Flame retardant poly (lactic acid) biocomposites based on azo‐boron coupled 4,4′‐sulfonyldiphenol and its combination with calcium lignosulfonate—Crystalline and mechanical properties

Poly (lactic acid) (PLA) has become an important biopolymer with excellent properties but has limited engineering applications where fire safety is ultimate. An efficient flame retardant (FR) for PLA biocomposites based on azo‐boron coupled with 4,4′‐sulfonyldiphenol‐(((1E,1′E)‐(sulfonylbis(6‐hydroxy‐3,1‐phenylene))bis (diazene‐2,1‐diyl))bis(3,1‐phenylene))diboronic acid (SBDA) was synthesized and characterized by FTIR, ¹H and ¹³C NMR spectra. SBDA was combined with calcium lignosulfonate (Calig) and compounded with PLA, and the FR, crystallization, and mechanical properties were investigated. The addition of 15 wt% FR (10 wt% Calig and 5 wt% SBDA) into PLA led to important reductions in peak heat release rate (PHRR) approximately 54%, total heat release (THR) approximately 28.6%, and the average effective heat of combustion (AEHC) approximately 29.4%. The fire performance index and fire growth index improved by approximately 56.4% and 33.1%, respectively. A V‐0 rating (vertical burning test) and a limiting oxygen index value of 28.8% were achieved for the FR PLA biocomposites. The combinatory SBDA/Calig reduced the segmental mobility of PLA in the organic‐inorganic interface with insignificant changes in the elongation at break and the Young Modulus. TG‐IR study showed significant reductions in pyrolysis gaseous products for the composites compared with PLA. This research work will expand the frontiers of knowledge on use of boron and calcium functionalized polyaromatic polyols for reducing the flammability of PLA.     

计算机辅助氧弹量热计探索火箭燃料的推进性能

本实验基于现行"综合化学实验"进行创新性改进。将一定压力的氮气充入氧弹,在以硝酸钾为氧化剂、三氧化二铁为催化剂的条件下,混合一定比例的蔗糖得到硝糖燃料,进行燃烧,采用环境恒温量热计记录蔗糖燃烧过程中的温度变化,再通过雷诺作图法校正产生的DT偏差,最终计算得到硝糖燃烧过程的恒容热效应,即为硝糖燃料的爆热值。当蔗糖:硝酸钾:氧化铁的质量比为39:59:2时,其爆热值最大,比冲最大。在上述实验的基础上,选择最佳配比的硝糖燃料,用于计算机仿真模拟火箭发射系统。通过改变燃烧室压力和燃料流速,计算得到该最佳配比硝糖燃料的比冲和火箭飞行高度,进而得到采用单级火箭将东方红一号卫星送入预定轨道的发动机参数。改变每一级火箭的燃料类型与比例,设计得到适于推进不同卫星进入预定轨道的二级火箭和三级火箭。通过设计氧弹量热计的拓展应用与计算机仿真模拟相结合的实验,达到已有实验的创新设计、启发学生创造性和引起科研兴趣的目的。     

吸热型碳氢燃料热沉的测定研究

改进并重新组装了自行研制的高温热导型流动热量计 ,利用电标定法测定了该仪器在 70 0℃和 80 0℃的热量常数。为检验仪器的可靠性 ,本仪器测定了氮气的热沉 ,结果表明实验值与用氮气的热容公式计算所得的计算值基本吻合。对自制的吸热型碳氢燃料 (FRA)和作为模型化合物的正庚烷的热沉进行了测定 ,发现在 70 0℃时两者的热沉值比较接近 ,分别为 3 0 7MJ kg和 3 2 3MJ kg。在 80 0℃时 ,两者都具有较高的热沉值 ,分别达到 5 6 9MJ kg和 6 6 0MJ kg ,该热沉值能够满足超高音速飞行器的热管理要求。     

The effects of wood-flour on combustion and thermal degradation behaviors of PVC in wood-flour/poly(vinyl chloride) composites

The effects of wood-flour on combustion and thermal degradation behaviors of PVC in wood-flour/poly (vinyl chloride) composites (WF-PVC) were investigated by using cone calorimeter (CONE) and TGA. The results show that thermal degradation behavior of WF-PVC composites has obvious characteristics of that of PVC. Interactions occur between wood-flour and PVC during the combustion and thermal degradation of WF-PVC composites. The thermal degradation of wood-flour can be accelerated by pure PVC. Moreover, the char formation can be raised by adding wood-flour to PVC. Compared with PVC at all flaming stage, when heat flux is kept at 50 kW m⁻², the average heat release rate (av-HRR), the total heat release (THR), the total smoke production (TSP) and the average specific extinction area (av-SEA) of WF-PVC composites are respectively reduced by 44%, 9.2%, 25.8% and 29.9%. In WF-PVC composites, the wood-flour has remarkable effects on the properties of heat release and smoke release of PVC.     

Synergistic effect of carbon nanotubes and decabromodiphenyl oxide/Sb2O3 in improving the flame retardancy of polystyrene

Brominated flame retardant polystyrene composites were prepared by melt blending polystyrene, decabromodiphenyl oxide, antimony oxide, multi-wall carbon nanotubes and montmorillonite clay. Synergy between carbon nanotubes and clay and the brominated fire retardant was studied by thermogravimetric analysis, microscale combustion calorimetry and cone calorimetry. Nanotubes are more efficient than clay in improving the flame retardancy of the materials and promoting carbonization in the polystyrene matrix. Comparison of the results from the microscale combustion calorimeter and the cone calorimeter indicate that the rate of change of the peak heat release rate reduction in the microscale combustion calorimeter was slower than that in the cone. Both heat release capacity and reduction in the peak heat release rate in the microscale combustion calorimeter are important for screening the flame retardant materials; they show good correlations with the cone parameters, peak heat release rate and total heat released.     

Determination of the flammability properties of polymeric materials: A novel method

Standard flammability tests, like the Cone Calorimeter, were developed several decades ago and provided sufficient flammability data for the purposes of the time. However, recent pyrolysis models have revealed the limitations of the standard test in providing adequate data for current flammability analysis and modelling. This paper reviews the assumptions in the standard test and proposes a novel sample holder for the cone calorimeter which incorporates a large block of aluminium at the rear face of the sample under test. This allows the heat losses at the rear face of the sample to be measured precisely and enables more accurate calculation of the material flammability properties. Tests of PA6 and a nano-composite of PA6 & Cloisite 30B, carried out using the standard and new sample holders, are presented and discussed. The peak of high heat release rate observed in standard tests of PA6 is not observed using the novel sample holder, where the burning behaviour of PA6 and the nano-composite material are largely similar. The implications of these observations are discussed.     

Studies on thermochemical properties of ionic liquids based on transition metal

A brown and transparent ionic liquid (IL), [C₄mim][FeCl₄], was prepared by mixing anhydrous FeCl₃ with 1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]), with molar ratio 1/1 under stirring in a glove box filled with dry argon. The molar enthalpies of solution, Δ_s H _m, of [C₄mim][FeCl₄], in water with various molalities were determined by a solution-reaction isoperibol calorimeter at 298.15 K. Considering the hydrolyzation of anion [FeCl₄]⁻ in dissolution process of the IL, a new method of determining the standard molar enthalpy of solution, Δ_s H _m⁰, was put forward on the bases of Pitzer solution theory of mixed electrolytes. The values of Δ_s H _m⁰ and the sum of Pitzer parameters: and were obtained, respectively. In terms of thermodynamic cycle and the lattice energy of IL calculated by Glasser’s lattice energy theory of ILs, the dissociation enthalpy of anion [FeCl₄]⁻, ΔH _dis≈5650 kJ mol⁻¹, for the reaction: [FeCl₄]⁻(g)→Fe³⁺(g)+4Cl⁻(g), was estimated. It is shown that large hydration enthalpies of ions have been compensated by large the dissociation enthalpy of [FeCl₄]⁻ anion, Δ_d H _m, in dissolution process of the IL.     

Single run heat capacity measurements

An outline for the data analysis of single-run heat capacity measurments by dual sample DSC is presented with the following features: 1. Heat flow correction by subtracting the contribution due to the sample pan, including correction for mismatched pan masses. 2. Heat flow and temperature correction with a nonlinear temperature calibration, temperature lag correction, and heating rate correction. 3. Calculation of the cell constants for both cell positions and evaluation of the asymmetry factor between cell positions A and B. 4. Heat capacity calibration and calculation with slope and asymmetry correction. 5. Calculation of heat capacity for multiple runs. 6. Data curve fitting for heat capacity.This work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 8818412 and the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. Thanks are given to TA Instruments, Inc. (New Castle, DE) for providing the commercial heat capacity software and helping with the acquisition of the calorimeter.     

Nd(Gly)2Cl3·3H2O和Pr(Ala)3Cl3·3H2O的热力学性质

利用精密自动绝热热量计测定了Nd(Gly)₂Cl₃·3H₂O在80-357K和Pr(Ala)₃Cl₃·3H₂O在80-374K温区的热容. 根据两个化合物的热容计算出了相对于参考温度298.15K的热力学函数(H_T?H_298.15)和(S_T?S_298.15). 根据热重(TG)分析结果, 提出了这两个稀土化合物可能的热分解机理. 利用溶解-反应恒温热量计测定相关化合物的溶解焓并设计盖斯热化学循环, 计算出了两个化合物的标准摩尔生成焓.     

石墨量热计测量相对论电子能谱的数值模拟

采用数值实验的方法对石墨量热计测量电子能谱的过程进行了模拟,并对解谱方法进行了研究。使用MCNP软件建立了实验模型,根据不同能量入射电子能量沉积分布情况确立了入射电子能量-沉积能量的传递函数,研究确定合适的函数求解方法,并采用添加人为扰动的方式对该函数求解方法的可靠性进行分析,最终得到了有效的解谱方法。