Graphene based thermoplastic masterbatches for conventional and additive manufacturing processes

Project Information

NANOMASTER

Grant agreement ID: 285718

Project closed

Start date 1 December 2011

End date 30 November 2015

Funded under

• Specific Programme "Cooperation": Nanosciences, Nanotechnologies, Materials and new Production Technologies

Total cost € 6 253 514,31

EU contribution € 4 199 974,00

Coordinated by

NETCOMPOSITES LIMITED
United Kingdom

Final Report Summary - NANOMASTER (Graphene based thermoplastic masterbatches for conventional and additive manufacturing processes)

Executive Summary:
The aims of the NanoMaster project are to reduce the amount of plastic used to make a component by 50% and hence reduce component weight by 50%, at the same time as imparting electrical and thermal functionality. This will be achieved by developing the next generation of graphene-reinforced nano-intermediate that can be used in existing high-throughput plastic component production processes.

Graphene reinforced polymers have been demonstrated at lab scale in both Europe and the USA, and it has been shown that very low loadings of graphene can have a dramatic impact on the mechanical and physical properties of the polymers it is added to, with small amounts of graphene doubling the strength and stiffness of commodity polymers whilst proving thermal and electrical conductivity. The use of graphene reinforced polymers has the potential to not only significantly reduce the amount of raw materials used in moulding components due to increase strength and stiffness, but also to open up a wide range of new applications through the use of thermally and electronically conductive polymers as well as improved fire retardance and improved gas barrier properties.

However, industrial compounding processes have only been developed in the United States, where Ovation Polymers are already offering graphene thermoplastic masterbatches and compounds based on graphene from XG Sciences. There is no equivalent capacity or company in Europe, as there is not enough understanding of the processing or applications of graphene-reinforced thermoplastics, or of the health and safety issues. Significant further work is required to scale-up the technology and prove its technical, economic and environmental sustainability before European industry and the wider community will be able to benefit.

The concept for this project is to develop the knowledge-based processing methods required to up-scale the production of graphene and expanded graphite reinforced thermoplastic masterbatches and compounds and, ultimately, enable its industrial commercialisation. The work will focus on developing processes for large scale rapid production of graphene, expanded graphite and nano-graphite, machinery and processing methods designed for efficient high throughput production of masterbatches and compounds and developing material systems which can be integrated into current conventional and additive manufacturing processes quickly, easily and safely. For the first time, industrial-scale quantities of graphene filled compounds and masterbatches will be available to European industry.

Successful development of these materials and processes will have a significant effect on the amount of polymer that needs to be used in a component to meet its performance criteria, and on the ability of plastic mouldings to delivery significantly enhanced functionality. These breakthroughs will open the door to a vast range of applications enabling the benefits to be exploited throughout Europe and beyond. They will also help to place European companies in a position to exploit the rapidly growing markets in the US and Asia-Pacific.

Project Context and Objectives:
The aims of the NanoMaster project are to reduce the amount of plastic used to make a component by 50% and hence reduce component weight by 50%, at the same time as imparting electrical and thermal functionality. This will be achieved by developing the next generation of graphene-reinforced nano-intermediate that can be used in existing high-throughput plastic component production processes.

Graphene reinforced polymers have been demonstrated at lab scale in both Europe and the USA, and it has been shown that very low loadings of graphene can have a dramatic impact on the mechanical and physical properties of the polymers it is added to, with small amounts of graphene doubling the strength and stiffness of commodity polymers whilst proving thermal and electrical conductivity. The use of graphene reinforced polymers has the potential to not only significantly reduce the amount of raw materials used in moulding components due to increase strength and stiffness, but also to open up a wide range of new applications through the use of thermally and electronically conductive polymers as well as improved fire retardance and improved gas barrier properties.

However, industrial compounding processes have only been developed in the United States, where Ovation Polymers are already offering graphene thermoplastic master batches and compounds based on graphene from XG Sciences. There is no equivalent capacity or company in Europe, as there is not enough understanding of the processing or applications of graphene-reinforced thermoplastics, or of the health and safety issues. Significant further work is required to scale-up the technology and prove its technical, economic and environmental sustainability before European industry and the wider community will be able to benefit.

The concept for this project is to develop the knowledge-based processing methods required to up-scale the production of graphene and expanded graphite reinforced thermoplastic master batches and compounds and, ultimately, enable its industrial commercialisation. The work will focus on developing processes for large scale rapid production of graphene, expanded graphite and nano-graphite, machinery and processing methods designed for efficient high throughput production of master batches and compounds and developing material systems which can be integrated into current conventional and additive manufacturing processes quickly, easily and safely. For the first time, industrial-scale quantities of graphene filled compounds and master batches will be available to European industry.

Successful development of these materials and processes will have a significant effect on the amount of polymer that needs to be used in a component to meet its performance criteria, and on the ability of plastic mouldings to delivery significantly enhanced functionality. These breakthroughs will open the door to a vast range of applications enabling the benefits to be exploited throughout Europe and beyond. They will also help to place European companies in a position to exploit the rapidly growing markets in the US and Asia-Pacific.
Project Results:
Work Package 1 – Definition of Materials and Applications
Within this kick-off work package, a number of ideas for case study components were outlined and their associated performance requirements were described.
Based on this, a small number of polymers were chosen which would form the basis of subsequent research with the project.
Target properties (and, linked to this, physical dimensions) for the graphite and graphene grades were also defined.

Work Package 2 – Development and Production of Graphene and Expanded Graphite
Throughout the course of the project, a number of different grades of graphene and expanded graphite were produced and tested on a laboratory scale. The influence of a range of properties – including thickness, lateral size, bulk density and surface functionalisation – on the subsequent properties of polymers nanocomposites containing these novel grades was then studied.
Based on these results, production of the most promising grades was up-scaled, such that the graphene grades could be produced in up to 25kg batches and the expanded graphite grades could, if required, be produced in tonne quantities.
At the end of the project, Imerys Graphite & Carbon launched the new product C-Therm301.

Work Package 3 – Dispersion and Compounding of Graphene and Nano-graphite
Our aim in work package 3 was to understand the processing factors that influence the production of well-dispersed nanocomposites via twin screw extrusion. Specifically, the effect of screw speed, screw configuration, residence time and temperature were all studied and the resulting specific mechanical energy (SME) was calculated. Once the optimum laboratory conditions were established, simulation software was used to determine the operating conditions required on a pilot scale extruder in order to deliver the same SME.
Work package 3 also investigated the recyclability of expanded graphite-polymer compounds. To do this, the compounded material was subject to three cycles of injection – moulding – regrinding – mechanical testing. No reduction in properties was observed, indicating that the materials have the potential to be readily recyclable.

Work Package 4 – Intermediate Materials for Conventional Moulding Techniques
Using the simulation data generated in work package 3, a new screw was designed and produced for use on the pilot-scale compounding extruder. Further modifications to the existing line were also carried out, in order to allow efficient feeding of the low bulk-density expanded graphite and graphene fillers.
This pilot line was then used to deliver quantities of various compounds to other partners; both for use in the evaluation of injection moulding and extrusion processing techniques and for further processing, to deliver materials which would subsequently be used to evaluate the selective laser sintering (SLS) and fused deposition modelling (FDM) processing techniques.

Work Package 5 – Intermediate Materials for Additive Manufacturing Techniques
The focus here was to deliver materials in a suitable form for use in the SLS and FDM processes, respectively.
For SLS, this meant developing graphite/graphene-polymer powders with a diameter of less than 100μm. Two approaches were considered. The first simply combined commercial SLS powder with graphene/graphite powder in a dry blending process. Whilst this did provide a material which would be used in experimental trials, for health and safety reason (i.e. the presence of un-bound high aspect ratio nanomaterials) it was deemed not to be a viable material for industrial use. Therefore, as an alternative, the production of graphite/graphene-filled polymer powders – via cryogenic grinding of compounds produced in work package 4. Laboratory scale cryogenic grinding was initial carried out to deliver materials for proof of concept trials and to evaluate different compounds. From here, a sub-contractor was employed to produce larger (multi-kilo) batches of the most promising grade.
For the FDM process, the feedstock must be in the form of narrow diameter filaments, with uniformity of diameter being particularly important for the majority of commercially available FDM printers. The material should also be sufficiently flexible to allow it to be spooled. In order to meet these requirements, modifications were made to a pilot scale filament extrusion line, which was subsequently used to produce filaments from a range of compounds in which the ductility of the material had been modified – either via the use of a blend of thermoplastics or via the incorporation of viscosity modifiers.
Once an optimum filament formulation had been determined, these filaments were evaluated within the consortium (in work package 7) and also made available to the wider “3D printing community” in an attempt to gain feedback from wider user-experience.

Work Package 6 – Processing of Graphene and Graphite Intermediates in Conventional Moulding Techniques
Given the case study components selected at the start of the project (and subsequently refined over the following months), this work package focussed primarily on developing optimised injection moulding parameters. Within this, the influence of a number of variables was studied, including:
• melt temperature;
• mould temperature;
• injection speed;
• screw speed;
• gate size and;
• back pressure.
In general, mechanical properties were found to be relatively consistent, however electrical conductivity varied much more significantly with differing injection moulding parameters.
The results of these detailed investigations were used to produce a free handbook (“Injection Moulding and Extrusion of Graphene and Nanographite Nanocomposites”) which was made available in electronic form towards the end of the project.

Work Package 7 – Production of Graphene and Graphite Reinforced Parts using Additive Manufacturing Techniques
The intermediate materials produced in work package 5 were evaluated firstly in terms of processability and, subsequently, in terms of the quality of parts which could be produced. For FDM filaments, the parameters investigated included:
• extrusion speed;
• extrusion temperature;
• scanning speed; and;
• cooling rate.
Alongside this, a series of novel machine modifications (covering both hardware software) were developed and evaluated. These included:
• a system to allow printing with multi-material printing;
• a positioning systems which would allow the use of a larger print head (which would be required for multi-material printing) and;
• a feeding system which can cope with irregular diameter filaments.
For SLS powders, key processing parameters investigated were:
• building chamber temperature;
• laser power;
• laser scan speed;
• hatch distance;
• No. of exposures and;
• layer thickness.

As with the analogous injection moulding parameter study, the key findings of these investigations were detailed in a publically available handbook (“Additive Manufacturing with Graphene and Nanographite Nanocomposites”), issued towards the end of the NanoMaster project.

Work Package 8 – Application to Case Studies
A number of case study components were produced to demonstrate both the materials and the processing techniques which had been developed during the project. These included:
• consumer electronic components;
o displaying cold-touch properties, or;
o combining a high-gloss black finish with good mechanical properties;
• automotive components;
o utilising electrical conductivity to provide liquid level sensing, or;
o featuring high thermal conductivity, for use in heat exchanger applications;
• LEGO demonstrators;
o having sufficient electrical conductivity in order to interact with tablet computers, smart phones etc.;
o having a sufficiently high thermal conductivity to be used within moulding tools.
In each case, the materials developed in NanoMaster have been compared with the existing commercial material – both in terms of technical performance and likely commercial viability.
Following on from these trials, Philips are looking at the possibility of introducing the cold touch materials into existing product lines as a replacement for metal components.

Work Package 9 – Health and Safety of Graphene Nanocomposites
The ultimate aim of this work package was to deliver practical guidance to those companies involved in the production, handling and processing of graphene family nanomaterials and their nanocomposites.
This began with a review of currently available literature (which was very limited at the start of the project, but did grow steadily over the following four years) to identify the potential hazards associated with graphene family nanomaterials. Alongside this, a survey on partners’ current working practices was carried out, in order to identify likely exposure scenarios.
The scenarios (i.e. processes) with the greatest potential for exposure were then studied more closely via exposure monitoring visits to several partner sites. During these visits, particle release data for each individual task was collected and general observations (e.g. regarding current procedures, existing engineering controls and PPE) were recorded. Based on the findings of these site visits, the key risks associated with each task were identified and, where relevant, recommendations were given as to how the process might be modified in order to lower risk.
In addition to this specific guidance, some general themes were also identified and these were used to provide input to the handbooks on injection moulding and additive manufacturing; prepared as part of work packages six and seven, respectively.

Work Package 10 – Dissemination
From the early stages of the project, all partners took an active role in promoting the project and its objectives and, subsequently, in disseminating the results which were obtained. Over the four years of the project, the project partners have prepared press releases, conference papers and videos, taken part in interviews, panel discussions and workshops and have delivered more than twenty five presentations at events across Europe.

Work Package 11 – Project Management
The only significant deviations from the original plan were the withdrawal of Aero Engine Controls from the consortium and, subsequently, the accession of LEGO.

Potential Impact:
Currently in Europe, graphene reinforced polymers have only been demonstrated at lab scale. It has been shown that very low loadings of graphene, 1% by weight or lower can have a dramatic impact of the mechanical and physical properties of the polymers it is added to. The use of graphene reinforced polymers has the potential to not only significantly reduce the amount of raw materials used in moulding components due to increase strength and stiffness, but also to open up a wide range of new applications through the use of thermally and electronically conductive polymers as well as improved fire retardance and improved gas barrier properties.

Significant further work is required to scale-up the technology and prove its technical, economic and environmental sustainability before European industry and the wider community will be able to benefit.

The NanoMaster project will lead to a breakthrough in the processing of graphene reinforced polymer composites through a number of key innovations. For the first time, industrial-scale quantities of graphene filled compounds and master batches will be available to European industry. These materials will have superior mechanical properties to their unfilled equivalent as well as improved thermal and electrical conductance, improved gas barrier properties and also improved fire performance. This will enable a wide range of new applications for polymers to be explored.

To achieve this overall advance, the project will encompass a series of major innovations in the knowledge-based processing of these materials:

• Use of novel processes for the production of graphene and expanded graphite on a large scale
• Innovative combinations of mechanical and chemical techniques to maximise the efficiency of the exfoliation process
• Use of novel surface functionalisation to improve dispersion and adhesion within a polymer matrix as well as fire retardance and electromagnetic compatibility shielding
• A synergistic approach to producing master batches and compounds by optimising both the filler and compounding process to each other
• Optimised mixtures of standard and bespoke graphene and expanded graphite to obtain maximum property improvement in the polymers at minimum cost and maximum scale-up potential
• In-line high-shear compounding techniques, including co-rotating twin screw compounding extrusion, to achieve high throughput of nano-filled thermoplastic resins
• Turn-key solutions for mixing master batches and compounds, containing concentrated pre-dispersed graphene and expanded graphite, into off-the-shelf thermoplastic resins, to enable rapid, straightforward implementation by industrial users, especially SMEs

These breakthroughs will open the door to a vast range of applications enabling the benefits to be exploited throughout Europe and beyond. They will also help to place European companies in a position to exploit the rapidly growing markets in the US and Asia-Pacific.

List of Websites:
www.nanomasterproject.eu