UV-Curing Additive Manufacturing of Bio-Based Thermosets: Effect of Diluent Concentration on Printing and Material Properties of Itaconic Acid-Based Materials

In the quest toward sustainable thermosets, researchhas been conductedon various polymer classes like epoxy, benzoxazines, acryl-/methacrylates,etc. One particular group that can also be utilized as sustainableinks for additive manufacturing is itaconic acid-based unsaturatedpolyester resins. However, due to increased viscosity of the resins,the use of reactive diluents is required to increase their processability.While research has focused on creating different polymeric structuresto expand the possible applications, the required amount of diluenthas not received equal attention. In this work, a group of itaconicacid-based polyesters was synthesized to create a series of formulationswith different reactive diluent contents. The physicochemical propertiesof the prepared formulations, along with their reactivity toward UVlight, were assessed via photo-differential scanning calorimetry (photo-DSC),real-time attenuated total reflectance (RT-ATR), and photorheologymeasurements. The same formulations were then used to fabricate testspecimens via digital light processing (DLP) three-dimensional (3D)printing, which were examined as to their thermomechanical propertiesby means of dynamic mechanical analysis (DMA) and thermogravimetricanalysis (TGA) measurements

Magnetic-Oriented Nickel Particles and Nickel-Coated Carbon Nanotubes: An Efficient Tool for Enhancing Thermal Conductivity of PDMS Composites

In this study, PDMS composites are thermally cured with nickel particles and nickel-coated carbon nanotubes as fillers. Both fillers are oriented with the aim to increase the thermal conductivity of the silicone polymer network, due to the formation of a continuous thermal path. Scanning electron microscopy (SEM) gives a picture of the polymer network's morphology, proving the effective alignment of the nickel particles. Rheology and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) studies confirm the full curing of the silicon network and no influence in the curing kinetics of the type and content of fillers and their orientation. Dynamic mechanical thermal analysis (DMTA) and tensile analysis show instead different thermo-mechanical behavior of the polymer network due to the presence of different fillers, different fillers percentage, and orientation. Finally, the thermal transmittance coefficient (k) is studied by means of hot disk analysis, revealing the increment of almost 200% due to magnetic filler orientation

Compact 3-manifolds via 4-colored graphs

We introduce a representation of compact 3-manifolds without spherical boundary components via (regular) 4-colored graphs, which turns out to be very convenient for computer aided study and tabulation. Our construction is a direct generalization of the one given in the eighties by S. Lins for closed 3-manifolds, which is in turn dual to the earlier construction introduced by Pezzana's school in Modena. In this context we establish some results concerning fundamental groups, connected sums, moves between graphs representing the same manifold, Heegaard genus and complexity, as well as an enumeration and classification of compact 3-manifolds representable by graphs with few vertices ($\le 6$ in the non-orientable case and $\le 8$ in the orientable one).Comment: 25 pages, 11 figures; changes suggested by referee: references added, figure 2 modified, results about classification of the manifolds in Proposition 17 announced at the end of section 9. Accepted for publication in RACSAM. The final publication is available at Springer (see DOI

Cationic UV Curing of Bioderived Epoxy Furan-Based Coatings: Tailoring the Final Properties by in Situ Formation of Hybrid Network and Addition of Monofunctional Monomer

Biobased monomers are becoming essential to develop green products to substitute for petroleum-based materials. In this study, biobased monomers, such as furfuryl alcohol and 2,5-furandimethanol, are successfully functionalized with epoxy functional groups producing glycidyl furfuryl alcohol (GFA) and diglycidyl furfuryl alcohol (DGFA), respectively. Herein, DGFA is investigated as an innovative cationic UV-curable monomer for coating applications. An easy tailoring of the properties of the final UV-cured coatings is demonstrated by varying the ratio of DGFA:GFA or creating a hybrid coating by using tetraethyl orthosilicate (TEOS) as a precursor of silica to form an inorganic network. Real-time Fourier transform infrared spectroscopy is used to monitor the cationic photopolymerization of DGFA formulations. Finally, glass transition, contact angle, thermal stability, and mechanical properties are investigated as a function of TEOS and GFA content in DGFA formulations. The thermal mechanical behavior is studied by dynamic mechanical thermal analysis. The thermal properties of the networks are analyzed by dynamic scanning calorimetry and thermogravimetric analysis

Bio-based monomers for UV-curable coatings: allylation of ferulic acid and investigation of photocured thiol-ene network

Ferulic acid (FA) is an unsaturated hydroxycinnamic acid that can be isolated from lignin. In this study, the biorenewable FA was allylated to result in a library of mono- or diallylated monomers, either having the inherent cinnamoyl double bond intact or saturated through hydrogenolysis. All monomers were photo-chemically cured with trimethylolpropane tris(3-mercaptopropionate) (TRIS) into crosslinked films in the presence of a photoinitiator (Irgacue 819). The reactivity of the FA-derived monomers toward TRIS was investigated in detail by photorheology and FT-IR spectroscopy to reveal details on the relative reaction rates for the different alkene groups. The thermo-mechanical properties of the crosslinked films were fully characterized by means of dynamic mechanical analysis (DMTA) and thermal calorimetry (DSC). It was demonstrated that the glass transition temperature of the final crosslinked network could be controlled by the addition of a monoallylated monomer. By increasing the content of the monoallylated compound, it was possible to observe a linear decrease of the Tg-values of the crosslinked films