Polyurea/polyurethane (PUa/PU) shell microcapsules (MCs), containing high loadings of isophorone diisocyanate (IPDI) in the core, were developed to enable the production of mono-component, eco-friendly and safer adhesive formulations for the footwear industry. IPDI microencapsulation was obtained via oil–in–water (O/W) microemulsion combined with interfacial polymerization. A methylene diphenyl diisocyanate (MDI) compound (a commercial blend of monomeric and polymeric species), with higher reactivity than IPDI and low viscosity, was added to the O phase to competitively contribute to the shell formation, improving its quality. Four different active H sources were tested, aimed at achieving a high encapsulation yield. The successful encapsulation of IPDI was confirmed by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), while the MCs’ morphology and size distribution were assessed by scanning electron microscopy (SEM). The incorporation of a multifunctional isocyanate silane in the O phase, as “latent” active H source, led to the formation of impermeable PUa/PU-silica hybrid shell MCs with more than 60 wt.% of pure encapsulated IPDI. A proof-of-concept study shows high peeling strength and a structural type of failure of the adhesive joint, revealing an effective IPDI release. These new engineered MCs are found to be promising crosslinkers for mono-component adhesives for high demanding applications.

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Additive manufacturing techniques established a new paradigm in the manufacture of composite materials providing a simple solution to build complex, custom designed shapes. In the biomedical field, 3D printing enabled the production of scaffolds with patient-specific requirements, controlling product architecture and microstructure, and have been proposed to regenerate a variety of tissues such as bone, cartilage, or the nervous system. Polymers reinforced with graphene or graphene derivatives have demonstrated potential interest for applications that require electrical and mechanical properties as well as enhanced cell response, presenting increasing interest for applications in the biomedical field. The present review focuses on graphene-based polymer nanocomposites developed for additive manufacturing fabrication, provides an overview of the manufacturing techniques available to reach the different biomedical applications, and summarizes relevant results obtained with 3D printed graphene/polymer scaffolds and biosensors.

We report on the encapsulation of high loadings of liquid isophorone diisocyanate (IPDI) in biodegradable, temperature-responsive poly(ε-caprolactone) (PCL) microcapsules (MCs), aimed to be applied as cross-linking agents for the development of a generation of safer and eco-innovative adhesives, which are one-component and self-reactive. The biodegradable PCL MCs were formed via the solvent evaporation method in combination with an oil-in-oil-in-water (O/O/W) doubleemulsion system. Two PCL grades with different molecular weights (MW), of 45000 and 80000 Da, were tested as the MCs' outer surface (shell) material. The use of a higher MW PCL, for the encapsulation of IPDI, resulted in core−shell MCs of smoother surface and a slightly smaller average shell thickness leading to remarkably high isocyanate loadings, up to 60 wt %. Also, a higher resistance of the MC's shell to air moisture diffusion was revealed by the longer shelf life exhibited by these MCs. The successful IPDI encapsulation and MCs' shell composition were revealed by Fourier transform infrared spectroscopy (FTIR) in combination with thermogravimetric analysis (TGA) and gel permeation chromatography (GPC), while the MCs' morphology and size distribution were assessed by scanning electron microscopy (SEM) and optical microscopy. Differential scanning calorimetry (DSC) in combination with adhesion proof-of-concept studies showed that the developed PCL MCs were able to respond to the external stimuli of temperature and pressure, typically employed during the adhesive application, revealing an effective IPDI release in the adhesive joint. The results obtained confirm the viability of the sustainably engineered MCs to be used as cross-linking agents and therefore enablers of eco-innovative high-performance adhesives. Finally, it should be stressed that the obtained MCs are potentially useful to provide self-healing capability to materials and that the developed technology may be used in the encapsulation of other reactive species by means of a purely physical process using biodegradable polymers.

Poly(butylene adipate-co-terephthalate) (PBAT), a biodegradable flexible, and tough polymer is herein used, for the first time, to encapsulate and protect isocyanate derivatives. Isocyanates are essential building blocks widely employed in the chemical industry for the production of high-performing materials. Microencapsulation of isocyanates eliminates the risks associated with their direct handling and protects them from moisture. In light of this, and having in mind eco-innovative products and sustainability, we present a straightforward process to encapsulate isophorone diisocyanate (IPDI) using this biodegradable polymer. Spherical and core-shell microcapsules (MCs) were produced by an emulsion system combined with the solvent evaporation method. The MCs present a regular surface, without holes or cracks, with a thin shell and high isocyanate loadings, up to 79 wt%. Additionally, the MCs showed very good isocyanate protection if not dispersed in organic or aqueous solutions. Effects of various process parameters were systematically studied, showing that a higher stirring speed (1000 rpm) and emulsifier amount (2.5 g), as well as a smaller PBAT amount (1.60 g), lead to smaller MCs and narrower size distribution.