Composites Manufactured by Stereolithography

Stereolithography (SLA) is a widely utilized rapid additive manufacturing process for prototypes and proof-of-concept models with high resolution. In order to create structurally sound components using SLA, reinforcement needs to be incorporated in the UV-based resins typically used. However, the introduction of reinforcement into vat-based SLA printers has had limited success due to a host of processing challenges including the creation of a homogeneous resin mixture and UV-inhibiting constituents. The effectiveness of using a dual curing system, consisting of a photo and thermal initiator, for the additive manufacturing of carbon fiber short-fiber composites via vat photopolymerization, was investigated. The necessary processing parameters were developed that resulted in successful printing and curing of composites at a 5% fiber volume. Manufacturing with reinforcements that have different densities from the resin creates separation issues, either suspending to the top or settling to the bottom. Following the approaches discussed in this chapter, an even distribution of short fibers was achieved throughout SLA printed samples using a modified commercial printer. Separation was overcome by inducing a continuous flow of reinforced liquid resin in the printer vat during printing. This flow field adaptation allows commercial SLA printers the ability to produce composite parts with different densities of the constituents utilized.

In Situ Formation of Core–Shell Nanoparticles in Epoxy Resin via Reversible Addition–Fragmentation Chain Transfer Dispersion Polymerization

We report for the first time in situ reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization in an epoxy resin mixture for toughening of epoxy. Good dispersion of latex particles in...

Use of Protein Repellents to Enhance the Antimicrobial Functionality of Quaternary Ammonium Containing Dental Materials

An advancement in preventing secondary caries has been the incorporation of quaternary ammonium containing (QAC) compounds into a composite resin mixture. The permanent positive charge on the monomers allows for electrostatic-based killing of bacteria. Spontaneous adsorption of salivary proteins onto restorations dampens the antimicrobial capabilities of QAC compounds. Protein-repellent monomers can work with QAC restorations to achieve the technology’s full potential. We discuss the theory behind macromolecular adsorption, direct and indirect characterization methods, and advances of protein repellent dental materials. The translation of protein adsorption to microbial colonization is covered, and the concerns and fallbacks of the state-of-the-art protein-resistant monomers are addressed. Last, we present new and exciting avenues for protein repellent monomer design that have yet to be explored in dental materials.

The effect of phenol-formaldehyde adhesive modification with fire retardant on the properties of birch plywood

The effect of phenol-formaldehyde adhesive modification with fire retardant on the properties of birch plywood. The study investigated how the modification of phenol-formaldehyde adhesive with a mixture of potassium carbonate and urea affect the properties of plywood. Based on the investigations of the viscosity, gel time and solid content of PF resin mixture containing various amounts of modifiers with various compositions it was found that modification led to major decrease in viscosity, caused the elongation of gelling time and reduced the solid content. In all variants modification of the resin led to significant improvement in plywood flammability evaluated on the basis of parameters such as: weight loss, time of ignition and burned area. The addition of fire retardant to the resin caused a decrease of shear strength. Composition of the modifier had a significant effect on bonding quality, however all plywood samples retained good values exceeding 1 N/mm2 required by EN 314-2 (1993).

A high-performance Fe and nitrogen doped catalyst derived from diazoniapentaphene salt and phenolic resin mixture for oxygen reduction reaction

A high-performance ORR catalyst has been synthesised by pyrolysis of quaternary nitrogen-containing 4a,8a-diazoniapentaphene dibromide (DAP), phenolic resin and FeBr2 mixture.