Fire‐safe agent integrated with oyster shell and melamine polyphosphate for thermoplastic polyurethane

At present, thermoplastic polyurethane (TPU) is widely used, but there are still many defects in fire safety, such as burning with heavy smoke and dripping. In this article, OS@MP was synthesized by modifying oyster shell (OS) powder with melamine polyphosphate (MP) and then served as fire‐safe agent for TPU. The fire performance of TPU composites were investigated using microscale combustion colorimeter (MCC), cone calorimeter test (CCT), smoke density test (SDT), and thermogravimetric analysis/Fourier transform infrared (TG‐FTIR) spectrum analysis. The MCC and CCT results revealed that OS@MP could reduce the fire hazards of TPU composites. The peak heat release rate (pHRR) of the sample with 10.0 wt% OS@MP decreased to 170.86 kW/m² from 1772.37 kW/m² for pure TPU. And, the SDT results showed that OS@MP could significantly reduce the smoke production of TPU composites. The TG‐FTIR also confirmed that the noncombustible gases (including CO₂, ammonia, and water vapor) produced by OS@MP have played a reinforcing role in TPU composites as well as a char formed on the surface of composites, which could act as a barrier to prevent the heat and air, reinforce the fire safety of TPU.     

氨基酸与蛋白质体系热容研究

氨基酸与蛋白质都是生命现象和分子生物学研究的最基本和最重要的研究对象.利用热力学方法,特别是从热容的角度出发对其研究,对深入了解蛋白质的折叠与伸展、变性机理、稳定性及生命体的新陈代谢等问题均具有一定的意义.近年来,研究者们对蛋白质或氨基酸体系的热容研究做了大量工作,取得了很大进展,本文对此进行了概述。     

STUDY ON THE EFFECTS OF TLCP ON PYROLYSIS OF PET AND ITS RETARDANT MECHANISM

The flame retardancy of aromatic thermotropic liquid crystal phosphorus-containing copolyester,TLCP,on PET was investigated.The results show that the presence of TLCP promotes char formation of the substrate and enhances thermal stability of char,hence delay its decomposition.SEM pictures show that the char formed from PET/TLCP is more compact, therefore is more resistant to fire and heat than that from pure PET.Evolved gas analysis by I.R measurements indicates that TLCP would decompose to produce phosp...     

Determination of fireline intensity by oxygen consumption calorimetry

Fireline intensity is one of the most relevant quantities used in forest fire science. It helps to evaluate the effects of fuel treatment on fire behavior, to establish limits for prescribed burning. It is also used as a quantitative basis to support fire suppression activities. However, its measurement is particularly tricky for different reasons: difficulty in measuring the weight of the fuel consumed in the active fire front, difficulty to evaluate the rate of spread of the fire front, and uncertainty on combustion efficiency. In this study, an innovative and original approach to directly measure the fireline intensity at laboratory scale is proposed. Based on the oxygen consumption calorimetry principle, this methodology is applied here in case of spreading fires, for the first time. It allows for directly measuring the heat released by the fire front. The results are then used to test the famous Byram’s formulation that is generally applied to determine the fireline intensity. Combustion efficiency and effective heat of combustion results are provided. The uncertainty and the use of a full scale calorimeter instead of a bench scale calorimeter for this study are discussed.     

Heat release and structural collapse of flexible polyurethane foam

Flexible polyurethane foam used in upholstered furniture remains one of the major fire hazards to date. The heat release rate of burning items made of foam depends strongly on the foam's physical behavior, notably its collapse to a burning liquid that can result in a pool fire. In this contribution, the cone calorimeter was used to study the physical processes and to determine their influence on foam combustion over a range of external heat fluxes. The initial stage of foam collapse can be described as the propagation of a liquid pyrolysis layer through the foam sample. The rate of propagation of the liquid layer was found to depend strongly on the convective heat transfer from the flame, which simultaneously defined and depended on the sample shape. The effective heat of combustion during foam collapse and pool fire was matched to the heat release potential of the components of the foam formulation to deduce which are consumed. The proposed analysis can serve to clarify the mechanism of flame retardant action, as demonstrated for a commercial brominated-phosphorous compound.     

Investigation of the thermal decomposition and flammability of PEEK and its carbon and glass-fibre composites

Conventional thermally durable materials such as metals are being replaced with heat resistant engineering polymers and their composites in applications where burn-through resistance and structural integrity after exposure to fire are required. Poly aryl ether ether ketone (PEEK) is one such engineering polymer. Little work has been published with regards to the flammability of PEEK and its filled composites. The current study aims to assess the flammability and fire behaviour of PEEK and its composites using thermogravimetric analysis, pyrolysis combustion flow calorimetry, limiting oxygen index, a vertical flame resistance test, and fire (cone) calorimetry.     

Experimental investigation of thermal properties and fire behavior of carbon/epoxy laminate and its foam core sandwich composite

According to structural characteristics, composites are classified as laminated structure and sandwich structure. Carbon/epoxy laminate and foam core sandwich composite are the most commonly used laminate and sandwich structure material in the aircraft industry. The flammability of epoxy resins and foam core material is an inherent hazard. Many previous studies focused primarily on their mechanical properties, while the studies on the thermal and fire properties of carbon/epoxy laminate and its foam core sandwich composite have rarely conducted. Therefore, to characterize their thermal and fire properties, a comprehensive experimental investigation and theoretical analysis were carried out in this work using thermogravimetric analysis, cone calorimeter, vertical/horizontal burning tests, limiting oxygen index and scanning electron microscope tests. Several typical characteristic parameters were obtained and analyzed, such as pyrolysis temperature, heat release rate, mass loss, flaming spread rate and limiting oxygen index. These experimental data coupled with theoretical analysis can provide support for fire risk assessment and fire protection design in aircrafts. The carbon/epoxy laminate and foam core sandwich composite are both characterized as the thermally thick materials. The ignition models and mass loss rate models were obtained. Foam core material negatively affects most of the thermal and fire properties of sandwich composite, but the foam core sandwich composite has self-extinguishing behavior during horizontal burning tests, whose LOI is higher than that of carbon/epoxy laminate. Thus, an important conclusion was reached that the ignition position and flame spread direction have critical effect on the fire behavior of foam core material.

     

火场助燃剂检验鉴定的干扰研究进展

火灾是影响公共安全最为常见的灾害之一,而放火更是严重威胁人民群众生命财产安全,属于典型的暴力犯罪.犯罪嫌疑人为了达到有效快速放火的目的,往往使用助燃剂实施放火,因而助燃剂的检验鉴定对于认定火灾性质起着至关重要的作用.然而火场情况复杂,容易对助燃剂物证检验鉴定产生较大干扰.在火灾发生发展的过程中,火场高温热环境会作用于已...     

Determination of the heats of gasification of polymers using differential scanning calorimetry

The amount of heat that is required to gasify unit mass of material is one of the key properties that define its ignition resistance and fire response. Knowledge of this property is necessary to assess a material's fire hazard in a particular fire scenario. Nevertheless, even for the most common polymers the values of this property are not well established. Here we present a method for determining the heat of gasification using differential scanning calorimetry and apply this method to a set of ten common plastics and engineering polymers.     

Fire behaviors study on 18650 batteries pack using a cone-calorimeter

To investigate the effects of different state of charges (SOCs), external heating powers and charging/discharging treatment on the fire behaviors of 18650 batteries pack, three groups of abuse experiments were conducted with the help of a cone-calorimeter. The fire hazards of batteries pack were characterized by measuring the flame photographs, battery surface temperature, ignition time, thermal runaway time, heat release rate and radiative heat flux. According to the results, it is found that the fire behaviors of batteries pack will appear in advance and behave more violent with the increase in SOC. Additionally, the higher heating power will exacerbate the fire hazards of batteries pack by increasing the surface temperature rise rate, the total heat released and the total heat flux of pack leading to an earlier thermal runaway and more rigorous consequence. Finally, the pack with discharging/charging treatment has a much lower heat released compared to the pack without any treatment due to the incomplete burning and incomplete release of energy. Besides, their fire behaviors also exhibit earlier and severer.

     

透明质酸及其衍生物作药物载体

透明质酸(HA)具有良好的生物相容性和生物降解性，是优良的药物载体。但其稳定性差，对强酸、强碱、热、自由基及透明质酸酶敏感，容易发生降解而限制了其应用。本文简要介绍HA的基本特性及应用，重点阐述了HA经不同的化学改性方法如酯化、交联、接枝所得衍生物作药物载体的最新研究进展。化学改性赋予了HA一系列的优良特性,如适当的机械强度、特殊的流变学特性、良好的稳定性、靶向性等,可提高、扩大HA作药物载体的性能和应用范围。最后展望了透明质酸及其衍生物作药物载体的应用前景。     

Ethylene propylene diene monomer rubber‐based heat shielding materials for solid rocket motor: Impact of Kevlar fiber reinforcement on the thermal and mechanical properties

This work scrutinizes the utilization of ethylene propylene diene monomer rubber matrix (EPDM) with an embodiment of aramid fiber for the heat shielding applications in solid rocket motor (SRM). Aramid fibers are aromatic poly‐paraphenylene terephthalamide, here deployed are Kevlar fibers (KF). However, the literature that encompasses the thermal and mechanical behavior with the fiber loading is reported nowhere else. The effect of fiber addition on the surface morphology and density was thoroughly studied, and it revealed that the EHSMs were of lower density to act as an efficient payload for the SRM. In this regard, the thermal conductivity, heat capacity, thermal diffusivity, fire behavior, and mechanical properties of the EPDM/KF‐based EHSMs were explored. The results revealed that the EHSMs are thermally insulating and thermally stable material with balanced mechanical properties that can engender the thermal and mechanical strains of the rocket motor. Furthermore, other analytical techniques such as scanning electron microscopy and energy dispersive X‐ray spectroscopy have been exploited to monitor the performance of the char residues of the EHSM to delineate its performance in the fire atmosphere.     

Thermal runaway and fire behavior investigation of lithium ion batteries using modified cone calorimeter

The lithium ion battery has been widely used, but it has high fire risk due to its flammable materials. In this study, a series of combustion tests are conducted on the 18650-type lithium ion batteries using the modified cone calorimeter. The temperature and voltage variation of the battery, heat release rate and gas generation during combustion are measured in this study. The battery is heated evenly by the self-made heater, and the reliable trigger temperatures of thermal runaway are obtained for different states of charge (SOCs) batteries in this study. The fire behavior of the 100% SOC batteries is shown in this paper. The net heat absorption by the battery before thermal runaway is calculated based on the heat transfer theory. It ranges from 56.81 to 64.05 kJ for 0 to 100% SOC batteries, which shows a decreasing trend as SOC increases. The peak combustion heat release rate of 100% SOC batteries is 3.747?±?0.858 kW. CH₄ and CO gases are detected before and after thermal runaway. The generation of CO shows an increasing trend as SOC increases. Some suggestions on the early warning system of battery thermal runaway are proposed based on this study.

     

LDPE/Mg-Al layered double hydroxide nanocomposite: Thermal and flammability properties

Layered double hydroxides (LDHs) are new nanofillers which exhibit improved thermal and flammability properties in various kinds of polymer matrices. These materials have certain advantages over conventional metal hydroxides and also layered silicates so far as the flame retardancy is concerned. In this article, flammability and thermal properties of the nanocomposite based on low density polyethylene (LDPE) and Mg-Al based layered double hydroxide (Mg-Al LDH) are reported in detail. The nanocomposites containing different LDH concentrations were prepared by melt-compounding using a tightly intermeshing co-rotating twin-screw extruder. The morphological analysis reveals an exfoliated/intercalated type LDH particle morphology in these nanocomposites. The thermogravimetric analysis (TGA) shows that even a small amount of LDH improves the thermal stability and onset decomposition temperature in comparison with the unfilled LDPE. The heat release rate (HRR) and its maximum (PHRR) during cone-calorimeter investigation are found to be reduced significantly with increasing LDH concentration. The nanocomposites not only exhibit reduced total heat released (measure of propensity to produce long duration fire), but also lower tendency to fast fire growth (measured by the ratio of PHRR and time of ignition). The limited oxygen index (LOI) and the dripping behavior are also improved with increasing LDH concentration.     

Fire retardant action of mineral fillers

Endothermically decomposing mineral fillers, such as aluminium or magnesium hydroxide, magnesium carbonate, or mixed magnesium/calcium carbonates and hydroxides, such as naturally occurring mixtures of huntite and hydromagnesite are in heavy demand as sustainable, environmentally benign fire retardants. They are more difficult to deploy than the halogenated flame retardants they are replacing, as their modes of action are more complex, and are not equally effective in different polymers. In addition to their presence (at levels up to 70%), reducing the flammable content of the material, they have three quantifiable fire retardant effects: heat absorption through endothermic decomposition; increased heat capacity of the polymer residue; increased heat capacity of the gas phase through the presence of water or carbon dioxide. These three contributions have been quantified for eight of the most common fire retardant mineral fillers, and the effects on standard fire tests such as the LOI, UL 94 and cone calorimeter discussed. By quantifying these estimable contributions, more subtle effects, which they might otherwise mask, may be identified.     

A review of candidate fire retardants for polyisoprene

Polyisoprene elastomer, as natural rubber (NR) or manufactured synthetically (IR), is used in rubber compounds for applications such as tyres, dampers and suspension elements. NR/IR compounds without fire retardants have a low resistance to burning, and emit large quantities of dense smoke. This is because polyisoprene readily decomposes upon heating, by random chain scission, vaporising into a mixture of small aromatic chemical species, which ignite readily and form smoke particles with negligible char residue formation. The effects of commonly used additives on the thermal decomposition and burning of polyisoprene are reviewed; whilst cross-linking agents have significant effects on physical and ageing properties, they have little effect on thermal decomposition and burning. Fillers such as carbon black and silicas reduce the fuel content by dilution of the polymer and the formation of a stabilising residue.Potential approaches for fire retarding IR are reviewed, identifying two main approaches; halogenated additives, or high loadings of aluminium hydroxide (ATH), neither of which are satisfactory. Other potential approaches are identified, including the use of phosphorus and nitrogen based additives as intumescent char formers, and with zeolites as char catalysts. Alternative inorganic fire retardants to ATH are identified for use, and zinc hydroxystannate and zinc borate are considered as synergists with ATH. Expandable graphite (EG) is identified for use in other elastomers and has potential for polyisoprene. Nano-scale fire retardants such as montmorillonite clay and multi-walled carbon nanotubes are reported typically as a secondary additive to hydrated fillers, but have yet to make a successful transition to industrial processing.     

塑料及其复合材料的摩擦学

综述了近年来国内外塑料及其复合材料的摩擦学研究的新进展,涉及到PTFE、PEEK、UHMWPE的合金以及塑料复合材料的重点研究领域,指出基于现代材料设计的摩擦学材料设计、塑料在热和应力作用下的蠕变和长期稳定性、塑料梯度功能材料和环保的绿色材料的摩擦学等方面是未来的发展方向。     

Study of the fire resistant behavior of unfilled and carbon nanofibers reinforced polybenzimidazole coating for structural applications

With increasing interest in epoxy‐based carbon fiber composites for structural applications, it is important to improve the fire resistant properties of these materials. The fire resistant performance of these materials can be improved either by using high performance epoxy resin for manufacturing carbon fiber composite or by protecting the previously used epoxy‐based composite with some fire resistant coating. In this context, work is carried out to evaluate the fire resistance performance of recently emerged high performance polybenzimidazole (PBI) when used as a coating material. Furthermore, the effect of carbon nanofibers (CNFs) on fire resistant properties of inherently flame retardant PBI coating was studied. Thermogravimetric analysis of carbon/epoxy composite, unfilled PBI and nano‐filled PBI shows that the carbon/epoxy composite maintained its thermal stability up to a temperature of 400°C and afterwards showed a large decrease in mass, while both unfilled PBI and nano‐filled PBI have shown thermal stability up to a temperature of 575°C corresponding to only 11% weight loss. Cone calorimeter test results show that unfilled PBI coating did not improve the fire retardant performance of carbon/epoxy composite. Conversely, nano‐filled PBI coating has shown a significant improvement in fire retardant performance of the carbon/epoxy composite in terms of increased ignition time, reduced average and peak heat release rate and reduced smoke and carbon monoxide emission. These results indicate that addition of carbon nanofibers to inherently flame retardant coating can significantly be helpful for improving the fire resistance performance of composite materials even with low coating thickness. Copyright © 2013 John Wiley & Sons, Ltd.