3D printed materials

Napadensky, E. 2005. Ink-jet 3d printing of photopolymers materials An emerging rapid prototyping technology. Proceedings—RadTech Europe 05 UV/EB 2 193-197. 

One of these new SFF technologies which aspires to reach a leading industry position is 3D Printing. Amongst the different existing SFF technologies, in recent years inkjet 3D Printing has experienced one of the fastest market penetration rates, it is expected that the development of improved materials wUl enhance this rate even more. 

UV curable Inkjet compositions formulated for use in two-dimensional (2D) Inkjet printers are typically formulated differently than compositions for PolyJet, for two types of reasons Those related to differences between existing 2D and 3D printers and those related to the different requirements for the solid material final property in 2D and 3D printing. 

Regarding the properties required of the solidified materials in 2D printing, the most important properties are generally related to thin material layers, such as color, adhesion to the substrate, hghtfastness, and scratch resistance, whereas in 3D printing, the most important properties are generally related to the bulk material mechanical and thermomechanical properties, for example tensile and flexural properties, impact resistance, and Glass Transition Temperature (Tg). 

Interestingly, polyesters can be readily processed via 3D printing. Polymer granules are melted inside the device. As the dispensing head moves, a polymer strand is ejected from a needle onto a collecting plate where the material sets. The deposition of subsequent layers enables the formation of complex three-dimensional structures. In some cases, the same technology can be extended towards polymer solutions. 

For example, stereolithography can be used. It is a liquid-based technique that utilizes LBL curing of a photosensitive hydrogel precursor solution by means of a laser. Alternatively, nozzle-based systems are applied. They process the material chemically as it passes through the nozzle (ink-jet printing, 3D printing cf. Section 3.10). Cells and biomolecules can be simultaneously printed with the scaffold material [79]. 

The use of an inkjet-type printhead to deliver a liquid or colloidal binder material to layers of a powdered build material is involved in 3D printing (8). The printing technique involves applying a layer of a powdered build material to a surface typically using a roller. After the build material is applied to the surface, the printhead delivers the liquid binder to predetermined areas of the layer of material. 

Powder compositions have been disclosed that can be used with the traditional 3D printing technology (32). 3D printed building materials with comparable compressive strength to standard concrete but greater tensile strength have been developed. 

A thermoplastic powder has been adapted for 3D printing. The powder includes a blend of a thermoplastic particulate material, and an adhesive particulate material, with the adhesive particulate material being adapted to bond the thermoplastic particulate material when a fluid activates the adhesive particulate material. 

The uses and applications of 3D printing for tissue engineering have been reviewed (35). Also, biodegradable materials can be printed that have proven ideal for bone tissue engineering, sometimes even with site specific growth factor and drug delivery abilities. 

E. Giller and D.X. Williams, Three dimensional printing material system and method using plasticizer-assisted sintering, US Patent 8506862, assigned to 3D Systems, Inc. (Rock Hill, SC), August 13, 2013. 

J.R Bredt, S.L. Clark, D.X. Williams, and M.J. DiCologero, Thermoplastic powder material system for appearance models from 3d printing systems, US Patent 7 569 273, assigned to Z Corporation (Burlington, MA), August 4, 2009. 

There are several processes that go by the name 3D printing. Some of these are compared in Table 3.2. Small desktop 3D printers are available, as well as large freestanding equipment. In one variation, the process starts by depositing a layer of powder object material at the top of a fabrication chamber. A roller then distributes and compresses the powder at the top of the fabrication chamber. A liquid adhesive is then deposited from a jet in a 2D pattern onto the layer of the powder, which becomes bonded in the areas where the adhesive is deposited, to form a layer of the object. Once a layer is completed, the fabrication piston moves down by the thickness of a layer, and the process is repeated until the entire object is formed... 

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