Functional 3D Printed Polymeric Materials

Denisse Ortiz-Acosta and Tanya Moore

## Abstract

Additive manufacturing (AM) is an emerging 3D printing technology that enables the design and rapid manufacturing of materials with complex microstructures. Advances in 3D printing have allowed manufacturing companies to expand from design and 3D printing of prototypes to the rapid manufacturing of end products. Additive manufacturing enables the manufacturing of components in a layer-by-layer fashion, opposite to common manufacturing methods that rely on machining, molding and subtractive methods to obtain the final product. AM employs a computer-aided design software that allows for the design of virtual objects and the control of the nozzle and/or stage of the 3D printer. Due to their versatility and wide range of mechanical and chemical properties, polymers are the most utilized materials for AM. Polymers used for AM covers thermoplastics, thermosets, elastomers, polymers with incorporated fillers, biopolymers, and polymers blended with biological materials. The architectural design and choice of polymers can lead to materials with enhanced functionalities, mechanical properties, porosity, and stability. This chapter focuses on the development of polymerbased 3D printing materials with multifunctionalities used specifically for the production of biomedical devices, electronic devices, and aerospace-relevant products.

Keywords: 3D printing, additive manufacturing, polymers, biomedical devices, aerospace, electronics

### 1. Introduction

3D printing is an additive manufacturing (AM) process that enables the manufacturing of components with complex geometries in a layer-by-layer fashion. 3D printing became popular after the first machine was introduced to the market in 1986 by Hull [1]. Charles Hull created the first stereolithography (SLA) manufacturing method which he used for the rapid design and manufacturing of small prototype plastic parts. Stereolithography uses light to activate polymers within a resin (photopolymerization) to create 3D, complex shapes [2, 3]. This SLA system was commercialized in 1987 by the company 3D Systems. Since this breakthrough invention, there has been great effort in producing machines that can process a variety of plastics. Some of the machines currently in the market are fused deposition modeling (FDM) [4, 5] and direct ink write (DIW) for extrusion-based processes [6, 7]. Powder bed fusion (PBF) and laser sintering (SLS) are used for processes requiring a laser to cure or fuse polymeric

materials [8]. Inkjet printers also use light to photopolymerize ink drops into complex shapes [9]. Extensive reviews on these processing and 3D printing technologies have been published elsewhere [4, 5, 10–14]. This chapter focuses on applications that use AM for the 3D printing of polymeric materials.

3. Polymers in 3D printing industry

Functional 3D Printed Polymeric Materials DOI: http://dx.doi.org/10.5772/intechopen.80686

method, and availability.

Figure 2.

5

Material selection chart for product design and manufacturing.

Careful attention is imperative when choosing a material to print a given part. While there are a variety of commercially available polymers, not one polymer is inclusive and will give one the properties needed for a specific application. Furthermore, a single AM technique is not capable of printing any one individual polymer available in the market. The selection of material depends on the application and the customers' needs. Figure 2 lists the decision criteria for the selection of a material. One must take into consideration the environment at which the part will be exposed and the properties required (e.g. temperature, mechanical load, humid-

Polymers have become consumer goods, for they are used to manufacture bottles, toys, tools, bags, phones, computers, tools, cushions, electronics and transpor-

developing materials that can be 3D printed, which allows for rapid manufacturing [2–4, 17]. Table 1 lists commercially available polymers used in some of the AM processes. Polycarbonate (PC), acrylonitrile butadiene styrene (ABS), poly ether ester ketone (PEEK), polyetherimide (ULTEM) and Nylon are common polymers used in processes requiring thermoplastics, or plastics that are processed by heating to a semi-liquid state and close to the melting point. Upon extrusion, the printed layers fuse and solidify. AM techniques that use thermoplastics are Fused-

Deposition Modeling (FDM), Jetting (InkJet), and Selective Laser Sintering (SLS). SLA and Direct Ink Writing (DIW) use thermosetting polymers in their liquid state, or polymers that become solids after curing. A chemical reaction occurs prior to the melting point, resulting in a solid-state material. In SLA and DIW, polymers are formulated to meet specific properties, most importantly rheological. For example, each layer should be self-supporting and should allow for the printing of multiple layers while retaining the designed geometry [14, 19–21]. Rheologically, this corresponds to a resin that has a yield stress at high oscillatory stresses, such that the

ity, chemical exposure, radiation, UV light), the processability, 3D printing

tation components [18]. Thus, it makes sense that efforts have focused on
