A Review on the Potential and Limitations of Recyclable Thermosets for Structural Applications

The outstanding performance of conventional thermosets arising from their covalently cross-linked networks directly results in a limited recyclability. The available commercial or close-to-commercial techniques facing this challenge can be divided into mechanical, thermal, and chemical processing. However, these methods typically require a high energy input and do not take the recycling of the thermoset matrix itself into account. Rather, they focus on retrieving the more valuable fibers, fillers, or substrates. To increase the circularity of thermoset products, many academic studies report potential solutions which require a reduced energy input by using degradable linkages or dynamic covalent bonds. However, the majority of these studies have limited potential for industrial implementation. This review aims to bridge the gap between the industrial and academic developments by focusing on those which are most relevant from a technological, sustainable and economic point of view. An overview is given of currently used approaches for the recycling of thermoset materials, the development of novel inherently recyclable thermosets and examples of possible applications that could reach the market in the near future.</p

Molecular Mobility in Amorphous Biobased Poly(ethylene 2,5-furandicarboxylate) and Poly(ethylene 2,4-furandicarboxylate)

Among all the emergent biobased polymers, poly(ethylene 2,5-furandicarboxylate) (2,5-PEF) seems to be particularly interesting for packaging applications. This work is focused on the investigation of the relaxation dynamics and the macromolecular mobility in totally amorphous 2,5-PEF as well as in the less studied poly(ethylene 2,4-furandicarboxylate) (2,4-PEF). Both biopolymers were investigated by differential scanning calorimetry and dielectric relaxation spectroscopy in a large range of temperatures and frequencies. The main parameters describing the relaxation dynamics and the molecular mobility in 2,5-PEF and 2,4-PEF, such as the glass transition temperature, the temperature dependence of the α and β relaxation times, the fragility index, and the apparent activation energy of the secondary relaxation, were determined and discussed. 2,5-PEF showed a higher value of the dielectric strength as compared to 2,4-PEF and other well-known polyesters, such as poly(ethylene terephthalate), which was confirmed by molecular dynamics simulations. According to the Angell's classification of glass-forming liquids, amorphous PEFs behave as stronger glass-formers in comparison with other polyesters, which may be correlated to the packing efficiency of the macromolecular chains and therefore to the free volume and the barrier properties.</p

The effect of me-substituents of 1,4-butanediol analogues on the thermal properties of biobased polyesters

Biobased 1,4‐butanediol analogues are used to tune the glass transition temperature and crystallization in a series of polyesters, and allow for the formation of stereocomplexes

Determination of the equilibrium enthalpy of melting of two-phase semi-crystalline polymers by fast scanning calorimetry

International audienc

Determination of the equilibrium enthalpy of melting of two-phase semi-crystalline polymers by fast scanning calorimetry

International audienc

Synthesis and Thermal Properties of Bio-Based Copolyesters from the Mixtures of 2,5- A nd 2,4-Furandicarboxylic Acid with Different Diols

Recent works highlighted how interesting are the properties of furan-based polyesters. Most of the attention has been focused on the homopolyester obtained with 2,5-furandicarboxylic acid and ethylene glycol, but other possibilities exist, which could help in tuning the final properties by carefully selecting the nature and proportion of the initial building blocks. This work reports the synthesis and properties (thermal stability, activation energy for thermal decomposition, glass transition temperature, and aptitude to crystallize) of three series of polyesters obtained by combining various amounts of two isomers of furandicarboxylic acid with different linear aliphatic diols, such as ethylene glycol, 1,3-propanediol, and 1,4-butanediol. This approach provided homopolymers and copolymers with high molecular weights, good thermal stability, broad processing windows, and a thermal behavior that can be tuned both in terms of glass transition temperature and crystallinity. In most cases, the mixtures of 2,5- A nd 2,4-isomers obtained during the Henkel disproportionation reaction can be directly used to synthetize furan-based copolyesters with good properties without the downstream processing typically performed to separate the isomers prior to polymerization, which may considerably reduce the time and costs for biomass valorization.</p