木塑复合材料蠕变性能的研究进展

简要介绍了材料的蠕变特性以及木塑复合材料蠕变性能较差的原因,并从影响木塑复合材料蠕变性能的温度、应力及加载方式、湿度等因素以及抗蠕变性研究两方面对木塑复合材料蠕变性能的研究进展进行了综述,展望了今后木塑复合材料蠕变性能研究的重点及方向.     

紫外辐射交联改善UHMWPE纤维蠕变性能研究进展

超高分子量聚乙烯(UHMWPE)纤维较差的抗蠕变性能影响了其应用。该文介绍了纤维发生蠕变机理及蠕变行为,综述了采用紫外辐射方法改善UHMWPE纤维蠕变性能的技术进展,并讨论了工艺特点和处理效果。     

短纤维增强SiC／Al复合材料在高温下粘弹性拉伸性能的细观力学分析

本文采用细观力学模型和有限元法研究短纤维增强ＳｉＣ／Ａｌ复合材料在高温下的粘弹性行为，着重讨论了纤维体分比和长径比对复合材料总体蠕变性能的影响。结果表明，随着纤维体分比和长径比的增加，纤维能显著抑制复合材料沿轴向蠕变行为。     

PMI泡沫的耐高温压缩蠕变性能

聚合物泡沫芯材的耐高温压缩蠕变性能对复合材料泡沫夹层结构的共固化成型有重要意义。本文介绍了聚甲基丙烯酰亚胺(PMI)泡沫耐高温压缩蠕变性能的研究现状,分析了PMI泡沫耐高温压缩蠕变性能的材料和环境影响因素,最后对可应用于泡沫耐高温压缩蠕变性能测试的几种方法进行了比较。     

HDPE/木粉复合材料抗蠕变性能研究

利用添加交联剂过氧化二异丙苯(DCP)及刚性树脂聚苯乙烯(PS)两种方法来改进高密度聚乙烯(HDPE)木塑复合材料的弯曲蠕变性能。研究了DCP、PS和木粉的含量对HDPE木塑复合材料抗蠕变性能及弯曲性能的影响。结果表明,随着DCP、PS用量的增加,木塑复合材料的弯曲性能提高,同时复合材料的蠕变性能增强,其蠕变形变降低。     

Al2O3f/Mg-6Al-0.5Nd-1Gd复合材料的高温压缩蠕变行为研究

研究了Al_2O_(3f)/Mg-6Al-0.5Nd-1Gd复合材料的高温蠕变行为。结果表明:随着蠕变温度由483K升高到513K,外加应力从60MPa增大到90MPa,复合材料的稳态蠕变速率增加,压缩蠕变性能变差;复合材料的蠕变行为主要受到位错攀移控制;复合材料中由于Al_2O_3短纤维增强相的添加,提高了材料的蠕变表观激活能Q_c和蠕变表观应力指数n;复合材料在载荷恒定时,随着蠕变温度由483K提高到513K,复合材料材料的蠕变门槛应力由57.2MPa降低为32.3MPa。     

应力腐蚀对玻璃钢影响的实验研究

本文提出了一种在应力腐蚀条件下测试玻璃钢蠕变性能的悬臂梁方法,通过对比实验探讨了应力腐蚀对玻璃钢蠕变性能的影响及其机理。结果表明：应力腐蚀作用使试验材料的蠕变强度、蠕变极限和蠕蛮横均减小;在应力腐蚀下,材料在不同时刻的蠕变强度的降低程度不同。     

纳米TiO_2对氨纶蠕变性能的影响

为了探究纳米TiO2对氨纶蠕变性能的影响,设计试验,对33.3 dtex普通氨纶和混有适量纳米TiO2的氨纶蠕变性能进行测试,结果表明:纳米TiO2不会改变氨纶的蠕变规律,但是可以减弱氨纶的蠕变速率和蠕变变形率,同时,可以提高氨纶的蠕变回复能力,一定程度上改善了氨纶的蠕变性能。     

连续纤维复合材料环形试样蠕变行为研究

对连续玻璃纤维复合材料进行了拉伸蠕变试验研究,为了模拟复合材料在压力容器中的受力状态并减少夹具加持力对试样的影响,采用环形复合材料试样拉伸蠕变试验方法。对复合材料环形试样的拉伸强度及不同应力等级下的拉伸蠕变性能进行了研究,并基于时间?应力等效原理,通过双对数法拟合出压力容器50年使用寿命时复合材料的最大蠕变应力,为复合材料压力容器的设计提供支持。并基于时间?应力等效原理,通过双对数法拟合出压力容器50年使用寿命时复合材料的最大蠕变应力应低于其拉伸强度的44.4 %。     

密封用PTFE复合材料的压缩蠕变性能

采用碳粉/石墨、青铜粉、玻璃纤维(GF)、碳纤维(CF)、聚苯酯(POB)等改性材料改性聚四氟乙烯(PTFE),通过冷压、烧结的方式制得改性PTFE复合材料,研究了载荷、温度等环境条件对不同改性PTFE复合材料压缩蠕变的影响,通过退火进一步改善复合材料的抗蠕变性能,研究了退火温度对复合材料压缩蠕变及力学和摩擦磨损性能的影响。结果表明,各改性材料均能降低PTFE的压缩蠕变量,其中碳粉/石墨改性的PTFE复合材料压缩蠕变量最小,其次为青铜粉改性的复合材料,其余依次为GF,POB和CF改性的复合材料;改性PTFE复合材料的压缩蠕变量随着载荷和温度的增加明显增大,碳粉/石墨改性的PTFE复合材料蠕变受载荷增加的影响最小,且高温(150℃)下的压缩蠕变量最小。在150～300℃下对改性PTFE复合材料进行退火处理,可使其压缩蠕变量减少20%～40%,最佳的退火温度为300℃,在此温度下进行退火对复合材料力学和摩擦磨损性能影响不大。     

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…     

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.     

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.     

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.     

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。     

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。     

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。     

几种针状焦性能对比

针状焦分石油系和煤系两大类,这主要取决于针状焦的原料来源。在同一系列中由于原料不同和工艺条件不同 ,针状焦的各自性能也不相同。针状焦是生产超高功率石墨电极和高功率石墨电极的主要原料 ,针状焦的性能对石墨电极的质量有至关重要的影响。所以对针状焦性能以及其对石墨电极质量影响的研究十分必要的。以下是常用的几种进口针状焦和国产针状焦的性能对比。１原料性能分析对比原料试样包括４种针状焦 ,其中两种为进口针状焦：三菱针状焦和新日化针状焦;另两种为国产针状焦：鞍山针状焦和锦州针状焦。其中除锦州针状焦是石油系针状焦外…     

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。