COMPOUNDS | ELECTRICALLY CONDUCTIVE
Right: Example of a plastic part that leverages the high mechanical performance and tunable electrical properties offered by high-quality recycled
carbon fibers
demand, especially in automo- tive and in general electronics, for new sustainable and cost-effective material solutions that impart various levels of electrical conductivity to plastics. The company now offers a range of recycled carbon fibre products based on ‘intermediate modulus’ carbon fibre, milled, cut or granulated, with an appropriate sizing to impart the necessary compat- ibility with the matrix polymer. The company says these intermediate modulus carbon fibres are stiffer than their standard modulus counterparts, but also inherently more conductive and generally faster at forming a conductive ‘percolating’ network at low fibre content within the polymer matrix (percolation occurs when the conducting fibres or fillers in the matrix make direct contact and is characterised by a sharp increase in conductivity). “With these, customers can now achieve the
IMAGE: APPLY
CARBON
in terms of inherent performance, fibre length distribution and dispersibility in the matrix polymer,” the company says. It now offers a range of
grades with moderate fibre lengths and narrow fibre length distributions for this sector.
Conductive devices Italian compounding company Lati recently
desired electrical conductivity levels at as low as 10 wt% fibre content, where regular ‘standard modu- lus’ fibres may require as much as 30 wt% fibre content,” says Miltner (Figure 6). Apply Carbon also sees a growing demand for 3D printing materials (especially for FFF produc- tion technology) offering improved performance. It says that one problem with FFF 3Dprint technology is that longer fibres result in higher viscosity during fabrication, which is not desirable, and higher risk of nozzle clogging. “The key is therefore to use carbon fibre grades that offer the best compromise
created a spin-off called Lati 3DLab dedicated to engineering and manufacturing of special thermo- plastic compounds suitable for FDM 3D printing. Among recently developed grades, electrically conductive materials have proved successful in printing of conductive devices used in medical, electronics, robotics and sensors. The use of a combination of carbon nanotubes and structured carbon black has allowed the company to reduce the electric resistivity of PLA-based plastic compounds below 10Ω while providing good homogeneity and isotropy of electrical properties. Physical properties have been maintained through the development of a multi- phase matrix that incorporates a non-melting elastomeric component. The resulting filament, sold by Filoalfa as
Alfaohm, has been used by the Tecnologico de Monterrey University in Mexico to 3D print a conductive sensor for point-of-care medical applications. After surface etching and carbon activation, this sensor was able to transport electrical signals from an electroanalytical sensing device used to detect the presence of specific chemical substances. “Exciting performances of conductive 3D printable compounds come together with fast fabrication time, quick switching to tailor made solutions and a very competitive bottom-line cost, specially when disposable parts are concerned,” says Luca Posca, Group Technical Assistance & Mar- keting Director at Lati. “These advantages may offer a winning step forward to innovative applica- tions as supercapacitors for hybrid or electric vehicles, lithium-ion batteries, electrokinetically- driven microfluidics and solar cells.“ Within its Luvocom ESD product line, the
Figure 6: Surface resistivity of PA66 reinforced with 300 micron recycled carbon fibre granulates. Data obtained at 10 and 30 wt% fibre content for standard modulus (SM) and intermediate modulus (IM) grades Source: Apply Carbon
58 COMPOUNDING WORLD | February 2022
LehVoss group now offers what it says are highly innovative non-carbon-modified high-temperature resistant thermoplastic ESD compounds, based on such polymers as PEI, PPS, and PAEKs. Additives, reinforcements and compounding technology can be varied to adjust mechanical and electrical
www.compoundingworld.com
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