聚丙烯降温母粒生产工艺的优化控制

介绍了聚丙烯降温母粒的基本作用,并利用正交试验设计方法,研究了输料段温度、熔融段温度、模头温度及螺杆转速对母粒过氧化物含量的影响,最终确定了适宜的加工工艺条件,生产出了过氧化物含量较高且稳定的聚丙烯降温母粒.     

用双螺杆挤出机制备丁腈橡胶/尼龙12热塑性弹性体

采用双螺杆挤出机通过动态硫化法制备了丁腈橡胶/尼龙12热塑性弹性体,考察了双螺杆挤出机的螺杆转速和机筒温度对所制备热塑性弹性体力学性能和微观形态的影响。结果表明,用双螺杆挤出机动态硫化制备的丁腈橡胶/尼龙12热塑性弹性体呈两相"海岛结构",即丁腈橡胶为分散相、尼龙12为连续相。随着挤出机螺杆转速的提高,弹性体的硬度、拉伸强度和扯断伸长率先增大后减小,撕裂强度和压缩永久变形逐渐降低;螺杆转速对弹性体耐油性能的影响不大;当螺杆转速增至400 r/min时,丁腈橡胶的粒径较小且分布均匀。随着双螺杆挤出机温度的升高,弹性体的硬度和拉伸强度逐渐增大,扯断伸长率、撕裂强度和压缩永久变形均先增大而后减小,耐油性能变差;温度升高使得丁腈橡胶难于在剪切作用下破碎,颗粒变大且分布不均。     

反应挤出尼龙6/玻璃纤维复合材料中试研究

在反应挤出玻璃纤维增强尼龙6的小试研究基础上,本文进行了反应挤出制备尼龙6/玻璃纤维复合材料中试研究,中试结果表明,双螺杆反应挤出机各段温度在240℃左右,螺杆转速在100rpm,当玻璃纤维含量在30%时,反应挤出/玻璃纤维增强尼龙6材料的综合力学性能较好,中试操作难度总体小于小试。     

改性聚乙烯醇熔融挤出发泡成型及影响因素的研究

采用水作增塑剂兼物理发泡剂,在普通单螺杆挤出设备上实现了聚乙烯醇的熔融挤出-连续发泡,研究了水含量、口模温度和螺杆转速对PVA发泡成型性能的影响.结果表明,适当的水含量、口模温度及螺杆转速是实现PVA/水体系的熔融挤出和PVA中水的可控、连续、稳定发泡的关键因素,通过调控组分、口模温度及螺杆转速,可调控PVA/水体系中水状态,获得发泡均匀、发泡率高的PVA发泡板材,表观密度约为O.4 g/cm3,综合性能良好.     

共聚尼龙6/66/1212的表观相图研究

采用显微熔点法测定了尼龙6／尼龙66／尼龙1212共聚物的表观相图,显示了共聚尼龙组分配比对其熔点的决定性作用,并给出共聚尼龙6／66／1212熔点与其各尼龙盐组分配比之间的定量关系。     

聚酯熔融加工中低聚物生成的影响因素

研究了不同螺杆转速、熔体停留时间、熔融温度及静态高温状态时,温度和时间对聚酯低聚物生成的影响。结果表明:低聚物的生成主要是热降解和热氧化降解以及力学降解共同作用的结果;当螺杆转速加快时,力学降解作用加强;高温下时间延长,低聚物含量也显著增加。因此适当的纺丝温度、螺杆转速和加工时间,对减少低聚物的生成及控制聚酯熔体的质量至关重要。     

尼龙6高聚碘的制备及表征

以尼龙6、碘化钾和碘为原料,采用溶剂合成法制备了尼龙6高聚碘,考察了反应物配比、反应时间、反应温度对尼龙6高聚碘含碘量的影响,并且对其进行了拉曼光谱和热重分析,对不同含碘量的尼龙6高聚碘的熔点和水中溶碘量进行了测定。实验结果表明,使用冰乙酸溶剂法合成的尼龙6高聚碘反应均匀,含碘量可控,反应后产物容易分离;拉曼图谱显示,用溶剂法制备的尼龙6高聚碘是I5-与I3-的混合物,热重分析表明,在尼龙6高聚碘中存在着两类键合强度不同的碘,在两个温度区域内逐次分解。尼龙6高聚碘的水溶性很小,其溶碘量随着高聚碘含碘量的增加而降低,熔点随之也逐步降低。     

挤出裂解工艺对聚乙烯蜡性能的影响

以单螺杆挤出机为裂解设备,聚乙烯951-050及2426 H为裂解原料,制备了聚乙烯蜡(PEW)产品,研究了聚乙烯蜡黏均分子量和熔点随螺杆的转速、裂解温度的变化规律,分析了氮气保护以及冷却工艺对聚乙烯蜡性能的影响。结果表明,聚乙烯蜡的熔点和黏均分子量均随着螺杆转速的增加而增加,随着裂解温度的增加而降低。在较高的螺杆转速内,裂解温度对聚乙烯蜡产物熔点的变化影响较小。当空气存在的条件下,聚乙烯裂解程度加深,产物颜色加深;相对于自然冷却法,聚乙烯蜡喷粉法降低了聚乙烯蜡的结晶能力,使聚乙烯蜡熔点降低。     

增强增韧尼龙6挤出工艺及纤维分散研究

使用双螺杆挤出机制备了增强增韧尼龙6,研究了不同挤出温度、螺杆转速对连续玻纤和短切玻纤增强材料力学性能的影响,使用统计法分析了材料中玻纤分散情况。结果表明,短切玻纤增强的力学材料性能高于连续玻纤增强材料。当螺杆转速为350 r/min,挤出温度为240~260℃时材料的性能较佳。     

注射成型中的熔体温度均匀性研究

注射成型中的熔体温度均匀性直接影响注射制品的最终质量，熔体温度均匀性的大小与螺杆设计，加工工艺条件关系密切，对不同工艺条件和螺杆几何参数时的轴向温差进行了测量，并讨论了轴向温差的形成机理及其与加工工艺条件和螺杆参数之间的关系。     

A new method to prepare low melting point polyamide‐6 and study crystallization behavior of polyamide‐6/calcium chloride complex by rheological method

A new method to prepare low melting point polyamide‐6 (LPA6) by complex reaction of calcium chloride (CaCl₂) and polyamide‐6 (PA6) in a co‐rotating twin screw extruder was reported. We employed a new rheological method to study the crystallization behavior of PA6/CaCl₂ complex and the mechanism of confined crystallization of PA6. Compared with differential scanning calorimetry (DSC), this method was more capable of detecting crystalline information. What's more, it was also an effective method for studying mechanism of confined crystallization. From the results of X‐ray diffraction, DSC, infrared spectroscopy, rheology, and mechanical properties, the complex reaction of CaCl₂ with the carbonyl oxygen atom in the amide group disrupted the intermolecular hydrogen bonding and confined the mobility of PA6 molecules. This could significantly reduce the crystallinity and melting temperature of PA6, and improve tensile strength and notched Izod impact strength. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41513.     

Contribution of the melting stage to the evolution of the morphology and chemical conversion of immiscible polyamide/polyethylene blends in twin‐screw extruders

This study investigates the effects of processing conditions (the screw speed, throughput, barrel temperature, and screw configuration) on the chemical conversion and morphology evolution of polyamide/polyolefin blends along a twin‐screw extruder. Polymer samples were collected rapidly at specific barrel locations with a special sampling device for subsequent chemical and morphological characterization. Increasing the screw speed or using more restrictive screw modules at the beginning of the melting zone promoted a faster reaction and better dispersion along the extruder. Increasing the throughput or decreasing the barrel temperature slowed the evolution of the morphology and chemical conversion along the extruder because of the lower melting rate. As soon as melting started, the chemical reaction took place. However, high chemical conversion rates required extensive melting, that is, significant interface generation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterization of polyamide 6 made by reactive extrusion. I. Synthesis and characterization of properties

The anionic polymerisation of ε-caprolactam in a corotating, intermeshing twin-screw extruder is discussed in terms of the materials formulation, extruder screw profile, and processing parameters such as temperature and screw speed. Using a variety of analytical characterization techniques, it is demonstrated that molecular mass, residual monomer content, and mechanical properties of the polyamide 6 are very sensitive to the reactive processing conditions employed. © 1994 John Wiley & Sons, Inc.     

Investigation of the melting behavior and morphology development of polymer blends in the melting zone of twin‐screw extruders

The melting behavior and the morphology development that runs parallel to it play central roles in the processing of polymer blends. We studied the impact of speed, melt throughput, continuous‐phase viscosity, screw configuration, and disperse‐phase content on the melting behavior and morphology development in the melting zone of a twin‐screw extruder. The polymer blend used incorporated polyamide‐6 (PA6) as its disperse phase and a high‐viscosity or low‐viscosity polypropylene as the matrix phase. The melting behavior of the polymer blend was investigated with press plates. A qualitative assessment was made of the processes, on basis of the optical impression gained from the transilluminated press plates. One key result was that the PA6 granules melted very rapidly in the polypropylene melt. We took samples over the length of the melting section to permit a quantitative assessment of the morphology. The results show a finely dispersed morphology already at the start of the melting section. This did not undergo any essential change as the blend passed through the extruder, and only a limited correlation was evident with the process parameters. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1986–2002, 2001     

Stirring-induced solution crystallization of ultra high molecular weight polyamide 6

Unstable solutions of ultrahigh molecular weight polyamide 6 have been prepared by adding a nonsolvent to the polymer solution. Crystallization of the polyamide from such a solution proceeds very slowly. It has been found, however, that vigorous stirring of the unstable solutions induces rapid fibrous crystallization of the polymer. The fiber mat consists of irregularly shaped fibers. A low temperature and a high stirring rate are among the conditions necessary to obtain a high yield of fibrous material. The fibers formed upon stirring have a higher molecular weight than the polyamide 6 molecules which remain in the solution. The melting point of the fibers depends on the speed of the paddle stirrer. The differential scanning calorimetry (DSC) thermogram reveals higher melting temperatures of the fibrous material if higher stirring rates have been applied.     

Effect of composition and processing conditions on the chemical and morphological evolution of PA‐6/EPM/ EPM‐g‐MA blends in a corotating twin‐screw extruder

This study investigated the effect of blend composition and processing conditions on the chemical conversion and morphological evolution of PA‐6/EPM/EPM‐g‐MA blends along a twin‐screw extruder. The maleic anhydride (MA) content of the modified rubber was found to decrease strongly, to a level of almost zero, and in the melting zone the particle size was dramatically reduced, from millimeters to submicrometers. Blend composition had a secondary effect on both chemical conversion and morphological development. The processing conditions, particularly the temperature profile and the screw speed, affected both the chemical conversion and the morphological evolution. Using low temperatures and low screw rotation it was possible to follow in detail the evolution of morphological development of a reactive blend in a twin‐screw extruder. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1535–1546, 2001     

Optimal two-stage single-screw design for polymethyl methacrylate extrusion by taguchi technique

The optimal screw design for polymethyl methacrylate (PMMA) extrusion was studied. The Taguchi method was used to determine the optimal screw geometry and processing conditions for the extrusion of PMMA sheet and/or film. To get the high quality of sheet and/or film, perfect melting, adequate melt temperature, and enough metering pressure were necessary. The six factors relating screw geometry and processing condition were chosen with three levels for each factor. The orthogonal array was selected as the most suitable for fabricating the experimental design, L₂₇3⁶, with 6 columns and 27 variations. The smaller-the-better was used as an optimization criterion. The optimal values of these parameters were 8D of feeding zone length, 15 mm of feeding zone depth, 4D of melting zone length, 3 of compression ratio, 49 rpm of screw speed, and 165/180/200/250/260/2660/260 of barrel temperature. Under these conditions, the completeness of melting of solid bed, the stability of solid bed, the melt pressure at vent zone, and the melt temperature at the end of screw were 0, 0, 0 bar, and 279.5 °C, respectively.     

Predicting the effect of screw wear on the performance of plasticating extruders

The effect of screw wear on the performance of a 2.5 in. diameter extruder is studied with the aid of computer simulations. The effect of progressively increasing flight clearance on the extrusion of low density polyethylene, polypropylene and nylon 6/6 is presented. The remedial effect of increased screw speed and its side effects on melting behavior, solids content, extrudate temperature and power consumption are also described.     

Study of the properties of compatibilized ABS/PA6 blends using response surface methodology

Styrene‐(maleic anhydride) copolymer (SMA) compatibilized blends of acrylonitrile‐butadiene rubber (ABS) and polyamide 6 (PA6) with a variety of compositions and compatibilizer levels were prepared at various screw speeds in a corotating twin screw extruder. A Box–Behnken model for three variables, with three levels, was chosen as an experimental design, and the mechanical properties of the blends were considered as the responses. Each response was analyzed and formulated versus the considered factors by the use of response surface methodology. Impact resistance increased with increased SMA concentration and reduced screw speed. In compatibilized samples, with an increase in PA6 content, higher impact resistance was observed. Increasing PA6 content and SMA concentration, as well as decreasing screw speed, gave improvements in both tensile and flexural strengths. In each case, all of the correlations among factors were studied. Grafting of SMA was proved by detecting the graft copolymer (SMA‐PA6) formed through extraction in formic acid and FTIR spectroscopy. Compared with uncompatibilized blends, compatibilized samples displayed more uniform and finer particle sizes, thereby proving the compatibilizing effect of the graft copolymer. The asymmetry trend in dispersed particle size before and after the phase inversion became more differentiated in the presence of the compatibilizer. Adding SMA lowered the phase inversion composition (based on PA6), whereas higher screw speed increased it. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers