Excellent Thermal Insulation Properties Research Articles

Thermal Performance Assessment of Aerogel Application in Additive Construction of Energy-Efficient Buildings

The main development direction of energy efficiency technologies in construction is the creation of various materials with complex structures and unique strength, thermal properties, and other properties. The aerogel is a material with high porosity and excellent thermal insulation properties. This paper provides state-of-the-art aerogel applications for the additive manufacturing of energy-efficient buildings. This work provides the experimental and numerical assessment results of the thermal conductivity of aerogel-enhanced blanket, the experimental assessment results of thermal performance of aerogel-enhanced building structure, the experimental assessment results of the aerogel application as a mixture powder component of the concrete mixture to printing buildings, and the experimental assessment results of the aerogel application as a parget powder component. Experimental results show the effect of aerogel powder component application: thermal conductivity decreased by 25%.

Study on the hydration reaction and pore structure of ecologically recycled mortar with corn cob aggregates

Ecologically recycled mortar with corn cob aggregates becomes a research hotspot. However, corn cobs consist of organic materials which have a negative impact on the hydration process of cement. Therefore, a knowledge of the effects of corn cob particle dosage on the hydration reaction process and microscopic pore is important. In this study, nuclear magnetic resonance (NMR) was used to quantitatively and visually observe the hydration reaction of the mortar, and it was found that the addition of corn cob particles resulted in a 22-fold increase in harmful pores and a 20% decrease in pore complexity. Moreover, the effects of corn cob particles on self-shrinkage after the exothermic hydration of mortar was investigated. The result demonstrates that mortar with corn cob particles exhibits a certain degree of plasticity and can bear a certain amount of load, while retaining up to 20% of its deformation energy. Despite the decrease of strength, high admixtures of corn cob particles have excellent thermal insulation properties. This attribute endows corn cob pellet eco-mortar (EM) with the ability to resist external loads, such as those caused by earthquakes and uneven settlement, and thus, provides this material with the potential to be utilized as a wall material.

Abundance and potential sources of floating polystyrene foam macro- and microplastics around Japan

Polystyrene foam is widely used due to its lightweight, impact resistance, and excellent thermal insulation properties. Meanwhile, weak adhesion between beads in polystyrene foam leads to fragmentation, generating a substantial amount of microplastics (<5 mm). Such polystyrene foam debris littered on beaches diminishes the aesthetic value of coastal areas, negatively impacting tourism. Due to its density lower than other plastics, polystyrene foam macroplastics float on the sea surface and, thus, they are significantly influenced by wind drag during oceanic transport. In contrast, polystyrene foam microplastics drifting beneath the sea surface are carried mostly by ocean currents. These properties of polystyrene foam macroplastics and microplastics hinder the elucidation of their transport, distribution, and fate in nature, despite their potential to adversely impact marine ecosystems. To elucidate the generation, transport, and fragmentation processes of polystyrene foam ocean plastics, we conducted concurrent visual observations and surface net towing from seven training vessels around Japan during 2014–2020. Overall, the abundances of polystyrene foam ocean plastics were higher in the Sea of Japan than in the North Pacific south of Japan. The average abundances of polystyrene foam microplastics and macroplastics were 0.33 pieces/m3 and 0.45 pieces/km, respectively, over the entire sea area around Japan. In the Sea of Japan, the peak abundances of polystyrene foam macroplastics occurred in upstream of the Tsushima Current, while the peak for microplastics occurred downstream, suggesting that continuous fragmentation occurred during transport between the two peaks. Backward-in-time particle tracking model experiments suggested that the sources of polystyrene foam macroplastics observed in the Sea of Japan included aquaculture buoys and styrene debris beached around the Tsushima Strait. The present study demonstrated that reducing the release of polystyrene foam aquaculture floats will likely diminish the abundance of ocean plastics in the Sea of Japan.

Ultra-flexible TiO2/SiO2 nanofiber membranes with layered structure for thermal insulation

High-performance thermally insulating ceramic materials with excellent mechanical and thermal insulation properties are essential for thermal management in extreme environments. In this work, SiO2 was introduced into the crystalline lattice and grain boundary of TiO2 to inhibit its phase transition and grain growth. Meanwhile, layered TiO2/SiO2 nanofiber membranes (TS NFMs) were designed and prepared. The TS NFMs had lightweight (44 mg/cm3), high tensile strength (4.55 MPa), ultra-flexibility, and low thermal conductivity (31.5 mW m−1·K−1). The prepared TS-1100 NFMs had excellent buckling fatigue resistance, which could undergo 100 buckling-recovery cycles at up to 80% strain. Low density and high diffuse reflectance endow the TS NFMs with excellent thermal insulation effects. A single-layer nanofiber membrane was composed of multiple layers of nanofibers. According to the principle of multi-level reflection, the multilayer structure had a better near-infrared reflection effect. Through the stacking effect of layers, a 10 mm thick sample composed of about 300 layers of nanofiber membranes could reduce the hot surface temperature from 1200 °C to about 220 °C, demonstrating an excellent comprehensive thermal insulation effect. The layered TS NFMs with ultra-flexibility, high tensile strength and high-temperature resistance (1100 °C) provide a dominant pathway in producing materials in extremely high-temperature environments.

Reusable, high specific surface areas, and excellent thermal stability Al2O3–SiO2 aerogel composites as high-temperature thermal insulators for radome applications

In this study, monolithic Al2O3–SiO2 aerogels with excellent thermal stability and high specific surface area were synthesized using boehmite nanorods (L=20–30 nm, D=3–5 nm). The high specific surface area of aerogels was maintained after calcination at 800 °C (663.54 m2/g), 1000 °C (486.91 m2/g), and 1100 °C (230.76 m2/g). The anti-sintering mechanism of the Al2O3-SiO2 aerogels was discussed. Thanks to the composite of Al2O3-SiO2 aerogel and mullite fibers, the disadvantages of brittleness and low strength of aerogel are overcome. The thermal conductivity of the composite is extremely low at 0.034 W/(m·K)-0.089 W/(m·K) (25 °C-1000 °C). Five muffle cycle back-temperature tests at 1000 °C and a butane blowtorch back-temperature test at 1350 °C also proved that the composites have excellent thermal insulation properties. Composites with excellent thermal insulation properties combined with lightweight, thinness, machinability, and good dielectric properties meet the need for high-temperature thermal insulating-wave transmitting integrated materials for hypersonic missile radomes.

High thermally conductive polyimide film designed with heterostructural Cring-C3N4 filler and multilayer strategy

With the emerging of advanced flexible electronic, the PI film with excellent thermally conductive, flexible, lightweight, electrically insulating qualities is in high demand as a potential substrate and encapsulation material. Conventional thermally conductive fillers such as ceramic, metal and carbon material with high hardness, high density or electrical conductivity are unsuitable to prepare the advanced PI film. Furthermore, the confined loading of thermally conductive filler in PI matrix limited by its film-forming property is another obstacle to optimizing the thermal conductivity of PI film. In this work, the development of novel filler (carbon nitride in-plane grafted by two-dimensional carbon material, Cring-C3N4) with intrinsic thermal conductivity and a design of three-layer structure for the introduction of high filler loading have dramatically improved the thermal conductivity of PI film. Benefitting by the planar heterostructure construction of g-C3N4 and Cring, the existence of Cring increases the phonon transfer rate in g-C3N4, and the presence of g-C3N4 prevents the electron movement in the facet of Cring-C3N4 endowing its excellent electrical insulation property. The design of three-layer structure in which the first and third layers served as mechanical support layers with a fixed filler content (20 wt%). The second layer has the higher filler content to enhance the quantity of thermally conductive filler in PI film. Resultantly, the maximum out-of-plane thermal conductivity of the PI/Cring-C3N4 composite film is 1.35 Wm−1K−1, which is 10 times higher than the pure PI film. In addition, the PI/Cring-C3N4 composite film exhibit excellent photothermal conversion ability in which the saturation temperature of PI/Cring-C3N4 can reach 283.6 °C under 0.75 W/cm2 laser radiation being 6 times higher than that of the corresponding PI film. After the incorporation of Cring-C3N4, the PI composite film still has excellent thermal stability, low CTE, electrical insulation and mechanical properties. This work provides a novel idea for the preparation of advanced high thermal conductivity PI film.

Emerging Trends in Sustainable Materials for Green Building Constructions

The national decision on the neutrality of global carbon emission as well as decarbonization focus drives the need for the transformation of the building and construction sector of the economy. Thus, green building materials and its production is a better means of achieving depletion in carbon emission. More so, to achieve excellent green development in the construction industry as well as the goal of decarbonization, there is a need to investigate the emerging trends in the sustainable materials for green buildings. Hence, this study focused on the review of some of the existing green materials and its effect on the building construction. Findings from literature studies revealed six different green building materials which include bamboo, cork, straw bale, reclaimed wood, sheep’s wool and hempcrete. It was reported that each of the green material have excellent thermal insulation property, low emission of CO2 and has the ability to be recycled, thus, bringing sustainability in the circular economy as well as eco-friendliness of the material. These findings expand the scope of green materials application and can inform the government to formulate policies that will encourage sustainable green buildings. Keyword: Sustainability, Development, Green Buildings, Green Materials, Emissions

Laser Ablation‐Induced Boron Nitride Aerogels with Intrinsic Photoluminescence for Efficient Information Encryption

AbstractBoron nitride (BN) aerogels, dual interconnecting network of BN nanoscale building blocks, and plenty of air within these nanoscale building blocks, have great potential in many emerging fields. However, fast synthesis and emerging applications, e.g., information encryption, are still challenging for advancing BN aerogels. Herein, intrinsic photoluminescent BN aerogels with programmable patterns are developed via laser ablating of melamine diborate (M2B) aerogel. The obtained BN aerogel exhibited typical hollow‐microsphere structures and blue fluorescence phenomenon, which are totally different from BN aerogels reported elsewhere. This BN aerogel exhibited excellent thermal insulation properties (0.027 W mK−1), transient fluorescence feature (3 ns average radiative lifetime), high quantum yield (18.45%), and excellent weather ability (e.g., resistance to high temperature, solar irradiation, and humidness). By programming the laser moving path, different fluorescent patterns (e.g., various security labels, secret matching keys, quick response codes) of BN aerogels can be processed, which promises excellent information encryption in the field of Internet of Things, etc. The results may inspire researchers to fabricate more aerogels with this fast laser‐ablation strategy and the resulting intrinsic fluorescent BN aerogels may find significant applications in some emerging fields.

Bending performance and failure modes of sinusoidal corrugated sandwich panels fabricated using stereolithography technology: Effects of geometric parameters

The sinusoidal wave corrugated sandwich panel is an exceptional component with outstanding performance, making it highly suitable for both military and civilian applications. Its strength, rigidity, lightweight nature, low density, simple structure, cost-effectiveness, high load-carrying efficiency, remarkable load-bearing capacity, as well as excellent sound insulation and thermal insulation properties, have positioned the sinusoidal wave corrugated sandwich panel as an ideal choice for energy absorption devices. To evaluate the bending performance of the sinusoidal wave corrugated sandwich panel, this study fabricated single-layer and double-layer sinusoidal wave core sandwich panels using the light-curing molding process described in this research. The research analyzed the impact of various geometric parameters, including skin thickness, core layer thickness, core height, and corrugation wavelength, on the bending performance and failure modes of the single-layer sinusoidal wave core sandwich panels through three-point bending loading tests. The failure modes of the sinusoidal wave corrugated sandwich panel were validated using finite element simulation. Additionally, the study examined the bending performance of the sandwich panels with double-layer sinusoidal wave cores and investigated the influence of wavelength distribution in the upper and lower core layers on the force–displacement curve and energy absorption capacity of the double-layer sinusoidal wave core sandwich panel. These findings provide valuable theoretical support for the design of lightweight and high-strength sandwich panels.

Environment-friendly, high-performance cellulose nanofiber-vanillin epoxy nanocomposite with excellent mechanical, thermal insulation and UV shielding properties

With the increased demand for biobased epoxy thermosets as an alternative to petroleum-based materials in various fields, developing environment-friendly and high-performance natural fiber-biobased epoxy nanocomposites is crucial for industrial applications. Herein, an environment-friendly nanocomposite is reported by introducing cellulose nanofiber (CNF) in situ interaction with lignin-derived vanillin epoxy (VE) monomer and 4, 4´-diaminodiphenyl methane (DDM) hardener that serves as a multifunctional platform. The CNF-VE nanocomposite is fabricated by simply dispersing the CNF suspension to the VE and DDM hardener solution through the in-situ reaction, and its mechanical properties and thermal insulation behavior, wettability, chemical resistance, and optical properties are evaluated with the CNF weight percent variation. The well-dispersed CNF-VE nanocomposite exhibited high tensile strength (∼127.78 ± 3.99 MPa) and strain-at-break (∼16.49 ± 0.61 %), haziness (∼50 %) and UV-shielding properties. The in situ loading of CNF forms covalent crosslinking with the VE and favors improving the mechanical properties along with the homogeneous dispersion of CNF. The CNF-VE nanocomposite also shows lower thermal conductivity (0.26 Wm−1K−1) than glass. The environment-friendly and high-performance nanocomposite provides multiple platforms and can be used for building materials.

Research on the heat resistance and electrical properties of fluorinated polyimide/nano-Al2O3/nano-Si3N4 composite materials

Polyimide (PI) refers to a polymer containing an imide ring characteristic structure on the main chain. It has excellent thermal stability, insulation properties and other characteristics. The Tesla transformer is the core component of the primary pulse source of the high-current electron beam accelerator. It is also an essential component of the energy storage pulse power supply. Therefore, it has broad application prospects in the fields of national defense and civil industry. If the insulation performance of the turn-to-turn coils of the Tesla transformer does not meet the standards, it will break down during high-voltage corona discharge, causing transformer failure. Therefore, it is crucial to improve the insulation performance of Tesla transformer inter-turn wrapping materials. The incorporation of fluorine-containing groups has proven to be a transformative strategy that significantly enhances the physical, chemical, optical, and electrical properties of PI films. In addition, numerous studies have demonstrated that introducing inorganic fillers into the polyimide matrix can substantially enhance the insulating properties of polyimide films. This paper specifically concentrates on elevating the insulating and thermal attributes of polyimide. Initially, a range of polyimide films was synthesized for performance assessment by employing various fluorinated dianhydride and diamine components, utilizing them as substrates. Then, we used nano-silicon nitride (nano-Si3N4) and nano-alumina (nano-Al2O3) as doping phases to prepare PI composite films, which reduced the dielectric constant and increased the breakdown strength.

An efficient fabrication method of lightweight aramid nanofibrous aerogels for high-efficient sound absorption and thermal properties

The aramid nanofibrous aerogels (ANFs) have various application prospects due to their ultra-light, high porosity and excellent properties of aramid fibers. However, the preparation of ANFs requires long preparation time and their ultra-dense pore structure leads to poor sound penetration and high sound energy reflectivity, which ultimately makes the overall sound absorption performance of ANFs poor. Therefore, a strategy for synthesis of ANFs is designed to achieve light weight, excellent thermal insulation performance and significantly improve sound absorption properties. This strategy combines cell pulverizing, pump-filtration molding, and directional freezing to ensure structural strength of the aerogel without the addition of cross-linking agents, and this process enables the ANFs to introduce in macro-pores while keeping nano-pores. The structure of multi-layered pores effectively reduces the reflectivity of incident acoustic energy and improves the sound absorption coefficient. The interconnected macro-pores and interlaced small pores of ANFs provide good sound absorption performance (sound absorption average (SAA) = 0.338), excellent flame retardant and thermal insulation properties (thermal conductivity = 0.0635 W (m*K)−1) with ultralight (density = 40.5 mg cm−3) in a thinner thickness (15 mm), which extend the potential of ANFs in areas of noise control and thermal insulation. In addition, the structure of multi-scaled pores can also be formed inside other aerogels by using the method of cell pulverization and filtration preparation, which can be helpful for improving their properties of thermal insulation and sound absorption.

Advanced hydrostable, recyclable and degradable cellulose hybrid films as renewable alternatives to synthetic plastics

Strong, tough and sustainable materials are in high demand in various engineering applications. We demonstrate a potential sustainable hybrid film made from natural cellulose and a biobased slurry. Through a simple and scalable approach, cellulose can be processed into an advanced material with over 2.8 and 9.2-fold increase in dry strength and toughness after curing and a 728-fold increase in wet strength, respectively. In addition, these hybrid composite films display an outstanding antioxidant activity surpassing 90 %, along with excellent ultraviolet radiation shielding and thermal insulation properties. Further, the hybrid films can be fabricated by integrating all-natural materials and still guarantee their unique functionality. We also demonstrate the feasibility of a circular bioeconomy by recycling the hybrid film using a green, deep eutectic solvent to fabricate a recycled hybrid film that displays excellent mechanical and optical properties. When recycling is unsuitable or economical, the hybrid film can naturally degrade in the soil under 6 months. These encouraging findings suggest the promise of cellulose hybrid films as a renewable, low-cost, tough, and strong material with the potential to replace nonrenewable synthetic plastics and products.

Preparation of multi-functional sepiolite-based foam concrete and its adsorption and thermal insulation properties

Abstract Foam concrete is one of the most valuable porous materials used in civil and industrial buildings. Sepiolite, a fibrous hydrous magnesium silicate, possesses exceptional qualities such as a low thermal conductivity, non-polluting nature, and eco-friendliness. In this paper, a multi-functional sepiolite-based foam concrete has been fabricated using a physical foaming technology. The high sepiolite content and unique hierarchical structure endow the foam concrete with excellent adsorption and thermal insulation properties. The foam concrete exhibits a high adsorption capacity towards methanal and ammonia gases. Furthermore, the foam concrete, with its high porosity and good forming ability, shows great potential for application in thermal-insulation materials and wastewater treatment.

Triple‐chain segments regulation enable shape memory and photo deformation of smart polyimide

AbstractIntegration of controllable deformation with excellent thermal stability, mechanical, and insulation properties can greatly expand the versatility of smart polyimides (PIs). However, the unique molecular structure of PI makes it difficult for its molecular chain to move, which is not conducive to the reversible transformation of highly stable PI under environmental conditions. In this study, a PI film integrating shape memory and photo deformation is prepared by constructing a chemical network with PI oligomer as the hard, hexamethylene diisocyanate (HDI) as the soft, and azobenzene as the functional chain segment. The PI films still have a high glass transition temperature Tg ~ 225°C, a high Young's modulus E ~ 3.5 GPa, and a good breakdown strength Eb ~ 176 kV/mm. Moreover, as the network point of the chemical network, the trifunctional crosslinking agent makes the PI produce the shape memory effect induced by light and heat. UV light can drive crosslinked photoresponsivity PI film to have special shape transformation under specific conditions, using azobenzene as photoresponsivity group. This study provides a new idea for the preparation of multifunctional PI, which makes it potentially applicable in the field of smart electric and electronic engineering.

Dual cross-linked and vertically oriented MXene/polyvinyl alcohol aerogel for ultrabroadband electromagnetic interference shielding and thermal camouflage

Lightweight and porous conductive aerogels have demonstrated great potential in electromagnetic interference (EMI) shielding and thermal camouflage, while the poor mechanical properties and structural stability usually limit their applications. Herein, vertically oriented and physically/chemically dual cross-linked Ti3C2TX MXene/polyvinyl alcohol (PVA) composite aerogel is prepared by ice-templated unidirectional freezing process and subsequent glutaraldehyde (GA) treatment. GA induced covalent crosslinking leads to the significantly enhanced structural stability and mechanical strength of the resultant MXene/PVA composite aerogels, which also endows them with desirable flame retardancy. The honeycomb-like structure of the composite aerogel contributes to its good anisotropic absorption-dominated EMI shielding performance over an ultrabroadband frequency range (8.2–40 GHz) with a low MXene content of 3.81 vol%. Furthermore, the excellent thermal insulation properties and low infrared emissivity of the highly oriented arranged MXene sheets bring the composite aerogel promising applications in thermal camouflage. Therefore, the lightweight and robust MXene/PVA composite aerogel demonstrates great potential in multi-scenario applications as a high-performance multifunctional EMI shielding material.

Lightweight, robust, porous heterocyclic para‐aramid aerogel hollow fibers for multifunctional applications

AbstractIn nature, many fibers with warmth‐retention properties, such as the hair of polar bears and rabbits, both have a hollow cross‐section structure. The static air in fiber cavities can effectively inhibit heat conduction and serve as an effective thermal insulator. In this work, the high‐performance heterocyclic para‐aramid polymer was selected as the spinning solution, and aerogel hollow fiber was prepared by coaxial wet spinning and freeze‐drying techniques. The effects of spinning solution concentration and lyophilized solvent on the micromorphology, mechanical properties, and specific surface area of heterocyclic para‐aramid aerogel hollow fiber (HPAAHF) were systematically studied. The produced HPAAHF possessed excellent mechanical properties (tensible strength ~3.85 MPa), high specific surface area (~ 260.90 m2 g−1), and lightweight advantages. The thermal conductivity of HPAAHF was only 0.0278 W m−1 K−1, indicating its excellent thermal insulation properties. The aerogel fabric exhibited outstanding flame retardancy properties, with a total heat release of only 0.7 MJ m−2 in the cone calorimetric experiment, making it a self‐extinguishing fabric. In addition, phase change material was injected into the hollow structure to obtain aerogel‐phase change material composite fibers, which exhibited great energy storage prospects. As a result, the high‐performance heterocyclic para‐aramid polymer‐based aerogel hollow fiber was successfully prepared and had multifunctional applications in thermal insulation, flame retardancy, and heat energy storage fields.

Facile construction strategy for intrinsically fire-safe and thermal-insulating bio-based chitosan aerogel

Bio-based aerogels have become a research hotspot in the emerging fields because of their remarkable biocompatibility, degradability and light weight, but their low strength and flammability limits their further application. In this study, chitosan (CS) containing flame retardant element was selected as the matrix, and a lightweight, flame retardant and thermal insulating CS aerogel was successfully prepared by the ion exchange between methylphosphonic acid (MPA) and acetic acid (HAc), and directional freeze-drying technology. The compressive strength and elastic modulus of CS@MPA aerogel were 15.2% and 8.5% higher than that of CS@HAc aerogel due to the 3D cross-linking structure between MPA and CS. Compared with CS@HAc aerogel, CA@MPA1.1 aerogel demonstrated excellent thermal insulating properties, and its thermal conductivity (25.46 mW/mK) was significantly lower than that of air (26.7 mW/mK). The introduction of MPA promoted the degradation and charring of CA@MPA aerogel, and the formation of high quality char layer efficiently exerted the barrier effect. Meanwhile, the phosphorus oxygen radicals and inert gases from the decomposition of CS@MPA aerogels effectively decreased the combustion intensity in gas phase. Therefore, the PHRR and THR of CS@MPA1.1 aerogels were decreased by 91.7% and 69.5% compared to CS@HAc aerogels. In summary, CS@MPA aerogel not only conforms to the current concept of sustainable development, but also possessed excellent thermal insulation, mechanical, and fire safety properties. It is expected to replace the traditional petrochemical-based materials, and shows broad application prospects in the fields of building insulation and energy storage.

Mechanical properties evolution of clays treated with rice husk ash subjected to freezing-thawing cycles

Rapidly growing urbanization and industrialization drive the continued development of soil stabilization and ground improvement techniques. Rice husk ash (RHA) is widely regarded as a highly promising construction material in civil engineering due to its excellent pozzolanic properties and has garnered significant attention from researchers. This paper presents an experimental study and a micro-mechanical discussion on the role of RHA in the mechanical improvement of soil. RHA was mixed with the native soil in varying proportions, ranging from 0% to 12%. Several laboratory tests were conducted, including standard proctor compaction tests, Atterberg limit tests, freeze-thaw tests, unconfined compression tests, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). The results indicated that the optimal moisture content (OMC) of the soil mixture increased while the maximum dry density (MDD) decreased with higher RHA dosage. The Atterberg limits of the soil mixture exhibited a positive correlation with the RHA content. A substantial enhancement in the soil's strength, stiffness, and ductility was observed upon the incorporation of RHA. It was noted that the strength loss of the untreated samples and those with 12% RHA was 34.91% and 12.89%, respectively, following 12 freeze-thaw cycles. Furthermore, XRD test results revealed that the treated specimen had an identical mineral composition to the control specimen, with no generation of hydration products. SEM analysis also highlighted that the filling effect of RHA significantly reduced pore content and pore connectivity within the soil, accompanied by a shift in the specimen's pores from mesopores to small and micropores. The excellent thermal insulation and heat retention properties of RHA, along with its pore-refining effect, make a positive contribution to enhancing the frost resistance of the specimens. These findings contribute to guiding the effective application of RHA in civil engineering, offering eco-friendly solutions for biomass waste management, and promoting the sustainable development of construction materials.

Preparation of DOPO coated conjugated microporous polymer hollow nanospheres with excellent flame retardancy and thermal insulation

Materials with thermal insulation and flame retardant properties are highly sought after in construction industry. In this study, two hollow-structured conjugated microporous polymer spheres (HCMPs) were successfully synthesized via the template method by polymerizing 1,3,5-triethynylbenzene with 3-amino-2,6-dibromopyridine and 2-amino-3,5-dibromopyridine respectively. To enhance flame retardant properties, HCMPs were impregnated with ethanol-soluble 6 H-dibenzo (C, E) (1,2) phosphine oxide-6-oxide (DOPO) (named as HCMP-FR), which maintains a hollow structure, enabling it to serve as a heat insulator, as observed under transmission electron microscope (TEM). The two types of HCMP-FR with a thermal conductivity of 0.047 W m−1 K−1 and 0.051 W m−1 K−1 respectively, exhibit excellent thermal insulation property. HCMP-FRs were added in to epoxy resin (EP) composites to further investigate the property of it. Under addition of 1.3%wt HCMP1-FR and HCMP2-FR, the thermal conductivity of EP composites (0.159 W m−1 K−1 and 0.146 W m−1 K−1) decreased by 25.3% and 31.4% compared with pure EP composites respectively, and the density (0.651 g cm−3 and 0.8 g cm−3) decreased by 42.1% and 22.5%, significantly reducing EP's thermal conductivity and density. The cone calorimeter (CC) tests show that the pHRR of EP composites at 0.6%wt addition was 859.04 kW m−2 and 904.35 kW m−2, respectively, which were 17.5% and 13.1% lower than that of pure EP, and the TSP decreased by 44.9% and 41.3% when 1.3% HCMP-FRs was added, which shows an excellent smoke depressing property. Therefore, the HCMP-FRs synthesized have highly promising for application in thermal insulation and flame retardancy of energy saving building.