聚乙烯醇改性及吹膜技术研究

研究了聚乙烯醇(PVA)改性及吹膜技术。经改性剂改性前后的IR分析结果表明，改性剂与PVA分子间发生了强烈的相互作用，并形成了较强的分子复合键。改性PVA塑化温度的研究表明，醇解度为88％的PVA，随相对分子质量的增加塑化温度升高。醇解度升高时，PVA塑化性能下降；改性剂用量增加，塑化温度下降。吹膜工艺研究表明，成膜助剂的加入能明显改善改性PFA的加工流动性，PVA膜对冷却效果要求较高，吹膜后的热定型处理能降低其吸湿性，延长水溶时间。     

发泡废纸板纤维/LDPE复合材料的加工流变性及泡孔形态

以废弃瓦楞纸板纤维和低密度聚乙烯(LDPE)为基体辅以相应的相容剂、 润滑剂和发泡剂, 利用挤出发泡法制备了发泡废纸板纤维/LDPE木塑复合材料。通过熔融指数仪研究了废纸板纤维含量、 相容剂马来酸酐接枝聚乙烯(MAH-g-PE)的用量、 润滑剂的种类与用量以及发泡剂偶氮二甲酰胺(AC)的用量对该复合材料加工流变特性的影响; 并利用SEM观察不同熔融指数的复合材料对泡孔形态的影响。结果表明: 随着废纸板纤维含量的增加, 复合材料的熔融指数(MFI)迅速下降; MAH-g-PE增加了纤维填料与树脂基体之间的相互作用, 复合材料的熔融指数随着相容剂用量的增加先降低后升高, 其含量的转变点为15%; PE蜡对复合材料的综合润滑作用最明显, 复合材料的熔融指数随着PE蜡的含量呈近线性变化; AC发泡剂的加入降低了复合材料的熔融指数, AC发泡剂的含量超过5%将使复合材料产生明显的壁滑移; 随着熔融指数的增加, 复合发泡材料的泡孔逐渐变大, 当熔融指数为1.5时, 泡孔大小适中且分布均匀。     

发泡废纸板纤维/LDPE复合材料的加工流变性及泡孔形态

以废弃瓦楞纸板纤维和低密度聚乙烯(LDPE)为基体辅以相应的相容剂、润滑剂和发泡剂,利用挤出发泡法制备了发泡废纸板纤维/LDPE木塑复合材料.通过熔融指数仪研究了废纸板纤维含量、相容剂马来酸酐接枝聚乙烯(MAH-g-PE)的用量、润滑剂的种类与用量以及发泡剂偶氮二甲酰胺(AC)的用量对该复合材料加工流变特性的影响;并利用SEM观察不同熔融指数的复合材料对泡孔形态的影响.结果表明:随着废纸板纤维含量的增加,复合材料的熔融指数(MFI)迅速下降;MAH-g-PE增加了纤维填料与树脂基体之间的相互作用,复合材料的熔融指数随着相容剂用量的增加先降低后升高,其含量的转变点为15％;PE蜡对复合材料的综合润滑作用最明显,复合材料的熔融指数随着PE蜡的含量呈近线性变化;AC发泡剂的加入降低了复合材料的熔融指数,AC发泡剂的含量超过5％将使复合材料产生明显的壁滑移;随着熔融指数的增加,复合发泡材料的泡孔逐渐变大,当熔融指数为1.5时,泡孔大小适中且分布均匀.     

纳米Ag~+-TiO_2/聚氯乙烯抗菌塑料制备及其性能

将纳米Ag+-TiO2用8%硅烷偶联剂(KH-560)进行表面改性,再与聚氯乙烯(PVC)树脂、增塑剂、润滑剂、稳定剂等混合,经熔融塑化,制得软质PVC抗菌塑料。考察了改性纳米Ag+-TiO2加入量对PVC抗菌塑料力学性能、加工流变性能和抗菌率的影响规律。研究表明:纳米Ag+-TiO2的加入可有效提高PVC塑料的力学性能和抗菌率,改善加工流变性能;当加入量为0.63%时,对大肠杆菌和金黄色葡萄球菌的抗菌率已超过90%;当Ag+-TiO2添加量为2.5%时,抗菌率超过99%,具有很好的抗菌效果。     

PA6/PAMAM共混物的加工与流变性能

研究了不同代数、不同用量的PAMAM树形分子对PA6／PAMAM共混物加工和流变性能的影响。结果表明：在PA6中加入少量的PAMAM树形分子即可显著提高PA的流变性能和加工性能,PAMAM可作为PA6的流变学改性剂和新型加工助剂。     

甘油增塑热塑性淀粉的流变相变性质

流变性质和相变性质是指导热塑性淀粉(TPS)生产加工的重要参数。文中利用转矩流变仪(密炼机)和差示扫描量热法(DSC)研究甘油增塑淀粉时TPS流变相变性质的变化。结果表明,甘油增塑时,对淀粉流变性能的影响与水不同;由于转子扭矩的变化主要由TPS相变产生,而甘油的润滑效应不利于淀粉塑化,因此TPS的塑化程度随着甘油含量的增多先减小后增大;升高转子转速会加大剪切力,加剧相变;同样初始温度越高,相变越容易发生,且温度对相变程度的影响显著于转速。     

甘油增塑热塑性淀粉的流变相变性质EI北大核心

流变性质和相变性质是指导热塑性淀粉(TPS)生产加工的重要参数。文中利用转矩流变仪(密炼机)和差示扫描量热法(DSC)研究甘油增塑淀粉时TPS流变相变性质的变化。结果表明,甘油增塑时,对淀粉流变性能的影响与水不同;由于转子扭矩的变化主要由TPS相变产生,而甘油的润滑效应不利于淀粉塑化,因此TPS的塑化程度随着甘油含量的增多先减小后增大;升高转子转速会加大剪切力,加剧相变;同样初始温度越高,相变越容易发生,且温度对相变程度的影响显著于转速。     

氯化聚氯乙烯热稳定剂种类及研究现状

概述了氯化聚氯乙烯(CPVC)热稳定剂的特性,介绍了CPVC热稳定剂种类及研究现状,包括铅盐类热稳定剂,金属皂类热稳定剂,有机锡类热稳定剂,有机锑类热稳定剂,沸石类热稳定剂,稀土类热稳定剂和辅助型热稳定剂,并对热稳定剂的发展趋势进行了展望。     

反应烧结碳化硅陶瓷用碳坯的制备

反应烧结碳化硅陶瓷的力学性能在很大程度上取决于素坯的制备.以木质碳粉为原料,采用注浆成型工艺制备出了纯碳素坯.讨论了碳粉、分散剂及稳定剂用量、碳粉含水率、球磨时间与料浆黏度、碳坯密度之间的关系:随着碳粉用量的增加,料浆黏度和碳坯密度同时升高;随着分散剂(K30)和稳定剂(CMC)用量的减小、球磨时间的延长,料浆黏度降低,碳坯密度增大;经过煅烧的碳粉,含水率极低,可以显著缩短注浆成型时的吃浆时间.     

高填充竹塑包装盒盒坯注塑成型工艺及性能研究

采用竹纤维与聚烯烃为主要原料,并辅以少量改性与加工助剂,通过同向平行双螺杆挤出造粒线,制备高填充竹塑复合材料颗粒,用于注塑成型包装盒盒坯。研究竹纤维填充量、润滑剂与填料对复合材料加工性能的影响,聚烯烃树脂与填料对成型周期的影响,以及树脂基体、模具温度对包装盒盒坯翘曲变形的影响。研究结果表明:随着竹纤维含量的增加,复合材料的熔融指数快速下降,竹纤维质量分数超过50%后下降速度减缓;润滑剂可以提高复合材料的熔融指数,且内外润滑平衡的复合润滑剂最稳定;滑石粉较碳酸钙更有利于改善复合材料的流动性。聚丙烯比聚乙烯基体复合材料的注塑冷却时间短,滑石粉在缩短冷却时间方面优于碳酸钙。竹塑包装盒盒坯的翘曲变形量随着混合树脂基体中聚丙烯含量的增加而减少,随着模具温度的变化出现波动,最佳模具温度为50℃左右。     

Nano-porous layer on steel surface as lubricant carrier

In cold forging of steels, metal soap on zinc-phosphate coating is excellent lubrication system. However, the system is not only less productive, but produces hazardous wastes. In this study, an alternative lubrication system using surface porous layer is proposed. Surface oxide on low carbon steel turns into porous layer by chemical reduction using hydrogen. It is found that liquid lubricant decreases the friction coefficient in compression greatly. The porous surface enhances the decrease, especially in the cases of heavy deformation.     

Optimization of Disintegration Time and Crushing Strength of a Tablet Formulation

In an experiment with a factorial design, the following aspects were scrutinized: the impact on disintegration time and crushing strength caused by the loss-on-drying of the granulation; the granule-size distribution; the lubricant concentration; the compression force; and the pre-compression. Both with regard to disintegration time and crushing strength, these factors were found to have a significant influence: the loss-on-drying of the granulation; the fraction less than 0.150 mm; the concentration of magnesium stearate; and the compression force. A reduction of the tablet disintegration time was obtained by means of an increase of the granulation moisture; by an increase of the fine fraction; or by a reduction of the lubricant concentration or the compression force. The tablet crushing strength was increased by reducing the deviation of the granulation loss-on-drying from approximately 4.6 %; by a reduction of the fine fraction; by decreasing the lubricant concentration; or by increasing the compression force. The fraction larger than 0.300 mm had no significant influence; nor did the pre-compression. Further, there were no significant interactions.

By means of superimposing contour plots of disintegration time and crushing strength, a region was obtained where the requirements of disintegration time and crushing strength could be satisfied by controlling the processing variables.     

Optimization of Disintegration Time and Crushing Strength of a Tablet Formulation

Abstract

In an experiment with a factorial design, the following aspects were scrutinized: the impact on disintegration time and crushing strength caused by the loss-on-drying of the granulation; the granule-size distribution; the lubricant concentration; the compression force; and the pre-compression. Both with regard to disintegration time and crushing strength, these factors were found to have a significant influence: the loss-on-drying of the granulation; the fraction less than 0.150 mm; the concentration of magnesium stearate; and the compression force. A reduction of the tablet disintegration time was obtained by means of an increase of the granulation moisture; by an increase of the fine fraction; or by a reduction of the lubricant concentration or the compression force. The tablet crushing strength was increased by reducing the deviation of the granulation loss-on-drying from approximately 4.6 %; by a reduction of the fine fraction; by decreasing the lubricant concentration; or by increasing the compression force. The fraction larger than 0.300 mm had no significant influence; nor did the pre-compression. Further, there were no significant interactions.

By means of superimposing contour plots of disintegration time and crushing strength, a region was obtained where the requirements of disintegration time and crushing strength could be satisfied by controlling the processing variables.     

The effect of nano-sized sintering aids on toughening behavior of silicon nitride

Processing plays an important role in determining the microstructure of silicon nitrides which in turn influences the mechanical properties, such as hardness and toughness. Sintering aids are an important processing parameter. The influence of the chemistry of sintering aids on properties of silicon nitrides is a well-explored subject. Here the size of sintering aids used and its impact on microstructure and mechanical properties is explored. Specifically the use of nano-scale versus micron-scale sintering aids is examined. Microstructures and mechanical properties for silicon nitrides hot-pressed with nano-sized sintering aids are compared with a reference silicon nitride hot-pressed with micron-sized sintering aids. Hardness and fracture toughness are determined at room temperature using hardness indents. Grain size and aspect ratio distributions are determined for the two silicon nitrides and their impact on mechanical properties are examined. Toughening behavior is studied by experimentally determining R-curves. Both toughness and toughening (R-curve) behavior are shown to improve with the use of nano-scale sintering aids.     

废纸浆增强HDPE复合材料的力学性能

将废旧瓦楞纸板粉碎制浆,与高密度聚乙烯通过注塑成型制备废纸浆/HDPE复合材料。研究了废纸浆含量,相容剂HDPE-g-MAH和LDPE-g-GMA,加工助剂S-105、TKM-M80和Deoflow A对废纸浆/HDPE复合材料力学性能的影响,通过扫描电镜SEM分析了复合材料的冲击断面,结果表明,HDPE-g-MAH和...     

PP对PBT/POE-g-MAH共混体系相形态和力学性能的影响

将聚丙烯(PP)与官能化聚烯烃弹性体(POE-g-M AH)共混,制备出4种新型增韧改性剂,研究了PP的含量和种类对PBT/POE-g-M AH共混体系相形态和力学性能的影响。SEM观察发现,新型增韧改性剂作为分散相具有以POE-g-M AH为软壳、PP为硬核的包藏结构。随着高熔体流动指数PP(EPF 30R)含量的增加,软壳层厚度逐渐减小,包藏结构分散相的相畴尺寸略有减小,分布更加均匀。但添加低熔体流动指数PP(EPS30R)后,包藏结构分散相的相畴尺寸变大,分布不均匀。力学性能测试表明,适量高熔体流动指数PP与POE-g-M AH并用具有显著的协同增韧作用。与PBT/POE-g-M AH体系相比,在相同的增韧剂总用量时,共混物在保持超高韧性的同时,拉伸强度损失最小。     

Effects of heat treatment process and niobium addition on the microstructure and mechanical properties of low carbon steel weld metal

The mechanical properties and microstructure were evaluated and analyzed by optical microscopy (OM) and transmission electron microscopy (TEM) for micro-alloy carbon steel weld metal with and without Nb addition, respectively, under different heat treatment processes including stress relief annealing, normalizing, and no treatment after welding. The strength and elongation of the weld metal without treatment after welding were improved with the addition of Nb element, and the impact toughness was not affected obviously with the Nb addition. After stress relief annealing, the strength decreased for the Nb-free weld metal, while the elongation and impact toughness increased. However, for the Nb-bearing weld metal, stress relief annealing improved the strength of the weld metal significantly, and deteriorated the elongation and impact toughness. In the case of normalizing treatment to the weld metal, it was shown that with the increase of the holding time at the normalizing temperature of 920 °C, for both the weld metals with and without Nb addition, the microstructure of the columnar grain zone (CGZ) was transformed from one of columnar grain into one of equiaxed grain. The grain size of the equiaxed grain zone (EGZ) increased initially, then remained almost unchanged with the prolonging of the holding time. The mechanical properties of the weld metal with and without Nb addition showed no obvious change with the increasing holding time. With the increase of the normalizing temperature, the strength of the Nb-bearing weld metal increased, while the elongation and impact toughness decreased significantly. OM and TEM analysis found that the fine NbC particles were precipitated at the normalizing temperature of 920 °C, which refined the grains of the weld metal and increased the impact toughness. With the increase of the normalizing temperature, the content of widmanstatten ferrite (WF) in the Nb-bearing weld metal increased, whereas the quantity of the NbC particles decreased, which improved the strength and lowered the impact toughness.     

高能同步辐射光源(HEPS)氦低温传输系统模拟与计算

使用EcosimPro商业软件和关联式编程两种方法,对HEPS氦低温传输系统进行了模拟和计算,研究了管道内径和管道粗糙度对管道压降的影响。结果表明流动压降随着管道内径的增大而减小,但降低的幅度越来越小,当管道直径从30.8 mm提高至56.8 mm,压降仅降低了约510 Pa;流动压降随粗糙度的增加而增加,但管径越大压降增加越小,当管径为30.8 mm时,选用电抛光管压降下降了954 Pa;管道的漏热量和降温复温时间随管径的增大而提升。通过计算分析最终选择主干来流管道公称直径为DN25,内径为30.8 mm的普通金属管,分支来流管道公称直径为DN10,内径为14.6 mm的普通金属管,主干回流管道公称直径为DN50,内径为56.8 mm的普通金属管,分支回气管道公称直径为DN20,内径为23.8 mm的普通金属管,满足工程需求。     

药芯焊丝Mo含量对低合金钢焊缝金属性能影响

通过在金红石型药芯焊丝中加入不同含量的金属Mo,研究了Mo对熔敷金属组织及力学性能的影响。研究表明,药芯焊丝中的Mo基本全部过渡到焊缝中;添加微量Mo时,焊缝金属强度显著提升,同时冲击韧性恶化严重;进一步增加Mo含量,焊缝金属强化效果不明显,而冲击性能继续下降。组织分析发现,增加焊丝中的Mo含量,首先会降低奥氏体转变温度,增加基体中的碳化物析出相;继续增加Mo时,碳化物含量减少,但M-A组元含量增加,导致韧性持续下降。     

树枝形聚合物/线性聚合物共混的研究进展

综述了国内外有关树枝形聚合物／线性聚合物共混物的形态结构、热性能、动态力学性能、流变性能和物理力学性能的研究进展，树枝形聚合物因其独特的结构和性能特点，可作为聚合物的加工助剂、流变学改性剂、增容剂以及增强或增韧剂。