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Search Results: 1 - 10 of 86786 matches for " 信春玲 "
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热塑性聚氨酯熔体粘弹性对发泡的影响研究
臧萌,,何亚东,闫宝瑞
- , 2018, DOI: 10.13543/j.bhxbzr.2018.02.007
Abstract: 采用旋转流变仪和差示扫描量热仪系统测试了3种结构不同热塑性聚氨酯(TPU)的动态流变性能和非等温结晶曲线,并结合间歇发泡实验探讨了TPU熔体粘弹性对发泡倍率和泡孔结构的影响。结果表明:3种TPU均表现出线性分子链特征;具有高的零切黏度及低频区储能模量的TPU表现出更大的熔体强度和更好的熔体弹性,有利于获得发泡倍率高、泡孔均匀的发泡材料。
Abstract:The dynamic rheological properties and non-isothermal crystallization curves of three thermoplastic polyurethane(TPU) samples have been tested using a dynamic rheometer and a differential scanning calorimeter. Batch foaming experiments were carried out in order to investigate the effect of the viscoelasticity of TPU on the expansion ratio and the cell structure. The results showed that the three TPU samples all exhibited linear molecular chain characteristics. The TPU sample with the highest zero shear viscosity and storage modulus in the low frequency range showed the highest melt strength and melt elasticity, making it easier to obtain a material with high foaming ratio and uniform cell structure.
环氧基低聚物改性聚对苯二甲酸乙二醇酯的流变性能和发泡性能
杨兆平,,何亚东
- , 2017, DOI: 10.13543/j.bhxbzr.2017.06.008
Abstract: 为了提高聚对苯二甲酸乙二醇酯(PET)的流变性能和发泡性能,采用环氧基扩链剂(ADR)对PET进行反应挤出改性,并利用动态旋转流变仪和单轴拉伸黏度仪对PET的流变性能进行系统表征,同时通过快速降压法研究了改性PET的发泡性能。流变测试结果表明:与未改性PET相比,ADR改性PET具有更高的复数黏度和低频区储能模量、更低的损耗角正切,呈现出明显的应变硬化现象;当ADR质量分数超过0.5%时,改性PET表现出凝胶结构的流变特性。采用间歇发泡工艺得到了发泡倍率为30倍、泡孔均匀细密的PET发泡材料,说明改性PET具有优异的可发泡性能。
Abstract:An epoxy-based chain extender (ADR) has been used to improve the rheological behavior and foaming properties of polyethylene terephthalate (PET) obtained by a reactive extrusion process. The rheological behavior of PETs was characterized by using a dynamic rheometer and a uniaxial stretching viscometer. In addition, a rapid depressurization method was used to investigate the foaming properties of the modified PETs. Rheological results showed that PETs modified with ADR had higher complex viscosity and storage modulus, and lower loss tangent than the neat PETs. Furthermore, the modified PETs exhibited obvious strain hardening. When the ADR content exceeded 0.5 wt%, a gel structure appeared in the modified PETs. The modified PETs exhibited obvious strain hardening during tensile rheological tests. PET foam, with an expansion ratio of 30 and a fine cell structure, was obtained by using a batch foaming process, indicating the excellent foaming performance of the modified PETs.
基于贝叶斯网络的频繁模式兴趣度计算及剪枝
,东?,胡学钢?,姚宏亮?
软件学报 , 2011, DOI: 10.3724/SP.J.1001.2011.03978
Abstract: 采用贝叶斯网络表示领域知识,提出一种基于领域知识的频繁项集和频繁属性集的兴趣度计算和剪枝方法bn-ejtr,其目的在于发现与当前领域知识不一致的知识,以解决频繁模式挖掘所面临的有趣性和冗余问题.针对兴趣度计算过程中批量推理的需求,bn-ejtr提供了一种基于扩展邻接树消元的贝叶斯网络推理算法,用于计算大量项集在贝叶斯网络中的支持度;同时,bn-ejtr提供了一种基于兴趣度阈值和拓扑有趣性的剪枝算法.实验结果表明,与同类方法相比,方法bn-ejtr具有良好的时间性能,而且剪枝效果明显;分析发现,经过剪
超临界流体微孔发泡注塑精确注气的探究
李亦哲,闫宝瑞,段涛,,何亚东
- , 2016, DOI: 10. 13543/ j. bhxbzr. 2016. 04. 016
Abstract: 超临界流体注入量直接影响着微孔发泡注塑成型制品中微泡孔的结构与数量,进而影响制品的力学性能。通过设计相关实验发现:微孔发泡注塑成型注气过程分为气涌与稳定流动两个阶段,且气涌量的大小主要与注气系统的硬件结构有关,在改进硬件结构后气涌量有较大程度的削减;稳定流动阶段的气流量则与相关注气参数有 关。为了验证这一结果,通过实验定量研究了超临界流体注气量与注气压差、限流元件孔径、注气时间、硬件结构之间的关系,得到了调节注气量的传递函数,该函数模型可以为实际生产中根据减重需求调节注气系统的一系列工艺参数提供依据。
Abstract:The gas injected amount of supercritical fluid (SCF) affects the number and the structure of micro bub-bles and thus affects the mechanical properties of products. There are two phases in the gas injection process. The quantity of gas surge is related to the hardware structure and can be reduced significantly when the structure is im-proved. The quantity of gas flowing in the steady stage is related to the gas injection parameters. In this work we have studied the relationships between the amount of gas injected, the gas injection pressure, the aperture of the current limiting element, the gas injection time and the hardware structure. These relationships provide a basis for adjusting the process parameters.
连续玻纤增强聚丙烯熔融浸渍过程降黏研究
李莹,曹敏华,,任峰,代俊锋,何亚东
- , 2018, DOI: 10.13543/j.bhxbzr.2018.01.005
Abstract: 将不同配比的高黏度聚丙烯与低黏度聚丙烯共混制备高低黏度树脂混配基体,旋转流变测试结果显示低黏度聚丙烯的加入显著降低了共混体系的黏度。以高低黏度聚丙烯共混物为热塑树脂基体,采用熔融浸渍方法制备连续玻纤增强聚丙烯热塑预浸带。研究发现随着低黏度聚丙烯含量的增加,热塑树脂基体的加工性能明显提高,预浸带制品的孔隙率及纤维断裂率逐渐降低。将各组预浸带模压成型后进行力学测试,结果显示低黏度聚丙烯的加入使层压板层间剪切强度、弯曲强度、拉伸强度均出现小幅度下降,而对冲击强度基本无影响。结合加工性能及力学性能,低黏度聚丙烯质量分数10%时共混物的综合性能最佳。
Abstract:Different percentages of high viscosity polypropylene were blended with low viscosity polypropylene. Rotational rheological tests showed that the addition of low viscosity polypropylene significantly reduced the viscosity of high viscosity polypropylene. Continuous glass fiber reinforced polypropylene thermoplastic prepregs were prepared by the melt impregnation method using high and low viscosity polypropylene blends as the thermoplastic resin matrix. It was found that the processing performance of the thermoplastic resin matrix was improved by increasing the content of low viscosity polypropylene, whilst the porosity and fiber breaking rate of the prepreg decreased. Each group of prepregs was molded and mechanically tested. The results show that the addition of low viscosity polypropylene causes the interlaminar shear strength, flexural strength and tensile strength to decrease slightly, but has no effect on the impact strength. In terms of the combined processing performance and mechanical properties, adding 10% low viscosity polypropylene was found to give the best overall performance.
4, 4′-二苯甲烷二异氰酸酯改性聚碳酸亚丙酯流变及发泡性能的研究
汪扬烨,何亚东,,杨兆平,黄强强
- , 2016, DOI: DOI:10.13543/j.bhxbzr.2016.05.008
Abstract: 采用4,4′-二苯甲烷二异氰酸酯(MDI)对聚碳酸亚丙酯(PPC)进行扩链改性,并用旋转流变仪表征改性PPC流变性能,采用间歇发泡装置对改性PPC进行发泡实验,研究温度及MDI含量对PPC发泡性能的影响。结果表明:MDI的加入有效提高了PPC的储能模量和复数黏度;随着发泡温度的升高,PPC的发泡倍率先增大后减小;70 ℃以下,随着MDI含量增加,泡孔平均直径减小,泡孔密度增大,发泡倍率降低;当MDI添加量达到0.7份时,发泡温区上限可以提高10 ℃左右,同时MDI的添加可以使PPC的收缩现象得到部分改善。
Abstract:Methane diisocyanate (MDI) has been used as a chain extender to modify poly(propylene carbonate) (PPC) and a dynamic rheometer was used to characterize the rheological properties of the resulting materials. A batch foaming process was used to investigate foaming properties of the modified blends at different temperatures. The results showed that the storage modulus and complex viscosity of the PPC increased significantly after the introduction of MDI. The expansion ratio of the PPC systems increased to a maximum value when the temperature reached 70 ℃, whereas it then decreased with further increases in temperature. Below 70 ℃, increasing the MDI content leads to a decrease in the mean cell diameter and expansion ratio, but an increase in the cell density. The foaming temperature upper limit can be improved by around 10 ℃ when the MDI content reached 0.7 phr. The results confirm that the phenomenon of PPC shrinkage can be ameliorated by introducing MDI into PPC.
三螺杆直接挤出制备 PP/ PA66 原位微纤复合材料的工艺研究
黄英,何亚东,姜李龙,杨昆晓,
- , 2016, DOI: 10. 13543/ j. bhxbzr. 2016. 06. 007
Abstract: 利用三角形排列三螺杆挤出机(TTSE)低温原位拉伸直接挤出制备了聚丙烯/ 聚己二酰己二胺(PP/ PA66)原位微纤复合材料,用响应曲面分析法(RSM)研究了工艺参数如PA66 含量、加工温度、剪切速率和喂料量对原位微纤复合材料微纤直径和长径比的影响。研究结果表明:加工工艺条件对PP/ PA66 微纤复合材料中的纤维直径和长径比影响很大,其中影响纤维长径比最显著的工艺参数是加工温度,其次是PA66 含量;当加工温度为245 ℃,PA66 质量分数为27%时,实验得到的PA66 微纤直径在2 ~5 μm 之间,最大长径比接近210,且最优工艺下微纤长径比的实际值与理论值偏差为3.84%,说明该分析方法较为可靠。
Abstract:In situ fibrillation polypropylene/ poly(hexamethylene adipamide) (PP/ PA66) composites have been prepared by using a triangle array triple-screw extruder(TTSE) at low temperatures. Response surface methodology was used to design the processing experiments and to analyze the effect of varying PA66 content, processing temperature, shear rate and feed rate on the diameter and aspect ratio of the resulting in situ microfibrils. The results revealed that the most important factor affecting the aspect ratio of the microfibrils is the processing temperature, followed by the PA66 content. The optimum, for preparing in situ microfibrils with maximum aspect ratio were found to be a temperature of processing factors 245 ℃ and a PA66 mass content of 27%. Under these processing conditions, in situ microfibrils with diameter 2 to 5 μm, and the maximum aspect ratio 210 were prepared. The deviation between the actual microfiber aspect ratio and the theoretical value under the optimal conditions was only 3.84%, indicating that the analysis method is relatively reliable.
玻纤布增强聚丙烯复合材料浸渍理论及实验研究
张志成,金泽宇,杨建军,,任峰,何亚东
- , 2016, DOI: 10.13543/j.bhxbzr.2016.02.005
Abstract: 采用薄膜叠压法制备玻纤布增强高黏度聚丙烯热塑复合材料,研究了高黏度聚丙烯熔体浸渍玻璃纤维布过程。通过旋转流变测试分析,可知高黏度聚丙烯树脂熔体在浸渍过程中表现为非牛顿流体特性。以达西定律为理论基础,结合材料物性参数和工艺参数,推导了非牛顿流体浸渍玻璃纤维布的浸渍模型。在不同的浸渍压力与存留时间条件下对模型进行实验验证,理论值与实验值基本吻合。利用建立的浸渍模型分析了浸渍工艺对复合材料浸渍过程的影响,结果表明通过升高温度和提高压力等途径可减小浸渍时间。
Abstract:Glass fabric reinforced high viscosity polypropylene (PP) composites have been fabricated using a film stacking procedure. An impregnation model has been developed for the consolidation phase to predict the void fraction of the resulting composites. When impregnated with glass fibers, rheological measurements and analysis confirm that the high viscosity polypropylene melt shows non-Newtonian fluid properties. An impregnation model of a non-Newtonian fluid into glass fabric has been developed based on Darcy's law and takes into account the material properties and processing parameters. The impregnation model was validated by comparing the model predictions with the experimental values for a range of applied pressures and dwell times, and the results show that the experimental results are consistent with the predictions of the impregnation model . The impregnation procedure has been studied using the model and the results show that the impregnation time in the film stacking procedure can indeed be shortened significantly by increasing the processing temperature and increasing the applied pressure.
基于ANSYS Workbench的新型SMX静态混合器的数值分析
李晓丹,何亚东,,王泽鸣,白雪
- , 2017, DOI: 10.13543/j.bhxbzr.2017.01.013
Abstract: 设计了一种新型SMX-G静态混合元件,并利用数值模拟的方法比较新型SMX-G和SMX型静态混合元件两种结构的出口平均温度、压力损失和混合效果。结合出口平均温度、压力损失及混合效果,提出了静态混合器的综合评价指标,并采用红外成像仪测温法对混合效果进行实验验证。结果表明:新型SMX-G静态混合器极大程度地减小了压力降,综合评价指标更高,保证了熔体流入机头的压力,从而显著提高了发泡制品的质量。
Abstract:We report a study of a new SMX-G static mixing element for which the average temperature, pressure loss and mixing efficiency of the SMX-G and SMX static mixing elements are compared by numerical simulation. The study gives a comprehensive evaluation index combined with the average temperature, pressure loss and mixing efficiency and the results were tested by infrared imaging. The results show that, compared with the conventional SMX-G mixer, the pressure drop of the new SMX-G static mixer is reduced significantly and the comprehensive evaluation index is higher, so that the pressure in the melt flowing into the head is maintained. As a result, the quality of the foamed product is significantly improved.
三螺杆挤出共混聚酰胺66/聚苯醚的工艺参数优化分析
杨昆晓,,姜李龙,黄英,何亚东
- , 2017, DOI: 10.13543/j.bhxbzr.2017.03.015
Abstract: 基于具有高黏度比的聚酰胺66/聚苯醚共混体系,研究了倒三角排列的三螺杆挤出机(TTSE)的工艺参数对共混物混合效果的影响。通过Box-Behnken响应面设计并分析实验结果,发现螺杆转速、产量和分散相占比对共混效果均有一定影响,通过工艺优化能够获得良好的分散效果;通过对比相同工艺下三、双螺杆挤(TSE)出机的共混效果,证明了拉伸流场对于共混效果和材料性能有明显的改善。
Abstract:The effect of varying the processing parameters of a triangular array triple-screw extruder (TTSE) in polymer blending has been studied using polyamide-66/polyphenylene oxide (PA66/PPO) as an example of a typical polymer blend with high viscosity ratio. The Box-Behnken response design method was utilized to analyze the experimental results. The screw speed, output and percentage of dispersion were shown to have significant impacts on the morphology of the resulting blends. A finer dispersion of PA66/PPO blends was achieved after optimization analysis. A comparative study of a twin screw extruder (TSE) and TTSE in PA66/PPO blending showed that the extensional flow in the TTSE could efficiently improve the dispersion and mechanical properties of the resulting blends.
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