单螺杆挤出机中聚合物混合状态的超声监测技术研究

设计了适用于聚合物混合状态在线监测的超声传感器,通过试验研究了碳酸钙、硫酸钡、玻纤等填充料在低密度聚乙烯(LDPE)中的超声回波信息,在φ90单螺杆挤出机上在线监测了线性低密度聚乙烯(LDPE)及LDPE与玻纤混合物的挤出状态.试验结果表明:超声回波信息可以较好地表征聚合物的混合状态,采用设计的超声传感器可以实现聚合物挤出混合状态的在线监测,同时也可以采用该传感器监测聚合物的黏度等信息.     

不同螺杆构型混合性能与接枝反应接枝率关系的研究

研究了不同螺杆构型的混合性能以及低密度聚乙烯熔融接枝马来酸酐的过程，探讨了不同螺杆构型的混合性能与接枝反应接枝率的关系。用酸碱滴定法对样品的接枝率进行了测定，并对物料在挤出机内的停留时间分布以及不同螺杆构型下两相聚合物的混合效果进行了研究。结果表明，螺杆元件的混合性能对接枝反应挤出过程有较大的影响，采用具有优异混合性能的捏合块元件时反应具有较高的接枝率，采用具有高拉伸性能的S形元件和具有高回混性能的非啮合多过程元件均能迅速提高接枝率。     

有机聚合物的交联结合方法(一)

依靠加热把形成硅烷改性有机聚合物的混合组成物用常法供给螺杆挤出机,接着加热混合而挤出硅烷改性有机聚合物的方法,在该螺杆式挤出机的有机聚合物的熔融段以后的部位在机筒或螺杆设置液体注入孔,从该注入孔注入硅氧烷缩合触媒混合挤出,将得到的挤出物与水分接触而形成硅烷改性有机聚合物的交联结合方法。本发明为关于有机聚合物的交联结合的改进,再具体说就是关于含有能加水分解的     

短圆管挤出模头中熔体取向行为对螺杆轴向振动响应的光散射研究

利用光散射测量方法研究了短圆管挤出模头中聚合物熔体取向行为对螺杆轴向振动的响应。研究结果表明,螺杆轴向振动使聚合物熔体的流动状态和大分子的取向发生了显著的变化,振动力场中振幅或频率的增加都会引起熔体中大分子取向程度的增大。     

间断副螺棱强化螺杆螺槽内混合行为表征

通过在螺杆螺槽内插入周期性间断结构副螺棱,建立新型螺杆计量段螺槽展开简化模型。借助动力学软件Ployflow,对聚合物在新型螺杆及普通螺杆螺槽内的流动情况进行模拟仿真,对比分析其流动混合效果,同时进行低密度聚乙烯(LDPE)/nano-CaCO_3的共混挤出试验验证。结果表明,副螺棱周期性的扰动可触发混沌混合,提高聚合物流体的分散准数,延长粒子在螺槽中的停留时间分布,同时试验挤出物脆断面的微观结构也显示新型螺杆具有更好的混合效果。     

基于超声波测量技术聚合物精密挤出成型制品质量精度的控制方法

根据超声波在传播介质中快速响应的特性,介绍基于超声波的聚合物管材壁厚及外径测量技术,在分析影响精密挤出制品质量因素的基础上,提出将超声波测距技术应用于精密医用导管挤出成型过程中,实现管材壁厚及外径的在线测量。通过挤出管材米重Gm(单位长度质量)-牵引机速度的闭环反馈控制,完成管材壁厚及圆度的在线精确控制,达到精密挤出导管几何截面尺寸高精度的要求。     

同向双螺杆挤出机变头变径变深螺杆组合及其应用

主要讨论啮合型同向双螺杆挤出机螺杆组合中变头变径变深组合理论及其应用实例。首先讨论了啮合型同向双螺杆挤出机各种螺杆元件的基本特性－－挤出特性、混合特性和扭矩菌耗特性对螺槽深度和螺纹头数的依赖性。正向螺纹元件、反向螺纹元件、捏合块元件的上述特性定量或定性分析有助于螺杆组合的理论分析,结合挤出过程各阶段对螺杆组合基本要求提出了变头变径变深螺杆组合原则。最后讨论了该螺杆组合在聚合物加工中的应用实例。     

螺杆组合对PP共混体系性能的影响

本文就同向双螺杆挤出机螺杆组合对聚合物改性体系性能的影响进行了实验室。阐述了同向双螺杆挤出螺纹元件输送和混合特性,提出了螺杆组合设计的一般原则。     

气辅挤出成型中挤出物直径的理论预测和实验研究

应用Polyflow软件对粘弹性聚合物熔体在气辅挤出口模内的流动进行了研究,得到了挤出物直径的挤出胀大比方程。模拟结果表明,熔体在滑移段的平均停留时间与材料松弛时间之比同挤出胀大比之间存在指数衰减关系。通过HDPE的气辅挤出成型实验,发现不同螺杆转速及挤出温度下挤出物直径的实验值与计算值达到很好的吻合,该计算方法可用于指导气辅口模设计。     

啮合同向双螺杆挤出机中组合螺杆性能的数值研究（Ⅰ）瞬态流场分析

采用聚合物流动分析软件POLYFLOW,数值模拟了聚合物熔体在组合式啮合同向双螺杆挤出机ZSK60的组合螺杆中的三维等温流动。在计算所得速度场和压力场的基础上,全面分析并讨论了由不同厚度和不同错列角的捏合块元件组成的组合螺杆的流场分布规律;研究了组合螺杆的输送性能和挤出稳定性;并分别采用平均剪切速率、平均特征剪切应力以及平均拉伸流动指数等瞬态混合指数表征了组合螺杆的瞬态混合特性。此外还考察了两种不同流变性质的聚合物熔体在组合螺杆中的瞬态流场分布规律。所得结论可为双螺杆挤出的数值模拟研究提供一定的方法指导,并为其工程实践提供一定的理论指导。     

用超声波检测方法评价注塑机螺杆混炼能力的研究

采用从国外引进的超声波检测系统以及实验室自行设计的超声波检测辅助装置,对碳酸钙填充的聚丙烯（PP）以及丙烯腈-丁二烯-苯乙烯共聚物（ABS）体系进行超声波检测,发现超声波声速随着碳酸钙含量的增加呈下降趋势;在注塑机喷嘴处进行超声波在线检测,从超声波声速波动情况以及制品的力学性能两方面,评价了不同注塑螺杆的混炼能力。     

Ultrasonic treatment of PP/CNT composites during twin‐screw extrusion: Effect of screw configuration

PP/CNT composites were prepared by means of an ultrasonic twin extruder with three screw configurations at ultrasonic amplitudes up to 13 μm to compare their efficiency in dispersing CNT in PP. Using these screw configurations, the pressure in the ultrasonic treatment zone was varied in order to elucidate the effect of pressure on ultrasonic cavitation behavior in PP and PP/CNT composites. Rheological and mechanical behaviors were analyzed to reflect the dispersion of CNT. The results indicated that the dispersion of CNT in PP is more related to the number of kneading elements in the screw configuration and less to the residence time. This was explained by simulating the mixing effect using the flow analysis network. Comparison of the complex viscosities of untreated and treated PP indicated that at the same amplitude of ultrasonic treatment, PP degraded more at lower ambient pressure. At the lowest ambient pressure, the cavitation in the polymer matrix was intense at the highest amplitude but it had not always led to the best dispersion due to the suppression of the cavitation in the agglomerates. Therefore, the ultrasonic treatment increased the dispersion level of CNT in PP with the best improvement not always occurring at the highest amplitude. Composites prepared at an ultrasonic amplitude of 10 μm in the screw configuration providing an intermediate pressure exhibited elongation at break as high as 320% compared to 247% for the untreated composites. POLYM. COMPOS., 38:2695–2706, 2017. © 2015 Society of Plastics Engineers     

Ultrasonic in‐line monitoring of polymer extrusion

In‐line ultrasonic monitoring of polymer co‐extrusion and twin‐screw extrusion are presented. Co‐extrusion of high density polyethylene (HDPE) and a thermoplastic elastomer based on polypropylene‐EPDM (ethylene‐propylene‐diene monomer) has been investigated by ultrasonic sensors consisting of piezoelectric transducers and clad buffer rods. One extremity of the rod (probing end) was installed flush with the die surface so as not to disturb the material flow. The other end was air cooled in order to protect the transducer from excessive heating. This approach has been demonstrated to be quite convenient for monitoring and controlling industrial material processes: first, it can work at temperatures up to 1000°C; second, the clad buffer rod probing end can be machined to the same shape as those of commercial temperature and pressure sensors commonly used in the extrusion process. Therefore, no modifications are required for the installation in the original equipment. The information obtained includes the position of the interface between polymers and the stability of the process. The same ultrasonic probe has also been installed on a barrel of a twin‐screw extruder. This study was performed using polyethylene and polystyrene. It has been verified that the ultrasonic sensor can be successfully operated along the extruder screw and that the ultrasound can give access to the material properties while the polymer is being processed. This means that the technique can be exploited to monitor and control in situ the characteristics of the polymer being transformed in operations typically performed on twinscrew extruders, such as compounding, visbreaking or reactive extrusion.     

Application of ultrasound in the determination of fundamental extrusion performance: Residence time distribution measurement

By means of new probe design and rapid data acquisition, we have succeeded in in‐line ultrasonic monitoring of residence time distribution (RTD) at the melting, mixing, and pumping zones as well as at the die exit of a Werner & Pfleiderer 30‐mm twin‐screw extruder by mounting the ultrasonic probes on the extruder barrel over the screw elements and at the die. The experimental systems were LDPE, CaCO₃‐filled LDPE, and a Kraton/LDPE blend. The ultrasonic data at each of the extruder functional zones are presented. The ultrasonic results have been used to evaluate an opical RTD measurement method by using an optical sensor side by side with one ultrasonic probe at the mixing zone of the extruder. The comparison of the ultrasonic and optical results has shown that the presented ultrasonic technique could be a good complement to the optical technique in the monitoring and understanding of RTD during polymer extrusion processes.     

In‐line monitoring and analysis of polymer melting behavior in an intermeshing counter‐rotating twin‐screw extruder by ultrasound waves

An ultrasound in‐line monitoring system that includes a homemade probe and a fast data acquisition system was used to investigate the melting behavior of linear low density polyethylene (LLDPE) in pellet form and four polyvinyl chloride (PVC) compounds in powder form in an intermeshing counter‐rotating twin‐screw extruder. Ultrasound signal patterns obtained from experiments revealed various melting phenomena in C‐chambers, depending on materials, processing conditions, and screw configurations. The experimental results suggest that PVC particles were suspended in the polymer melt in the melting process of most PVC compounds, while melted film was still observed in the melting process of the PVC/dimethyl phthalate (DMP) system and the PVC/polybutylene adipate (PBA) system. Based on the analysis of wave attenuation, the normalized amplitude ratio K was used to characterize the melting level and uniformity across screw channels at screw speeds of 40 and 50 rpm, respectively. POLYM. ENG. SCI., 45:998–1010, 2005. © 2005 Society of Plastics Engineers     

螺杆结构对轮胎胶粉超声波脱硫工艺及性能的影响

采用负载超声波发生装置的同向旋转双螺杆挤出机对40目废旧轮胎胶粉（GTR）进行超声波脱硫,考察了两种不同结构螺杆对脱硫过程中的口型压力和功率消耗、脱硫GTR（DGTR）的外观形貌、流变性能、硫化特性及DGTR硫化胶力学性能的影响。结果表明,在13 μm超声波振幅和含较多捏合块部件螺杆的作用下得到的DGTR的凝胶含量、黏度及储能模量较低,说明含捏合元件的螺杆剪切作用更强,能使GTR获得更高程度的脱硫。该条件下所制得的DGTR硫化胶的拉伸强度和100%定伸应力较低,扯断伸长率较高。     

Analysis of mixing during melt-melt blending in twin screw extruders using reactive polymer tracers

Mixing during melt-melt blending of segregated polypropylene melt streams in a co-rotating twin screw extruder was experimentally investigated. The mixing limited reaction between two polymer reactive tracers, which are terminally functionalized polyolefin oligomers, was used to determine the mixing performance of a kneading block section. The selected functional groups were succinic anhydride and a primary amine, and Fourier-Transform Infrared Spectrometry (FT-IR) was used to determine the anhydride conversion. In the absence of interfacial tension, the reaction conversion was directly related to the amount of interfacial area generated. Experiments were completed to study the effects of operating conditions, kneading block design, and polymer material properties. The screw speed effect was observed to be non-linear because of competing contributions from shear rate, residence time, channel fill, and viscous heating. The mixing performance of kneading blocks backed by a reverse conveying element was observed to follow the trend of: forward > reverse > neutral. For each kneading block design, the mixing performance decreased with an increase in polymer viscosity.     

Effect of ultrasonic wave on the degradation of polypropylene melt and morphology of its blend with polystyrene

A new method using high intensity ultrasonic wave has been developed for the degradation of polymer melt in an intensive mixer. For the effective transfer of ultrasonic energy, experimental apparatus was specially designed so that polymer melt can be in direct contact with the ultrasonic horn. In this research, we observed that the significant degradation of polypropylene (PP) melt in a mixer occurs due to the action of ultrasonic wave without any aid of additives or solvents. To compare the degradation efficiency of ultrasonic irradiation with that of peroxide, additional experiments were performed to practice the peroxide-aided degradation by mixing 1 part of dicumyl peroxide with PP in the mixer. It was also found that the direct sonication on polymer mixture in melt state reduces the domain sizes and stabilizes the phase morphology of the blend. It is suggested that ultrasound assisted melt mixing can lead to in situ copolymer formation between the components and consequently provide an effective route to compatibilize immiscible polymer blends.     

A Computer Model for Single-Screw Plasticating Extrusion

A fully predictive computer model has been developed for a single-screw plasticating extrusion (with conventional screws). The model takes into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, melt conveying) and the die, and describes an operation of the extruder-die system, making it possible to predict a mass flow rate of the polymer, pressure and temperature profiles along the screw channel and in the die, solid bed profile, and power consumption. Moreover, mixing degree, temperature fluctuation and viscoelastic properties of the polymer are estimated. The simulation parameters are the material and rheological properties of the polymer, the screw, hopper and die geometry, and the operating conditions (screw speed and barrel temperature profile). Such a comprehensive approach to the modeling of extrusion creates the possibility of optimizing the process, for example, from the point of view of the quality of extrusion. The model has been verified experimentally for a low-density polyethylene on a 45 mm diameter single-screw extruder.     

振动力场对高密度聚乙烯固体物料输送压力的影响

在自行设计的动态固体物料压实试验机上,对高密度聚乙烯固体物料分别做了稳态和动态压实试验,研究了振动力场对固体物料输送过程的影响。结果表明:有振动力场存在时,螺槽中固体物料的压力明显高于稳态压实时的压力;在振动力场作用下,在一定范围内,增大振幅或者提高振动频率,都能明显提高螺槽中固体物料的压力,且压力随时间增加上升得更快;振动力场的引入可以加速固体物料的压实,使螺槽中提早建立固体物料的输送压力,且使压实效果更好。