聚烯烃/PET共混物的微纤形成及力学性能

研究了聚烯烃/聚对苯二甲酸乙二酯(PET)共混物的微纤形成、制备工艺条件、连续相聚烯烃的选择和力学性能。用单螺杆挤出机挤出嵌段共聚聚丙烯(PP-B)/PET和高密度聚乙烯/PET时,挤出产物中会形成部分短而粗的微纤;采用"熔融挤出—热拉伸—淬火"工艺制备的PP-B/PET共混物中会生成更多长径比较大的PET微纤,且随拉伸比的增加,微纤数量增多,长径比增大,共混物的熔体流动速率降低;在挤出工艺条件下,最适合的连续相是PP-B,最适宜的工艺条件是:从进料口到机头温度分别为220,250,260,220℃,螺杆转速为50 r/min,拉伸比为3;PP-B/PET原位微纤共混物的拉伸屈服应力比纯PP-B提高约33%;增大拉伸比可提高共混物的拉伸屈服应力和抗冲击性能。     

PET熔融挤出后的特性黏数变化

分别使用单螺杆挤出机、双螺杆挤出机、反应型挤出机挤出聚对苯二甲酸乙二酯(PET),研究其在不同挤出温度、不同螺杆转速下熔融挤出后PET的特性黏数变化情况。使用双螺杆挤出机时,PET降解最严重,特性黏数平均降低23.5%。使用单螺杆挤出机:在较低挤出温度时挤出产物基本不降解;在高温时挤出产物降解明显,挤出温度每提高10℃,产物特性黏数平均降低5.8%;较高的螺杆转速有利于防止PET的降解;原料含水量越低,PET分子越不易降解。使用反应型挤出机时,PET热降解程度大于使用单螺杆挤出机。PET最适合使用单螺杆挤出机,在较低挤出温度、较高螺杆转速、物料经过烘干的情况下进行熔融挤出加工。     

PET/PBT共混物的结构与特性黏度变化

分别使用单螺杆挤出机、双螺杆挤出机和反应挤出机制备了不同配比的聚对苯二甲酸乙二醇酯(PET)/聚对苯二甲酸丁二醇酯(PBT)共混物,用差示扫描量热仪(DSC)、13C-核磁共振仪和乌氏黏度计对其进行了表征。结果表明,单螺杆挤出机制备的PET/PBT共混物的DSC曲线与溶液共混制备的相同,挤出过程中没有发生酯交换反应,双螺杆挤出机和反应挤出机制备的PET/PBT共混物过程中也没有发生酯交换反应;反应挤出机制备的PET/PBT共混物的特性黏度最高,双螺杆挤出机制备的特性黏度最低。     

mLLDPE及mLLDPE/LDPE共混物挤出加工性能的研究

使用双螺杆挤出机、单螺杆挤出机研究了mLLDPE及mLLDPE/LDPE共混物挤出表面、螺杆扭矩与喂料速度、螺杆转速之间的关系 ,并讨论了有机硅对mLLDPE/LDPE共混物挤出性能的影响     

PET瓶片的稳定挤出扩链

使用两台螺杆头部结构有差异的反应挤出机,在配方和工艺完全相同的条件下研究了聚对苯二甲酸乙二酯(PET)瓶片在挤出过程中熔体压力波动和扩链反应情况。结果表明:使用头部设计有改进型直槽混炼件的35型反应螺杆,无论是直接挤出还是混合有扩链剂均苯四甲酸二酐的挤出,挤出过程中的压力波动均比头部为普通螺纹的30型反应螺杆显著降低,而且熔体压力平均值也高;使用35型反应螺杆挤出产物的特性黏数([η])略高于30型反应螺杆挤出的;提高螺杆转速既有利于提高挤出产物的[η],又有利于提高机头处的熔体压力平均值,相当于提高了挤出机产量。使用头部设计有改进型直槽混炼件的反应螺杆非常有利于稳定挤出PET瓶片,成型制品。     

加工条件对聚丁二酸丁二醇酯/聚丙烯原位微纤化共混物形态的影响

采用单螺杆挤出机组合狭缝机头制备聚丁二酸丁二醇酯(PBS)/聚丙烯(PP)原位微纤化共混物,研究了加工温度、螺杆转速对其形态的影响.结果表明,机头温度160℃时形成的纤维比机头温度170℃时纤维平均直径小,长径比大,纤维区域厚度百分数(Φ值)高;当机头温度为170℃、螺杆转速为20 r/min时,在狭缝机头出口靠近上下壁面处开始形成纤维,随着转速的提高,纤维平均直径逐渐减小,Φ值增大.     

HDPE/PA6原位微纤共混物的制备与性能

采用挤出-拉伸工艺制备了高密度聚乙烯(HDPE)/聚酰胺6(PA6)原位微纤共混物,探索了单螺杆挤出机的螺筒温度、螺杆转速、PA6用量及热拉伸比对产物微纤形成、熔体流动速率(MFR)和应力应变性能的影响。结果表明,PA6质量分数在5%～20%,HDPE/PA6在200,230,250,210℃(机头)的挤出机中熔融挤出,螺杆转速20～50r/min,料条经15℃水浴短时间冷却,再在70～75℃的空气中进行热拉伸,可以在HDPE连续相中形成直径5～10μm的PA6微纤。随PA6用量增加,HDPE/PA6原位微纤共混物的MFR急剧降低,拉伸强度显著提高,形成的微纤能够显著增强HDPE。     

通过挤出机头强剪切制备LDPE/PET原位微纤复合材料

通过自主设计制造的强剪切机头试验挤出并采用扫描电子显微镜(SEM)对挤出产物微观形态进行观察,研究了低密度聚乙烯/聚对苯二甲酸乙二醇酯(LDPE/PET)共混物在挤出过程中原位成纤情况。结果表明:提高分散相PET用量,缩小强剪切机头中的走料间隙、增大转子的转速和提高牵引切粒速度,都会降低挤出产物的熔体流动速率(MFR);用SEM观察正向刻蚀和反向刻蚀产物低温脆断面的微观形态表明,共混物中有大量的微纤形成,微纤的直径在3~5μm,平均长径比超过10。     

KP系列二阶式双螺杆／单螺杆挤出机组

二阶式挤出机组由1台双螺杆混炼机，1台单螺杆挤出机和1台磨面切粒机组成，适用于硬(软)质PVC和XLPE等热敏性及剪切敏性的混炼挤出造粒。其特点是发挥双螺杆和单螺杆各自的优热势；在双螺杆混炼中，物料通过混炼，剪切元件进行均匀混合，在单螺杆挤出机中，物料由缓慢转动的螺杆挤出，避免物料产生剪切热。各区段温度得到最佳控制，防止了热敏性及剪切敏性物料的降解，具有低能耗、高产量、产品质量稳定的特点。     

双转子连续混炼机中PP/PET原位复合共混的研究

利用双转子连续混炼机进行了聚丙烯/聚对苯二甲酸乙二醇酷(PP/PET)原位共混实验。通过分析共混物的微观形貌,探讨了流变行为对PET原位复合材料形成微纤的影响,以及共混温度、组分含量、剪切速率等对微纤形成的作用,并研究了组分相容性与成纤的关系,最后,探讨了PET组分含量对材料拉伸强度的影响及其作用机制。研究结果表明,在双转子连续混炼机中通过控制各加工参数,PET分散相在PP基体中可以获得显著成纤,并有利于提高复合材料的拉伸性能。     

Influence of processing window and weight ratio on the morphology of the extruded and drawn PET/PP blends

To obtain polyethylene terephthalate (PET)/polypropylene (PP) microfibrillar composite (MFC) with good mechanical properties, a high content of PET fibrils in the drawn strand (i.e. PET droplets in the extrudate) is preferred. However, a phase inversion (from PP matrix to PET matrix) takes place when the concentration of the PET reaches 40 wt% at the screw speed of 40 rpm (rounds per minute). This “PP domains in PET matrix” phase structure is the undesired phase structure for preparing MFC. However, the desired phase structure of “PET droplets in PP matrix” can be regained by adopting a low screw speed (20 rpm) during extrusion of the PET/PP (40/60); if a higher screw speed is adopted (80 rpm), then a suitable amount of PP grafted maleic anhydride (PP‐g‐MA) should be incorporated. The PET/PP blends which demonstrate the desired “PET droplets in PP matrix” phase structure were stretched into strands, and PET/PP MFC was prepared. The MFC with high content of PET microfibrils as the reinforcement exhibits superior tensile properties than the neat PP. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

往复式销钉螺杆挤出机混合机理概述

结合研制实践 ,分析了往复式销钉螺杆挤出机挤压系统的特点 ,阐述了该类机型的混合机理 ,并与常规的单、双螺杆挤出机作了比较     

Study on PET/PP microfibrillar composites. I. Morphological development in melt extrusion

Poly(ethylene terephthalate)/polypropylene (PET/PP) blends of different compositions were extruded through a 2‐mm capillary die using a corotating twin‐screw extruder. The extrudates were cryogenically fractured and examined using scanning electron microscopy. The viscosity ratio of the constituent polymers alone was found not suitable for explaining the polymer blend morphology. At a PET concentration of 20%, the extrudate consists of three regions: The skin layer, about 10 μm thick, has a lower concentration of the dispersed PET phase than that of the overall concentration. The intermediate region, about 400 μm thick, has profuse PET fibers and some small PET particles. The central region, approximately 800 μm in diameter, contains mainly PET particles that are generally bigger. A low barrel temperature, low die temperature, and fast cooling rate helped to retain the fibers near the extrudate skin. Meanwhile, variation of the barrel temperature, die temperature, and cooling media did not affect the PET particle‐size distribution significantly in the central region of the extrudate. A high screw speed and a high postextrusion drawing speed were very effective in producing fibers in the extrudates through elongation of the particles. At a PET concentration of 30%, coalescence of the PET phase was prevalent, leading to the formation of PET platelets near the extrudate skin and irregular PET networks in the central region of the extrudate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3100–3109, 2003     

Evaluation of mechanical properties of polypropylene/polycarbonate/SEBS ternary polymer blends using Taguchi experimental analysis

In this work, ternary polymer blends based on polypropylene (PP)/polycarbonate (PC)/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) (SEBS) triblock copolymer and a reactive maleic anhydride grafted SEBS (SEBS‐g‐MAH) at fixed compositions are prepared using twin‐screw extruder at different levels of die temperature (235‐245‐255°C), screw speed (70‐100‐130 rpm), and blending sequence (M1‐M2‐M3). In M₁ procedure, all of the components are dry blended and extruded simultaneously using Brabender twin‐screw extruder, whereas in M₂ procedure, PC, SEBS, and SEBS‐g‐MAH minor phases are first preblended in twin‐screw extruder and after granulating are added to PP continuous phase in twin‐screw extruder. Consequently, in M₃ procedure, PP and SEBS‐g‐MAH are first preblended and then are extruded with other components. The influence of these parameters as processing conditions on mechanical properties of PP/PC/SEBS ternary blends is investigated using L9 Taguchi experimental design. The responding variables are impact strength and tensile properties (Young's modulus and yield stress), which are influenced by the morphology of ternary blend, and the results are used to perform the analysis of mean effect as well. It is shown that the resulted morphology, tensile properties, and impact strength are influenced by extrusion variables. Additionally, the optimum processing conditions of ternary PP/PC/SEBS blends were achieved via Taguchi analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of poly(ethylene terephthalate)/polypropylene microfibrillar composites. I. Morphological development in melt extrusion

Poly(ethylene terephthalate)/polypropylene (PET/PP) blends of different compositions were extruded through a 2‐mm capillary die using a corotating twin‐screw extruder. The extrudates were cryogenically fractured and examined using scanning electron microscopy. The viscosity ratio of the constituent polymers alone was found to be unsuitable for explaining the polymer blend morphology. At a PET concentration of 20%, the extrudate consists of three regions. The skin layer, which is about 10 μm thick, has a lower concentration of the dispersed PET phase than the overall concentration. The intermediate region, which is about 400 μm thick, has profuse PET fibers and some small PET particles. The central region, which is approximately 800 μm in diameter, mainly contains PET particles that are generally bigger. A low barrel temperature, low die temperature, and fast cooling rate helped to retain the fibers near the extrudate skin. Meanwhile, the variation of the barrel temperature, die temperature, and cooling media did not produce a significant affect on the PET particle size distribution in the central region of the extrudate. A high screw speed and a high postextrusion drawing speed were very effective in producing fibers in the extrudates through elongation of particles. At a PET concentration of 30%, coalescence of the PET phase was prevalent, leading to the formation of PET platelets near the extrudate skin and irregular PET networks in the central region of the extrudate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1743–1752, 2003     

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.     

Morphology development of in situ compatibilized semicrystalline polymer blends in a co-rotating twin-screw extruder

This paper concerns the morphology development of in situ compatibilized semicrystalline polymer blends in a co-rotating, intermeshing twin-screw extruder, using polypropylene (PP) and polyamide 6 (PA-6) blends as model systems. The morphology of in situ compatibilized blends develops much faster that of mechanical ones. The size of the dispersed phase (PA-6) undergoes a 10⁴ fold reduction from a few millimeters to sub-micron during its phase transition from solid pellets to a viscoelastic fluid. The final morphology is reached as soon as the phase transition is completed, which usually requires only a small fraction of the screw length in a co-rotating twin screw extruder. Screw profiles and processing conditions (screw speed, throughput and barrel temperature) control the PA-6's melting location and/or rate, but do not have significant impact on the ultimate morphology and mechanical properties of in situ compatibilized blends. The finding that morphology of PP/PA-6 reactive blend develops rapidly makes it possible to produce compatibilized PP/PA-6 blends by the so-called one-step reactive extrusion. It integrates the traditionally separated free radical grafting of maleic anhydride onto PP and the compatibilization of PP/PA-6 into a single extrusion step.     

RESIDENCE TIME DISTRIBUTION IN A SCREW EXTRUDER

It has been studied that the residence time distribution(RTD)function in a screw extruder in relation to that in thescrew and that in the die.For a complex flow field such as that between screw and die,it was supposed that the RTDfunction in the screw and that in the die were almost independent on each other.Therefore,a probabilistic method wasused to predict the RTD function in a complete extruder from that in the screw and that in the die.The experiments fordetermining the RTD were based on a stimulus-response technique.The results predicted,both in single-screw extruderand in twin-screw extruder,were in good agreement with those experimentally obtained.     

聚丙烯/聚乙烯共混物环状型坯挤出膨胀和垂伸的研究

利用双螺杆挤出机将聚丙烯分别与不同熔体流动速率的聚乙烯进行共混,通过环状型坯挤出,研究了共混物的型坯膨胀和垂伸情况。结果表明,聚丙烯与较高熔体流动速率的聚乙烯共混后,其型坯直径膨胀的变化范围较宽,垂伸较明显。     

Numerical simulation of a single-screw plasticating extruder

A fully-predictive steady-state computer model has been developed for a single-screw plasticating extruder. Included in the model are a model for solids flow in the feed hopper; a variation of the Darnell and Mol model for the solids conveying zone; a variation of Tadmor's melting model for the melting zone; an implicit finite difference solution of the mass, momentum, and energy conservation equations for the melt-conveying zone of the extruder and die; and a predictive correlation for the extrudate swell at the die exit. A temperature- and shear-rate-dependent viscosity equation is used to describe the melt-flow behavior in the model. The parameters in the viscosity equation are obtained by applying regression analysis to Instron capillary rheometer data. Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions, the following are predicted: flow rate of the polymer, pressure and temperature profiles along the extruder screw channel and in the die, and extrudate swell at the die exit. The predictions have been confirmed with experimental results from a 11/2 in. (38 mm) diameter, 24:1 L/D single-screw extruder with a 3/16 in. (4.76 mm) diameter cylindrical red die. High- and low-density polyethylene resins were used.