Multilayered Composites with Carbon Nanotubes for Electromagnetic Shielding Application.

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Polylactic acid (PLA) is a biodegradable polymer with potential for composite applications.
• Multiwall carbon nanotubes (MWCNTs) are known for their electrical and mechanical properties.
• Effective electromagnetic interference (EMI) shielding materials are crucial for electronic devices.

Purpose of the Study:

• To investigate the microwave dielectric properties and absorption of bulk PLA/MWCNT composites.
• To design and evaluate layered (laminate) PLA/MWCNT structures with gradient MWCNT concentrations for enhanced microwave shielding.
• To compare different laminate designs and their impact on mechanical and shielding properties.

Main Methods:

• Preparation of bulk polylactic acid (PLA)/multiwall carbon nanotube (MWCNT) composites.
• Investigation of dielectric properties and microwave absorption across wide frequency ranges (20 Hz-1 MHz and 24-40 GHz).
• Fabrication and characterization of five-layer and nine-layer laminate structures with varying MWCNT concentrations (0.2-8.0 vol.%).

Main Results:

• Percolation threshold for bulk PLA/MWCNT composites identified near 0.2 vol.% MWCNT.
• Optimal microwave dielectric properties and absorption observed in composites with 3.0-5.0 vol.% MWCNT.
• Layered structures with gradient MWCNT concentration achieved high microwave shielding (up to 26 dB) in the 24-40 GHz range, outperforming single-layer composites.

Conclusions:

• Layered PLA/MWCNT structures with gradient MWCNT concentration offer superior microwave shielding compared to bulk composites.
• The proposed laminate design demonstrates significant potential for efficient electromagnetic shielding applications.
• MWCNT addition enhances mechanical properties (elastic modulus and tensile strength) of PLA composites.