Digital Light Processing 3D Printing of Enhanced Polymers via Interlayer Welding

Abstract

Digital light processing (DLP) 3D printing is advantageous in high printing efficiency and printing resolution for fabricating complex structures across various applications. However, the layer‐by‐layer curing manner of DLP leads to weak interlayer adhesion and the anisotropic mechanical properties of printed objects. Here, linear polymers are introduced into commercial resins to weld the interlayer by the diffusion and entanglement of linear polymers after DLP printing via heat treatment. This introduction of linear polymers not only shows a strengthening and toughening effect on the printed objects, but also has no negative impact on the DLP printability. The tensile strengths of objects containing 4.7 wt% polycaprolactone can reach up to ≈500% of that of neat samples in any printing direction. This simple strategy by adding linear polymers into printing resins provides an effective access to prepare DLP printed objects with improved mechanical properties as well as ensure printing resolution and printing efficiency.

Introducing Dynamic Bonds in Light‐based 3D Printing

“…In general, there are two basic requirements for the photoresins applicable to most lightbased 3D printing tech niques: rapid photocuring and moderate flowability (vis cosity). [21,22,27,48,51] Rapid photopolymerization reactions allow liquid monomers to change from liquid to solid under light irradiation. Moreover, to ensure that the liquid photoresins can evenly spread in the printable area during SLA or DLP printing process, a good fluidity (low viscosity) is necessary (typically ten to hundreds of mPa•s).…”

“…Thus, most printed 3D objects consist of covalently crosslinked thermo sets. [24][25][26][27] Although this permanent crosslinking offers superior mechanical, thermal and chemical stability, it limits multi functionality, such as adaptability, healability and recyclability, which restricts the diverse and more demanding application scenarios of 3D printed objects. Also, it causes a great concern to the environment due to their nonprocessable, singleuse nature.…”

3D printing of ultra-high viscosity resin by a linear scan-based vat photopolymerization system

“…Also, the large exposure area during printing needs to be compromised by changing the orientation of the model. Besides, printed part behaves mechanically anisotropy in vertical and horizontal directions 11 , which is affected by the degree of polymerization and post-print curing process 12 .…”

Infrared Spectroscopic and Mechanical Analysis of Supramolecular Self-Healing in 3D Printable Urea Photoresins

“…One of the main strategies to increase toughness in polymer networks is to include monomers and oligomers with sacrificial bonds to dissipate energy. − Because of their reversibility, noncovalent interactions can dissipate excess energy; increasing the mechanical strength of thermosets without sacrificing their elongation before failure. − Hydrogen bonding is a noncovalent interaction used to tune mechanical properties and also to provide self-healing ability to polymers. − This functionality can be incorporated in the polymer network main chain to promote strong packing and cooperative association or as a pendant unit to maintain mobility in the polymer chain and a noncooperative association with independent hydrogen bonding units . The capability of hydrogen bonding in tuning the mechanical properties of polymers is particularly useful for 3DP, as one of the main issues with this process is that the mechanical performance of 3D printed parts is deficient compared to molded parts. , …”

“…18 The capability of hydrogen bonding in tuning the mechanical properties of polymers is particularly useful for 3DP, 19 as one of the main issues with this process is that the mechanical performance of 3D printed parts is deficient compared to molded parts. 20,21 Several functional groups that provide hydrogen bonding donors and acceptors have been used in extrusion and VP-3DP to fine-tune the mechanical performance of soft materials and elastomers, such as amides, 22 ureas, 23 and urethanes, 24,25 without affecting their printability. Among them, ureas have been shown to increase mechanical strength without sacrificing elongation and toughness and to enable self-healing ability.…”