Thermal properties of polyurethanes synthesized using waste polyurethane foam glycolysates

In this work thermal transitions and thermal stability of polyurethane intermediates and polyurethanes were investigated. The intermediates were obtained by glycolysis of waste polyurethane (PUR) in the reaction with hexamethylene glycol (HDO). The excess of HDO was not separated from the product after the glycolysis process was finished. The effects of different mass ratio of HDO to PUR foam on selected physicochemical properties (hydroxyl number, Brookfield viscosity and density) were also determined. The polyurethanes were synthesized from the obtained intermediates by the prepolymer method using diisocyanate (MDI) and glycolysis product of molecular mass in range 700/1000 g mol^–1. Hexamethylene glycol, 1,4-butanediol and ethylene glycol were used as chain extender agents. Influence of NCO groups concentration in prepolymer on glass transition temperature (T _g) and storage and loss modulus (E’, E’’) of polyurethanes were investigated by the DMTA method. Thermal decomposition of obtained glycolysates and polyurethanes was followed by thermogravimetry coupled with Fourier transform infrared spectroscopy. Main products of thermal decomposition were identified.     

Thermal degradation characteristics of rigid polyurethane foam and the volatile products analysis with TG-FTIR-MS

Thermal degradation characteristics of rigid polyurethane (PUR) foam in both air and nitrogen gaseous environments were studied using thermogravimetry and differential scanning calorimetry (TG-DSC) hyphenated techniques. And in situ Fourier Transform Infrared (FTIR) was employed to investigate the characteristic functional groups of the decomposition residues at different temperatures. It is found that the thermal degradation of PUR material in air and N₂ present a three-stage and a two-stage process, respectively. And the degradation reaction rate of PUR in air is accelerated significantly due to the presence of oxygen. The thermal degradation mechanism of PUR under non-oxidizing gaseous environment was evaluated using a TGA instrument coupled with Fourier Transform Infrared and mass spectrometer (TG-FTIR-MS). HCFC-141b served as blowing agent is detected at the initial stage. The urethane bond groups of PUR start to break up into isocyanates segments and polyols segments from about 200 °C. With an increase of temperature, the polyols decompose into some kinds of aliphatic ether alcohol. In the temperature range of 350–500 °C, the dominant volatile products are primary amines, secondary amines, vinyl ethers and CO₂.     

抽提物对生物质热裂解机理的影响研究

利用惰性溶剂从生物质中提取得到相应抽提物,在热重红外联用仪上研究了抽提物的热裂解行为,并探讨了其对生物质热裂解的影响。结果表明,因不同种类生物质中木质素结构单元中紫丁香基和愈创木基数量不同,从而导致抽提物成分存在差异,相应的热裂解产物分布也不一致。水曲柳抽提物因含有较多的酚类物质而在热解高温段生成了甲醇和甲烷。相比于原样,抽提残渣反应活化能增加,且主要产物析出时间提前,同时酸类物质和直链烷烃析出量减少,而水、CO2、CO和醛类物质的产量则有所增加。     

Effect of surface modification of montmorillonite on the properties of rigid polyurethane foam composites

<正>This study investigated the influence of various organically modified montmorillonites(organoclays) on the structure and properties of rigid polyurethane foam(RPUF) nanocomposites.The organoclays were modified with cetyltrimethyl ammonium bromide(CTAB),methyl tallow bis(2-hydroxyethyl) quaternary ammonium chloride (MT2ETOH) and tris(hydroxymethyl)aminomethane(THMA) and denoted as CMMT,Cloisite 30B and OMMT, respectively.MT2ETOH and THMA contain hydroxyl groups,while THMA does not have long aliphatic tail in its molecule. X-ray diffraction and transmission electron microscopy show that OMMT and Cloisite 30B can be partially exfoliated in the RPUF nanocomposites because their intercalating agents MT2ETOH and THMA can react with isocyanate.However, CMMT modified with nonreactive CTAB is mainly intercalated in the RPUF matrices.At a relatively low filler content,the RPUF/CMMT composite foam has a higher specific compressive strength(the ratio of compressive strength against the apparent density of the foams),while at relatively high filler contents,RPUF/Cloisite 30B and RPUF/OMMT composites have higher specific compressive strengths,higher modulus and more uniform pore size than the RPUF/CMMT composite.     

Facile fabrication of hydrophobic octadecylamine-functionalized polyurethane foam for oil spill cleanup

To improve the hydrophobic property of polyurethane foam for oil spill cleanup, the polyurethane foam with nitrile groups is modified by grafting with oleophilic octadecylamine. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and optical contact angle measuring device are used to characterize the modified polyurethane foam. The results show that the octadecylamine has been successfully grafted onto the polyurethane foam and improved the foam hydrophobicity. The modified foam exhibits higher contact angle (146.3 ± 2.8°) compared to the unmodified foam (121.4 ± 3.2°). Moreover, the water sorption of the modified foam is 0.11g/g, which is much lower than that of the unmodified foam (0.84g/g). On the other hand, the sorption capacity of the modified foam for toluene, gasoline and diesel sorption is increased by 20?40%. Therefore, the polyurethane foam prepared by us can be effectively used in oil/solvent spill cleanup.     

Fabrication and characterization of functional graded polyurethane foam (FGPUF)

In this study, functionally graded polyurethane foams (FGPUFs) were produced using a layer‐by‐layer casting technique. Discontinuous FGPUFs were fabricated by this method. The scanning electron microscopy was used to study the morphology of all specimens. The mechanical properties of the polyurethane foams (PUFs) were evaluated by compression, indentation force deflection, drop weight tests, and dynamic mechanical thermal analysis. Scanning electron microscopy micrographs taken from different zones of functionally graded material showed the variation of the morphology of cells as well as the suitable interfaces between the layers of PUF. Investigation of mechanical properties suggested that FGPUF specimens have an optimum behavior between other specimens in compression and indentation force deflection tests. The results of drop weight test showed that FGPUF samples behaved like an energy absorber (14.31 KN) in comparison to other PUFs. The results of dynamic mechanical thermal analysis data showed an improvement in glass transition temperature (T_g) to −47.2°C and stability of modulus of FGPUFs as temperature increases.     

基于TG-FTIR的生物质催化热解试验研究

运用热重－傅里叶红外光谱联用技术(TG-FTIR),以麦秸为研究对象,探讨催化与非催化条件下生物质的热解挥发分析出特性,分析研究热解温度、催化剂种类对生物质热解主要析出产物的影响。通过热重TG和DTG曲线,获得了相关热解特性参数及动力学参数。结果表明,添加NiO和CaO存在两个失重峰,并促进麦秸热解反应进行,降低表观活化能,其中NiO对提高热解析出产率作用更显著。通过红外光谱对热解产物实时测量的分析表明,CO与CO2的析出与失重峰基本一致,而CH4的析出滞后于前两者。添加NiO和CaO有利于减少热解产物中的CO2的浓度,促进挥发分产物CO、CH4的生成。其中CaO更有利于生物质在温度800℃以下的热解性能改善,而NiO在800℃以上具有更好的催化作用。     

空心玻璃微珠对聚氨酯泡沫燃烧和力学性能的影响

通过向聚氨酯发泡体系中添加空心玻璃微珠,制备出空心玻璃微珠聚氨酯三相泡沫.研究了空心玻璃微珠添加量、聚磷酸铵(APP)用量、膨胀阻燃体系(IFR)浓度等因素对聚氨酯泡沫燃烧和力学性能的影响.结果表明,单独添加空心玻璃微珠对聚氨酯泡沫的氧指数和水平燃烧速度影响不大.添加APP或IFR后,空心玻璃微珠聚氨酯三相泡沫的阻燃效...     

Effect of blowing agent content on the structure and flame-retardant properties of rigid polyurethane foam/expanded graphite composites

Driven by global environmental issues, the development of green building materials has become an immediate focus. In this work, n-pentane was used as an environmentally friendly blowing agent to prepare flame-retardant rigid polyurethane foam (RPUF) with the addition of expandable graphite (EG) successfully, and the effect of n-pentane content on flame retardancy and compressive properties of RPUF/EG composites was investigated through limit oxygen index (LOI), vertical burning test (UL-94), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and compressive properties test. SEM results show that the content of EG and n-pentane causes a change in the cell structure of RPUF. The change of the n-pentane content has also an obvious effect on the thermal stability, flame retardancy, and specific compressive strength of RPUF/EG composites. In addition, the cell structure of RPUF matrix has an obvious influence on the distribution of EG in the composites, which indirectly affects the flame-retardant efficiency of EG. This research explores the conditions for the application of environmentally friendly RPUF and expands its application prospects.     

Immobilization of cellulase using polyurethane foam

Cellulase was covalently immobilized using a hydrophilic polyurethane foam (Hypol®FHP 2002). Compared to the free enzyme, immobilized cellulase showed a dramatic decrease (7.5-fold) in the Michaelis constant for carboxymethylcellulose. The immobilized enzyme also had a broader and more basic pH optimum (pH 5.5–6.0), a greater stability under heat-denaturing or liquid nitrogen-freezing conditions, and was relatively more efficient in utilizing insoluble cellulose substrates. High molecular weight compounds (Blue Dextran) could move throughout the foam matrix, indicating permeability to insoluble celluloses; activity could be further improved 2.4-fold after powdering, foams under liquid nitrogen. The improved kinetic and stability features of the immobilized cellulase combined with advantageous properties of the polyurethane foam (resistance to enzymatic degradation, plasticity of shape and size) suggest that this mechanism of cellulase immobilization has high potential for application in the industrial degradation of celluloses.     

Impact of ambient and vacuum pressure on the physico mechanical properties of flexible polyurethane foam reinforced with CaCO3

This study investigates the effects of variable pressure conditions (550 and 1013 mbar) on the physico-mechanical and structural properties of flexible polyurethane foam, incorporating different compositions of calcium carbonate (CaCO₃) filler. The objective is to achieve sustained mechanical and structural properties of flexible polyurethane foam while reducing costs through variable pressure foaming technology. With CaCO₃ filler concentrations ranging from 20 to 100 parts per hundred (pphp) of polyol, it was found that foam produced at low pressure (550 mbar) demonstrated improved resilience and durability, particularly with CaCO₃ compositions up to 100 pphp. Conversely, foam produced at standard atmospheric pressure (1013 mbar) using compositions up to 100 pphp did not exhibit significant enhancements in physico-mechanical properties. The study employs various characterization techniques, including mechanical testing, scanning electron microscopy, differential scanning calorimetry, thermal gravimetric analysis, and Fourier transform infrared spectroscopic analysis, to assess the flexible polyurethane foam. It provides a detailed examination of the effects of variable pressure on cellular structure, cell size, filler distributions, mechanical properties, and thermal stability of flexible polyurethane foam using CaCO₃ filler.     

Determination of lead and cadmium in tap water and apple leaves after preconcentration on a new acetylacetone bonded polyurethane foam sorbent

The present work describes a rapid, cost-effective analytical procedure for the determination of lead and cadmium in environmental samples by off-line preconcentration with polyurethane foam (PUF) functionalised with acetylacetone by covalent coupling through the–N=N–group. The optimum pH ranges for quantitative uptake were 5–7, 6–7 for lead and cadmium, respectively. The kinetics of metal uptake by the new foam was found to be fast, reaching equilibrium in a few minutes. Metal ions were sorbed in the minicolumn, eluted with acid solutions and determined by flame atomic absorption spectrometer (FAAS). Under the optimum conditions, the preconcentration factors obtained were 288 for Cd and 224 for Pb. The limits of detection of the proposed procedure were 0.09 and 0.07 µg L^?1 for Pb and Cd, respectively. The relative standard deviation (RSD) was less than 10%. The accuracy of the method was estimated by using environmental samples that were spiked with Cd and Pb ions. The capacity of the acetylacetone bonded PUF (AA-BPUF) sorbent at optimum conditions has been found to be 4.5, 6.9 µmol g^?1 of sorbent for Pb and Cd, respectively.     

Experimental investigation and numerical simulation of the combustion of flexible polyurethane foam with larger geometries

Numerical modelling of the combustion of flexible polyurethane foam (FPUF) is challenging, as the structural collapse and shrinkage of the foam complicate its pyrolysis, and two fuel items are involved in the combustion. Two-layer pyrolysis models were established based on the bench-scale tests over the past decade, but the accuracy was limited when simulating the combustion of FPUF with larger geometries. To improve the accuracy of the numerical simulation, small-scale experiments were conducted to investigate the combustion of FPUF with a larger geometry. Firstly, numerical simulations using a two-layer pyrolysis model proposed in the most recent research were performed to simulate the combustion of FPUF in the small-scale experiments. It was found that the heat release rate (HRR) was over-predicted in the initial combustion stage. Subsequently, based on the analysis of the visual and measured data obtained from the small-scale experiments, a three-layer model was proposed to describe the pyrolysis of FPUF in flaming combustion. The three-layer model was validated with the comparison of the predicted and experimental data. The results indicate that the numerical simulation using the three-layer model has a better performance in replicating the combustion of FPUF under well-ventilated conditions. While, the capability of the three-layer model was limited when it was used to simulate the combustion of FPUF in under-ventilated conditions, as it is found that ventilation influences the HRR of FPUF to a significant extent.     

Preparation and properties of negative ion/polyurethane flexible foam composites

Abstract

In this study, negative ionpowder was modified with a silane coupling agent and then added to the polyurethane flexible foam to prepare NI/PU flexible foam composites by the one-step foaming method. The effects of the amount of negative ion powder on the mechanical properties, thermal properties and release of negative ions were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and negative ion detectors. The SEM results showed that modified negative ion powder could be more uniformly distributed around the cell walls of the polyurethane flexible foam. The thermal stability, tensile strength and resilience of the NI/PU flexible foam composite were improved with the increase of the amount of modified negative ion powder. Increasing the amount of modified negative ion powder could also result in an increase in the release of negative ions, and it reached 5500/cm³ or higher at a negative ion content of 3%.     

钾元素对生物质主要组分热解特性的影响

采用热重-红外联用仪对松木及生物质主要化学组分半纤维素、纤维素、木质素的热解特性及钾元素对其热解特性的影响进行了研究.结果表明,半纤维素、纤维素、木质素发生热解的主要温度分别为200~350 ℃、300~365 ℃和200~600 ℃;半纤维热解产物中CO、CO₂较多;纤维素热解产物中LG和醛酮类化合物最多;木质素热解主要形成固体产物,气体中CH₄相对含量较高.三种组分共热解过程中发生相互作用使热解温度提高、固体产物增加,气体中CO增加而CH₄减少.添加K₂CO₃后半纤维素和纤维素热解温度区间向低温方向移动,固体产率提高.K对纤维素作用最明显,CO、CO₂气体与固体产物产率明显增加,醛酮类和酸类物质的产率降低;木质素受K影响相对较小,热解固体产物略有增加,挥发分中H₂O和羰基物质增加;三组分共热解减弱了钾元素的催化作用.     

Fire retarded polyurethane foam composites based on steel slag/ammonium polyphosphate system: A novel strategy for utilization of metallurgical solid waste

A series of FR-RPUF composites were prepared by a one-step water foaming process with ammonium polyphosphate (APP) and steel slag (SS) as flame retardants. Thermogravimetric analysis (TG), limiting oxygen index (LOI), UL-94 vertical combustion test, microscale combustion calorimetry (MCC), TG-Fourier transform infrared spectrometry (TG-FTIR), scanning electron microscopy (SEM), Raman spectra and FTIR were used to investigate the thermal stability, flame retardancy, combustion performance, gas phase products, and char residue morphology of FR-RPUF composites. TG test results showed that the initial decomposition temperature (T_-5wt%) and char residue rate at 700°C of RPUF/APP/SS composites were significantly enhanced by the addition of APP and SS, and the thermal stability of the composites was improved. Flame retardant test results confirmed the significantly increased LOI values of RPUF/APP/SS composites with V-0 rating. TG-FTIR also confirmed the obviously decreased release of toxic gases and flammable gases in the combustion of RPUF/APP/SS composites. SEM and Raman spectra of char residues for the composites suggested that APP/SS system improved the compactness and graphitization degree of char layer for RPUF/APP/SS composite. The above researches provide a new strategy for the utilization of SS in fire safety engineering.     

聚氨酯/环氧树脂互穿网络聚合物的性能研究

互穿聚合物网络（Interpenetrating polymer net-work,简称IPN）广泛应用的为聚氨酯基的互穿网络聚合物。其合成多集中在弹性体方面。本文用同步法合成的聚氨酯／环氧树脂互穿网络硬质泡沫塑料材料（简称PU／ERIPNF）,机械性能较好,并研究了其动态力学性能及形态变化。     

Synthesis,characterization of low density polyhydroxy polyurethane foam and its application for separation and determination of gold in water and ores samples

In this work, a new type of sorbent (low density polyhydroxy polyurethane Foam, LPPF) was synthesis by using water hydrolysis of polyurethanediazonium chloride salt. LPPF was characterized using different tools e.g. elemental analysis, UV–vis and IR spectra, TGA, SEM, density and pH_ZPC. It was tested for separation, preconcentration and determination of gold in environmental samples using batch and dynamic techniques. The sorption experimental data was fitted by the pseudo-first kinetic mathematical equation (R² = 0.991). The sorption rate of the Au (III) ions is very fast, the half-life (t_1/2) ≈ 34 s. The equilibrium process is well described by the Freundlich isotherm model, the R² value is 0.967, which attributed to the heterogeneous surface structure of the LPPF. The breakthrough capacity of LPPF and the recovery of gold ions were 0.36 mmol g⁻¹ (70.5 mg g⁻¹) and 99–100%, respectively. The lower detection limit of gold by using spectrophotometric method is 3.3 ng L⁻¹ with preconcentration factors ≈ 450 (RSD ∼ 1.66%, n = 4). The values of ΔG and ΔH for the sorption of gold onto LPPF were −12.5 and −103.5 kJ mol⁻¹, respectively, which indicate that the sorption of Au (III) onto LPPF is spontaneous and exothermic reaction. The obtained results indicate that the ion chelation and ion association might be the most probable mechanism of gold sorption onto LPPF. The study shows LPPF has the potential of application as an efficient sorbent for the extraction and determination of gold in water, gold alloys pharmaceutical and granite samples.     

Lanthanum phenylphosphonate–based multilayered coating for reducing flammability and smoke production of flexible polyurethane foam

In the present work, lanthanum phenylphosphonate (LaPP)–based multilayered film was fabricated on the surface of flexible polyurethane (PU) foam by layer‐by‐layer self‐assembled method. The successful deposition of the coating was confirmed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX). Subsequently, the thermal decomposition and burning behavior of untreated and treated PU foams were investigated by thermogravimetric analysis (TGA) and cone calorimeter, respectively. The TGA results indicated that T_max2 of treated PU foams were increased by approximately 15°C to 20°C as compared with untreated PU foam. The peak heat release rate (PHRR) and total heat release (THR) of PU‐6 (with 19.5 wt% weight gain) were 188 kW/m² and 20.3 MJ/m², with reductions of 70% and 15% as compared with those of untreated PU foam, respectively. Meanwhile, the smoke production of treated PU foam was suppressed after the construction of LaPP‐based coating.     

Determination of lead in water samples after its separation and preconcentration by 4,5-dihydroxy-1,3-benzenedisulfonic acid functionalised polyurethane foam

A new sorbent based on polyurethane foam functionalised with 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron-PUF) was synthesised. This material was used in the development of a procedure for preconcentration of lead, with subsequent detection by flame atomic absorption spectrometry (FAAS). The influence of some variables involved in the extraction process was studied. Analytical parameters were evaluated using 50 and 500?mL of Pb (II) solution. Under optimum conditions, the system showed enrichment factors of 38 (50?mL) and 114 (500?mL). The detection limits obtained were 0.5 and 1.1?µg?L^?1 when volumes of 500 and 50?mL of Pb (II), respectively, were used. The method was applied to the determination of lead content in well water and drinking water samples collected in the town of Amelia Rodrigues, Bahia, Brazil.