Vertically Aligned Nickel 2‑Methylimidazole Metal–Organic Framework Fabricated from Graphene Oxides for Enhancing Fire Safety of Polystyrene

In this work, flowerlike nickel 2-methylimidazole metal–organic framework (Ni-MOF) was prepared by a solvothermal method. Vertically aligned Ni-MOF was fabricated from graphene oxide (GO) solution in the same way. The combination of GO and Ni-MOF (GOF) obviously suppressed the agglomeration of Ni-MOF sheets. As-synthesized, GOF has bigger pore volume and specific surface area, which are beneficial for volatile degradation products adsorption. It is noteworthy that the addition of GOF obviously reduced the fire hazard of polystyrene (PS). More than 33% decrease in the peak heat release rate for the PS/GOF composite was obtained when the content of the additives is only 1.0 wt %. Meanwhile, the reductions of total smoke and CO production were also prominent during the combustion of PS/GOF, respectively 21% and 52.3% decreases compared with that of pure PS. The synergism effects between layered GO and porous Ni-MOF realized the improved performances of PS. Thus, this work paves a feasible pathway to design efficient flame retardants for enhancing fire safety of polymers

DOPO-Modified Two-Dimensional Co-Based Metal–Organic Framework: Preparation and Application for Enhancing Fire Safety of Poly(lactic acid)

Co-based metal–organic framework (Co-MOF) nanosheets were successfully synthesized by the organic ligands with Schiff base structure. The laminated structure gives Co-MOF nanosheets a great advantage in the application in the flame retardant field. Meanwhile, −CN– from Schiff base potentially provides active sites for further modification. In this work, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was used to modify Co-MOF (DOPO@Co-MOF) to further enhance its flame retardant efficiency. It is attractive that DOPO has a synergistic effect with Co-MOF on improving fire safety of poly­(lactic acid) (PLA). The obvious decrease in the values of peak heat release (27%), peak smoke production (56%), and total CO yield (20%) confirmed the enhanced fire safety of PLA composites. The possible flame retardant mechanism was proposed based on characterization results. Moreover, the addition of DOPO@Co-MOF had a positive influence on the mechanical performance, including tensile properties and impact resistance. This work designed and synthesized two-dimensional MOFs with active groups. As-prepared Co-MOF with expected structure shows a novel direction of preparing MOFs for flame retardant application

Layer-by-Layer Assembly of Hypophosphorous Acid-Modified Chitosan Based Coating for Flame-Retardant Polyester–Cotton Blends

Hypophosphorous acid-modified chitosan (PCS), as a novel phosphorus-containing chitosan derivative, was first successfully synthesized and characterized by Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. Subsequently, thin films of the ecofriendly PCS and branched polyethylenimine were deposited on polyester–cotton (PTCO) blends by the layer-by-layer assembly technique, in an effort to enhance their thermal properties and fire resistance properties. Thermogravimetric analysis, thermogravimetric analysis–Fourier transform infrared spectrometry, scanning electron microscopy, and horizontal flame test (HFT) were used to investigate the quality of the coatings as well as their fire resistance performance. The thermal and thermal oxidation stabilities at high temperature were enhanced for all coated PTCO blends. During the HFT, the afterglow phenomenon was eliminated for all coated blends, and self-extinguishing was achieved for the PCS2-20BL sample. It was found that the enhancement of the intumescent effect by the high phosphorus content in these coatings was conducive to achieving this superior performance

Construction of Bimetallic ZIF-Derived Co–Ni LDHs on the Surfaces of GO or CNTs with a Recyclable Method: Toward Reduced Toxicity of Gaseous Thermal Decomposition Products of Unsaturated Polyester Resin

This work proposed an idea of recycling in preparing Co–Ni layered double hydroxide (LDH)-derived flame retardants. A novel and feasible method was developed to synthesize CO–Ni LDH-decorated graphene oxide (GO) and carbon nanotubes (CNTs), by sacrificing bimetal zeolitic imidazolate frameworks (ZIFs). Organic ligands that departed from ZIFs were recyclable and can be reused to synthesize ZIFs. ZIFs, as transitional objects, in situ synthesized on the surfaces of GO or CNTs directly suppressed the re-stacking of the carbides and facilitated the preparation of GO@LDHs and CNTs@LDHs. As-prepared hybrids catalytically reduced toxic CO yield during the thermal decomposition of unsaturated polyester resin (UPR). What is more, the release behaviors of aromatic compounds were also suppressed during the pyrolysis process of UPR composites. The addition of GO@LDHs and CNTs@LDHs obviously inhibited the heat release and smoke emission behaviors of the UPR matrix during combustion. Mechanical properties of the UPR matrix also improved by inclusion of the carbides derivatives. This work paved a feasible method to prepare well-dispersed carbides@Co–Ni LDH nanocomposites with a more environmentally friendly method

Novel Flame-Actuated Soft Actuator Based on a Multilayer Liquid Crystal Elastomer/Hydrogel Composite

A novel flame-actuated soft actuator based on a multilayer liquid crystal elastomer/hydrogel composite was fabricated in this work. Flame is a preferable external stimulus over light, heat, and electricity in terms of its abundant accessibility in a fire scenario. Nevertheless, employing flame as the external stimulus introduces novel challenges for soft actuator materials as they must possess incombustible properties. Here, hydrogel layers are grafted on both surfaces of the liquid crystal elastomer (LCE), resulting in the fabrication of a trilayered LCE-hydrogel composite. The LCE-hydrogel composite demonstrates remarkable flame retardancy, shape memory performance, and tailorable surface adhesion. The hydrogel’s remarkable water absorption and heat insulation properties confer excellent flame retardancy to the composite, preventing ignition for at least 10 s during the open flame test. The shape memory performance is attributed to the orientation of the internal LCE layer and the flexibility of the external hydrogel layers. The surface adhesion of the hydrogel layers is tailored by adjusting their water content. As the water content decreases from 100 to 60%, the surface adhesion energy increases from 6.2 to 70.3 J/m2. A flame-actuated, clip-like soft robot capable of cyclically grasping and releasing objects was constructed, showcasing its promising application potential. This work presents an unprecedented flame-actuated LCE-based composite for the first time, which offers a fresh perspective for researchers to investigate alternative actuation approaches in the field of soft robotics

Novel Flame-Actuated Soft Actuator Based on a Multilayer Liquid Crystal Elastomer/Hydrogel Composite

A novel flame-actuated soft actuator based on a multilayer liquid crystal elastomer/hydrogel composite was fabricated in this work. Flame is a preferable external stimulus over light, heat, and electricity in terms of its abundant accessibility in a fire scenario. Nevertheless, employing flame as the external stimulus introduces novel challenges for soft actuator materials as they must possess incombustible properties. Here, hydrogel layers are grafted on both surfaces of the liquid crystal elastomer (LCE), resulting in the fabrication of a trilayered LCE-hydrogel composite. The LCE-hydrogel composite demonstrates remarkable flame retardancy, shape memory performance, and tailorable surface adhesion. The hydrogel’s remarkable water absorption and heat insulation properties confer excellent flame retardancy to the composite, preventing ignition for at least 10 s during the open flame test. The shape memory performance is attributed to the orientation of the internal LCE layer and the flexibility of the external hydrogel layers. The surface adhesion of the hydrogel layers is tailored by adjusting their water content. As the water content decreases from 100 to 60%, the surface adhesion energy increases from 6.2 to 70.3 J/m2. A flame-actuated, clip-like soft robot capable of cyclically grasping and releasing objects was constructed, showcasing its promising application potential. This work presents an unprecedented flame-actuated LCE-based composite for the first time, which offers a fresh perspective for researchers to investigate alternative actuation approaches in the field of soft robotics

Novel Flame-Actuated Soft Actuator Based on a Multilayer Liquid Crystal Elastomer/Hydrogel Composite

A novel flame-actuated soft actuator based on a multilayer liquid crystal elastomer/hydrogel composite was fabricated in this work. Flame is a preferable external stimulus over light, heat, and electricity in terms of its abundant accessibility in a fire scenario. Nevertheless, employing flame as the external stimulus introduces novel challenges for soft actuator materials as they must possess incombustible properties. Here, hydrogel layers are grafted on both surfaces of the liquid crystal elastomer (LCE), resulting in the fabrication of a trilayered LCE-hydrogel composite. The LCE-hydrogel composite demonstrates remarkable flame retardancy, shape memory performance, and tailorable surface adhesion. The hydrogel’s remarkable water absorption and heat insulation properties confer excellent flame retardancy to the composite, preventing ignition for at least 10 s during the open flame test. The shape memory performance is attributed to the orientation of the internal LCE layer and the flexibility of the external hydrogel layers. The surface adhesion of the hydrogel layers is tailored by adjusting their water content. As the water content decreases from 100 to 60%, the surface adhesion energy increases from 6.2 to 70.3 J/m2. A flame-actuated, clip-like soft robot capable of cyclically grasping and releasing objects was constructed, showcasing its promising application potential. This work presents an unprecedented flame-actuated LCE-based composite for the first time, which offers a fresh perspective for researchers to investigate alternative actuation approaches in the field of soft robotics

Novel Flame-Actuated Soft Actuator Based on a Multilayer Liquid Crystal Elastomer/Hydrogel Composite

A novel flame-actuated soft actuator based on a multilayer liquid crystal elastomer/hydrogel composite was fabricated in this work. Flame is a preferable external stimulus over light, heat, and electricity in terms of its abundant accessibility in a fire scenario. Nevertheless, employing flame as the external stimulus introduces novel challenges for soft actuator materials as they must possess incombustible properties. Here, hydrogel layers are grafted on both surfaces of the liquid crystal elastomer (LCE), resulting in the fabrication of a trilayered LCE-hydrogel composite. The LCE-hydrogel composite demonstrates remarkable flame retardancy, shape memory performance, and tailorable surface adhesion. The hydrogel’s remarkable water absorption and heat insulation properties confer excellent flame retardancy to the composite, preventing ignition for at least 10 s during the open flame test. The shape memory performance is attributed to the orientation of the internal LCE layer and the flexibility of the external hydrogel layers. The surface adhesion of the hydrogel layers is tailored by adjusting their water content. As the water content decreases from 100 to 60%, the surface adhesion energy increases from 6.2 to 70.3 J/m2. A flame-actuated, clip-like soft robot capable of cyclically grasping and releasing objects was constructed, showcasing its promising application potential. This work presents an unprecedented flame-actuated LCE-based composite for the first time, which offers a fresh perspective for researchers to investigate alternative actuation approaches in the field of soft robotics