Development of CNTs-filled photopolymer for projection stereolithography

Abstract

Purpose Polymeric parts produced by 3D stereolithography (SL) process have poorer mechanical properties as compared to their counterparts fabricated via conventional methods, such as injection or compression molding. Adding nanofillers in the photopolymer resin for SL could help improve mechanical properties. This study aims to achieve enhancement in mechanical properties of parts fabricated by SL, for functional applications, by using well-dispersed nanofillers in the photopolymers, together with suitable post-processing. Design/methodology/approach Carbon nanotubes (CNTs) have high strength and Young’s modulus, making them attractive nanofillers. However, dispersion of CNTs in photopolymer is a critical challenge, as they tend to agglomerate easily. Achieving good dispersion is crucial to improve the mechanical properties; thus, suitable dispersion mechanisms and processes are examined. Solvent exchange process was found to improve the dispersion of multiwalled carbon nanotubes in the photopolymer. The UV-absorbing nature of CNTs was also discovered to affect the curing properties. With suitable post processing, coupled with thermal curing, the mechanical properties of SL parts made from CNTs-filled resin improved significantly. Findings With the addition of 0.25 wt.% CNTs into the photopolymer, tensile stress and elongation of the 3D printed parts increased by 70 and 46 per cent, respectively. With the significant improvement, the achieved tensile strength is comparable to parts manufactured by conventional methods. Practical implications This allows functional parts to be manufactured using SL. Originality/value In this paper, an improved procedure to incorporate CNTs into the photopolymer was developed. Furthermore, because of strong UV-absorption nature of CNTs, curing properties of photopolymer and SL parts with and without CNT fillers were studied. Optimized curing parameters were determined and additional post-processing step for thermal curing was discovered as an essential step in order to further enhance the mechanical properties of SL composite parts.

Advances in additive manufacturing of shape memory polymer composites

“…The main concern when printing via vat photopolymerization is the high viscosity of the composite resin and the light scattering produced by the filler particles. For instance, CNTs are strong UV absorbers; this presents problems when curing the photopolymer resin (Choong et al, 2020;Eng et al, 2017). Hengky et al (Eng et al, 2017) suggested that using conductive nanoparticles such as CNT in SLA could provide enhanced mechanical properties, electrical and thermal conductivity.…”

“…For instance, CNTs are strong UV absorbers; this presents problems when curing the photopolymer resin (Choong et al, 2020;Eng et al, 2017). Hengky et al (Eng et al, 2017) suggested that using conductive nanoparticles such as CNT in SLA could provide enhanced mechanical properties, electrical and thermal conductivity. Particle alignment accomplished while printing is still something that is not fully understood.…”

Nanomaterials for 3D Printing of Polymers via Stereolithography: Concept, Technologies, and Applications

“…[ 121 ] These materials are usually added to improve the mechanical properties of the final product, [ 122 ] but they can also be used to add new proprieties to the resin, such as thermal resistance, electrical properties, cell viability and others. [ 123 ] In stereolithography, different types of nanomaterials have been mixed in photopolymer resins such as clay, [ 122,124 ] carbon nanotubes (CNTs) and multiwalled carbon nanotubes (MWCNTs), [ 125–127 ] graphene, [ 128 ] nanocellulose crystal (CNC), [ 52,129 ] nanosilicates, [ 130 ] and many others.…”

Graphene oxide/epoxy acrylate nanocomposite production via SLA and importance of graphene oxide surface modification for mechanical properties

“…In a similar work, researchers are advanced the mechanical properties of polymer parts by exfoliating and homogeneously dispersing of montmorillonite nanoclays (plate-shaped) into the photocurable resin via several mixing steps. They achieved significant increases at elongation by more than 100% and enhanced the tensile stress and Young’s Modulus in the x-y plane (Eng et al , 2017). In addition, other researchers three-dimensional printed graphene oxide-based nanocomposite without surface modification.…”

“…They used nano silica fillers for modifying the light scattering characteristics of the resin and they succeed to reduce curing time from 4 s to 0.7 s for each layer. In another study, Eng et al (2017) improved the mechanical properties such as tensile strength up to 70% and elongation up to 46% of Stereolithography (SLA) printed photo polymer by adding carbon nanotubes into the resin. In a similar work, researchers are advanced the mechanical properties of polymer parts by exfoliating and homogeneously dispersing of montmorillonite nanoclays (plate-shaped) into the photocurable resin via several mixing steps.…”