Enhanced Mechanical Performance of Segregated Carbon Nanotube/Poly(lactic acid) Composite for Efficient Electromagnetic Interference Shielding

Lightweight electromagnetic interference shielding poly(L-lactic acid)/poly(D-lactic acid)/carbon nanotubes composite foams prepared by supercritical CO2 foaming

Lightweight and biodegradable polymer composites with efficient electromagnetic interference (EMI) shielding performance are of great significance for controlling pollution caused by plastic waste and electromagnetic radiation. Herein, poly(lactic acid) (PLA)/carbon nanotubes (CNTs) composites were prepared through a melt blending method. By adding a small amount of poly(D-lactic acid) to poly(L-lactic acid) (PLLA), the EMI shielding performance of the composites was improved because an enhanced viscoelasticity and suitable crystallinity could help to construct fine CNT conductive networks. When the PDLA content was 2 wt%, the EMI shielding effectiveness (SE) of the PLLA-2PDLA-10CNTs reached 27.1 dB at 26.5 GHz. Based on these findings, a green supercritical CO₂ foaming method was employed to prepare lightweight PLLA/PDLA/CNTs composites. For the PLLA-2PDLA-10CNTs foams, when the expansion ratio was 1.24, the EMI SE was 20.1 dB at 26.5 GHz. In addition, the EMI shielding mechanism of the foams was dominated by absorption. This paper provides a facile way to prepare lightweight and environmentally friendly materials for EMI shielding applications.

Graphene derivatives in bioplastic: A comprehensive review of properties and future perspectives

The research and technological advancements observed in the latest years in the nanotechnology field translated into significant application developments in various areas. This is particularly true for the renewable polymers area, where the nano-reinforcement of biobased materials leads to an increase in their technique and economic competitiveness. The efforts were predominantly focused on materials development and energy consumption minimization. However, attention must also be given to the widespread commercialization and the full characterization of any particular potential toxicological and environmental impact. Some of the most important nanomaterials used in recent years as fillers in the bioplastic industry are graphene-based materials (GBMs). GBMs have high surface area and biocompatibility and have interesting characterizations such as strangeness and flexibility. In this paper, the current state of the art for these GBMs in the bioplastics area, their challenges, and the strategies to overcome them are analyzed.

A Healable and Mechanically Enhanced Composite with Segregated Conductive Network Structure for High-Efficient Electromagnetic Interference Shielding

The cationic waterborne polyurethanes microspheres with Diels-Alder bonds were synthesized for the first time. The electrostatic attraction not only endows the composite with segregated structure to gain high electromagnetic-interference shielding effectiveness, but also greatly enhances mechanical properties. Efficient healing property was realized under heating environment. It is still challenging for conductive polymer composite-based electromagnetic interference (EMI) shielding materials to achieve long-term stability while maintaining high EMI shielding effectiveness (EMI SE), especially undergoing external mechanical stimuli, such as scratches or large deformations. Herein, an electrostatic assembly strategy is adopted to design a healable and segregated carbon nanotube (CNT)/graphene oxide (GO)/polyurethane (PU) composite with excellent and reliable EMI SE, even bearing complex mechanical condition. The negatively charged CNT/GO hybrid is facilely adsorbed on the surface of positively charged PU microsphere to motivate formation of segregated conductive networks in CNT/GO/PU composite, establishing a high EMI SE of 52.7 dB at only 10 wt% CNT/GO loading. The Diels-Alder bonds in PU microsphere endow the CNT/GO/PU composite suffering three cutting/healing cycles with EMI SE retention up to 90%. Additionally, the electrostatic attraction between CNT/GO hybrid and PU microsphere helps to strong interfacial bonding in the composite, resulting in high tensile strength of 43.1 MPa and elongation at break of 626%. The healing efficiency of elongation at break achieves 95% when the composite endured three cutting/healing cycles. This work demonstrates a novel strategy for developing segregated EMI shielding composite with healable features and excellent mechanical performance and shows great potential in the durable and high precision electrical instruments.

Graphene Derivatives in Biopolymer-Based Composites for Food Packaging Applications

This review aims to showcase the current use of graphene derivatives, graphene-based nanomaterials in particular, in biopolymer-based composites for food packaging applications. A brief introduction regarding the valuable attributes of available and emergent bioplastic materials is made so that their contributions to the packaging field can be understood. Furthermore, their drawbacks are also disclosed to highlight the benefits that graphene derivatives can bring to bio-based formulations, from physicochemical to mechanical, barrier, and functional properties as antioxidant activity or electrical conductivity. The reported improvements in biopolymer-based composites carried out by graphene derivatives in the last three years are discussed, pointing to their potential for innovative food packaging applications such as electrically conductive food packaging.

An anisotropic layer-by-layer carbon nanotube/boron nitride/rubber composite and its application in electromagnetic shielding

Multifunctional polymer composites with anisotropic properties are attracting interest as they fulfil the growing demand of multitasking materials. In this work, anisotropic polymer composites have been fabricated by combining the layer-by-layer (LBL) filtration method with the alternative assembling of carbon nanotubes (CNTs) and hexagonal boron nitride flakes (hBN) on natural rubber latex particles (NR). The layered composites exhibit anisotropic thermal and electrical conductivities, which are tailored through the layer formulations. The best composite consists of four layers of NR modified with 8 phr (parts per Hundred Rubber) CNTs (∼7.4 wt%) and four alternate layers with 12 phr hBN (∼10.7 wt%). The composites exhibit an electromagnetic interference (EMI) shielding effectiveness of 22.41 ± 0.14 dB mm^-1 at 10.3 GHz and a thermal conductivity equal to 0.25 W m^-1 K^-1. Furthermore, when the layered composite is used as an electrical thermal heater the surface reaches a stable temperature of ∼103 °C in approx. 2 min, with an input bias of 2.5 V.

Morphological, thermal, rheological and mechanical properties of poly (butylene carbonate) reinforced by stereocomplex polylactide

Fully biodegradable blends of poly (butylene carbonate) (PBC) and a bioresource-based stereocomplex polylactide (sc-PLA) were prepared by melt compounding at a temperature far below the melting point (T_m) of sc-PLA, and above the T_m of PBC, poly (l-lactide) (PLLA) and poly(d-lactide) (PDLA). sc-PLA was uniformly dispersed in the PBC matrix as spherical particles. Interestingly, the size of the dispersed sc-PLA particles did not increase significantly with increasing amounts of PLLA and PDLA. sc-PLA accelerated the non-isothermal and isothermal melt crystallization of PBC. Simultaneously, the thermal decomposition temperature of the PBC/sc-PLA blends increased by about 46 °C. The solid filler sc-PLA could reinforce the PBC matrix over a relatively wide temperature range. Consequently, formation of the percolation network structure of spherical sc-PLA in the blends significantly improved the rheological and mechanical properties of PBC after incorporation of sc-PLA. This report may open a new avenue to achieve higher-performance biodegradable polymer blend materials.