Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

A review on selective laser sintering/melting (SLS/SLM) of aluminium alloy powders: Processing, microstructure, and properties

Reference EPFL-ARTICLE-184271doi:10.1016/j.compositesa.2012.08.001View record in Web of Science Record created on 2013-02-27, modified on 2017-05-10

Composites Part A: Applied Science and Manufacturing

Biopolymers are generally considered an eco-friendly alternative to petrochemical polymers due to the renewable feedstock used to produce them and their biodegradability. However, the farming practices used to grow these feedstocks often carry significant environmental burdens, and the production energy can be higher than for petrochemical polymers. Life cycle assessments (LCAs) are available in the literature, which make comparisons between biopolymers and various petrochemical polymers, however the results can be very disparate. This review has therefore been undertaken, focusing on three biodegradable biopolymers, poly(lactic acid) (PLA), poly(hydroxyalkanoates) (PHAs), and starch-based polymers, in an attempt to determine the environmental impact of each in comparison to petrochemical polymers. Reasons are explored for the discrepancies between these published LCAs. The majority of studies focused only on the consumption of non-renewable energy and global warming potential and often found these biopolymers to be superior to petrochemically derived polymers. In contrast, studies which considered other environmental impact categories as well as those which were regional or product specific often found that this conclusion could not be drawn. Despite some unfavorable results for these biopolymers, the immature nature of these technologies needs to be taken into account as future optimization and improvements in process efficiencies are expected.

Life cycle assessments of biodegradable, commercial biopolymers—A critical review

https://dr.ntu.edu.sg/bitstream/10356/141560/3/Polymeric%20composites%20for%20powder-based%20additive%20manufacturingmanuscript%20RV10.pdf

Polymeric composites for powder-based additive manufacturing : materials and applications

https://core.ac.uk/download/pdf/11777204.pdf

Impact properties of acrylate rubber-modified PVC: Influence of temperature

Manufacturing complex parts by the laser sintering process requires a minimum amount of energy input for consolidation of polymer particles to occur; however too much energy can result in a decline in mechanical properties. This decrease is thought to be the result of polymer chain degradation. A stable sintering region (SSR) has been proposed to describe the optimum temperature range for successful laser sintering. This article will aim to quantify the SSR for polyamide-12 by using thermogravimetric analysis (TGA) to provide a framework for identifying key laser sintering processing parameters. Weight loss with respect to temperature is the main measurement output of the TGA procedure. However, the precise temperature and thermal history of a material is difficult to quantify during the laser sintering process; instead an energy input approach has been developed. A degradation energy was calculated from the TGA data and was used in conjunction with a laser sintering formula called energy melt ratio to prescribe build parameters for laser sintered parts. The mechanical properties of these parts illustrated the effect of degradation at various levels of energy input. Implications for this work include optimizing the material selection process for polymer laser sintering materials beyond polyamide-12. © 2012 Society of Plastics Engineers.

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Methods for quantifying the stable sintering region in laser sintered polyamide-12

Laser sintering (LS) of polymer materials is a process that has been developed over the last two decades and has been applied in industries ranging from aerospace to sporting goods. However, one of the current major limitations of the process is the restricted range of usable materials. Various material characteristics have been proposed as being important to optimise the laser sintering process, key aspects of which have been combined in this work to develop an understanding of the most crucial requirements for LS process design and materials selection. Using the favourable characteristics of polyamide-12 (the most often used material for laser sintering) as a benchmark, a previously un-sintered thermoplastic elastomer material was identified as being suitable for the LS process, through a combination of information from Differential Scanning Calorimetry (DSC), hot stage microscopy (HSM) and knowledge of viscosity data. Subsequent laser sintering builds confirmed the viability of this new material, and tensile test results were favourable when compared with materials that are currently commercially available, thereby demonstrating the efficacy of the chosen selection process.

A targeted material selection process for polymers in laser sintering

A detailed knowledge of the physical properties of plastics is essential to understanding and extending their use. This book promotes the relationship between processing parameters and product performance by first examining morphology in terms of texture and orientation. The basic structure of plastics is explained, along with the characterization of both polymer and plastics products. Thermal and melt properties relevant to processing are considered, and the principal shaping methods are outlined, highlighting the large number of variables. The key areas of deformation and fracture are given extensive treatment. Engineers and chemists as well as physicists and technicians in the industry will find this book extremely valuable to their research.

Physics of Plastics: Processing, Properties, and Materials Engineering

Nanocomposites consisting of an epoxy network matrix and a silica reinforcing phase were produced from a resin mixture functionalized with alkoxysilane coupling agents. Particulate nanocomposites were obtained by dispersing silica-organosol particles in the resin, while bicontinuous phase nanocomposirtes were obtained by the in-situ hydrolysis and condensation of tetraethoxysilane containing minor amounts of γ-glycidoxyl trimethoxysilane. Functionalization of the epoxy resin with an amine silane coupling agent was found to be more effective in aiding the dispersion of silica sol particles in the resin than the corresponding resin functionalized with a mercaptan silane coupling agent. Similar differences in the efficiency of coupling agent grafted on to the epoxy resin were observed for bicontinuous phase nanocomposites. The amine silane functionalization produces denser silica domains, which results in a higher rubber-plateau modulus and higher resistance to solvent penetration. The study also showed that the particulate nanocomposites are very ineffective in improving the solvent resistance of the base resin, even when the resin is grafted with a very efficient amine silane coupling agent, which promotes interfacial bonding. The different types of morphology were characterized by transmission electron microscopy and small angle X-ray scattering analysis.

B. Haworth

Papers

Impact properties of acrylate rubber-modified PVC: Influence of temperature

Methods for quantifying the stable sintering region in laser sintered polyamide-12

A targeted material selection process for polymers in laser sintering

Physics of Plastics: Processing, Properties, and Materials Engineering

Substantiating the role of phase bicontinuity and interfacial bonding in epoxy-silica nanocomposites