三元乙丙橡胶挤出压力振荡现象的影响因素

采用恒速型双筒毛细管流变仪研究了剪切速率、口模温度和含氟弹性体偏氟乙烯-六氟丙烯-四氟乙烯共聚物(PPA)对三元乙丙橡胶(EPDM)挤出压力振荡现象的影响.结果表明,EPDM高速挤出时,升高温度可以推迟挤出压力振荡现象的发生;振荡周期和振幅均随剪切速率的增加而减小;加入PPA可以改善EPDM挤出物的外观,且挤出压力低于纯EPDM,PPA质量分数越大,其降低幅度越大.     

聚烯烃熔体两类挤出畸变现象的定量描述

采用恒速型双毛细管流变仪研究一批聚烯烃熔体的高速挤出行为.定义了定量描述两类挤出畸变现象--鲨鱼皮畸变和挤出压力振荡的若干物理参数.定量描述了温度、挤出速率、熔体材质及成分对挤出压力振荡和鲨鱼皮畸变的影响规律.发现线型聚合物熔体高速挤出时易发生鲨鱼皮畸变和挤出压力振荡,而支化聚合物或主链含大侧基聚合物熔体很少出现同类畸变.挤出速率增大,压力振荡的频率加大,振荡加剧;挤出温度升高,开始发生振荡的临界剪切速率增高,熔体流动不稳定性减轻;但对同一熔体而言,不同温度下开始发生压力振荡的临界剪切应力变化不大.     

含氟弹性体对聚烯烃挤出性能的改善

熔体破裂是挤出成型中遇到的最严重的问题。在树脂中掺入适量的含氟弹性体,是减轻甚至消除熔体破裂的有效措施。PPA2231及FKM-A是较有代表性的两种含氟弹性体。本文介绍了物料制备及实验的方法,利用毛细管流变仪的大量实验结果,详尽分析了这两种含氟弹性体对LLDPE、HDPE及PP这三种聚烯烃树脂挤出性能的效应。并简述了在挤出加工时,含氟弹性体还可降低熔体温度,减小机头压力,提高挤出效率。     

微量PPA对m-LLDPE高速挤出流变性能的影响

采用恒速型双毛细管流变仪研究了含氟弹性体(PPA)对茂金属催化线性低密度聚乙烯(m-LLDPE)熔体高速挤出不稳定行为的影响。结果表明,微量PPA的加入能推迟甚至抑制鲨鱼皮畸变,能明显改善粘-滑畸变。加入微量PPA后,挤出压力下降,管壁上应力集中效应减弱,挤出压力振荡现象减弱甚至消失,流动曲线由断裂逐渐变得连续。     

含氟弹性体对LLDPE熔体流变性能的影响

通过改变含氟弹性体(PPA)的含量,研究了PPA对线型低密度聚乙烯(LLDPE)熔体流变行为的影响.研究发现,将PPA加入到LLDPE中,熔体的挤出压力、挤出胀大比均减小,发生鲨鱼皮畸变和挤出压力振荡等不稳定流动现象时的临界剪切速率提高,扩大了加工范围;足量的PPA甚至可完全消除鲨鱼皮畸变现象.     

EPDM/PP热塑性弹性体的制备及其流变特性

以聚丙烯(PP)和三元乙丙橡胶(EPDM)等为原料,采用完全动态硫化共混技术制备EPDM/PP热塑性弹性体(TPV),使用毛细管流变仪对TPV熔体的流变特性进行测试。分别研究了剪切速率、挤出温度对黏度、剪切应力和挤出胀大比的影响,以及不同条件下熔体流过毛细管口模时流速对压力降的影响。结果表明,TPV熔体是假塑性流体,其剪切应力随剪切速率增大而增大,随挤出温度的升高而降低;黏度随剪切速率和挤出温度的增大而降低;挤出胀大比则随剪切速率和挤出温度的增大而增大;毛细管口模的压力降也随流速和毛细管口模长度的增大而增大。     

HDPE及其共混物的挤出压力振荡现象

采用恒速型双毛细管流变仪研究高密度聚乙烯及其共混物的压力振荡现象,测量了压力振荡的振幅及频率,计算了熔体在管壁的滑移速率和临界外推滑移长度。结果表明,发生压力振荡时,熔体与毛细管壁的界面出现“时黏时滑”转变。黏界面时,挤出物表面出现“鲨鱼皮”现象;滑界面时,挤出物表面粗糙,类似于无规破裂。随剪切速率的增加,压力振荡的振幅减小,而滑移速率、临界外推滑移长度及振荡频率均有提高。升高挤出温度和采用共混改性都可抑制压力振荡现象。     

内胎胶挤出流动中出口压力降的估算

应用前文中提出的出口压力降△exit与挤出胀大比的关系式,估算了挤出条件下内胎胶的出口压力损失。结果表明,当温度一定时,△exit随着剪切速率的增加而增大;而在固定的剪切速率下,△exit则随着温度的升高而下降。     

ABS挤出过程中流变性能的测试

利用恒速式毛细管流变仪研究了（丙烯腈／丁二烯／苯乙烯）共聚物（ABS）的流变性能,并测试计算了挤出膨胀比和非牛顿指数。结果表明,ABS的表观粘度随温度的升高及剪切速率的增加而降低;非牛顿指数随温度的升高而增大;挤出膨胀比与剪切速率及管模的长径比成正比。     

PP/MRP复合材料熔体挤出胀大行为的研究

采用熔体流动速率仪考察了温度、剪切应力、以及微胶囊红磷(MRP)含量对聚丙烯(PP)/MRP复合体系熔体挤出胀大比的影响。结果表明:PP/MRP复合体系熔体的挤出胀大比随着温度的升高而呈减小的趋势,随剪切应力的增加而显著增大,并且在185℃时,挤出胀大比与剪切应力之间基本符合线性关系;MRP含量增大,则PP/MRP复合体系熔体的挤出胀大比值呈减小的趋势。     

乙烯酮(双乙烯酮)下游产品废水的治理技术

乙烯酮(双乙烯酮)是十分重要的化工中间体,其下游产品较多。江苏某化工厂开发生产乙烯酮(双乙烯酮)下游产品三十多个,年生产规模三万多吨,是国内以乙烯酮(双乙烯酮)为中间体生产精细化学品的综合骨干企业。针对乙烯酮(双乙烯酮)下游产品废水特点,该厂结合企业实际,开展了产品优化,结构调整,清洁生产,资源循环利用,节水降耗等工作,从源头削减了污染物的生产。同时投资二千多万元新建预处理装置三套,6000m3/d废水生化处理装置一套,使全厂乙烯酮(双乙烯酮)下游产品的废水得到了有效的治理。     

A study of miscibility of blends of polybutadienes of varying microstructure

The miscibility of various amorphous polybutadienes with mixed microstructures of 1,4 addition units (cis, 1,4 and trans 1,4) and 1,2 addition units have been investigated. The studies here involved optical transparency, differential scanning calorimetry, and small angle light scattering. It was found that a 90 percent (cis) 1, 4 addition polybutadiene was immiscible with high (91 percent) 1,2 addition polybutadiene. Reduction of the 1,2 content to 71 percent induced an upper critical solution temperature (UCST) with the cis 1,4 polymer. Polybutadienes with 50 percent and 10 percent 1,2 contents were miscible above the crystalline melting temperature of the cis 1,4 polybutadiene. Immiscibility of the 91 percent 1,2 addition polymer was also found with a 10 percent 1,2 polybutadiene. The latter polymer also exhibits an UCST with the 71 percent 1,2 polymer. The results are used to interpret the characteristics of blends of polybutadienes of varying microstructure.     

几种乙炔加压设备性能的比较

阐述并比较了几种加压设备在乙炔加压清净过程中的性能和特点。     

粉煤灰中烧失量检测的不确定度分析

以F类粉煤灰为例,详细介绍了测定粉煤灰中烧失量的步骤、计算数学模型、影响测量不确定度的因素以及各项测量不确定度分量评定,人员、设备、材料、方法、环境都是影响测量不确定的因素。     

生物油的成分分析及物性测定

以添加FeCl2的ZnCl2-KCl混合熔盐裂解纤维素和秸秆,制得生物油。采用傅立叶变换红外光谱法和气相色谱-质谱法分析生物油的成分。结果表明,生物油中成分复杂,含有氧元素、多种有机化合物,主要包括酮类、醛类、酚类及羧酸类等。测定了20～80℃生物油的密度和粘度,发现生物油的密度与温度呈较好线性关系,而生物油的粘度均大于水的粘度,且不同熔盐体系对秸秆生物油的粘度无较大影响。     

Effect of degree of deacetylation of chitosan on the kinetics of ultrasonic degradation of chitosan

The objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003     

分解炉扩径的技术改造

我厂3号回转窑(Φ4m×60m)生产线在1996年年底由SP窑(产量912t/d)改为NSP窑(产量1320t/d),预分解系统为四级旋风预热器带离线式分解炉