Study of lanthanide triflates as new curing initiators for DGEBA

Rheology of Polymer Processing in Spain (1995-2020)

The contribution of Spanish scientists to the rheology involved in polymer processing during the last 25 years is investigated. It is shown that the performed research covers, at different levels, all industrial polymeric materials: thermoplastics, thermosets, adhesives, biopolymers, composites and nanocomposites, and polymer modified bitumen. Therefore, the rheological behaviour of these materials in processing methods such as extrusion, injection moulding, additive manufacturing, and others is discussed, based on the literature results. A detailed view of the most outstanding achievements, based on the rheological criteria of the authors, is offered.

The production of lactic acid from chemi-thermomechanical pulps using a chemo-catalytic approach

Previous work has shown that sulfonation and oxidation of chemi-thermomechanical pulps (CTMPs) significantly enhanced enzyme accessibility to cellulose while recovering the majority of carbohydrates in the water-insoluble component. In the work reported here, modified (sulfonated and oxidized) CTMPs derived from hard-and-softwoods were used to produce a DL-mix of lactic acid via a chemo-catalytic approach using lanthanide triflate (Ln (OTf)₃) catalysts (Ln = La, Nd, Er, and Yb). It was apparent that sulfonation and oxidation of chemi-thermomechanical pulps (CTMPs) also enhanced Ln(OTf)₃ catalyst accessibility to the carbohydrate components of the pulps, with the Er(OTf)₃ catalysts resulting in significant lactic acid production. Under optimum conditions (250 °C, 60 min, 0.5 mmol catalyst g^-1 biomass), 72% and 67% of the respective total carbohydrate present in the hard-and-softwood CTMPs could be converted to lactic acid compared to the respective 59% and 51% yields obtained after energy-intensive ball milling.

Improved epoxy thermosets by the use of poly(ethyleneimine) derivatives

Epoxy resins are commonly used as thermosetting materials due to their excellent mechanical properties, high adhesion to many substrates and good heat and chemical resistances. This type of thermosets is intensively used in a wide range of fields, where they act as fiber-reinforced materials, general-purpose adhesives, high-performance coatings and encapsulating materials. These materials are formed by the chemical reaction of multifunctional epoxy monomers forming a polymer network produced through an irreversible way. In this article the improvement of the characteristics of epoxy thermosets using different hyperbranched poly(ethyleneimine) (PEI) derivatives will be explained.

Mechanistic approach to a photochemical/thermal dual-cure initiating system based on pyrylium salt–hydroperoxide for epoxide cationic polymerization

An initiating system based on pyrylium salts and the hydroperoxide group is a promising method to perform a dual-cure of epoxides via cationic polymerization.

Spectroscopic evidence of the mechanism involved in the cationic diglycidyl ether of bisphenol A curing with rare earth metal triflates

The cross-linking of diglycidyl ether of bisphenol A (DGEBA) using three rare earth triflates as initiators (lanthanum, ytterbium, and scandium) was studied by in situ Fourier transform infrared (FT-IR) spectroscopy. Cationic ring opening of epoxides can proceed through two different mechanisms: activated monomer (AM) and active chain end (ACE). Using advanced chemometric methods such as perturbation-correlation moving-window two dimensional correlation spectroscopy (PCMW2D) and multivariate curve resolution-alternating least squares (MCR-ALS) it has been possible to obtain spectroscopic evidence of the two mechanisms. Traditionally, the demonstration of different mechanism pathways requires designing specific experiments. The novelty of the present study is to find, without a specific experimental design, spectroscopic evidence of the pathway of the polymerization process and to analyze the effect of these initiators, as well as the evolution of the species that takes part in the curing process by structural techniques such as attenuated total reflection (ATR) FT-IR.