高相对分子质量聚乙烯冻胶纤维的双螺杆纺丝工艺

采用双螺杆挤出纺丝工艺,探讨了高原液浓度、高相对分子质量聚乙烯(HMWPE)的溶解性及可纺性,研究了双螺杆转速及温度对所得HMWPE冻胶纤维黏均分子量的影响。结果表明:双螺杆挤出机可以完成适当浓度HMWPE的溶胀、溶解和挤出纺丝,原液PE质量分数为20%～40%时制得的冻胶纤维具有一定高倍拉伸性能;随螺杆转速的增加,制得的HMWPE纤维黏均分子量稍有提高或变化不大,至一定螺杆转速后又开始降低;HMWPE纤维的黏均分子量随纺丝螺杆输送段温度的提高而变高,至一定温度后又大大降低;HMWPE原液PE质量分数为20%和30%时,最佳螺杆输送段温度为240℃,而原液PE质量分数为40%时,最佳螺杆输送段温度为250℃。     

挤出循环对聚丙烯/竹粉复合材料力学及发泡性能的影响

通过双螺杆挤出机对30％(质量分数,下同)竹粉增强聚丙烯(PP/BP)复合材料进行循环加工,研究了挤出循环次数对PP/BP复合材料流变性能、力学性能和发泡性能的影响.结果表明,随着挤出循环次数的增加,PP/BP复合材料的表观黏度(η)先升高后降低,力学性能先增强后减弱,经第6次挤出循环后,其η、弹性模量和弯曲模量比1次...     

工艺条件对沥青炭纤维/ABS树脂复合材料导电性及力学性能的影响

研究了单螺杆挤出机挤出温度及螺杆转速对沥青炭纤维填充ＡＢＳ树脂复合材料导电性及力学性能的影响。结果表明,纤维经挤出后,纤维长度有不同程度的降低,长径比减小,随着挤出的升高及螺杆转速的降低,纤维长径比增大,挤出条件对复合材料电性能及力学性能的影响主要可归结为长径比对材料的影响,随着长径比增加,复合材料的导电性及拉伸强度均有增大。此外,复合材料导电性及拉伸强度随复合材料中纤维填加量的增多而增大。     

沟槽机筒单螺杆挤出机塑化特性的实验研究

采用剖分式机筒单螺杆挤出机实验平台,对熔融段沟槽机筒单螺杆挤出机塑化过程中熔融起始点、熔融长度、熔体温度/压力等塑化性能及产量进行了实验研究,比较了不同物料在不同工艺条件下对沟槽机筒单螺杆挤出机塑化特性的影响。结果表明,增大螺杆转速或提高机筒温度,塑化过程实际所需熔融长度增加,但对熔融起始点影响不大;熔融段机筒沟槽内熔体温度和熔体压力随螺杆转速增大无明显变化;随螺杆转速增大,沟槽机筒单螺杆挤出机挤出产量呈线性增加,表现出良好的挤出特性。     

热水浴拉伸对聚丙烯腈初生纤维结构和性能的影响

研究了聚丙烯腈(PAN)初生纤维在热水浴拉伸过程中超分子结构和力学性能的变化。结果表明:PAN初生纤维中的内应力随拉伸温度的升高而减小,随拉伸速率和拉伸倍数的提高而增大;初生纤维在热水浴中的玻璃化转变温度约为80℃,当水浴温度低于和高于80℃时,纤维分别发生冷拉和高弹形变;PAN初生纤维的结晶度和晶区取向度随拉伸温度的升高先增大后减小,随拉伸速率和拉伸倍数的升高而增大。     

聚丙烯腈-二甲基亚砜溶液挤出胀大的研究

使用毛细管流变仪对聚丙烯腈(PAN)的二甲基亚砜(DMSO)溶液的挤出胀大进行了研究。研究发现,孔口胀大比(B)随表观剪切速率(γ)、溶液浓度的增大而增大;随毛细管长径比(L/D)增大、温度(T)升高、滤布层数(N)增多而减小;L/D增大或γ增大时,孔口胀大比活化能(EB)下降,C％增大,EB也增加。     

扁平腈纶湿法成形过程中的挤出胀大行为的模拟

应用Polyflow软件通过理论模拟的方法,对扁平腈纶(PAN纤维)湿法成形过程中的挤出胀大行为进行模拟,建立了喷丝孔口挤出胀大比与纺丝工艺参数之间的关系,研究了纺丝温度、喷头挤出速度、负拉伸率、凝固浴温度等工艺参数对挤出胀大比的影响规律。结果表明:挤出胀大比随着挤出速度、负拉伸率的增大而增大,随着纺丝温度的增大而减小,而挤出胀大比受凝固浴温度的影响较小;对模拟结果进行了实验验证,在喷丝板为0. 1 mm×0. 04 mm、板厚为1 mm、纺丝温度40℃、凝固浴温度10℃、凝固浴质量分数14%、入口流量2. 21×10~(-3)mL/s、喷丝头负拉伸率为-43%的条件下,纺丝制得的扁平PAN纤维的扁平度达到6. 4,线密度为11 dtex,且可纺性好,模拟结果具有合理性。     

K-M公司提高双螺杆效率

为满足不断增长的PVC型材挤出线速度的要求，克劳斯-马费(K-M)公司已开发出长/径比26的平行双螺杆挤出机。在这一代挤出机中的KMD 164-26D可以通过增加45%的螺杆转矩以及将喂料口与卸料口间的加工设备加长45%，获得1 200kg/h的型材产量或1 900kg/h的管材产量。 较长的机筒增加了材料的滞留时间，保证了完全塑炼，而较长的预压缩区可获得优质压缩和良好的材料混炼。 对高表面硬度和螺杆的钼表面硬化涂层而言，深氮化钢机筒可防止磨耗和撕裂。 K-M公司提高双螺杆效率@姚琳     

Купаг(聚偏氟乙烯)的品种、性能及加工应用(二)

Kynar 树脂的加工指导Eynar Flex 2800作电缆护套的加工1.挤出工艺(1)挤出温度分布如下加料段 204～232℃,过渡段 232～246℃,计量段 246～260℃,机头 300～327℃,熔融温度 300～330℃,十字机头处的压力 6,000～9,000psi。(2)挤出设备挤出机应在它最大挤出量的70～85%处操作,这也是选择何种大小之挤出机的标准。机筒:长径比24:1,机筒内衬 Xaloy306、101、800或同类合金钢,至少要有三段     

PAN/DMSO溶液的挤出对初生纤维结构的影响

应用扫描电子显微镜(SEM)和X射线衍射仪(XRD)研究了在一定的凝固条件下,挤出剪切速率(.γ)对聚丙烯腈(PAN)初生纤维聚集态及形态结构的影响规律。结果表明:随着.γ的增加,初生纤维的结晶度增大,晶粒尺寸减小;初生纤维的表面上产生了沿着轴向分布的沟槽,.γ越高,沟槽越深,初生纤维的截面结构变得不均匀,出现了一些大孔和皮芯结构;随着.γ的增加;初生纤维中的二甲基亚砜(DMSO)残留量增加。控制.γ在11 721~14 651 s-1,PAN/DMSO溶液流动性能好,可获得表面沟槽均匀、缺陷少、晶粒尺寸小且结晶度高的结构致密的PAN初生纤维。     

同向旋转三螺杆挤出机固体输送段输送特性研究

基于离散元法分别对同向旋转的三螺杆以及双螺杆挤出机固体输送行为进行仿真模拟,对三螺杆挤出机颗粒速度分布以及受力分布进行分析,将三螺杆和双螺杆挤出机颗粒填充效率、输送质量以及质量流率进行对比分析.结果表明,位于螺棱和机筒附近位置的颗粒受到螺棱推力及机筒摩擦力影响较大,具有较高的速度;挤出机内部各区域颗粒填充顺序受螺杆旋转...     

Effect of high‐shear mixing by twin‐screw extruder on the dispersion and homogeneity of polyacrylonitrile/carbon nanotube composite solution

High‐shear mixing experiments using twin‐screw extruder were conducted to study the effect of shearing on carbon nanotube (CNT) dispersion in polyacrylonitrile (PAN) polymer solution. Different types of CNTs (few‐wall carbon nanotube and single‐wall carbon nanotube) were used to prepare composite solution at 0.5 wt% with respect to the PAN polymer through various preparation conditions. The resulting PAN/CNT composite solution was characterized using various techniques including dynamic light scattering, preparative ultracentrifuge method, optical microscopy, solution rheology, and high‐resolution transmission electron microscopy. With increasing the number of extrusion cycle, it was observed that the CNT bundle size was moderately reduced, while solution homogeneity and macroscopic CNT dispersion was significantly improved. POLYM. COMPOS., 38:719–726, 2017. © 2015 Society of Plastics Engineers     

双螺杆挤出丁苯透明抗冲树脂溶液脱挥工艺

将质量分数为20．00％的丁苯透明抗冲树脂溶液经浓缩器提浓至质量分数不小于30．00％后,送入同向啮合式双螺杆挤出机,在多段真空状态下脱除溶剂,研究了双螺杆挤出脱挥工艺中的温度、真空度、停留时间和螺杆转速工艺务件,并与湿法凝聚工艺进行了产品分子参数和能耗对比。结果表明,双螺杆挤出脱除溶剂工艺适用于丁苯透明抗冲树脂溶液脱除溶剂,其能耗远低于湿法凝聚,所得产品的性能与国外同类产品基本相当。     

ABS/PS共混改性研究

采用在材料熔融挤出共混过程中提高双螺杆挤出机螺杆转速的方法,研究了较高螺杆转速条件下双螺杆挤出机的机械剪切应力和弹性体的种类、用量等因素对丙烯腈-丁二烯-苯乙烯共聚物(ABS)/聚苯乙烯(PS)共混材料力学性能和加工流动性能的影响。结果表明,双螺杆挤出机的高剪切应力可促进分散相颗粒的分散和界面结合力的增强,引起共混材料力学性能和熔体流动速率的改善。丁腈橡胶(NBR)粉末对ABS/PS共混材料具有增容增韧作用,挤出共混温度为220℃,螺杆转速在720 r/min,NBR粉末质量分数为10%时,ABS/PS共混材料的缺口冲击强度为16.4 kJ/m2,比改性前约提高1.6倍,达到ABS树脂冲击韧性的指标,并保持了良好的加工流动性。     

Continuous devulcanization of waste tires by using a Co‐rotating twin screw extruder: Effects of screw configuration,temperature profile,and devulcanization agent concentration

Recently, for reasons both economical and environmental, recycling of waste tires based on (styrene butadiene rubber)/(natural rubber) (SBR/NR) has been widely considered. Response surface methodology (RSM) has been used to predict SBR/NR devulcanization behavior in a co‐rotating twin screw extruder. In this study, variable parameters were barrel temperature, screw configuration, and content of devulcanization agent. A Box‐Behnken design for the three variables, at three levels, was chosen. The sol fraction of devulcanized rubber, Δtorque (difference between maximum and minimum curing torque), and mechanical properties of revulcanizate samples were considered as the responses. The results indicated that an increase of devulcanization agent content at a certain temperature caused the sol fraction to increase. Samples including a higher sol fraction showed a lower cross‐link density. Sol fraction for high shear rate screw configuration was lower than that for other screw configurations. Tensile strength of revulcanized rubber showed a decrease with a rise of devulcanization temperature. Moreover, a relationship connecting the residence time in the extruder with stagger angle and length of different kneading blocks were obtained. J. VINYL ADDIT. TECHNOL., 19:65–72, 2013. © 2013 Society of Plastics Engineers     

单螺杆FDM线材挤出机机筒结构分析与优化设计

对机筒的加热器位置、机筒长度和机筒内径等影响单螺杆FDM线材挤出机挤出成型的机筒结构因素进行了分析,以压力梯度、出口平均温度和流场平均温度为试验指标,基于ANSYS Workbench软件进行正交试验和极差分析,得到最优因素组合。并在试压工况、正常工况、极限工况和极限冷态工况等4种工况下,对采用最优因素组合设计的机筒进行了热力耦合试验验证。试验结果表明:当机筒的加热器位置43 mm、机筒长度270 mm、机筒内径15 mm时,单螺杆FDM线材挤出机出丝顺利,效率较高且安全可靠。     

饲料加工同向平行双螺杆挤出机的研制

介绍与德国专家共同研制开发的新型饲料加工同向平行双螺杆挤出机的配置及各部分结构特点,其中机头结构的设计具有独创性,成功地攻克了淀粉挤出困难的难题;挤压系统长径比只有16～20,螺杆组合也较特殊,与普通机型相比差别较大。并简要介绍了用该设备加工淀粉鱼饲料的加工工艺。     

Behavior of fully filled regions in a non‐intermeshing twin‐screw extruder

Twin‐screw extruders are operated with sequential filled and partially filled regions in order to perform the required unit processes. Channel fill length, defined as the length of fully filled regions in an extrusion screw, is gaining importance as a design parameter because of its implications on residence time distribution, distributive and dispersive mixing, and also process stability. A detailed study—experimental and theoretical—of the behavior of fill lengths in response to operating conditions (throughput, screw speed) and screw geometry is presented in this paper. Mean residence times were also measured for each geometry and operating condition. The apparatus consisted of a non‐intermeshing counter‐rotating twin‐screw extruder (NITSE) with a transparent (acrylic) barrel, fed with corn syrup (Newtonian at room temperature). Fill length exhibits a nonlinear relationship with specific throughput (Q/N), with the slope increasing monotonously as the throughput Q increases at a given screw speed N. The mean residence time exhibits a strong linear relationship with inverse specific throughput and inverse fill length. A theoretical model was developed to predict the filled length based on pressure‐throughput relationships taken from literature for this system, and the predictions were found to agree very well with experimental observations.     

Investigation of the poly(vinyl chloride) extrusion process using a feed throat with a feed pocket

The effectiveness of the extrusion process depends on a number of factors, the most important being barrel design, e.g., longitudinal or helical grooves; screw, feed opening, and polymer hopper designs are significant in this respect, too. The effect of these factors on the extrusion process has been thoroughly discussed in the available literature. This notwithstanding, there is little information providing insight on the effect of a feed pocket made below the feed opening, on the side of the barrel toward which the screw rotates, on the main characteristics of the extrusion process. For the experiments, five special profile inserts with different feed pocket depths were made and then mounted in the extruder barrel equipped with a 25‐mm diameter screw. The extrusion of plasticized poly(vinyl chloride) (PVC) at the screw speed ranging from 30 to 150 rpm was investigated. Presented graphically as charts, the obtained results show the dependences of extrudate temperature, extruder screw torque, polymer output, power supplied to the extruder and conveyed by the polymer, unit energy consumption and energy efficiency on the feed pocket depth, and screw speed. It has been found that the feed pocket made in the extruder barrel has little effect on the course and effectiveness of plasticized PVC extrusion and does not worsen the studied properties of the received extrudate; yet, it should be taken into account to ensure the highest polymer output and lowest energy consumption. POLYM. ENG. SCI., 54:2037–2045, 2014. © 2013 Society of Plastics Engineers