets based on thiol-isocyanate-epoxy networks has been prepared via sequential dual-curing methodology where both reactions are activated by temperature. The sequential dual behaviour of the new system proposed here is based on the faster reaction kinetic of the first curing stage, i.e. the isocyanate-thiol coupling, which proceeds at a relatively low temperature, compared to the second stage, i.e. the epoxy-thiol reaction, between the remaining thiol functionalities and the epoxy groups that takes place at a higher temperature. Furthermore, the effect of using different aliphatic isocyanates was investigated. Both reactions have a click character and the intermediate/final materials show a wide range of properties depending on the relative contribution of both curing stages thanks to the selected ratio between the isocyanate and epoxy groups. The new thermosets obtained were characterized from the thermal and dynamic mechanical point of view, resulting excellent candidates as smart materials due to their narrow transitions, which favours fast and controlled changes in their macromolecular features.Postprint (author's final draft

    New epoxy composite thermosets with enhanced thermal conductivity and high Tg obtained by cationic homopolymerization

    No full text
    Thermal dissipation is a critical aspect for the performance and lifetime of electronic devices. In this work, novel composites based on a cycloaliphatic epoxy matrix and BN fillers, obtained by cationic curing of mixtures of 3,4-epoxy cyclohexylmethyl 3,4-epoxy cyclohexane carboxylate (ECC) with several amounts of hexagonal boron nitride (BN) were prepared and characterized. As cationic initiator a commercial benzylanilinium salt was used, which by addition of triethanolamine, exhibited an excellent latent character and storage stability. The effect of the formulation composition was studied by calorimetry and rheological measurements. The variation of thermal conductivity, thermal stability, thermal expansion coefficient, and thermomechanical and mechanical properties of the composites with the load of BN filler (ranging from 10 to 40 wt%) was evaluated. An improvement of an 800% (1.04 W/m路K) in thermal conductivity was reached in materials with glass transition temperatures >200掳C without any loss in electrical insulation

    Thermal Conductive Composites Prepared by Addition of Several Ceramic Fillers to Thermally Cationic Curing Cycloaliphatic Epoxy Resins

    No full text
    Novel composite coatings prepared from 3,4-epoxy cyclohexylmethyl 3,4-epoxycyclohexane carboxylate (ECC) and different ceramic fillers have been prepared to improve the thermal dissipation of electronic devices. As latent cationic initiator, a benzylanilinium salt with triethanolamine has been used, which leads to a polyether matrix. Different proportions of Al2O3, AlN and SiC as fillers were added to the reactive formulation. The effect of the fillers selected and their proportions on the evolution of the curing was studied by calorimetry and rheometry. The thermal conductivity, thermal stability, thermal expansion coefficient and thermomechanical and mechanical properties of the composites were evaluated. An improvement of 820% in thermal conductivity in reference to the neat material was reached with a 75 wt % of AlN, whereas glass transition temperatures higher than 200 °C were determined in all the composites

    Tailor-made thermosets obtained by sequential dual-curing combining isocyanate-thiol and epoxy-thiol click reactions

    No full text
    In this work, a new family of thermosets based on thiol-isocyanate-epoxy networks has been prepared via sequential dual-curing methodology where both reactions are activated by temperature. The sequential dual behaviour of the new system proposed here is based on the faster reaction kinetic of the first curing stage, i.e. the isocyanate-thiol coupling, which proceeds at a relatively low temperature, compared to the second stage, i.e. the epoxy-thiol reaction, between the remaining thiol functionalities and the epoxy groups that takes place at a higher temperature. Furthermore, the effect of using different aliphatic isocyanates was investigated. Both reactions have a click character and the intermediate/final materials show a wide range of properties depending on the relative contribution of both curing stages thanks to the selected ratio between the isocyanate and epoxy groups. The new thermosets obtained were characterized from the thermal and dynamic mechanical point of view, resulting excellent candidates as smart materials due to their narrow transitions, which favours fast and controlled changes in their macromolecular features

    New epoxy composite thermosets with enhanced thermal conductivity and high Tg obtained by cationic homopolymerization

    No full text
    Thermal dissipation is a critical aspect for the performance and lifetime of electronic devices. In this work, novel composites based on a cycloaliphatic epoxy matrix and BN fillers, obtained by cationic curing of mixtures of 3,4-epoxy cyclohexylmethyl 3,4-epoxy cyclohexane carboxylate (ECC) with several amounts of hexagonal boron nitride (BN) were prepared and characterized. As cationic initiator a commercial benzylanilinium salt was used, which by addition of triethanolamine, exhibited an excellent latent character and storage stability. The effect of the formulation composition was studied by calorimetry and rheological measurements. The variation of thermal conductivity, thermal stability, thermal expansion coefficient, and thermomechanical and mechanical properties of the composites with the load of BN filler (ranging from 10 to 40 wt%) was evaluated. An improvement of an 800% (1.04 W/m路K) in thermal conductivity was reached in materials with glass transition temperatures >200掳C without any loss in electrical insulation
    corecore