Development of new water-treatment-resistant fire- and bioprotective preparations for wood

Fire-retardant formulations for wood were developed, and the efficiency of their fireproofing properties, resistance to water, thermal decomposition, and effect of additives on these properties were studied.     

丝素蛋白-聚氨酯复合水凝胶的制备及性能研究

以聚乙二醇(PEG)、聚氧化丙烯二醇(PPG)、异弗尔酮二异氰酸酯(IPDI)为主要原料制备聚氨酯预聚体(PU),与丝素蛋白水溶液(SF)交联制得丝素蛋白-聚氨酯(SF-PU)复合水凝胶.分别利用ATR、SEM对水凝胶组成、结构及微观形貌进行表征;DSC、吸水溶胀测试探讨了丝素蛋白与聚氨酯的质量比(SF/PU)以及聚氨酯中不同软段质量比(PEG/PPG)对SF-PU水凝胶热性能、溶胀性能的影响.结果表明,SF-PU水凝胶具有多孔结构;样品中不同的SF/PU、PEG/PPG均对材料的玻璃化转变温度、结晶度及溶胀性能产生影响,且当水凝胶组分为SF/PU=1/25、PEG/PPG=2/1时,平衡溶胀比(ESR)可达到440%;水凝胶在溶胀初始阶段符合菲克扩散模型,整个溶胀过程遵循溶胀动力学2级方程.     

Composition of a wood combustion inhibitor based on a magnesium complex containing phosphorus and nitrogen

A flame retardant for wood impregnation based on a magnesium complex containing phosphorus and nitrogen was developed. It considerably reduces the wood loss in fire tests. Application of the flame retardant in an amount of 300 g m^–2 allows preparation of materials with the fire performance corresponding to group I of materials. The mechanism of the fireproofing action of the flame retardant on wood and the thermal degradation of the impregnated wood were studied.     

Influence of particle size and kinetic parameters on tire pyrolysis

One of the most important parameters that can significantly affect the cost of the tire pyrolysis process is the time needed for thermal decomposition of the tire material. In this work, the influence of particle size and kinetics of thermal decomposition on the pyrolysis time was studied. The apparent kinetic parameters of tire thermal decomposition were estimated using three different approaches based on thermogravimetry measurements. In separate experiments, tire particles with different sizes were pyrolyzed under isothermal conditions in a laboratory flow reactor at different residence times of the particles in the reactor and the data recorded were employed in the determination of tire conversion during the thermal decomposition. A mathematical model of tire pyrolysis considering heat conduction in the tire particles was developed. All three types of estimated kinetic parameters were used to determine the conversion behavior at isothermal conditions and the results were compared with experimental data obtained. The model was used also to calculate the pyrolysis time in an industrial scale reactor at different temperatures and particle sizes.     

Crosslinking of mixtures of DGEBA with 1,6-dioxaspiro[4.4]nonan-2,7-dione initiated by tertiary amines, Part II: Thermo-mechanical properties and reworkability

The copolymerization of a DGEBA epoxy resin and a bislactone was studied using different anionic initiators. In the previous work, the kinetics of the process was studied and the differences were observed which could affect the thermal and mechanical properties of the materials. In the present work, the thermo-mechanical properties of these materials have been investigated. An important influence of the final curing temperature on the thermal properties of the materials was detected. The addition of bislactone improved the thermal degradation of the materials due to the introduction of ester groups into the network, which in turn allowed partial or complete recovery and reworkability of the coated material via hydrolysis of the thermoset. In addition, the materials exhibited superior flexibility and toughness, in comparison to the pure DGEBA material.     

Effect of fireproofing formulation modifiers on the thermal decomposition process of wood

Effect of modifiers of fireproofing formulations for wood, based on phosphorus-and-nitrogen-containing compounds, on the process of thermal decomposition and properties of wood treated with these formulations was studied.     

先锋褐煤的热处理和水热处理改质

通过先锋褐煤热处理和水热处理,结合处理煤结构与性质表征,研究了热处理和水热处理对先锋褐煤结构、抽提和溶胀性能的影响,探讨了热处理过程水的作用。结果表明,低于热解温度下的热处理以非共价键解缔合及部分弱共价键热解为主,水与煤的水热反应能够抑制水热处理过程中煤的热解和小分子化合物释放。高温热处理以热解和脱氧为主,水热反应可以稳定煤热解活性基团,避免其二次裂解和交联,在一定程度上提高处理煤的混合溶剂抽提率,改善其溶胀性能。     

Isothermal Degradation of PVC/MBS Blends

The process of thermal degradation of poly(vinyl chloride)/poly(methyl methacrylate-butadiene-styrene) (PVC/MBS) blends was investigated by means of isothermal thermogravimetry in nitrogen. The total mass loss was determined after 120 min. The kinetic parameters of the degradation process were determined by applying two kinetic models: the model which assumes autocatalytic degradation (Prout-Tompkins) and the model of two-dimensional diffusion. It was established that the thermal degradation at lower degrees of conversion (α<0.20) was well described by the former model, but the latter model was applicable at higher degrees of conversion. The thermal stability of blends at a certain temperature of isothermal degradation depends on the blend composition and the shell/core ratio in MBS, and on the adhesion in the boundary layer in PVC/MBS blends. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal degradation of copolymers of styrene and 4-nitrostyrene

The thermal degradation of styrene-4-nitrostyrene copolymers (SNS) has been studied using differential thermal analysis (DTA) and thermogravimetry (TGA) under isothermal and dynamic conditions in dynamic nitrogen. The apparent activation energy of the degradative process was determined following several methods of thermogravimetric analysis. The stability decreases as the nitrostyrene content in the copolymer increases. Fourier-transform infra-red spectroscopy has been used to analyze the degradation products at various degrees of conversion.     

Synthesis, characterization and properties of biodegradable polylactic acid-β-cyclodextrin cross-linked copolymer microgels

The novel biodegradable polylactic acid-β-cyclodextrin (PLA-β-CD) cross-linked copolymer microgels were prepared by the radical copolymerization of PLA macromonomer and polymerizable β-CD derivatives. The β-CD derivatives with various numbers of polymerizable vinyl groups were synthesized from 1-allyloxy-2,3-epoxy propane (also called allylglycidyl ether, AGE) and β-CD. The chemical structures of polymerizable monomers were determined by NMR. The thermal properties, size, morphology, in vitro degradation and swelling behavior of the microgels were investigated. The results indicated that the microgels were stable under thermal conditions up to 200 °C. The microgels were spherical in aqueous solution. The hydrophilicity of the microgels increased with increasing β-CD contents, while the swelling ratios and degradation rate decreased. The more vinyl groups on β-CD, the higher cross-linked density, which resulted in a decrease of the swelling ratios and the rate of degradation.     

PPESK/PES共混物热性能及动态机械性能研究

采用熔融共混法制备了不同重量比例的新型含二氮杂萘酮结构聚芳醚砜酮(PPESK)与聚醚砜(PES)共混物.利用热失重(TGA)及动态热机械仪(DMTA)对该共混物的热性能及动态机械性能进行了研究.研究结果表明,在氮气氛围中,PPESK热分解分为两步反应进行,反应级数n=1,说明PPESK在氮气氛围中的热分解反应类型与β(升温速率)无关而与材料物性有关;采用Ozawa方法得出在15%热失重前,热分解活化能的平均值为240 kJ/mol;随着升温速率的提高,PPESK热降解速率有减缓趋势.在280℃以前,PPESK储能模量值随温度变化较小,保持在较高值,温度在280~330℃之间,储能模量值降低幅度突变.另外,PPESK中加入PES会降低其储能模量值及其热稳定性.     

Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants

The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (E_α). The increased E_α indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased E_α after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the E_α of fire-retarded cellulose thermal insulation compared with the KAS and FWO methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

     

Fireproofing of polyurethane by organophosphonates

In this work, we have studied the degradation processes of polyurethane containing phosphonate groups used as a fireproofing agent. These studies are undertaken by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) measurements. It is found that fireproofing agents with phosphonate react with oxygen in the air and prevent the complete combustion of the material. It is also found that the energy released during combustion is low when comparison is performed with other fireproofing materials.     

Synthesis and physicochemical characterization of biodegradable and pH‐responsive hydrogels based on polyphosphoester for protein delivery

In this work, a series of biodegradable and pH‐responsive hydrogels based on polyphosphoester and poly(acrylic acid) are presented. A novel biodegradable macrocrosslinker α‐methacryloyloxyethyl ω‐acryloyl poly(ethyl ethylene phosphate) (HEMA‐PEOP‐Ac) was synthesized by first ring‐opening polymerization of the cyclic monomer 2‐ethoxy‐2‐oxo‐1,3,2‐dioxaphospholane using HEMA as the initiator and Sn(Oct)₂ as catalyst, and subsequent conversion of hydroxyl into vinyl group. The hydrogels were then fabricated by the copolymerization of the macromonomer with acrylic acid, and their swelling/deswelling and degradation behaviors were investigated. The results demonstrated that the crosslinking density and pH values of media strongly influenced both the swelling ratio and the degradation rate of the hydrogels. The rheological properties of these hydrogels were also studied from which the storage modulus (G′) showed clear dependence on the crosslinking density. MTT and “live/dead” assay showed that these hydrogels were compatible to fibroblast cells, not exhibiting apparent cytotoxicity even at high concentrations. Moreover, in vitro bovine serum albumin release from these hydrogels was also investigated, and it could be found that the release profiles showed a burst effect followed by a continuous release phase, and the release rate was inversely proportional to the crosslinking density of hydrogels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1919–1930, 2010     

Development of reinforced hydrogels — I. Radiation induced graft copolymerization of methylmethacrylate on non-woven polypropylene fabric

Polypropylene (PP) fibers were grafted with methylmethacrylate. Effects of direct and pre-irradiation method and monomer concentration on the degree of grafting were investigated. The grafted PP fibers were characterized by swelling measurements, IR spectroscopy and by its mechanical and thermal properties. It was found that the direct method was more efficient than the indirect or pre-irradiation method and the monomer concentration for highest degree of grafting was 40% of MMA. Mechanical properties (tensile strength) and thermal stability decrease with grafting yield. Those changes were related to degradation of tie molecules between crystals and formation of rigid branches of PMMA on PP amorphous phase.     

Degradation Thermique D'Un Polystyrene Choc Ignifuge Par Un Melange Intumescent

The study of the thermal degradation of the fireproof polystyrene—butadiene copolymer by an intumescent system: ammonium polyphosphate (APP)—pentaerythritol (PER)—talc (TAL), was done through an experimental process. Thermogravimetry under air sweeping was used. We observed for the degradation rate of the mixture with fireproofing agents, in the field of 20 to 50% mass loss, a better linear increasing when this mixture contains more TAL and the ratio APP/PER is smaller.

This revised version was published online in November 2005 with corrections to the Cover Date.     

Characterization and comparative study of pyrolysis kinetics of the rice husk and the elephant grass

A comparative evaluation of different biomasses allows the choice that presents the best potential as fuel for energy production. The knowledge of the thermal and kinetics parameters of the biomass in the process of thermal conversion is fundamental as their chemical and physical characterization. Various methodologies have been developed for the determination of kinetic parameters as apparent activation energy and reaction order from the thermogravimetric analysis. In this work, the apparent activation energy needed to break the bonds of hemicelluloses and cellulose of rice husk and elephant grass during the thermal conversion was evaluated according to the kinetics models of Flynn and Wall and Model Free Kinetics developed by Vyazovkin. The biomass elephant grass and rice husk were characterized for moisture, ash and volatile matter by ASTM E871, ASTM E1755, ASTM E872, respectively, and fixed carbon by difference. The percentage of carbon, hydrogen, nitrogen, and oxygen were determined by ultimate analysis. The elephant grass showed to be more suitable for production of bio-oil through pyrolysis due to the higher percentage of volatile, less ash content and less energy required to break the bonds of hemicellulose and cellulose than rice husk in the thermal conversion process.     

Aging behavior and thermal degradation of fluoroelastomer reactive blends with poly-phenol hydroxy EPDM

In this paper, the aging behavior of the reactive blends of fluoroelastomer (FPM) with poly-phenol hydroxy ethylene propylene diene monomer rubber (PHEPDM) in hot air was firstly investigated. The aging mechanism was analyzed by the swelling experiment, attenuated total-reflectance Fourier-transform infrared (FTIR-ATR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the aging process increased the crosslinking density and the content of double bond. The O/F or O/C ratios increased and then decreased during aging because of the oxidation reaction of molecular chain and the surface migration of fluoro group. Secondly, thermogravimetric analysis (TGA) was used to study the thermal degradation behavior of the reactive blends. The apparent degradation activation energy (E) of FPM/PHEPDM reactive blends was calculated by the Kissinger and Coats-Redfern methods, respectively. The results showed that the FPM/PHEPDM reactive blends had higher thermal degradation temperature but lower E than FPM. Both the thermal degradation process of FPM/PHEPDM reactive blends and FPM were determined by nucleation and growth mechanism (Am). The general mechanism function was [−ln(1 − α)]^1/m. The optimum value of m was between 1/3 and 1/2 for FPM/PHEPDM reactive blends, but 1/2 for FPM. From the results above, it was deduced that the special structure of PHEPDM made itself surrounded by fluoroelastomer and protected from hot-air aging and thermal degradation.     

Structure and properties of polyimide films during a far‐infrared‐induced imidization process

The conversion of poly(amic acid) into polyimide (PI) was achieved with far‐infrared radiation (FIR) and conventional thermal treatments. The structure and properties of PI films during different stages of imidization were studied with Fourier transform infrared spectroscopy, weight‐loss analysis during imidization, tensile property measurements, and dynamic mechanical thermal analysis. The effects of the imidization degree, postimidization, and solvent on the thermal and mechanical properties of PI films were quantitatively investigated. The corresponding structural changes were also examined. The experimental results showed that the imidization process proceeded more quickly and more completely in an FIR oven than in a conventional oven. A prolonged FIR treatment at a lower temperature (25–100 °C) accelerated the imidization process. The tensile stress–strain curves had a fanlike distribution with the development of the FIR imidization process and a fishtail distribution with conventional thermal imidization. During FIR imidization, the best tensile properties were obtained at 340 °C, and thermooxidative degradation occurred at about 420 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2490–2501, 2004     

Monitoring the moisture-related degradation of ethylene propylene rubber cable by electrical and SEM methods

Several electrical approaches were used to monitor the electrical degradation of ethylene propylene rubber (EPR) cable under (1) high temperature water submerged for long-term, (2) room temperature water submerged after thermal and radiation aging, and (3) loss-of-coolant accident simulation conditions. The moisture-related degradation behavior was investigated by the correlation of electrical measurements, moisture content analysis, and scanning electron microscope (SEM) observation. The results indicate that void size and density of insulation material strongly affect the material's water resistant capability and electrical degradation. Also, the void size of insulation material after moisture-related degradation is much bigger than that after thermal and radiation aging, and the former causes material swelling. Combining insulation resistance and dissipation factor condition monitoring (CM) techniques can provide useful means for monitoring cable degradation while the cable is exposed to moisture and high temperature/radiation environment. The Arrhenius model is applied together with appropriate acceptance criteria obtained by insulation resistance measurement to calculate cable remaining life. According to test results and the remaining life calculation, it is shown that the moisture-related degradation of EPR cable can be early assessed by insulation resistance measurement, which is a non-destructive prognostic CM technique.