Implementation of a safe-by-design approach in the development of new open pilot lines for the manufacture of carbon nanotube-based nano-enabled products

The project PLATFORM (H2020, GA 646307) aims to develop three new pilot lines (PPLs) for the manufacture of carbon nanotube-based nano-enabled products (buckypapers, treated prepregs, doped veils), for the European aeronautics and automotive industries (a Technology Readiness Level 6 - TRL6 -is expected at the end of the project). The Machinery Directive 2006/42/EC (MD) - transposed into the respective national legislations -is the European regulatory framework for the design and construction of new machinery, as the future PPLs. PPLs are not required to comply with the provisions of the MD until they are put into service - expected in 2020, after project completion - but then, the MD will be fully applicable. In this regulatory context, the project PLATFORM is aligning the design of the PPLs according to the MD requirements, in order to facilitate the CE marking in 2020 (TRL9) and avoid potential economic costs associated with future re-adaptations or modifications needed to ensure compliance with the MD. This paper discusses the methodological approach followed by the project PLATFORM to integrate all the nanosafety aspects in the design of the PPLs, in order to achieve safe designs in conformity with the relevant Essential Health and Safety Requirements (EHSRs) of the MD. Since machinery must be designed and constructed taking into account the results of the risk assessment (RA), this paper describes the systematic and iterative approach for RA and risk reduction followed to eliminate hazards as far practicable and to adequately reduce risks by the implementation of protective measures. This process has been guided by the harmonized standards EN ISO 12100 and EN ISO 14123, taking the relevant phases of life cycle, expected uses and operation modes of the PPLs into account. A specific tool to guide the safe design of the PPLs and facilitate the RA process has also been produced by the project (PLATFORM -SbD toolkit).The project PLATFORM has received funding from the European Union's Horizon 2020 research and innovation programme, under grant agreement No 646307

Application of standardization for the design and construction of carbon nanotube-based product pilot lines in compliance with EU regulation on machinery

The "PLATFORM" manufacturing ecosystem for pilot production of pre-commercial CNT-based nano-enabled products, consists of three pilot lines (PPLs) for the manufacture of buckypapers, doped prepregs and doped veils. The PPLs have been constructed with the ultimate goal to commercialize these products in the European market in 2020/2022.This goal requires having the PPLs in compliance with the applicable product safety regulation by that date (CE marking). The main EU regulation for new machinery (as the PPLs) is the Directive 2006/42/EC on Machinery (MD). This Directive sets out the general mandatory Essential Health and Safety Requirements (EHSRs) related to the design and construction of machinery, while particular technical specifications for fulfilling them are provided in European harmonized standards. Application of harmonized standards is voluntary but confers a presumption of conformity with the EHSRs they cover. The PPLs are unique machines for own use and must comply with the MD before they are put into service, in 2020/2022. But the MD does not provide specific EHSRs for nanosafety and no harmonized standards are available in this field for the safe design of the PPLs. In this context, this paper shows the standardization strategy followed by the project PLATFORM (GA 646307) to design the PPLs in compliance with the EHSR referred to the risks to health resulting from hazardous substances emitted by machinery (MD, Annex I, EHSR 1.5.13). In the absence of nanosafety harmonized standards to satisfy the aforementioned EHSR, the design and design verification of the PPLs were carried out through A & B - type harmonized standards (e.g. EN ISO 12100, EN ISO 14123-1/2), and other European and international standards.The projects PLATFORM and OASIS have received funding from the European Union’s Horizon 2020 research and innovation programme, under grant agreements Nº 646307 and Nº 814581, respectively. This paper reflects only the authors’ views, and the Commission is not responsible for any use that may be made of the information contained therein

Relationship between Viscosity, Microstructure and Electrical Conductivity in Copolyamide Hot Melt Adhesives Containing Carbon Nanotubes

The polymeric adhesive used for the bonding of thermoplastic and thermoset composites forms an insulating layer which causes a real problem for lightning strike protection. In order to make that interlayer electrically conductive, we studied a new group of electrically conductive adhesives based on hot melt copolyamides and multi-walled carbon nanotubes fabricated by the extrusion method. The purpose of this work was to test four types of hot melts to determine the effect of their viscosity on the dispersion of 7 wt % multi-walled carbon nanotubes and electrical conductivity. It was found that the dispersion of multi-walled carbon nanotubes, understood as the amount of the agglomerates in the copolyamide matrix, is not dependent on the level of the viscosity of the polymer. However, the electrical conductivity, analyzed by four-probe method and dielectric spectroscopy, increases when the number of carbon nanotube agglomerates decreases, with the highest value achieved being 0.67 S/m. The inclusion of 7 wt % multi-walled carbon nanotubes into each copolyamide improved their thermal stability and changed their melting points by only a few degrees. The addition of carbon nanotubes makes the adhesive’s surface more hydrophilic or hydrophobic depending on the type of copolyamide used

Electrically Conductive Adhesive Based on Thermoplastic Hot Melt Copolyamide and Multi-Walled Carbon Nanotubes

For the bonding of the lightweight composite parts, it is desired to apply electrically conductive adhesive to maintain the ability to shield electromagnetic interference. Among various solvent-based adhesives, there is a new group of thermoplastic hot melt adhesives that are easy to use, solidify quickly, and are environment-friendly. To make them electrically conductive, a copolyamide-based hot melt adhesive was mixed with 5 and 10 wt% of carbon nanotubes using a melt-blending process. Well-dispersed nanotubes, observed by a high-resolution scanning microscope, led to the formation of a percolated network at both concentrations. It resulted in the electrical conductivity of 3.38 S/m achieved for 10 wt% with a bonding strength of 4.8 MPa examined by a lap shear test. Compared to neat copolyamide, Young’s modulus increased up to 0.6 GPa and tensile strength up to 30.4 MPa. The carbon nanotubes improved the thermal stability of 20 °C and shifted the glass transition of 10 °C to a higher value. The very low viscosity of the neat adhesive increased about 5–6 orders of magnitude at both concentrations, even at elevated temperatures. With a simultaneous growth in storage and loss modulus this indicates the strong interactions between polymer and carbon nanotubes

Hot-melt adhesives based on co-polyamide and multiwalled carbon nanotubes

Composites of two hot melt adhesives based on co-polyamides, one high viscosity (coPA_A), the other low viscosity (coPA_B), and multiwalled carbon nanotubes (MWCNTs) were prepared using twin-screw extrusion via dilution of masterbatches. Examination of these composites across the length scales confirmed that the MWCNTs were uniformly dispersed and distributed in the polymer matrices, although some micron size agglomerations were also observed. A rheological percolation was determined from oscillatory rheology measurements at a mass fraction of MWCNTs below 0.01 for coPA_B and, between 0.01 and 0.02 for coPA_A. Significant increases in complex viscosity and storage modulus confirmed the “pseudo-solid” like behavior of the composite materials. Electrical percolation, determined from dielectric spectroscopy was, found to be at 0.03 and 0.01 MWCNT mass fraction for coPA_A and coPA_B based composites, respectively. Addition of MWCNTs resulted in heterogeneous nucleation and altered the crystallization kinetics of both copolymers. Indirect evidence from contact angle measurements and surface energy calculations confirmed that MWCNT addition enhanced the adhesive properties of coPA_B to a level similar to coPA_A

Fibers of Thermoplastic Copolyamides with Carbon Nanotubes for Electromagnetic Shielding Applications

Polymer composites containing carbon nanofillers are extensively developed for electromagnetic shielding applications, where lightweight and flexible materials are required. One example of the microwave absorbers can be thermoplastic fibers fabricated from copolyamide hot melt adhesives and 7 wt% of multi-walled carbon nanotubes, as presented in this paper. A broadband dielectric spectroscopy confirmed that the addition of carbon nanotubes significantly increased microwave electrical properties of the thin (diameter about 100 μm) thermoplastic fibers. Moreover, the dielectric properties are improved for the thicker fibers, and they are almost stable at the frequency range 26–40 GHz and not dependent on the temperature. The variances in the dielectric properties of the fibers are associated with the degree of orientation of carbon nanotubes and the presence of bundles, which were examined using a high-resolution scanning microscope. Analyzing the mechanical properties of the nanocomposite fibers, as an effect of the carbon nanotubes addition, an improvement in the stiffness of the fibers was observed, together with a decrease in the fibers’ elongation and tensile strength

Relationship between viscosity, microstructure and electrical conductivity in copolyamide hot melt adhesives containing carbon nanotubes

The polymeric adhesive used for the bonding of thermoplastic and thermoset composites forms an insulating layer which causes a real problem for lightning strike protection. In order to make that interlayer electrically conductive, we studied a new group of electrically conductive adhesives based on hot melt copolyamides and multi-walled carbon nanotubes fabricated by the extrusion method. The purpose of this work was to test four types of hot melts to determine the effect of their viscosity on the dispersion of 7 wt % multi-walled carbon nanotubes and electrical conductivity. It was found that the dispersion of multi-walled carbon nanotubes, understood as the amount of the agglomerates in the copolyamide matrix, is not dependent on the level of the viscosity of the polymer. However, the electrical conductivity, analyzed by four-probe method and dielectric spectroscopy, increases when the number of carbon nanotube agglomerates decreases, with the highest value achieved being 0.67 S/m. The inclusion of 7 wt % multi-walled carbon nanotubes into each copolyamide improved their thermal stability and changed their melting points by only a few degrees. The addition of carbon nanotubes makes the adhesive’s surface more hydrophilic or hydrophobic depending on the type of copolyamide use

The Composites of Polyamide 12 and Metal Oxides with High Antimicrobial Activity

The lack of resistance of plastic objects to various pathogens and their increasing activity in our daily life have made researchers develop polymeric materials with biocidal properties. Hence, this paper describes the thermoplastic composites of Polyamide 12 mixed with 1–5 wt % of the nanoparticles of zinc, copper, and titanium oxides prepared by a twin-screw extrusion process and injection moulding. A satisfactory biocidal activity of polyamide 12 nanocomposites was obtained thanks to homogenously dispersed metal oxides in the polymer matrix and the wettability of the metal oxides by PA12. At 4 wt % of the metal oxides, the contact angles were the lowest and it resulted in obtaining the highest reduction rate of the Escherichia coli (87%), Candida albicans (53%), and Herpes simplex 1 (90%). The interactions of the nanocomposites with the fibroblasts show early apoptosis (11.85–27.79%), late apoptosis (0.81–5.04%), and necrosis (0.18–0.31%), which confirms the lack of toxicity of used metal oxides. Moreover, the used oxides affect slightly the thermal and rheological properties of PA12, which was determined by oscillatory rheology, thermogravimetric analysis, and differential scanning calorimetry