Free radical photopolymerization process for fiber-reinforced polymer: Effect on the mechanical properties

Radical photoinitiation with LEDs and applications in the 3D printing of composites

Radical initiation upon LED light irradiation is discussed herein as well as its application in additive manufacturing. The ability of manufacturing complex structures, freedom of design, low energy consumption, fast prototyping, and excellent spatial resolution are the main benefits of the 3D printing technology by photopolymerization. Therefore, the 3D printing of composites through photopolymerization processes is developing rapidly in the academia and industry, and has been a turning point of additive manufacturing (AM). In the present review, an overview of radical initiation with LEDs (i.e., the photopolymerization LED technology, the photoinitiating systems, and the polymerizable media) and of the main 3D printing methods by photopolymerization, materials, and their applications in different fields has been carried out. As a challenging topic, the issue of light penetration in a filled matrix for the access to composites is discussed, including the light transmittance of the composite, the mismatch of the refractive index between the filler and the monomer, the factors of the filler, and the adverse influence of low light penetration on the 3D printing process. In particular, the popular applications of 3D printing by photopolymerization in biomedical science, electronic industry, materials for adsorption, and 4D printing are discussed. Overall, this review gives an overview of the 3D printing of polymer matrix composites through photopolymerization processes as a benchmark for future research and development.

Influence of the Fibre Content, Exposure Time, and Compaction Pressure on the Mechanical Properties of Ultraviolet-Cured Composites

A new process for the impregnation, consolidation, and curing of glass-fibre-reinforced polyester composites was developed to reduce manufacturing costs and secure end properties that compete with other traditional materials. This new process, based on the ultraviolet (UV) curing of prepregs, could be a viable alternative to infusion and other processes. In this paper, we showed that glass fibre composites 3 mm thick could be easily formed using suitable photoinitiating systems. We achieved improved mechanical properties through the application of favourable parameters to traditional manufacturing processes such as hand lay-up and infusion. The prepreg polymerization was monitored by dielectric analysis (DEA), and we evaluated the relationship between the UV radiation exposure time and curing degree. Both the exposure time and compaction pressure affected the fibre content of composites and interlaminar shear strength. Experimental results showed that compaction pressures higher than 4 bar are necessary to increase the mechanical properties of the UV-cured composites. Finally, the properties of the composites manufactured by this new process were compared to the properties of composites manufactured using traditional processes such as hand lay-up and infusion.

Multifunctional biphenyl derivatives as photosensitisers in various types of photopolymerization processes, including IPN formation, 3D printing of photocurable multiwalled carbon nanotubes (MWCNTs) fluorescent composites

Summary of properties and applications of multifunctional of biphenyl derivatives as photosensitisers in various types of photopolymerization processes, including IPN formation, 3D printing of photocurable multiwalled carbon nanotubes (MWCNTs) fluorescent composites.