湿热与拉伸载荷耦合作用下玻纤/环氧复合材料的吸湿特性

为探究环境温度、相对湿度和外部拉伸载荷对聚合物基复合材料吸湿性能的影响,提出一种以温度、水分浓度和基体八面体剪应力为变量的特殊形式的Gibbs自由能函数,获得了湿热与拉伸载荷耦合作用下复合材料水分扩散控制方程。制备E-玻纤/环氧6509树脂复合材料层压板,通过自制压缩弹簧加载装置施加恒定拉伸载荷,在不同湿热环境下开展加速吸湿实验,利用响应曲面法获得代理模型以表征环境因素对平衡吸湿量和湿扩散系数的影响。结果表明:拉伸载荷作用下,基体八面体剪应力越大,复合材料的湿扩散系数和平衡吸湿量越大;升温能加速复合材料吸湿,而提高相对湿度会明显增加平衡吸湿量。利用响应面法获得的代理模型能够准确地预测玻璃纤维/环氧树脂复合材料在湿热与拉伸载荷耦合作用下的吸湿行为。     

运动训练器材用碳纤维复合材料的湿热老化行为研究

采用真空辅助成型的方法制备运动训练器材碳纤维复合材料层合板,研究了40℃和60℃的湿热老化环境下碳纤维复合材料的吸湿率、拉伸强度、弯曲强度、压缩强度和剪切强度变化,并观察了不同老化条件下的拉伸断口形貌。结果表明,温度越高,运动训练器材碳纤维复合材料的平衡吸湿率、线性段斜率和扩散系数越大。当湿热老化温度为40℃和60℃时,随着老化时间延长,碳纤维复合材料的拉伸强度、弯曲强度都先增后减,分别在老化时间为14d和7d时取得最大值。当湿热老化温度为40℃和60℃时,随着老化时间延长,碳纤维复合材料的压缩强度先增大后减小,在老化时间为35d时取得最大值。当湿热老化温度为40℃时,随着老化时间延长,碳纤维复合材料的剪切强度先增大后减小,在老化时间为7d时取得最大值;当湿热老化温度为60℃时,随着老化时间延长,碳纤维复合材料的剪切强度逐渐减小。碳纤维复合材料在湿热环境下的力学性能变化,主要与温度和湿度共同作用下碳纤维复合材料的增塑和固化有关。     

碳纤维增强MC尼龙复合材料吸湿行为研究

采用液态原位聚合法制备了碳纤维(CF)增强浇铸尼龙(MC尼龙)复合材料,研究了其吸湿行为?分别考察了CF体积分数、CF编织结构和外加载荷对MC尼龙／CF复合材料吸湿行为的影响。结果表明,随着CF体积分数的增加,复合材料的平衡吸湿率减小;三维编织结构的CF增强MC尼龙复合材料的吸湿速率及平衡吸湿率均低于长的CF增强MC尼龙;外加载荷使该复合材料的吸湿能力降低。     

改性双马树脂/碳纤维复合材料体系耐湿热性能研究

对5428/T700复合材料的吸湿率、不同吸湿条件下的玻璃化转变温度及高温湿态力学性能进行了研究。结果表明,5428/T700体系具有较低的吸湿率,经70℃去离子水水煮72 h,吸湿率为0.5%,饱和吸湿率(水煮360 h)为0.8%。而且随着复合材料吸湿量的增加,其Tg下降缓慢;5428/T700复合材料在干态170℃下的弯曲性能和层间剪切性能保持率在70%以上,在湿态150℃下的弯曲性能和层间剪切性能保持率在50%以上;5428/T700复合材料在湿态150℃下的开孔压缩强度保持率在80%以上。     

单向CF/PA6复合材料性能劣化及老化寿命预测

利用热压成型工艺制备出碳纤维(CF)/尼龙6(PA6)复合材料单向板,并将复合材料试样置于蒸馏水热水浴中,分别在25,60,80℃下进行不同时间的湿热老化,再对湿热老化后复合材料试样进行吸湿测试、三点弯曲测试、微观形貌表征,探究复合材料的吸湿规律、力学性能劣化规律和微观形貌变化,并对复合材料的长期寿命进行预测。结果发现,复合材料在25,60℃下的吸湿行为基本符合Fick扩散定律,而80℃下在老化最后阶段出现了背离Fick扩散定律现象。复合材料的弯曲强度随老化温度、老化时间的增加呈下降趋势,分别在25,60,80℃下老化120 d后,试样弯曲强度分别下降了22.78%,25.0%,26.25%。但是老化温度、老化时间对弯曲弹性模量无显著影响,且CF与PA6树脂之间的界面黏合性能随着温度、时间的增加逐渐变差。以绍兴2021年平均温度作为服役温度,基于加速老化测试模型和阿伦尼乌斯理论建立了CF/PA6复合材料在服役环境下剩余弯曲强度的预测模型,可预测到1 400 d后,CF/PA6复合材料的弯曲强度保留率在64.8%左右。     

吸湿行为对PMI泡沫性能及应用的影响

研究了在不同条件处理下，聚甲基丙烯酰亚胺（PMI）泡沫的密度、孔径和厚度对其吸湿行为的影响，并实验验证PMI泡沫吸湿后对其力学性能、烘干可逆性及粘接性能的影响。结果表明，PMI泡沫密度越大，吸湿速率越小；孔径越大，吸湿速率越大；厚度越大，吸湿速率越小，饱和吸湿率越低；吸湿后，PMI泡沫刚性下降，韧性增强，粘接时易出现缺陷；在短期的高湿环境或浸水下，PMI泡沫性能烘干可逆，长期在高湿环境或浸水条件下处理后，PMI泡沫性能出现不可逆下降。     

碳纤维增强双马来酰亚胺树脂复合材料耐湿热性能

采用改性双马来酰亚胺树脂与碳纤维制备了耐热及耐湿热性能优异的复合材料。通过红外光谱分析、不同温度下力学性能测试及动态力学性能测试分析等,考察了该复合材料耐热及耐湿热性能;从吸湿特性、物理、化学特性及热应力等方面分析了湿热处理前、后复合材料高温环境下力学性能衰减机理。结果表明,复合材料吸湿初始阶段符合Fick第二定律,平衡吸湿率为0.97%~1.32%;湿热处理对复合材料基体化学结构和玻璃化转变温度基本无影响;界面处不断增大的热应力削弱界面结合强度,这是高温环境下力学性能下降的关键因素;与国内外同类复合材料相比,该复合材料湿热处理前、后在高温下弯曲性能和层间剪切强度保持率较高,耐热及耐湿热性能出众。     

GFRP层合板在湿热环境和碱性腐蚀介质中的老化行为

研究了玻璃纤维增强环氧乙烯基酯树脂基复合材料(GFRP层合板)在湿热和碱性腐蚀介质中的老化行为,测试了不同老化时间后材料的吸湿率和抗弯强度,通过扫描电子显微镜观察了复合材料的表面、纤维和弯曲断口形貌在不同老化时间下的变化,并且通过红外光谱和热重分析仪分析了复合材料在介质老化中的化学变化和初始分解温度的变化。结果表明:在湿热环境和碱性腐蚀介质中,复合材料吸湿率均随老化时间延长而增大,纤维/基体界面结合紧密度随吸湿率的增加而下降,碱溶液下的吸湿率高于湿热条件下的吸湿率;树脂基体的水解、玻璃纤维的腐蚀降解、纤维/基体脱黏、树脂大分子链间结合力的破坏和树脂交联密度的降低是材料性能下降的主要原因。     

玻璃纤维二维平纹编织复合材料高温弯曲力学行为研究

对玻璃纤维2维平纹编织复合材料在6个不同温度下的弯曲性能进行了实验测试,研究了温度对编织复合材料层合板的载荷-挠度曲线、弯曲强度、弯曲模量和失效模式的影响。结果表明:在三点弯曲载荷作用下,2维编织复合材料层合板跨中发生了局部纤维束屈曲失效和基体的开裂与分层失效。温度对玻璃纤维复合材料的力学性能和失效形式产生了重要影响。在高温环境中玻璃纤维2维平纹编织复合材料的弯曲力学性能迅速下降,当试验温度从20℃升高至115℃时,层合板的弯曲强度和模量分别下降了91%和66%。随着温度的升高,2维编织复合材料层合板的弯曲失效变形行为也发生了转变,逐渐由脆性破坏转变为塑性变形失效。     

熔融挤出温度对PA6/CaCl2复合材料结构与性能的影响

采用熔融挤出的方法,制备了PA6/CaCl2复合材料,研究了熔融挤出温度对PA6/CaCl2复合材料的结晶行为和性能的影响。实验结果表明：随熔融挤出温度的提高,CaCl2与PA6的络合反应程度越大,PA6/CaCl2复合材料的结晶度越小,结晶不完善程度越大,复合材料的粘度越大,熔体流动速率越小。随熔融挤出温度的提高,复合材料的拉伸强度先增大后减小,最后近似趋于定值,冲击强度、弯曲强度随熔融挤出温度的提高总体呈增加趋势。     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases.     

骑式摩托车油箱喷涂工艺的改进

面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

用两个形状指数表征粉煤灰颗粒形貌的研究

引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。     

典型煤碳燃烧特性研究和数值模拟

本文以三种典型煤的碳燃烧为研究对象，分别采用简单一维沉降燃烧方式和等温加热燃烧方式，实验研究了煤在快速加热条件下，其碳的初期和中，后期燃烧过程。以实验为基础，建立了煤的碳燃烧模型，变工况数值模拟了煤的碳燃烧过程，揭示了煤不同条件下的单颗粒碳燃烧特性。     

氢气纯度分析方法准确性的探讨

ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l／3为氧气,2／3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中：A一混…     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.     

环氧树脂羟基值测定方法的研究

利用乙酸酐、吡啶和浓硫酸混合的乙酰化试剂测定环氧树脂中羟基值含量的方法具有操作简便、滴定终点明显和分析结果误差小等优点。     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。