高分子片状板材热分析测试影响因素的研究

研究了高分子片状板材的取样位置、样品尺寸、升温速率、热历史及气流速率对DSC及(或)TGA测试结果的影响,简要分析了各因素影响测试结果的原因。结果表明,升温速率对测试结果影响很大,热历史对测试结果有一定影响,取样位置及一定范围内的样品尺寸对测试结果影响不大,气流速率对测试结果影响较微。     

测试条件对静态热机械分析仪测试CLTE的影响

利用静态热机械分析仪（TMA）测试了聚丙烯（PP）的线性热膨胀系数（CLTE）,考察了PP在不同的测试条件下的线性热膨胀系数的变化规律,结果表明力值、升温速率、热历史和测试方向对CLTE结果有影响。     

测试因素对一次性医用口罩通气阻力的影响

针对一次性医用口罩(DMMs)通气阻力测试结果不稳定情况,从测试设备稳定性、气体流量、样品不同位置、气流方向、预处理、测试时间方面展开了研究。结果表明,气体流量、样品不同位置和预处理对口罩的通气阻力有较大影响,测试时间和气流方向对口罩通气阻力无明显影响。研究结果对各生产厂商开发优异DMMs及生产过程质量控制有重要意义。     

热重分析法测试玻纤增强PP和改性PA6塑料中低含量炭黑的研究

采用热重分析法(TGA法),分别以通用塑料中的玻纤增强PP和工程塑料中的改性PA6为代表,首先重点研究塑料体系中低含量(小于1%)炭黑测试的通用关键影响因素,随后验证低含量炭黑测试方法的测试准确性和通用性,最后简要分析造成上述两种材料中低含量炭黑结果差异性的原因。结果表明:测试分段程序和处理程序的选择、坩埚的影响和空白样品影响是低含量炭黑测试的三点通用关键影响因素,本文测试程序分为热解段、降温段和煅烧段,处理程序的炭黑处理温度区间根据炭黑母粒煅烧段的DTG曲线确定,坩埚经二次处理,空白样品测试结果作空白刨除;使用本文炭黑测试方法测试上述两种塑料体系中不同浓度的低含量炭黑,结果可控制在(理论添加量±0.05)%以内,准确性高;此外,提出"有机碳+无机碳+其它"模型,有助于快速理解炭黑测试方法并用于日常产品质量监控或材料逆向分析。     

阻燃PC/聚酯合金中酯交换反应程度的表征

聚碳酸酯(PC)与聚酯做成合金后可发生酯交换反应,影响材料的性能及稳定性,采用几种不同的手段去量化这二者之间的反应,为阻燃合金配方的设计提供指导作用。利用差式扫描量热仪(DSC)和静态热分析仪(TMA)对PC与聚酯之间的反应程度进行判别及量化。结果表明,酯交换反应程度越小时,DSC和TMA测试结果是DSC测得?t_m和?t_c越小,TMA测得的平均线性膨胀系数越大。     

聚丙烯DSC测试影响因素探究

以聚丙烯注塑成型样品为例,分别以不同温度对样品进行状态调节、不同升温速率消除样品热历史和不同降温速率冷却对样品进行DSC实验,分析其对测试结果的影响.结果表明:以不同温度对样品进行状态调节后进行实验,其第一次升温熔融峰温受状态调节温度影响出现先增大后减小,最大偏差2℃,对随后的降温过程和第二次升温过程无影响;以5℃/m...     

微波消解-电感耦合等离子体发射光谱(ICP-OES)法测生物质中的碱金属和碱土金属

为研究并解决测试生物质样品中碱金属和碱土金属含量的干扰,采用微波消解-电感耦合等离子体发射光谱(ICP-OES)法对生物质中的碱金属和碱土金属钾、钙、钠、镁元素进行测定,考察了样品消解后不同的酸体系,共存元素干扰对钾、钠、钙、镁含量测定的干扰研究。经过研究表明,接近分析标准曲线酸浓度的样品干扰小,铅、铟、钛、锰元素对钠元素测定造成干扰,砷、铜、镉对钙元素测定干扰,铝对钾元素测定有干扰,镁测定不受共存元素干扰影响,运用干扰系数法可以减少共存元素对测定元素的误差。各待测元素标准曲线相关系数大于0.9996,检出限为0.0014~0.023 mg/L,玉米芯各元素的相对标准偏差为0.98%~1.9%,加标回收率为80.2%~106%;西瓜皮的各元素相对标准偏差为0.91%~2.3%,加标回收率为85.3%~106%。方法用于测定国家标准物质GBW07603,各元素结果均在标准值参考范围内。方法用于测定生物质中碱金属和碱土金属的结果,用t检验法与离子色谱测定值进行比对,结果无显著性差异。     

汽车用塑料材料耐溶剂性能测试方法影响因素研究

针对吉利和奔驰两大汽车主机厂汽车用塑料材料耐溶剂测试标准中的不确定因素进行分析,考察了在不同的测试条件下,20%滑石粉填充聚丙烯(PP+T20)和30%玻纤增强尼龙(PA6+GF30)两款材料耐溶剂性能的影响因素。结果表明擦拭速度和擦拭面积对测试结果没有影响,样品色差、样品光泽残存率和测试布沾色灰度等级几乎没有变化;随着擦拭的力值逐渐增加,样品表面状态变化不大,但是擦拭布沾色程度逐渐加重;同时,随着擦拭次数增多,样品色差增大、光泽残存率减小、测试布灰度等级变差,对结果影响显著;PA6+GF30材料的耐溶剂性能优于PP+T20材料。     

牛血清蛋白在共聚物水凝胶接触镜材料上的沉积过程研究

将水凝胶膜样品置于牛血清蛋白(BSA)的水溶液中,沉积一定时间后,采用染料染色结合分光光度法分析沉积前后BSA浓度的变化,计算沉积量,并采用洗脱法测试BSA与水凝胶材料的结合程度.结果表明,BSA的沉积过程为不可逆过程;BSA的沉积作用不受共聚物水凝胶材料中NVP(N-乙烯基吡咯烷酮)结构单元吸附作用的控制;BSA与水凝胶材料松散结合,很容易洗脱;沉积在水凝胶膜表面上的BSA对后续沉积过程无影响.     

季铵型阴离子交换纤维填充微柱吸附分离As(V)/As(Ⅲ)

借助季铵型阴离子交换纤维在弱酸性介质中对As(V)和As(Ⅲ)吸附效果的差异性,结合紫外分光光度法,建立了一种利用纤维填充微柱分离As(V)和As(Ⅲ)的新方法。考察了样品pH、样品流速、初始浓度等因素对As(Ⅲ)和As(V)分离效果的影响。在最优工艺条件下,吸附柱对砷含量在1.0~12.0mg/L的样品的分离效率在95%以上,微柱可重复使用15次以上,再生性良好。     

脂肪族聚酰胺热膨胀行为的研究

通过热膨胀测试,示差扫描量热分析(DSC)、广角X射线衍射(WAXD)与傅里叶变换红外光谱(FTIR)等方法研究了4种脂肪族聚酰胺玻璃化转变温度(Tg)、结晶行为以及氢键强度对热膨胀行为的影响,探索了影响脂肪族聚酰胺热膨胀的本质.DSC和X射线衍射结果表明,聚酰胺中结晶部分的热膨胀系数要低于无定形部分,但聚酰胺的熔融温度和结晶度对热膨胀的影响不够明确.相比较其它脂肪族聚酰胺,聚酰胺56(PA56)具有较高的玻璃化转变温度和较低的亚甲基/酰胺基(CH2/CONH)比例,表现出较低的热膨胀系数.研究发现,在相同条件下制备的脂肪族聚酰胺体系中,CH2/CONH比例或Tg与热膨胀系数具有明显的线性关系,随着CH2/CONH比例的降低或Tg的升高,热膨胀系数显著减小.FTIR的结果表明,聚酰胺分子链间的氢键密度和氢键强度随温度升高衰减的程度是影响其热膨胀行为的关键因素.     

A light-through-side cell and co-used furnace designed for micro-Raman spectra study on volatile melts

A new type of sample cell specially designed for micro-Raman spectra study on volatile melts is described.The cell is made of quartz.The lower section of the cell is circular ring-shaped and the one-end-closed hole in the cell is used for locating the heating body.The tube attached to the cell lid for placing the thermal couple is inserted into the sample,which ensures that the temperature measurement accuracy is good.The cell can be sealed for reducing the effect of the composition change caused by the inhomogeneous volatilization.During the Raman spectra scanning,the laser beam is transmitted into the cell through the side but not the top.Meanwhile,a furnace has been designed to match the cell.The heating body is closely coupled with the sample cell, and there is a hole on the side wall of the furnace for the entrance of the microlens.The assembly has performed well in the tested Raman spectrum measurement of molten NaNO₃ at 602℃.     

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

The purpose of this study was to investigate the influence of ionic strength of the carrier liquid, cross flow rate, focus flow rate, and sample load on the retention behavior of liposomes in asymmetric flow field‐flow fractionation (AF4). Two differently prepared samples of large unilamellar vesicles (LUV) were used. Experiments were performed varying the factors systematically and evaluating their effect on both retention behavior of the liposomes and on particle size as obtained from online coupled multi‐angle light scattering (MALS) analysis. The results showed that the focus flow rate had the least influence on the elution of liposomes. Elution of LUV is mainly governed by the chosen cross flow condition and ionic strength of the carrier liquid as well as its sample load. Optimal fractionation and size analysis were achieved using a sample load of about 10 μg, a cross flow gradient from 1.0 to 0.1 mL/min over 35 min and a carrier solution of NaNO₃ with a concentration of 10 mM.     

Influence of the heating rate on the temperature profiles and on the conversion rate of powdery cellulose and pine sawdust

An experimental study of the thermal decomposition of powdered cellulose and pine sawdust has been performed. The influence of the heating rate on the temperature profiles in the sample and on the solid conversion rate has been studied. A mathematical model without adjustable parameters has been used to calculate the temperature at different points in the solid bed and the average total solid conversion. The experimental results have been compared with those calculated by the model. A good agreement has been obtained for sawdust. Some differences are observed for cellulose at high heating rates, and the influence of the thermal conductivity and the reaction heat on the results has been analysed.     

The detection of ignition temperatures of various materials by photothermal analysis

The ignition temperatures of various common materials were detected by means of a photothermal analysis apparatus. The sample is heated in a tube furnace which is programmed at a linear heating rate; a photomultiplier tube located at the end of the furnace tube is used to detect the ignition process. This technique is potentially useful and is most advantageous when used to supplement DTA or TG data. The instrumental factors which influence the ignition temperature, such as heating rate, furnace atmosphere, and so on. were investigated. Factors such as the sample surface area, mass. density, and others can affect the reproducibility of the curves even if the instrumental factors are held constant.     

Influence of the Heating Rate in the Thermal Decomposition of HMX

This work refers to a study of the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (HMX) by differential scanning calorimetry (DSC) in non-isothermal conditions, with heating rates from1 to 25°C min⁻¹. The influence of the heating rate, the particle and the sample size were verified. The activation energy was calculated using the peak temperature shift method, proposed by Ozawa and a significant variation in the results was observed according to the range of the used heating rates. As the heating rate was increased, different conversions and self-heating effects were observed at the respective DSC peaks, indicating that the use of this method was inadequate and it may lead to incorrect results, which, in turn, could explain the wide range of activation energy values published in literature. At lower heating rates HMX decomposition occurs on the solid state and at higher ones decomposition occurs after melting practically at the same temperature, which does not depend on the heating rate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Complementary DSC and dilatometric investigation of M-PTFE pyrotechnic compositions

Results of high thermal resolution microcalorimetric and dilatometric measurements performed on reducer — polytetrafluoroethylene (M-PTFE) pyrotechnic compositions have been discussed. The materials were selected for the study because of their behaviour in combustion tests. Two complementary thermal properties, i.e. the specific heat and coefficient of linear thermal expansion (CLTE), have been analysed in detail. The specific heat was obtained from DSC measurements performed from −20 to 375°C. Measurements of CLTE and linear expansion were carried out from −40 to 270°C. In both cases the measurements were performed on thermocycling with the high thermal resolution preserved. A special attention has been paid to a two-stage phase transition occurring just below the room temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structure of piperidinoethyl esters of alkoxyphenylcarbamic acids and their thermodynamic parameters

The melting temperature of nine piperidinoethyl esters of alkoxyphenylcarbamic acid (hexaoxy-octyloxy) including all site isomers was investigated. The analyses were performed using DSC apparatus, sample mass ranged from 0.2 to 2.5 mg, heating rate was 5 K min^-1 and in static air atmosphere. On the basis of melting peak, thermodynamic figures like: enthalpy, entropy, height and area of the peak and temperature of the partial peak were fixed. For evaluation of the results Principal Component Analysis was applied. Thanks to this method the influence of length (mass) and position of alkoxy substituents on the thermodynamic parameters of melting of compounds under investigation were determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

X射线衍射测试样品位置对谱线峰位和强度的影响

鉴于X’Pert Pro MRD多晶X射线衍射仪的样品台5维可移动,研究了样品的位置对物相测试中谱线峰强度和峰位的影响.结果表明,样品表面低于或者高于光路中心,都会造成谱图峰位的偏移,对峰强度影响不明显.当样品表面低于光路中心位置时,峰位呈减小趋势.当样品表面高于光路中心位置时,峰位呈增加趋势.当水平位置放置了不同厚度的样品进行批处理测试时,谱线的峰强度会受到最厚的样品的影响,峰位的变化不明显.