Progress in 3D printing of polymer composite materials in Ningbo
With the continuous development of technology, 3D printing technology emerged as a new digital analog manufacturing technology and developed rapidly. Among them, the fused deposition technology has the advantages of simple equipment, clean process, low operating cost and no excessive processing residues, and is widely used in the fields of rapid prototyping and education. However, the existing molten deposition materials are mainly general-purpose plastics such as ABS and PLA, and it is necessary to develop a 3D printing molding technology suitable for high-strength engineering plastics for industrial products.
Xu Gaojie, a key laboratory for additive manufacturing at the Institute of Materials Technology and Engineering, Chinese Academy of Sciences, conducted a series of research work on high-performance engineering plastic 3D printing technology. The semi-crystalline nylon 12 and high-strength polyetherimide with high toughness and fatigue resistance were selected as the matrix. The influence of melt rheological properties on the sintering characteristics of molten filaments was studied. 3D for high performance engineering plastics. Printing process parameters and industrial usability were studied. It has been found that semi-crystalline polymers have good rheological properties and rapid sintering characteristics, and can obtain mechanical properties close to injection molded parts under suitable printing conditions. Expanded the application of high temperature and high strength engineering plastics in fused deposition technology (Rapid Prototyping Journal, 2017, 23(6), 973–982. High Performance Polymers, 2019, 31(1): 97-106.).
The voids generated by the superposition process of the fused deposition layer inevitably reduce the mechanical strength of the 3D printed product, which seriously restricts the application and promotion of the fused deposition technique. Based on process research, the researchers developed nylon 12/graphene oxide and nylon 12/carbon fiber composites. The study found that the two fillers can achieve orientation distribution during the fused deposition process, which not only effectively improves the mechanical strength of the product (GNPs 7% and CFs 251.1%), but also flexibly regulates the thermal conductivity of the product (up 51.4%). (Journal of Applied Polymer Science, 2017, 134(39), 45332.; Materials & Design, 2018, 139: 283-292.).
Recently, the researchers used polylactic acid (PLA) as the matrix and thermoplastic polyurethane (TPU) as the filler to realize the in-situ fiber formation of elastomer TPU through the whole process of fused deposition technology. The average length of fibrous TPU can be realized from 67.24. Precision regulation from μm to 103.72μm. At the same time, TPU fiber formation effectively improves its interface bonding with the PLA matrix. It is found that the grid-like TPU formed by 3D printing can effectively compensate the weakening effect of the printing gap on the mechanical strength of the printing part, so that the toughness of the product can reach or exceed the injection molding level. The fused deposition in-situ fiber technology provides a simple and effective method for preparing high tough polylactic acid complex structural parts (Macromolecular Materials and Engineering, 2019, 1900107).
The above work was funded by the National Natural Science Foundation of China (11574331, 11674335) and the Ningbo Science and Technology Bureau (2016B10005, 2018A610009).