Architecting fire safe hierarchical polymer nanocomposite films with excellent electromagnetic interference shielding via interface engineering

Highly flame retardancy, barrier, mechanical and persistent antibacterial polylactic acid film with high-parallel interconnected thousand layered cake architecture

In this work, a bio-based material (CGP) is obtained by combing chitosan, gelatin and polyvinyl alcohol through a simple solution mixing to simultaneously address polylactic acid film (PLA)' flammability and poor barrier, toughness and antibacterial properties by soaking. The results of open fire testing show that modified PLA films can effectively prolong the combustion time, improve the thermal stability and reduce the release of heat in the cone calorimeter test. For the PLA sample after soaking for 5 times (PLA-5) in particular, it can reduce the peak heat release rate (pHRR) and total heat release (THR) values to 85.8 kW/m2 and 1.3 MJ/m2 from the values of 129.5 kW/m2 and 1.8 MJ/m2 for PLA, respectively. Structural analysis suggests that CGP primarily operates in the condensed phase by forming physical barriers. Meanwhile, the modified PLA films can exhibit superior barrier effects, which indicate the oxygen transmission rate value of PLA-5 decreases to 0.9 cm3/(m2·day) from the 392.5 cm3/(m2·day) of raw PLA film. Moreover, the PLA-5 also have excellent toughness (the value increased to 200.5 % from 31.0 %) and persistent antibacterial effects (it still has 100 % sterilization after 500 days).

Optimization of CoFe2O4 nanoparticles and graphite fillers to endow thermoplastic polyurethane nanocomposites with superior electromagnetic interference shielding performance

The rapid growth, integration, and miniaturization of electronics have raised significant concerns about how to handle issues with electromagnetic interference (EMI), which has increased demand for the creation of EMI shielding materials. In order to effectively shield against electromagnetic interference (EMI), this study developed a variety of thermoplastic polyurethane (TPU)-based nanocomposites in conjunction with CoFe2O4 nanoparticles and graphite. The filler percentage and nanocomposite thickness were tuned and optimized. The designed GF15-TPU nanocomposite, which has a 5 mm thickness, 15 weight percent cobalt ferrite nanoparticles, and 35 weight percent graphite, showed the highest total EMI shielding effectiveness value of 41.5 dB in the 8.2-12.4 GHz frequency range, or 99.993% shielding efficiency, out of all the prepared polymer nanocomposites. According to experimental findings, the nanocomposite's dipole polarization, interfacial polarization, conduction loss, eddy current loss, natural resonance, exchange resonance, multiple scattering, and high attenuation significantly contribute to improving its electromagnetic interference shielding properties. The created TPU-based nanocomposites containing graphite and CoFe2O4 nanoparticles have the potential to be used in communication systems, defense, spacecraft, and aircraft as EMI shielding materials.

In-situ photo-crosslinkable elastomer based on polyalphaolefin/halloysite nanohybrid

In this research, new injectable and in situ photocurable elastomeric nanohybrids have been fabricated from polyalphaolefin (PAO) resins and halloysite nanofiller. In this regard, the co-oligomerization of long α-olefin monomers (C6, C8 and C10) with alkenol counterparts was carried out via a simple cationic route to provide OH-functionalized PAOs. The newly formed PAO type copolymer resins as well as halloysite nanoclay were then equipped with photocurable CC bonds containing an acrylate moiety. After the characterization of the final chemical substances and also of the intermediate structures, experimentally and computationally by means of Density Functional Theory (DFT) calculations, the neat treated PAO and PAO/halloysite nanohybrids were subjected to a curing process by visible light irradiation (λ ∼ 475 nm, blue light). The crosslinking efficiency of the neat resins and the formed nanohybrid was evaluated using shrinkage strain-time curves and equilibrium swelling method. The suggested nanohybrid is not only biocompatible (96 % in the MTT assay), and hydrophilic (with a water contact angle of 61°), but also exhibits an easy, fast and robust curing process with great potential for coating and sealing technologies for medical devices.

A fire resistant MXene-based flexible film with excellent Joule heating and electromagnetic interference shielding performance

Flexible films with thermal management capability and efficient electromagnetic interference (EMI) shielding performance are highly needed for electronic devices. Moreover, it remains difficult to integrate fire safety performance into the multifunctional film. Thus, a facile multi-interfacial engineering strategy was proposed to prepare a fire resistant MXene-based flexible film with excellent Joule heating and EMI Shielding performance. Specifically, the neighboring and interlayer MXene sheets were respectively bridged by graphene oxide and carbon nanotube via multiple physical and chemical interactions, thus formed a optimized hierarchical microstructure. The resultant film possessesd outstanding Joule heating performance including wide electrical-to-thermal temperature and sensitive conversion ability. Simultaneously, the film exhibited high EMI shielding efficiency (99.97%). Most significantly, after being burned up to 60 min, the film still maintained its flexibility and multifunctional perfprmance benefiting from a large expanded protective layer. The excellent fire resistance and multi-functions endowed the film wide application prospects in advanced electronics.

Realizing balanced flame retardancy and electromagnetic interference shielding in hierarchical elastomer nanocomposites

The combination of electromagnetic interference (EMI) shielding performance and flame-retardant property is essential for applications in the field of electronics and electrics. To date, there have been few successful cases in achieving such portfolios, due to the different mechanisms and even mutual exclusivity of these two attributes. Herein, an ammonium polyphosphate@chitosan@carbon nanotube (APP@CS@MWCNT) core-multishell hybrid was synthesized by microencapsulation technology. Then, the hybrid was introduced into TPU matrix to fabricate TPU composites, acting as surface layer. Meanwhile, MXene film was used as intermediate layer to construct hierarchical TPU composites. The obtained results showed that after introduction of 1 wt% APP@CS@MWCNT hybrid, the peak of heat release rate (PHRR) and the peak of smoke produce rate (PSPR) of TPU composites decreased by 67.4% and 35.6%, respectively, compared with those of pure TPU. Owing to multiple reflection losses, interface polarization losses, and charge carrier movement-induced thermal dissipation, TPU/15AC@4M-SW exhibited the highest EMI shielding performance, and obtained shielding effectiveness values of 35.7 dB and 38.9 dB in X band and K band, respectively.

Tunable construction of fire safe and mechanically strong hierarchical composites towards electromagnetic interference shielding

Cotton fabric composites were designed to be protected by fire safe thermoplastic polyurethane (TPU) composites for developing electromagnetic interference (EMI) shielding polymer composites with superior mechanical properties. Herein, the as-prepared MXene was coated onto the fiber surface of cotton and then thermally compressed with TPU composites, which were filled with the sodium dodecyl sulfate modified layered double hydroxides functionalized the short carbon fiber hybrids through melt blending method. Then, a series of highly fire safe cotton/TPU hierarchical composites were constructed by a designed thermal compression technique. For instance, the obtained cotton/TPU hierarchical sample showed greatly reduced peak of heat release rate, peak of carbon monoxide production rate and peak of carbon dioxide production rate of TPU by 50.1%, 52.1% and 55.4%, respectively. Furthermore, the cotton/TPU hierarchical composites possessed the EMI shielding effectiveness of 40.0 dB in the X band and 54.6 dB in the K band. The mechanical property of the cotton/TPU hierarchical composites was also reinforced, where the elongation at break and toughness values of the TPU/SCF/mLDH1/C2 hierarchical composite were 21.47 and 18.30 times higher than those of pure TPU, respectively. These mechanically strong hierarchical composites have brought a promising attempt to broaden their practical application, removing the fire hazards and electromagnetic waves radiation from the environment.