High-performance Thermal Insulation Materials Research Articles

Lightweight, ultrahigh-strength and flame-retardant cellulose aerogel crosslinked with a reactive P/N-rich curdlan derivative

Cellulose aerogel, recognized for its eco-friendliness, bio-sustainability and excellent thermal insulation property, holds immense potential as an insulation material. However, the application of cellulose aerogel has been hindered by its inherent drawbacks, particularly its low strength and flammability. In this study, a reactive P/N-rich curdlan derivative (NT) was synthesized and characterized. Lightweight, ultrahigh-strength and flame-retardant composite aerogels were then prepared by slow freezing, freeze-drying and chemical crosslinking methods. Composite aerogel crosslinked with 30% NT exhibited exceptional thermal insulation property with a low thermal conductivity of 33.9 mW/(m·K), which rivaled the value of petroleum-based thermal insulation materials. It possessed an ultrahigh compressive modulus (0.786 MPa) at low density (21.6 mg/cm3), which supported >12,000 times its weight. It also displayed superior flame-retardant property, with a limiting oxygen index of up to 33.1% and a V-0 rating in the UL-94 test. This study provides a new insight into the high-value utilization of natural polysaccharide and an innovative solution to the problem of low strength and flammability of cellulose aerogel. Cellulose aerogels with ultrahigh strength, superior flame retardancy and thermal insulation property possess a promising application in the fields of construction, aerospace and thermal protective clothing as high-performance thermal insulation materials.

Fire-resistant and thermal-insulating alginate aerogel with intelligent bionic armor for exceptional mechanical and fire early-warning performance

Intelligent bio-based aerogels have attracted increasing attention in several key areas due to their unique porous structure and sustainability, but they suffer from poor fire safety, strength, and durability under harsh conditions. Here, we prepared sodium alginate/hydroxyapatite/graphene oxide (SA@HAP@GO) aerogel by in-situ growth and directional assembly technology, and an intelligent “bionic armor” was put on the surface of SA aerogel. It not only endows aerogel with high strength (2.3 MPa) and long-time water resistance (30 days) but also maintains the lightweight (0.039 g cm−3) and thermal insulation properties (0.03537 W m-1K−1) of original aerogel. Under fire conditions, the compact physical barrier makes aerogel obtain the excellent fire-resistant stability and fire-safety performance. Besides, the directional assembly of GO and the chelating effect of Ca2+ on aerogel surface promote the formation of a three-dimensional electron transport network during reduction process, thus achieving a fast and long-lasting fire early-warning response (1.95 s). The corresponding mechanism was demonstrated by molecular theoretical calculation and experiments. This multifunctional aerogel provides a new way for sustainable and high-performance thermal-insulation materials and shows a wide application in energy security.

Ceramic Fiber-Reinforced Polyimide Aerogel Composites with Improved Shape Stability against Shrinkage.

Polyimide (PI) aerogels, renowned for their nano-porous structure and exceptional performance across a spectrum of applications, often encounter significant challenges during fabrication, primarily due to severe shrinkage. In this study, we innovatively incorporated ceramic fibers of varying diameters into the PI aerogel matrix to enhance the shape stability against shrinkage. The structure of the resulting ceramic fiber-reinforced PI (CF-PI) aerogel composites as well as their performance in thermal decomposition, thermal insulation, and compression resistance were characterized. The results revealed that the CF-PI aerogel composites dried by supercritical ethanol achieved greatly reduced shrinkage as low as 5.0 vol.% and low thermal conductivity ranging from 31.2 mW·m-1·K-1 to 35.3 mW·m-1·K-1, showcasing their excellent performance in shape stability and thermal insulation. These composites also inherited the superior residue-forming ability of ceramic fibers and the robust mechanical attributes of PI, thereby exhibiting enhanced thermal stability and compression resistance. Besides, the effects of different drying conditions on the structure and properties of CF-PI aerogels were also discussed. The coupling use of supercritical ethanol drying with the addition of ceramic fibers is preferred. This preferred condition gives birth to low-shrinkage CF-PI aerogel composites, which also stand out for their integrated advantages include high thermal stability, low thermal conductivity, and high mechanical strength. These advantages attribute to CF-PI aerogel composites substantial potential for a wide range of applications, particularly as high-performance thermal insulation materials for extreme conditions.

Carbon/ZrO2 aerogel composite microtube superfoam.

High-performance thermal insulation materials with broad application prospects have attracted great attention. The introduction of new microstructures into thermal protection materials can significantly improve the thermal insulation performance. The tubular microstructure has obvious advantages such as thermal insulation, lightweight, mechanical, and other properties. Therefore, the microtubular structure has become an important reference microstructure for the development of high-performance thermal insulation materials. In this paper, the carbon/ZrO2 aerogel composite microtube superfoams with excellent thermal protection properties were prepared by a vacuum filtration and high-temperature carbonization method. The ZrO2 aerogel precursor solution can be quickly and uniformly adsorbed on the inner and outer walls of cellulose microtubules. These adsorbed ZrO2 aerogel precursor solution films can be converted into ZrO2 alcohol gel shells under the acceleration and promotion effect of citric acid at 65 °C. The micromorphology of the ZrO2 aerogel shell on the inner and outer walls of the composite microtubes can be efficiently controlled by the concentration of the ZrO2 aerogel precursor solution and the carbonization temperature. The carbon/ZrO2 aerogel composite microtube superfoam exhibits a lower thermal conductivity, lower density, good mechanical properties, and high ablation resistance. The thermal conductivity of the carbon/ZrO2 aerogel composite microtube superfoam is as low as 0.040 ± 0.001 W m-1 K-1. The residual rate of the carbon/ZrO2 aerogel composite microtube superfoam is still as high as 84.33% after butane flame ablation for up to 3600 seconds.

Direct Synthesis of Polyimide Curly Nanofibrous Aerogels for High-Performance Thermal Insulation Under Extreme Temperature.

Maintaining human body temperature is one of the basic needs for living, which requires high-performance thermal insulation materials to prevent heat exchange with external environment. However, the most widely used fibrous thermal insulation materials always suffer from the heavy weight, weak mechanical property, and moderate capacity to suppress heat transfer, resulting in limited personal cold and thermal protection performance. Here, an ultralight, mechanically robust, and thermally insulating polyimide (PI) aerogel is directly synthesized via constructing 3D interlocked curly nanofibrous networks during electrospinning. Controlling the solution/water molecule interaction enables the rapid phase inversion of charged jets, while the multiple jets are ejected by regulating charge density of the fluids, thus synergistically allowing numerous curly nanofibers to interlock and cross-link with each other to form porous aerogel structure. The resulted PI aerogel integrates the ultralight property with density of 2.4mg cm-3, extreme temperature tolerance (mechanical robustness over -196 to 300 °C), and thermal insulation performance with ultralow thermal conductivity of 22.4mW m-1 K-1, providing an ideal candidate to keep human thermal comfort under extreme temperature. This work can provide a source of inspiration for the design and development of nanofibrous aerogels for various applications.

Preparation of SiO2/Fe2O3 composite aerogels for thermal insulation enhancement

Silica aerogel, with a unique nano-network structure, serves as a high-performance thermal insulation material. However, silica aerogel possesses a high infrared wave transmission ratio above 300 °C, whose thermal conductivity increases and thermal insulation performance further decreases with the increasing temperature. Introducing opacifiers to silica aerogel is a crucial strategy for addressing this issue. In this work, the ferric oxide exerted as an opacifier was incorporated into the main-phase silica aerogel to improve its thermal insulation at high temperatures. The SiO2/Fe2O3 composite aerogels were created via the two-step sol-gel process followed by supercritical drying, which involved doping ferric nitrate nonahydrate as a Fe2O3 precursor into the silica sol generated with tetraethoxysilane. In this way, SiO2/Fe2O3 composite aerogels with low density (0.04 g/cm3), high specific surface area (705 cm2/g), and low thermal conductivity (0.026 W/(m K)) were obtained by structural adjustment. The incorporation of Fe2O3 improves the thermal insulating properties of silica aerogels. After heat treatment at 1100 °C, the thermal conductivity of the SiO2/Fe2O3 composite aerogel was 0.167 W/(m K), lower than that of the pure silica aerogel (0.249 W/(m K)). Furthermore, the SiO2/Fe2O3 composite aerogel maintained its amorphous structure and exhibited a specific surface area of approximately 94.56 cm2/g, which was three times that of the pure silica aerogel. When subjected to 5-min heating at 1000 °C, the maximum surface temperature of the heat delivery surface of the SiO2/Fe2O3 composite aerogel reached 280.8 °C, whereas the pure silica aerogel reached 353.8 °C.

Preparation of DOPO-KH550 modified hollow glass microspheres/PVA composite aerogel for thermal insulation and flame retardancy

The creation of high-performance thermal insulation and flame-retardant materials is of great importance for minimizing energy consumption and reducing fire risk for modern buildings. Herein, we report the creation of a new composite aerogel, which was prepared by incorporation of 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-Oxide-3-Aminopropyl triethoxysilane (DOPO-KH550) modified hollow glass microspheres (HGM) into polyvinyl alcohol (PVA) using citric acid as a cross-linker, as a kind of thermal insulation and flame retardant materials (abbreviated as PVA-DKHGM). The as-synthesized PVA-DKHGM composite exhibits superior thermal conductivity of 0.0187 W m−1 K−1, owing to the hollow structure of the hollow glass microspheres and rich porosity. Besides, it reaches V-0 level at the UL-94 test and the peak heat release rate (pHRR) was measured to be 114.93 (kW/m2) which is lower than most composites now. These results are attributed to the synergy effect of the hollow glass microsphere and DOPO-KH550 which offers the composites aerogel excellent flame retardancy. Owing to its advantages such as lightweight, highly porous, thermally stable, simple to prepare, high mechanical strength, and can be further scaled up, our PVA-DKHGM aerogel may hold great potential for practical applications in construction of energy-saving modern buildings.

Thermal Insulation Mechanism, Preparation, and Modification of Nanocellulose Aerogels: A Review.

Energy problems have become increasingly prominent. The use of thermal insulation materials is an effective measure to save energy. As an efficient energy-saving material, nanocellulose aerogels have broad application prospects. However, nanocellulose aerogels have problems such as poor mechanical properties, high flammability, and they easily absorbs water from the environment. These defects restrict their thermal insulation performance and severely limit their application. This review analyzes the thermal insulation mechanism of nanocellulose aerogels and summarizes the methods of preparing them from biomass raw materials. In addition, aiming at the inherent defects of nanocellulose aerogels, this review focuses on the methods used to improve their mechanical properties, flame retardancy, and hydrophobicity in order to prepare high-performance thermal insulation materials in line with the concept of sustainable development, thereby promoting energy conservation, rational use, and expanding the application of nanocellulose aerogels.

Enhancing thermal insulation and mechanical strength of porous ceramic through size-graded MA Hollow Spheres

In this study, a series of porous ceramics were prepared using different ratios of small and large size MA hollow ceramic spheres as pore-forming agents, and their thermal insulation properties were investigated. The results showed that increasing the proportion of small size hollow ceramic spheres could effectively decrease the thermal conductivity and improve the compressive strength of the porous ceramics. The optimal porous ceramic was prepared with a ratio of 10∼50 of small and large size hollow ceramic spheres, which had a thermal conductivity of 0.368 W/(m·K) at 800 °C and a compressive strength of 22.43 MPa. Microscopic analysis indicated that the enhanced thermal insulation and mechanical properties were due to the improved pore structure and the enhanced bonding strength between the ceramic spheres and the matrix. The findings provide valuable insights for the development of high-performance thermal insulation materials.

Dual-Phasic, Well-Aligned, and Strong Flexible Hydrophobic Ceramic Membranes for Efficient Thermal Insulation in Extreme Conditions.

The inherent brittleness and hydrophilicity of ceramics pose a great challenge to designing a reliable structure that can resist mechanical loads and moisture in extreme conditions with high temperature and high humidity. Here, we report a two-phase hydrophobic silica-zirconia composite ceramic nanofiber membrane (H-ZSNFM) with exceptional mechanical robustness and high-temperature hydrophobic resistance. For the dual-phasic nanofibers, the amorphous silica blocked the connection of zirconia nanocrystals, and the lattice distortion was observed due to Si in the ZrO2 lattice. H-ZSNFM has strong strength (5-8.4 MPa), high hydrophobic temperature resistance (450 °C), high porosity (89%), low density (40 mg/cm3), low thermal conductivity (30 mW/m·K), and excellent thermal radiation reflectivity (90%). By simulating the actual high-temperature and high-humidity environment, 10-mm-thick H-ZSNFMs can reduce the heat source from 1365 to 380 °C and maintain complete hydrophobicity even in a water vapor environment of 350 °C. This means that it has superior insulation and waterproof performance even in a high-temperature water environment. For firefighting clothing, H-ZSNFM displayed waterproof and insulation layers, which have excellent thermal protection performance and achieve incompatibility between water and fire, providing valuable time for fire rescue and a safety line of defense for emergency personnel. This design strategy with mechanical robust and hydrophobic temperature resistance applies to the development of many other types of high-performance thermal insulation materials and presents a competitive material system for thermal protection in extreme conditions.

Fiber-reinforced alumina-carbon core-shell aerogel composite with heat-induced gradient structure for thermal protection up to 1800 °C

High performance thermal insulation materials are urgently demanded for hypersonic spacecraft. Aerogels are considered as promising candidates owing to their low density and low thermal conductivity. However, some deficiencies, such as the unsatisfactory high-temperature thermal insulation properties and the non-exfoliation-resistant particle porous structure of ceramic aerogels, the ease of oxidation and large carbonization shrinkage of carbon aerogels, remain great challenges for their further applications in high-temperature aerobic ablation environments. Here, we report a multiscale fiber-reinforced Al2O3-carbon core–shell aerogel composites with low density (0.23–0.31 g·cm−3), excellent mechanical properties (4.89 MPa at 10% strain) and ultra-low carbonization shrinkage (as low as 1.33%). Benefiting from the synergistic effect of in situ nano-doped light-shading carbon layers, porous Al2O3 ceramic rod skeleton and oriented fibers, the composites demonstrate an extremely low high-temperature thermal conductivity (0.055 W·m−1·K−1 at 1200 °C) that is far superior to those of existing high-temperature insulating aerogel composites. In addition, the unique heat-induced gradient structure also confers outstanding thermal protection properties to the composite at 1800 °C with a liner ablation rate of 6.44 μm·s-1and a mass loss rate of 0.167 mg·s−1. This work not only opens a new path for the preparation of thermal superinsulating materials used for spacecraft, but also provides a simple solution to the difficulty of compatibility between low-density insulating porous skeleton and ablation-resistant tough structures, thereby enabling thermal insulation materials to possess desired ablation-resistant properties.

Halloysite-based aerogels by bidirectional freezing with mechanical properties, thermal insulation and flame retardancy

Halloysite (Hal) is a natural nanotubular clay mineral with the characteristics of low price and easy availability. The aerogels prepared by Hal are low thermal conductivities, good thermal stabilities and low flammability, which have great application prospects in the field of thermal insulation with flame retardancy. However, they typically suffer from inferior mechanical property and difficulty of mechanically resilient or flexible. Herein, aerogels with anisotropic mechanical properties were prepared by bidirectionally freezing aqueous suspensions of Hal with a small proportion of chitosan (CS). The directionally aligned porous structure gave the aerogels prominent strength in the direction of lamellar orientation, and superelasticity in the vertical direction. The Hal-based aerogels showed good performance in the combination of thermal insulation and flame retardancy. The thermal equilibrium temperatures of Hal/CS aerogels at 50 °C and 100 °C are 27.5 °C and 35.2 °C, respectively. They also remained unscathed after 180 s of burning in a candle flame. The present study provided a versatile method for design and fabrication aerogels for high-performance thermal insulation materials and had significance in the high-value utilization of Hal mineral resources.

An efficient approach to fabricate lightweight polyimide/aramid sponge with excellent heat insulation and sound absorption performance

Polyimide sponges have bright prospects in the weight reduction, heat insulation, and sound absorption equipment of aerospace, navigation, and other area due to their unique three-dimensional cellular structure and outstanding comprehensive performance. However, most polyimide sponges suffered from long and complex fabrication processes. Herein, an efficient and scalable approach, i.e. water-based foam forming, was proposed to fabricate ultralight and porous polyimide/aramid sponges (PASG). Attributed to the bubble-template nature of foam-forming, PASGs exhibit high porosity (>99%) and ultra-low density (∼10 mg/cm3), and possess excellent thermal and sound insulation performance with an optimum thermal conductivity of 34.89 mW/m·K and noise reduction coefficient of 0.41. Besides, PASGs demonstrate outstanding mechanical properties after 500 compression cycles. This strategy providing more possibilities for developing the next generation of high-performance thermal insulation and noise reduction materials.

Ultra-elastic and super-insulating biomass PEBA nanoporous foams achieved by combining in-situ fibrillation with microcellular foaming

High-performance thermal insulation materials play a critical role in thermal management and saving energy. The current conventional thermal insulation materials cannot meet the increasing requirements of thermal management for thermal insulation performance. The advanced insulating materials represented by silica aerogels have excellent thermal insulation properties, but the brittleness limits their applications. Herein, we reported a flexible and environmentally friendly method to prepare ultra-elastic and super-insulating bio-based nanocellular material by means of microcellular foaming of in-situ fibrillated PA reinforced PEBA nanocomposites with the mixture of CO2 and N2 as blowing agents. Thanks to the significantly reduced air thermal conductivity within nanoscale cells, the nanoporous foam exhibits outstanding thermally insulating properties with a thermal conductivity of as low as 25.6 mW/m K. More importantly, the nanoporous foam also shows excellent compression and stretch resilience and outstanding flexibility. The excellent thermal insulation, ultra-elasticity, biomass and biodegradability, environmental friendliness, and manufacturing scalability make the material attractive for high-performance thermal management applications.

A facile method to prepare high-performance thermal insulation and flame retardant materials from amine-linked porous organic polymers

Developing porous functional materials with good thermal insulation and flame retardant properties is of great importance in modern eco-friendly buildings. Herein, we report the one-step synthesis of imine chain monolithic porous phosphorus-containing organic porous polymers (PPOPs) using Schiff base polycondensation reaction and as an example of efficient thermal insulation and flame retardant. Experimental results show that the PPOPs have low thermal conductivity (0.055 W·m−1·K−1) and excellent flame retardant properties. Measurements by microcalorimetry (MCC) showed a peak heat release rate (pHRR) value was 23.9 W·g−1, which is nearly an order of magnitude lower than that of most currently reported flame retardant materials. Using PPOPs in the epoxy resin (EP) matrix, the prepared EP composites exhibited excellent flame retardant properties. Cone calorimeter (CC) tests showed that the peak heat release rate (pHRR) and peak smoke release rate (pSPR) during combustion of PPOPs/EP composites were reduced by 42.0% and 36.4%, respectively, compared with pure EP. Tensile tests showed that the addition of PPOPs improved the mechanical properties of the composites to some extent. In addition, PPOPs can be designed into different shapes for practical applications compared with those fragile inorganic insulation materials and powders that were usually non-processable. Taking these advantages into account, PPOPs have great potential for modern building applications as monolithic foams or coatings with both excellent flame retardancy and thermal insulation properties.

Engineering a superinsulating wall with a beneficial thermal nonuniformity factor to improve building energy efficiency

To increase the energy efficiency of buildings and lower carbon emissions, heat losses through exterior walls could be considerably decreased by using high-performance thermal insulation materials with superlow thermal conductivities or superhigh heat capacities. A superinsulating layer would result in a highly nonuniform distribution of thermal resistance and capacitance within the exterior wall. An interesting problem concerns how to engineer the nonuniform thermal distribution for given total resistances and capacitances to improve energy efficiency. This paper proposes using a thermal nonuniformity factor to quantitatively characterize the nonuniform distribution of thermal resistance and capacitance in an exterior wall built with superthermal aerogel insulating panels and given total resistance and capacitance values. Various thermal nonuniformity factors for several insulation modes were investigated by calculating the relevant transmission loads through the walls. The effect of the thermal nonuniformity factor on the wall transmission load was explored to improve the energy efficiency of a building. The results indicated that the wall heat flux could be greatly decreased by engineering walls with a high nonuniformity factor. For instance, engineering a wall in a sandwich mode with thermal nonuniformity factor of 0.97 could decrease the wall heat flux by ∼35% compared to a uniform wall. These findings on engineering walls based on thermal nonuniformity factors to decrease the wall heat flux could be a useful reference for superinsulated buildings and for further improving thermal insulating performance and building energy efficiency.

Ultralight and heat-insulating mesoporous polyimide aerogels cross-linked with aminated SiO2 nanoparticles

Ideally, excellent heat-insulating material should have low thermal conductivity, low density, excellent resistance to high and low temperatures and good mechanical properties. But few materials can meet all the above requirements at the same time. Take polyimide (PI) aerogel as an example. Although it has the advantages of lightweight, good mechanical properties and excellent temperature resistance, the value of its thermal conductivity is often unsatisfactory. To solve this problem, a series of mesoporous polyimide aerogels using aminated SiO2 nanoparticles as cross-linker have been prepared. By changing the content of SiO2 and the synthetic methods, the key properties of PI aerogels such as the density and thermal conductivity were effectively tuned. These aerogels have low density, high specific modulus, significantly low thermal conductivity (~20 mW m−1 K−1), and excellent high temperature resistance. Their general properties (shrinkage, density, compression performances, specific surface area, pore size distribution, high temperature resistance) and their application potential as lightweight, high-performance thermal insulation materials in harsh environments are discussed.

Enhanced workability, durability, and thermal properties of cement-based composites with aerogel and paraffin coated recycled aggregates

The use of construction and demolition (C&D) wastes in building materials is a key step toward a sustainable construction industry. In this context, the application of recycled concrete aggregates (RCAs) in cement composite mixtures has been investigated by various researchers. The results available in the literature indicate that cement mortar adhered to the surface of RCAs leads to high water absorption and large porosity in cementitious mixtures. As a result, lower workability, durability, and mechanical properties in comparison to conventional aggregates are often known as the main attributes of mixtures containing RCAs. Additionally, improving the thermal energy storage capability of RCAs by using high-performance thermal insulation materials, such as phase change materials (PCMs) and aerogel can assist in minimizing the energy consumption in buildings. Accordingly, this paper aims at characterizing RCA mixtures with enhanced workability, durability, and thermal properties. The effect of using paraffin coated recycled concrete aggregates (PCRAs) and aerogel aggregates on the mechanical, thermal, and durability properties of cement composites are investigated in this paper. Results of dry density, compressive strength, water absorption content, permeable voids, thermal conductivity, rapid chloride migration test (RCMT), capillary water absorption, and scanning electron microscopy (SEM) tests along with energy-dispersive X-ray spectroscopy (EDX) are reported to evaluate the effect of several variables on the investigated concrete mixtures. Results of the conducted tests indicate that using PCRA significantly improves the durability characteristics of mixtures such as water absorption content, permeable voids, and RCMT, while it slightly decreases the compressive strength of mixtures with respect to the control mixture. In addition, aerogel aggregates significantly improve the thermal conductivity of mixtures while reduced the mechanical and durability characteristics.

Thermal insulation TiN aerogels prepared by a combined freeze-casting and carbothermal reduction-nitridation technique

With the rapid development of energy sources and aerospace engineering, high-performance thermal insulation materials with multiple functions are attracting more and more attentions. Non-oxide ceramic aerogels have application potential in thermal insulation under harsh conditions owing to their good thermal insulation performance and chemical stability. In this work, TiN aerogels were prepared by a combined freeze-casting and carbothermal reduction-nitridation method utilizing TiO2 and chitosan as raw materials, at 1473 K for 3 h, with a C/TiO2 molar ratio of 3/1. They showed a specific surface area of 167 m2/g and ultralow density of 0.07 g/cm3 (the relative density of 1.3 %). Their thermal conductivity value was only 0.166 ± 0.0054 W/(m K at 673 K (TiO2 solid content of 5 wt%). Moreover, the prepared aerogels possessed reasonably high mechanical strength and good high-temperature service performance, suggesting that they can be used under high-temperature conditions as an insulation material.

Preparation and Characterization of a Type of Green Vacuum Insulation Panel Prepared with Straw Core Material.

The Vacuum Insulation Panel (VIP), regarded as the most promising high-performance thermal insulation material, still has application limitations because of its high cost. In this paper, VIPs using natural straw as the core material are prepared. The fiber saturation point (FSP) is important in order to determine the optimum for the use of renewable straw materials as a potential VIP core. The microstructure of straw core material, together with the relationship between the moisture content, the diametral compression strength, and the thermal conductivity of as-prepared straw VIPs are investigated. Compression characteristics of straw core material and heat insulation mechanism within the straw VIP envelope enclosure are analyzed. Total thermal conductivity of a straw VIP is sensitive to both the inner pressure and the moisture content of straw core material. The optimum drying process for straw VIPs is heating the straw core material at a temperature of 120 ℃ for 60 min, with its center-of-panel value being about 3.8 mW/(m·K).