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GRAPHENE REINFORCE COMPOSITES FOR 3D PRINTING TECHNOLOGY

Periodic Reporting for period 1 - 3D - PRINTGRAPH (GRAPHENE REINFORCE COMPOSITES FOR 3D PRINTING TECHNOLOGY)

Reporting period: 2016-09-16 to 2018-09-15

3D printing is a process for creating 3 dimensional physical objects from a 3D computer digital design, with the potential to significantly reduce resource and energy demands as well as process-related CO2 emissions. In this sense, Pike Research lists it as one of the Five Disruptive Cleantech Innovations which are technologies that enable fundamental large-scale change. It is expected to deliver dramatic ecological benefits to future generations since it allows the production of goods much closer to the consumer, decreasing significantly energy consumption and greenhouse emissions due to transportation. Likewise, it is considered as a new industrial revolution due to its potential of democratizing manufacturing processes through online-distributed blueprints and localized production. Despite 3D printing is still at an early stage, in a recent report the global market potential of 3DP by 2025 is estimated at 230–550 billion US $. Since in 1986 the first 3D printer was created by Charles Hull, 3D printing technology has undergone constant development becoming one of the most used methods for developing prototypes. The range of applications is huge, finding multiple sectors where 3DP is used, such as: medical and dental field, aerospace, automotive, jewelry, art, design, sculpture, architecture, fashion, food, but prototyping is still today’s largest application. European Union has established the graphene research as a priority in R&D. Its recognition as one of the Future and Emerging Technologies (FET) ensures an investment of € 1000 million for the next years (Graphene FET Flagship). Also, Graphene Technologies and Stratasys announced a partnership to co-develop graphene-enhanced 3D-printing materials.

In this sense, recent literature shows several works dealing with the development of prototypes using composites as printing materials, however only few of them explore the use of graphene, therefore new original research involving graphene-nanocomposites materials in 3D printing is necessary.

The overall objectives are sumarized as follow:

1. Designing novel strategies for the integration of graphene layers into several low melting point polymers in order to improve their conductivity and mechanical reinforcement.
2. Determining the structural, morphological, superficial and electrochemical properties of the new engineered materials in order to make a rational selection before the integration stage.
3. Implementing the novel materials in 3D printing for the development of real prototypes through two different 3D printing technologies: FDM and Poly Jet.
The work carried out during the fellowship has consisted of developing 3D-printable graphene-based nanocomposites with advances properties. During the synthesis of the material, the efforts have been directed towards the integration step, where the polymer and filler (graphene-based structures) join into one unique material. We employed solution-blending method for integrating the filler into the polymer structure, which allows increasing the dispersability of the graphene-based structure in the solvent with the polymer matrix and therefore improving the electrical and thermal properties of the nanocomposites. In this sense, two different strategies at this point were evaluated: i) by reducing “in situ” graphene oxide (GO) as precursor of graphene during the integration step through hydrazine as reducing agent and ii) by mixing in solution the already reduced graphene oxide (RGO) with the polymer. In first place, in both cases we synthesized graphene oxide as starting material from graphite flakes. In parallel to this work a third graphene-based structure was also synthesized, chemically expanded graphite (CEG), to be integrated with the polymer, which showed similar properties to those composites based on reduced graphene oxide (RGO) or even better properties in some cases. Graphene oxide was synthesized by following the well know Hummer’s method. On the other hand, chemically expanded graphite (CEG) was synthesized according to the methods described in literature. To carry out the synthesis of the nanocomposites employing GO and CEG as fillers, we followed the schemes of the Figure 7. Therefore, characterization methods were carried out for graphenic structures and nanocomposites. In this sense, we employed different characterization tecniques, including: SEM/EDX, TEM, XPS, BET, XRD, Raman, TGA, DSC and synchrotron radiation (SAXS/WAXS at ALBA facilities and BESSY facilities), and electrical conductivity. With the analysis of all these techniques, we have have been able to confirm that the graphene nanocomposites are provided with improved properties like better electrical conductivity when compared to the original polymers. During the secondment at EURECAT (ASCAMM), it has been carried out the molding of the composites into three dimensional structures, by employing new ultrasonication technology developed by EURECAT.

The results obtained from the work carried out during the fellowship have been presented in several internationally recognized scientific conferences as well as in internal technical meetings. In the Tables 6 and 7, information related to the attended conferences within the project is given.
One of the greatest limitations of 3D printing is marked by the printing material. Due to this, in recent years, several research groups and companies are working on finding new materials with advanced properties suitable for the development of prototypes. In this sense, layered graphene is an emerging material for 3D printing, due to the combination of its impressive conductivity and the 3D nature of the printed structures enabling the generation of a high surface areas with good electrical properties and hierarchical pore structures and porous channels, allowing its utilization in the fabrication of electronic devices, like batteries, sensors or RF antennas which will represent a great breakthrough in such technologies. The use of graphene-enhanced nanocomposite materials in 3D printing could have a disruptive impact due to the highly improved properties with respect to the traditional materials used , e.g. plastics, by increasing thermal and electrical conductivity or making the materials mechanically stronger. Considering all this, the new graphene-based composites we have develop for this project leave open the possibility to be used as materials for making conductive pieces through 3D printing, which could have a high impact in the field of manufacturing small conductive pieces for electronic devices.