3D-printing of easily recyclable all-ceramic thick LiCoO2 electrodes with enhanced areal capacity for Li-ion batteries using a highly filled thermoplastic filament.

In this work, the production of thick ceramic LiCoO2 (LCO) electrodes using a conventional desktop 3D-printing was developed as an alternative to conventional electrode manufacturing for Li-ion batteries. Firstly, the filament formulation, based on LCO powders and a sacrificial polymers blend, is optimized to achieve suitable features (viscosity, flexibility and mechanical consistency) to be used in the 3-D printing. Printing parameters were optimized to produce defect-free bodies with coin geometry (12 mm diameter and 230-850 µm thickness). Thermal debinding and sintering were studied in order to obtain all ceramic LCO electrodes with adequate porosity. The additive-free sintered electrodes (850 µm thickness) have enhanced areal and volumetric capacities (up to 28 mA·h·cm-2 and 354 mA·h·cm-3) due to their extremely high mass loading (up to 285 mg·cm-2). Thus, the Li//LCO half-cell delivered an energy density of 1310 W·h·L-1. The ceramic nature of the electrode permits the use of a thin film of paint gold as current collector, reducing considerably the polarization of thick electrodes. Thus, the whole manufacturing process developed in this work is a complete solvent-free method to produce tuneable shape electrodes with enhanced energy density, opening the door for the manufacturing of high-density batteries with complex geometries and good recyclable.

Injectable self-curing bioactive acrylic-glass composites charged with specific anti-inflammatory/analgesic agent.

Injectable bioactive acrylic formulations based on poly(methyl methacrylate) (PMMA) and different amounts of bioactive glasses in the system SiO2-CaO-Na2O-P2O5 have been prepared in the presence of the anti-inflammatory analgesic drug fosfosal, the sodium salt of 2-phosphonoxibenzoic acid, to be used in minimally invasive surgery. The injectability of the formulations evaluated according to the established protocol was around 80%. The experimental formulations provided maximum temperatures in the range 50-60 degrees C, which were lower than those of commercial acrylic bone cements currently used in percutaneous vertebroplasty (PVP). Residual monomer content of any formulation was inferior to 5%. Compressive yield strength of dry specimens was in the range 80-95 MPa, but it decreased after immersion in SBF to values in the range 30-50 MPa, due to the dissolution of the bioactive glasses and the drug in the medium. The release of fosfosal was evaluated in vitro (pH = 7.0). The release profile against time obtained from a PMMA cement was quasi-linear and the 80% of the initial amount of drug was released in 175 h. However, for bioactive cements, the 80-100% of the fosfosal charged was released in approximately 48 h, due to the dissolution of the glasses in the medium. Values of weight loss of the cements determined gravimetrically ranged between 16% and 26% depending on the initial amount of fosfosal, i.e. 20 or 30 wt%, respectively. The weight loss and the water uptake were simultaneous processes, and values of hydration degree were around 10-14%. The formation of an apatite-like layer was detected on the surface of the cements at different periods of time depending on the composition of the bioactive glasses. The cements containing the glasses with P2O5 produced the growth of the apatite layer in shorter periods of time. The presence of fosfosal accelerated the precipitation of this layer independently on the glasses. The in vivo biocompatibility studied by intramuscular implantation in rats showed the absence of an anti-inflammatory response and a fibrous layer around the implant for the cement prepared with PMMA/fosfosal which is attributed to the therapeutic action of fosfosal acting in situ. The response to cements prepared with bioactive glasses and fosfosal showed a mild inflammatory reaction with the formation of the typical fibrous capsule around the implanted material.

Acrylic bone cements incorporating polymeric active components derived from salicylic acid: curing parameters and properties.

A methacrylic monomer derived from salicylic acid, 5-hydroxy-2-methacrylamido benzoic acid, 5-HMA, was incorporated with 2-hydroxyethyl methacrylate, (HEMA), in different proportions to the liquid phase of classical bone cement formulations. The monomer 5-HMA shows the ability to form molecular complexes with calcium atoms in order to improve osteointegration in the application of bone cement formulations used for the fixation of joint prostheses such as knee and hip. Kinetic parameters, peak temperature and setting time of the bone cement formulations prepared were determined, obtaining lower peak temperature values when 5-HMA was incorporated, with respect to classical acrylic bone cements based on PMMA. Mechanical and thermal properties as well as surface energy values, have been determined for all cured bone cement formulations.

Application of tertiary amines with reduced toxicity to the curing process of acrylic bone cements.

4-Dimethylaminobenzyl alcohol (DMOH) and 4-dimethylaminobenzyl methacrylate (DMMO) were used as the activators in the benzoyl peroxide initiated redox polymerization for the preparation of acrylic bone cement based on poly(methylmethacrylate) beads of different particle size. The residual monomer content of the cured cements was about 2 wt %, independent of the redox system used in the polymerization, indicating that the activating effect of the tertiary aromatic amines DMOH or DMMO was sufficient to reach a polymerization conversion similar to that obtained with the benzoyl peroxide (BPO) N,N-dimethyl-4-toluidine (DMT) system. The BPO/DMOH and BPO/DMMO redox systems provided exotherms of decreasing peak temperature and increasing setting time, and the cured materials presented higher average molecular weight and similar glass transition temperatures in comparison with those obtained when DMT was used as the activator. In addition, these activators are three times less toxic than the classical DMT.

Oxygen transport through methacrylate-based hydrogels with potential biological capability.

The permeability to oxygen of hydrogels prepared from copolymers of 2-hydroxymethyl methacrylate and p-methacryloxyl-oxyacetanilide have been studied by using an oxygen electrode in combination with a permeometer. The transmissibility Dk/L and the permeability Dk (where D, k and L are, respectively, the diffusion coefficient, the Henry constant and the thickness of the hydrogel) are measured by a combination of steady state and transitory state measurements. Both transport coefficients increase with the water content, which in turn depends on the copolymer composition. The values of these quantities tend toward a limiting value for water-saturated hydrogels. The ratio of the characteristic volume for diffusion of the oxygen molecule to the free volume of water per mole water is found to be in the vicinity of 0.10, and this value increases slightly as the fraction of the hydrophilic comonomer in the hydrogel increases. A detailed comparison of the biogels studied with six commercial contact lenses has also been performed.

New aspects of the effect of size and size distribution on the setting parameters and mechanical properties of acrylic bone cements.

The effect of the size and the size distribution of poly(methyl methacrylate) (PMMA) beads on the classical kinetic parameters, peak temperature and setting time, for acrylic bone cement formulations prepared with PMMA particles in the range 10-60 microns of average diameter and a relatively wide size distribution is analysed. In addition, the combined effects of the concentration of the free radical initiator benzoyl peroxide and the activator N, N-dimethyl-4-toluidine for the different particle sizes are studied and compared with those commercially available formulations like CMW or Rostal. The results obtained indicated that the use of PMMA particles with average diameter of 50-60 microns, and a relatively wide size distribution (10-140 microns diameter), significantly changes the curing parameters (peak temperature and setting time) of the cement formulations in comparison with the classical behaviour of the commercial systems of CMW and Rostal, without any noticeable loss in the mechanical properties, such as tensile strength, elastic moduli, and compressive strength and plastic strain.