聚丙烯发泡塑料挤出胀大行为的实验研究

使用HAAKE挤出流变仪研究了聚丙烯发泡塑料挤出胀大行为，考察了毛细管数、螺杆转速和温度等参数与PP发泡塑料挤出胀大的关系，同时指出气泡的存在对发泡制品挤出胀大有较大影响，分析了气泡体积的大小等对PP发泡塑料的挤出胀大的影响。     

用毛细管流变仪研究发泡聚丙烯(PP)挤出胀大行为

利用毛细管流变仪研究发泡聚丙烯(PP)挤出胀大行为,观察了压力、温度等参数与膨胀率的关系,分析加入不同的AC发泡剂和CaCO3后其膨胀率不同的变化情况,指出这不仅仅是因为发泡体系弹性的变化,气泡的存在也对其膨胀率影响很大。     

低密度聚乙烯毛细管动态挤出时的挤出胀大研究

在振动场的作用下,ＬＤＰＥ熔体于毛细管中动态挤出与稳态挤出时相比,挤出物的挤出胀大比减小,减小程度与施加的振动强度有关。在相同流率时于一定振幅条件下,挤出物胀大比变化与频率成非线性变化。结果表明,动态挤出时挤出物弹性效应得到改善,从而为聚合物的挤出成型加工带来巨大的益处。     

HDPE在挤出温度条件下流变行为的研究

利用毛细管流变仪研究了不同温度条件下HDPE的流变行为。测定了不同温度条件下HDPE的流变特性并绘制了流变曲线。流变曲线的分析表明，HDPE的流变行为受温度的影响很大，同时由于该材料本身的特性，在挤出加工温度条件下，其流变曲线存在第一及第二光滑区。随剪切速率增加，表观粘度下降。     

聚丙烯发泡体系挤出胀大模型的研究

运用正交实验的方法和数学回归的方法,对实验数据进行分析,得到了聚丙烯发泡体系剪切速率与切应力的关系,以及胀大比与毛细管数的关系表达式。通过结果检验可知,本文确立的胀大模型可以用于预测聚丙烯发泡体系胀大比。     

聚合物气辅挤出的挤出胀大研究

在自行研制的气辅挤出实验装置上对气体辅助挤出过程中挤出胀大现象进行了研究,传统挤出和气辅挤出的对比实验表明,气辅挤出可以极大地减小挤出过程中的挤出胀大;研究了螺杆转速、辅助挤出气体压力和流量对挤出胀大的影响．并采用CFD有限元通用软件FIDAP分析了气辅挤出过程中口模内的速度场和压力场,表明气辅挤出过程中聚合物熔体各点的速度和压力趋于一致,可减小挤出制品在挤出时产生的内应力和变形．有利于提高制品加工精度。     

LLDPE熔体短口型挤出中胀大行为的研究

应用毛细管流变仪 ,考察了线性低密度聚乙烯 (LLDPE)熔体于短口型挤出中的胀大现象及其影响因素。结果显示 ,挤出胀大比 (B)与入口压力降 (ΔΡen)之间关系服从指数律 ;B与壁面剪切应力 (τw)之间近乎线性关系 ;B对温度的依赖性不太明显。在相同条件下 ,口型入口角为 12 0°的B值低于 90°时的B值     

黏弹流体挤出胀大行为的研究进展

介绍了聚合物挤出胀大的理论机理及数值模拟,并综述了最近几年黏弹流体挤出胀大行为的研究进展。最后指出目前存在的一些问题,并展望发展前景。     

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。     

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。     

Extrusion die swell of carbon black-filled natural rubber

Extrusion die swell of natural rubber compounded with a wide variety of carbon blacks has been determined in a capillary rheometer using a long circular die. The range of variation of carbon black loading, surface area, and structure are, respectively, 10 to 60 phr, 44 to 124 m²/g, and 78 to 120 cc/100 g. The effective carbon black volume fraction φ_e not participating in the strain recovery leading to die swell is assumed to be the sum of the actual filler volume fraction and the fraction of unextractable rubber determined experimentally for each compound. Bagley and Duffey's analysis of extrusion die swell of unfilled polymers as unconstrained elastic recovery was adopted for a filled elastomeric system whose relative shear modulus (G/G₀) is assumed to vary as (1 ? φ_e)^?N. The matrix shear modulus G₀, originally introduced by Nakazima and Shida on the basis of a linearized approximation, will depend on the shear stress level because of nonlinear deformation. The power N will vary with shear stress which changes the orientation of carbon black aggregates. Except for these features, die swell data for a wide range of carbon black compounds fall on a single curve when plotted in the manner of the predicted relation between the wall shear stress, die swell, and φ_e. Replacing φ_e by Medalia's φ′ based on an equivalent sphere concept introduces a larger scatter around the mean curve.     

Die‐swell behavior during the short‐tube flow of rubber compounds

In this study, the flow properties and die‐swell ratios (B's) of two kinds of rubber compounds (SI was a calcium carbonate filled natural rubber compound, and SII was a carbon‐black‐filled natural rubber/butadiene–styrene rubber/cis‐1,4‐butadiene rubber compound) in a short‐tube extrusion flow were measured by means of a capillary rheometer under test conditions with a temperature of 90°C and an apparent shear rate varying from 10 to 4000 s^?1 to identify the effects of extrusion conditions on the rheological behavior of the materials and to estimate B. The shear flow roughly obeyed the power law, whereas B increased nonlinearly with increasing extrusion rate. Under the same shear rates, the viscosity of SII was higher than that of SI, whereas the values of B of SI were higher than those of SII. Furthermore, B of the rubber compounds was estimated by means of an extrudate swell equation published in a previous work. The results show that the predictions of B were close to the measured data from the experiments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

医用管件挤出设备

以超过 45年服务于医用装备业的经验支持 ,Davis- Standard提供医用管件制造的一整套挤出设备。系统的主要特色是挤出机 ,加料螺杆 ,综合控制系统和相关下游部件。　　 Davis- Standard设备的设计是为了热塑性塑料和化合物均能使用 ,并可调整来加工腐蚀性聚合物 ,高温材料和非热塑性塑料。挤出机规格从 1 9～75 mm,当有需要 ,开槽加料喉和排空套管筒可以安装于挤出机中。具有螺杆混合装备的熔体耜可用于特殊用途。以下是主要主要设备。　　挤出机要 DS- 1 5 HM空气冷却挤出机 ,具有双缩减的变速箱 ,硬结构钢焊接的基座和大加料开口。后…     

An experimental investigation of capillary extrudate swell in relation to parison swell behavior in blow molding

An experimental study was carried out to study and characterize the capillary extrudate swell and parison swell behavior in extrusion blow molding of two commercial blow molding grade high density polyethylene resins. The capillary extrudate swell behavior of these resins were determined employing a capillary rheometer and a special thermostatting chamber. Parison swell behavior was determined using an Impco A13-R12 reciprocating screw blow molding machine in conjunction with cinematography and pinch-off. The experimental conditions under which capillary extrudate and parison swell data can be related are elucidated. Excellent agreement is found between the area swell values determined on the basis of capillary and parison swell experiments.     

高速挤出PVC通讯电缆绝缘材料

分析了国外高性能ＰＶＣ电缆料,在全部使用国产原材料和助剂的前提下,研制了高速挤出ＰＶＣ通讯电料。该料可以在很高的挤出速度下加下成薄壁电线在１０００ｍ／ｍｉｎ的速度下可长时间稳定加工,具有很好的电性能、机械性能及耐老化性能;加工时不存在口模冒烟现象,清模周期长;产品外观光滑,致密, 有光泽手感良好。     

Extrudate swell behavior of glass fiber filled polyamide 6

This paper discusses the extrudate swell behavior of glass-filled polyamide 6. The key features of the experiments were the facility to extrude directly into a density matched oil kept at extrusion temperature and thus, the ability to measure the diameter of the extrudate of the glass-filled polyamide immediately upon exit from the die, without the extrudate contacting air and as a function of time in a chamber under isothermal and neutrally-buoyant conditions. The concentration and orientation of the fibers of the extrudates were also studied using X-ray radiography in a post-mortem fashion. A skin/core morphology, where uniaxially aligned fibers constitute the skin zone and the core contains a reduced concentration of fibers, was observed.     

Die swell of thermoplastic polyurethanes: A peculiar behavior

The instantaneous and equilibrium isothermal die swell ratios of thermoplastic polyurethanes have been measured by two methods. The incidence of some structural, geometrical, and processing parameters has been analyzed. The experimentation reveals the atypical behavior of these polymers related to a structural evolution during processing that greatly depends on the residence time in temperature under shearing and that probably results from the cumulated effects of multiple recombinations and chain cuts. This thermo‐mechanical degradation affects the rheological properties of these polymers. The maximal behavior variations are observed for short times and stabilize above a specific critical time. Taking into account the effect of these rheological alterations on the generating mechanisms of die swell allows us to interpret all the experimental results (atypical or not) in terms of magnitude and direction of variation of the phenomenon. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1710–1724, 2001     

Extrudate swell of high density polyethylene. Part III: Extrusion blow molding die geometry effects

Two high density polyethylene resins—801 and 802— are examined with regard to their isothermal, time-dependent, and nonisothermal swelling properties when emerging from two annular and three diverging dies. The short time swelling characteristics of samples 801 and 802 are very important for these dies, resulting in a lower diameter swell for the latter, independent of the die geometry or flow rate. Output variations have much less impact on the swelling behavior than small changes in the geometry of the die mandrel. Accordingly, shear stress and shear rate parameters alone cannot be used to explain the swelling properties of a HDPE resin in the different die geometries. Straight annular dies induce higher diameter swelling than diverging dies.     

ABS/中空微珠复合材料挤出流动中的弹性行为

应用熔体流动速率测定仪考察了丙烯腈-丁二烯-苯乙烯三元共聚物（ABS）／中空微珠复合材料的弹性行为。结果表明,在200℃,当剪切应力（τw）小于120kPa时,挤出胀大比（B）随着τw的增大而增大,但增幅减小;当τw大于120kPa时,B增幅增大。在200℃时,B随着剪切速率的增大而增大;随着温度的上升,B增大,两者较好地符合线性关系;在200℃时,B随着填料含量的增加而增大,两者呈较好的二次函数关系。