Thermal Protection Properties Research Articles

The thermal protection and comfort properties of aerogel and PCM-coated fabric for firefighter garment

The study evaluates the simultaneous use of aerogel and phase change material (PCM) on the face cloth of thermal liner in firefighter’s protective garment. Aerogel is commonly used to resist incoming heat flux in the field of high heat protection and to prevent the loss of body heat in the cold environment clothing. In high heat protection clothing, aerogel not only resists the incoming heat fluxes but also blocks the outbound body heat. As a result the wearer suffers from internal increase of body temperature. Previous studies identified the potential use of aerogel in firefighter’s protective clothing. However there was no clear approach to resolve the problem associated with body heat release. Current study focuses on the problem by applying PCM along with aerogel on fabric. The ambient-side of a thermal liner face cloth was coated with silica aerogel particles; meanwhile, the next to skin side was coated with PCM/aerogel composite powder. The new thermal liner revealed superior thermal protection and comfort. It extended the time to reach pain threshold and increased the pain alarm time. The Fourier transform infrared analysis of the aerogel/PCM composite powder showed the presence of PCM in nanoporous aerogel particles while the differential scanning calorimeter quantified the heat absorbing capacity of the new composite powder. Scanning electron microscope, air permeability tester, and jPOR macro of ImageJ software were used for the surface characteristics and porosity analysis of coated liner. The thermal stability of the composite powder was investigated through an infrared thermal camera. No dripping or form deterioration was observed when the composite powder was heated over a temperature three times above the melting temperature of the pure PCM.

Correction factors for assessing immersion suits under harsh conditions

Many immersion suit standards require testing of thermal protective properties in calm, circulating water while these suits are typically used in harsher environments where they often underperform. Yet it can be expensive and logistically challenging to test immersion suits in realistic conditions. The goal of this work was to develop a set of correction factors that would allow suits to be tested in calm water yet ensure they will offer sufficient protection in harsher conditions. Two immersion studies, one dry and the other with 500 mL of water within the suit, were conducted in wind and waves to measure the change in suit insulation. In both studies, wind and waves resulted in a significantly lower immersed insulation value compared to calm water. The minimum required thermal insulation for maintaining heat balance can be calculated for a given mean skin temperature, metabolic heat production, and water temperature. Combining the physiological limits of sustainable cold water immersion and actual suit insulation, correction factors can be deduced for harsh conditions compared to calm. The minimum in-situ suit insulation to maintain thermal balance is 1.553–0.0624·TW + 0.00018·TW2 for a dry calm condition. Multiplicative correction factors to the above equation are 1.37, 1.25, and 1.72 for wind + waves, 500 mL suit wetness, and both combined, respectively. Calm water certification tests of suit insulation should meet or exceed the minimum in-situ requirements to maintain thermal balance, and correction factors should be applied for a more realistic determination of minimum insulation for harsh conditions.

Comparison of thermal manikins to human thermoregulatory responses

Immersion suits are lifesaving appliances (LSA) designed to protect the wearer if they become accidently immersed in cold water by reducing the cold shock response and delaying the onset of hypothermia. Immersion suits are certified to both national and international standards; some of which require the thermal protective properties to be tested using humans or thermal manikins. The ethical nature of testing with humans has been questioned [1] due to the physically grueling nature of these tests, thus testing with manikins may be preferential. However, previous work has shown that discrepancies exist between thermal manikins and humans that could result in immersion suit selection that would benefit the former more than the latter who would ultimately use it [2]. This study investigated the thermoregulatory responses of humans and compared them to a thermal manikin while wearing immersion ensembles with insulation distributed in various configurations hypothesized to be beneficial to humans and manikins.

Influence of molecular weight of PEG on thermal and fire protection properties of PEPA-containing polyether flame retardants with high water solubility

Abstract A series of novel PEPA-containing polyether (PAPEG) flame retardants with high water solubility were synthesized by pentaerythritol phosphate (PEPA), phosphorus oxychloride (POCl3) and polyethylene glycol (PEG) with different molecular weight. Their chemical structures were confirmed by 1H nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The influence of molecular weight of PEG on the thermal property of PAPEGs was investigated by thermogravimetric analysis (TGA) and a possible thermal degradation mechanism was speculated to illustrate the char-forming ability of PEG. Afterwards, the influence of molecular weight of PEG on the fire protection of the transparent fire resistant coatings (FRC) was investigated in detail by fire protection test, intumescence ratio, scanning electron microscopy (SEM) and TGA. The fire protection test found that the coatings with low molecular weight PEG presented good fire retardancy, supplying effective fire protection for the plywood boards. The intumescence ratio and SEM results well demonstrated that the fire protection of coatings and foam structure of char layers were significantly improved when the molecular weight of PEG was low. TGA result showed that the residual weights of the fire resistant coatings presented the order of FRC200 > FRC150 > FRC400 > FRC600. It indicated that low molecular weight PEG could enhance the char-forming ability of the coatings. TGA and real-time FTIR results proved that blowing agent and carbon source degraded in the same temperature range, which resulted in the formation of intumescent char layer.

Evaluating cold, wind, and moisture protection of different coverings for prehospital maritime transportation-a thermal manikin and human study.

Prehospital maritime transportation in northern areas sets high demands on hypothermia prevention. To prevent body cooling and hypothermia of seriously-ill or injured casualties during transportation, casualty coverings must provide adequate thermal insulation and protection against cold, wind, moisture, and water splashes. The aim of this study was to determine the thermal protective properties of different types of casualty coverings and to evaluate which would be adequate for use under difficult maritime conditions (cold, high wind speed, and water splashes). In addition, the study evaluated the need for thermal protection of a casualty and verified the optimum system for maritime casualty transportation. The study consisted of two parts: (1) the definition and comparison of the thermal protective properties of different casualty coverings in a laboratory; and (2) the evaluation of the chosen optimum protective covering for maritime prehospital transportation. The thermal insulations of ten different casualty coverings were measured according to the European standard for sleeping bags (EN 13537) using a thermal manikin in a climate chamber (-5°C) with wind speeds of 0.3 m/s and 4.0 m/s, and during moisture simulations. The second phase consisted of measurements of skin and core temperatures, air temperature, and relative humidity inside the clothing of four male test subjects during authentic maritime prehospital transportation in a partially-covered motor boat. Wind (4 m/s) decreased the total thermal insulation of coverings by 11%-45%. The decrement of thermal insulation due to the added moisture inside the coverings was the lowest (approximately 22%-29%) when a waterproof reflective sheet inside blankets or bubble wrap was used, whereas vapor-tight rescue bags and bubble wrap provide the most protection against external water splashes. During authentic maritime transportation lasting 30 minutes, mean skin temperature decreased on average by 0.5°C when a windproof and water-resistant rescue bag was used over layered winter clothing. The selected optimum rescue bag consisted of insulating and water-resistant layers providing sufficient protection against cold, wind, and water splashes during prehospital transportation lasting 30 minutes in the uncovered portion of a motor boat. The minimum thermal insulation for safe maritime transportation (30 minutes) is 0.46 m²K/W at a temperature of -5°C and a wind speed of 10 m/s.

Synthesis, structure and thermal protective behavior of silica aerogel/PET nonwoven fiber composite

In recent years, flexible, mechanically strong and environmental friendly thermal insulation materials have attracted considerable attention. In this work, silica aerogel/polyethylene terephthalate (PET) nonwoven fiber composite with desirable characteristics was prepared via a two-step sol-gel process followed by an ambient drying method through immersing the PET nonwoven fiber into silica sol. The silica aerogel particles were characterized by FTIR, FE-SEM, TGA and nitrogen adsorption analysis. The morphology and hydrophobic properties of neat PET nonwoven fiber and its silica aerogel composite were also investigated. For studying thermal protective properties, the thermal diffusivity was calculated from temperature distribution curves. The mean pore size of 11 nm, the surface area of 606 m2/g and the total pore volume of 1.77 cm3/g for the silica aerogel particles in the composite are obtained from nitrogen adsorption analysis, indicating the aerogel can maintain its high porosity in the nonwoven composite structure. Silica aerogel particles were efficiently covered the surface of the PET fibers and completely filled the micron size pores of the nonwoven fiber leading to a stronger hydrophobicity and higher thermal insulation performance in the aerogel composite samples compared to the neat PET nonwoven. In this regard, an almost 64 % decrease in the thermal diffusivity was achieved with 66 wt% silica aerogel.

Study on effect of blend ratio on thermal comfort properties of cotton/nylon-blended fabrics with high-performance Kermel fibre

This study presents the thermal comfort properties of woven fabrics made of Kermel, cotton/nylon and cotton/nylon /Kermel-blended yarns. Our aim in this study is to combine the high comfort properties of cotton/nylon fibres with high thermal protective properties of Kermel fibre in different woven fabrics. Thus, Kermel (100%), cotton/nylon (50:50) and four blends of the 50% cotton fibres with nylon and Kermel (40:10, 30:20, 20:30 and 10:40) were spun on a ring-spinning frame and twisted into two-folded yarns with the same yarn count of 30/2(Ne) and twist level of 560 TPM. Using the produced yarns, woven fabrics with identical characteristic and structure were also produced. Then, the thermal comfort and physical properties of fabrics were studied in terms of fabric porosity, thermal resistance, thermal conductivity, water vapour resistance and air permeability. The results show that the porosity, air permeability and thermal resistance increase with Kermel fibre blend ratio. Conversely, the water vapour resistance decreases with increase of Kermel fibre blend ratio up to 40%, while 100% Kermel-woven fabric exhibits a higher water vapour resistance value. Nevertheless, the thermal conductivity of cotton/nylon-blended Kermel woven fabric is unchanged with increase of Kermel fibre blend ratio up to 40%, whereas at 100% Kermel fibre blend ratio, the lowest thermal conductivity is obtained. The obtained results implied that woven fabric produced from cotton/nylon (50/10) blended with 40% Kermel fibre resulted in proper thermal comfort properties.

Thermal Protection Performance of Metallic Honeycomb Core Panel Structures in Non-Steady Thermal Environments

The thermal protection characteristics of metallic honeycomb core panel structures in high-temperature environments are important parameters for the structure design of thermal protection for high-speed aircraft. A self-developed transient aerodynamic thermal simulation system for high-speed aircraft is used to test the thermal protection performance of metallic honeycomb core panels in a dynamic high-temperature environment at temperatures up to 950°C. The heat transfer characteristics of metallic honeycomb core panels in transient and steady states and the heat shield effects at various temperatures are determined. By considering the internal radiation of honeycomb core panels as well as the heat transfer between a metal structure and air within a honeycomb core cavity, three-dimensional finite element models are established for numerical simulations and computations of the thermal protection properties of metallic honeycomb core panels. The experimental results agree well with the numerical simulations. The credibility and effectiveness of the numerical simulation are verified. These results provide a solid foundation for replacement of expensive thermal simulations with numerical simulations to a certain extent. Several issues are discussed, such as the changes in the heat shield efficiency of the metallic honeycomb core panel in a complex dynamic high-temperature environment, the relevance of thermal protection efficiency, the rate of heating surface temperature change, and the selection of the metal surface emissivity. These findings offer important reference values for research in metal honeycomb thermal protection structures of high-speed aircraft.

Evaluation of Light Protective Properties of High Performance Aramid Fabrics

The aramid fabrics have been widely used in aerospace, military and protective clothes for light radiation stability properties. The reflection and transmission properties of two kinds of materials (Kevlar 49 fabric and Kevlar 49/Nomex blended fabric) and three weaves of aramid fabrics with different wavelength spectrum were evaluated by ultraviolet-visible-near infrared (UV–Vis–NIR) spectrophotometer analysis. The effects of fabric layers on the reflection and transmission performances of aramid fabric were also discussed. It indicated that the aramid fabrics have good thermal and light protective properties.

Heat transfer mechanism of the C/SiC ceramics pyramidal lattice composites

An innovative design of pyramidal lattice composites with high temperature C/SiC ceramics as constituent has been proposed for the purpose of thermal protection system design. A sample with dimensions of 230×130×20mm was firstly fabricated by interweaving and chemical vapor infiltration (CVI) method. Heat transfer mechanism of C/SiC lattice has been discovered to explore the optimal design of its excellent thermal protective properties. Optimal geometry parameter selection criterion has been proposed to balance the heat insulation and mechanical properties including stiffness and yield failure surface. And the critical surface emissivity was found for the dominant heat transfer mechanism transition from thermal conduction to thermal cavity radiation in the lattice. Simultaneously, the maximum temperature location transferred from the location of rod end to the center of panel. Filling insulation materials and surface modification to change the surface emissivity has been proved to be a significant way to improve the thermal protective properties. This novel design provides promising material candidate for thermal protection system.

MATHEMATICAL MODELING OF HEAT-SHIELDING CHARACTERISTICS OF SAND FREE LIGHTWEIGHT CONCRETE WALL STONES

The article reports on theoretical research results of sand free lightweight concrete wall stones thermal protective properties. Calculated values of resistance referred to stone wall masonrys thermal exchange on cement-sand and warm mortars are got using the method worked out by the article writersCalculation of three-dimension thermal fields in the external wall fragment was performed by using the method of finite elements provided in ANSIS software package.

Test Research for Thermal Protective Properties of Mobile Refuge Chamber

In this paper we have a discussion on heat insulation method of the using of mobile refuge chamber for coal mine and the improved scheme was put forward to improve the performance of thermal protective properties of the refuge chamber. Then according to the theoretical analysis and the external heating test methods to be compared,we conduct an analysis.The test method are introduced, and the factors caused the temperature changes are analyzed based on the test.These results have directive significance for the further improvement of refuge chambers.

A novel function – Thermal protective properties of an antifreeze protein from the summer desert beetle Microdera punctipennis

It is well known that antifreeze proteins play an important role in protecting poikilothermic organisms from freezing. However, the transcripts of antifreeze protein genes, Mpafps, were observed in the desert beetle Microdera punctipennis in summer. The mRNA levels of Mpafps increased significantly after heat shock at 50°C, which implies that a novel function may exist in the antifreeze proteins from M. punctipennis. Southern blot analysis suggested the presence of multiple copies of the Mpafps family in the genome. Transcripts of two cDNAs encoding antifreeze proteins (Mpafps77 and Mpafps52) were isolated from beetles collected in the summer. The deduced amino acid sequences of the MpAFPs expressed in the summer are shorter by one 12-residue repeat and have significantly different C-terminal end sequences relative to the AFPs expressed in winter. Mpafps77 was constructed and expressed in Escherichia coli as a fusion protein, maltose-binding protein (MBP)-MpAFPS77. An in vitro heat protection assay was done by measuring the survival of bacteria and yeast that were exposed to 50 and 42°C, respectively and showed that the fusion protein significantly increased the thermal tolerance of these cells. It also increased the thermotolerance of the lactate dehydrogenase (LDH) enzyme at 65°C. These studies are the first biochemical demonstration of a thermal protective function for MpAFP and suggest some novel protective mechanisms may be present in M. punctipennis.

Application of Phenolic Foam Plate in the Exterior Wall Thermal Insulation

With the deep reform of national policy of building energy conservation and the increasing requirements of building fire protection, building insulation industry appeared a hitherto unknown development opportunity and challenge. This paper introduces the research and application of phenolic foam plate, modified phenolic foam plate with thermal insulation, fire prevention, environmental protection and other excellent properties, puts forward in the field of building energy conservation should be vigorously promoted the application of phenolic foam.

Preparation, properties and thermal control applications of silica aerogel infiltrated with solid–liquid phase change materials

In this study, silica aerogel saturated with erythritol as phase change materials (PCMs) was prepared by melt infiltration. The properties of the composite were determined by scanning electronic microscope (SEM), Fourier transformation-infrared spectroscope (FT-IR) and differential scanning calorimeter (DSC). In the novel composite, erythritol with high latent heat of fusion was used as PCM for thermal control, whereas nanoporous silica aerogel was prepared as the phase change matrix to provide structural strength and prevent leakage of the melted erythritol. Nitrogen gas adsorption curves and SEM analysis indicate that the pore structure of silica aerogel was porous and connected with each other. FT-IR analysis showed that the composite formation of silica aerogel and erythritol were physical, whereas DSC analysis showed that the melting point and heat storage capacity of the composite were 123.8°C and 289.92 kJ/kg, respectively. The thermal protection properties of phase change composites were designed under laboratory conditions using a thermal measurement setup of a simulated thermal environment of an aircraft. The phase change composite produced by the study can be used for thermal protection applications. Compared with the paraffin–silica aerogel composite, the erythritol–silica aerogel composite could rapidly control the rising temperature by absorbing heat under high thermal environments.

Testing fire protective properties of intumescent coatings by in-line temperature measurements on a cone calorimeter

An experimental setup was proposed for evaluating the thermal shielding efficiency of intumescent coatings. In particular, a cone calorimeter as heater source was coupled with a thermocouple as detector of the temperature of steel plates coated with intumescent coatings. According to ENV 13381-4 test procedure, the heating curves of the setup was measured by plate thermocouple and compared with ISO 834 standard curve. Meanwhile, the comparison was also made between temperature profiles of blank steel plates at different heat fluxes and unprotected steel elements under ISO fire. The possible correlation between bench scale and large scale test was hence discussed. Several factors (heat flux, distance to cone heater, coating thickness, sample size, edge effect and heat insulator) were deeply investigated and discussed: significant relationships between these parameters and the thermal protective properties of the intumescent coating were evidenced; furthermore a fully developed intumescent char could be obtained by controlling the aforementioned parameters. As a conclusion, the proposed bench-scale test was found to be comparable to the large scale test only in the early heating stages.

An investigation on post-fire behavior of hybrid nanocomposites under bending loads

This work focuses on residual bending properties of hybrid nanocomposites after intense heat conditions. Carbon fiber/epoxy-nanoclay and carbon fiber/epoxy-graphene nanosheets were manufactured. The nanoparticles employed were Cloisite 30B nanoclay and surface modified graphene nanosheets. The epoxy system was RemLam M/HY956. For short beam samples exposed to 800 KW/m 2 heat flux, for a various period of time up to 120 s, the addition of nanoparticles (nanoclay and graphene nanosheets) increased the unburned thickness from 0.16 mm (original) to 2.63 mm and 2.74 mm, respectively. When the two-dimensional (plates) samples were tested, the improvement on heat performance was reduced. The unburned thickness improved close to 10% with the presence of nanoclay. The addition of graphene nanosheets leads to a decrease in unburned thickness of 12.8%. This result can be due to the good thermal protection properties of the graphene nanosheets. Using SEM analysis, it was observed that when the hybrid nanocomposites were subjected to a large heat flux, nanoparticles remained trapped inside the char layers. Finally, the proposed model seems to overestimate the residual bending response by 8%.

The Effects of Silk Screened Emblems on Thermal Protective Performance of Wildland Fire Fighter Protective Clothing Systems under Two Moisture Conditions

The objective of this study is to determine the effects of silk screened emblems on thermal protective performance of wildland fire fighter protective clothing systems under two moisture conditions. Three outerwear conditions (current emblem, new emblem, blank) were combined with both underwear conditions (emblem, blank) to produce six clothing systems. The two moisture conditions were both layers conditioned (dry) and top layer conditioned/lower layer saturated with water (wet). Both radiant protective performance (RPP) testing and thermal mannequin testing were used to evaluate the clothing systems. The data showed a decline in thermal protective properties of the clothing systems under conditions of high heat flux and wet inner layer. While both jacket emblems performed better than the blank jacket, one emblem was more protective under radiant exposure conditions while the other was found to be superior in the thermal mannequin tests.

Thermo-Protecting Properties of Intumescent Compositions

Intumescent fire retardants have wide applications due to thermo-protective properties, which decrease heat flow on the polymer surface. In this work we present the experimental investigation of thermal-protection properties of a number of polymer mixtures (polycarbonate + ABS plastic, epoxy resin, etc.) with different fire retardant additions.

Aqueous Foams for Frost Protection of Plants: Stability and Protective Properties

Efficient technology has been developed for aqueous foam protection of plants against radiative night cooling. Experimental and mathematical simulations together with field tests were carried out in a search of foaming solutions and methods of application of the foam layer that provide optimal protection. A new parameter—insulation endurance—was developed for evaluating the thermal protective properties of unstable insulation materials such as aqueous foam. This parameter combines properties that are the most important for successful protection of plants—heat resistivity and stability. Based on this parameter, the experimental data were interpreted and used to choose the foaming solutions that provide sufficient protection of plants during a night of frost. Foams were studied when applied in various configurations, directly over soil surface and spread over a mesh which covers the plants.