熔融挤出-固相增黏循环处理对PET性能的影响

将特性黏数为0.679 dL/g的纤维级聚对苯二甲酸乙二酯(PET)切片进行5次熔融挤出-固相增黏循环处理,对固相增黏后的PET切片进行纺丝,分析了处理后的PET切片的热性能,测试了PET纤维的断裂强度及色值。结果表明:随着PET熔融挤出-固相增黏循环处理次数的增加,固相增黏后PET切片的特性黏数下降,熔点降低,纤维断裂强度和断裂伸长率下降,色值b值增加,L值减小;5次固相增黏后PET切片的特性黏数均大于0.75 dL/g,但其可纺性变差,纤维力学性能下降。     

PET瓶片反应挤出后的特性黏度变化

研究了聚对苯二甲酸乙二醇酯(PET)瓶片在熔融挤出过程中取样时间、螺筒温度、螺杆转速、缩聚段真空度、扩链剂用量、瓶片含水量等对挤出产物特性黏度(η)的影响。结果表明:提高螺杆转速、降低螺筒温度、提高缩聚段真空度,都有利于提高挤出产物的η;填加少量的扩链剂均苯四甲酸二酐,可以使挤出产物的η达到0.83dL/g;当瓶片含水量低于2.0%时,使用该试验型反应挤出机不影响挤出产物的η,瓶片含水量高时会略微降低产物的η。     

PET的特性黏数对其扁丝力学性能的影响

在20 L聚合反应釜上制备不同特性黏数([η])的聚对苯二甲酸乙二醇酯(PET)切片,经熔融挤出、冷辊铸片、裂膜、静态单向拉伸制备PET扁丝,讨论了[η]对PET扁丝力学性能的影响规律。结果表明:在拉伸倍数一定、[η]为0.606～0.744 dL/g的条件下,随着[η]的升高,PET扁丝的拉伸强度、弹性模量、屈服强度及屈服伸长率呈逐渐升高趋势,尤其是当[η]高于0.714 dL/g时,升高幅度更明显,而断裂伸长率呈逐渐降低趋势;PET扁丝拉伸强度设定为400 MPa时,随着[η]的升高,其拉伸倍数逐渐减小;PET扁丝断裂伸长率设定为25%时,随着[η]的升高,其拉伸倍数先增大后减小;实验范围内,兼顾PET扁丝使用性能和加工性能的要求,控制PET的[η]约0.71 dL/g、拉伸倍数5～6较为合适。     

复合成核剂对PET结晶速率和特性黏数的影响

采用差示扫描量热分析仪和乌氏黏度计研究了不同成核剂及其复配对聚对苯二甲酸乙二醇酯（PET）结晶速率和特性黏数的影响。结果表明,复合成核剂对于提高PET成核结晶速率[半结晶时间（t1/2）为32.3~45.3 s]的效果优于单一成核剂（t1/2为42.9~57.9 s）;同时部分复合成核剂能有效减小PET特性黏数的降低幅度。     

PET的挤出吹塑

ＰＥＴ的挤出吹塑有广阔的发展前景。本文简单介绍了ＰＥＴ挤出吹塑的发展过程，着重分析适于抗日出吹塑的高熔体粘度（ＭＨＶ）ＰＥＴ的主要性能及其挤出吹塑的机械和工艺条件。     

聚碳酸酯熔融挤出后的物性变化

利用配有BM分离型螺杆的单螺杆挤出机研究了聚碳酸酯(PC)颗粒在不同条件下经熔融挤出后的特性黏数([η])和熔体流动速率(MFR)的变化.结果发现:在300℃以下的挤出温度、不同螺杆转速下对烘干的PC树脂挤出加工时,基本不会改变PC的[η]和MFR,因而难以用测定[η]或相对分子质量的方法判别PC是新料还是回收料;在120℃,-0.1 MPa干燥1.0 h可保证把料彻底烘干,延长干燥时间可促进PC料的固相缩聚,提高[η],有利于PC的加工;经多次热加工的PC树脂或PC含有少量水分时,挤出产物的[η]明显下降,MFR显著变大,不利于加工.     

PET/PBT扩链反应共混物的结晶熔融行为

用差示扫描量热法（ＤＳＣ）考察了添加扩链剂进行反应性共混后ＰＥＴ／ＰＢＴ的结晶熔融行为。共混体系的特性粘数随反应时间的增加先升后降,冷结晶温度随时间的增加逐渐升高,熔体结晶温度和熔点随之下降     

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。     

Polymer nanofibers prepared by template melt extrusion

Combining the template method with the extrusion technology, polymer nanofibers have been prepared when molten polymer is forced through the pores of anodic aluminum membrane and cooled to complete the nanofiber formation process. The microstructures of nanofibers are determined by SEM, TEM, XRD, and DSC. The results suggest that the PE nanofibers consist of extended‐chain crystals and the transition from an orthorhombic to a hexagonal phase and the latter phase melting occurs at 159.8°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1018–1023, 2006     

着色剂对PET树脂特性粘度的影响

依据色素分子的性质,将着色剂进行了分类,并以此为基础讨论不同着色剂对聚酯特性粘度的影响,通过Mark-Houwink公式,推导了着色剂的加入与聚酯特性粘度之间的关系,发现小分子染料会使聚酯特性粘度迅速下降,聚合染料基本不影响聚酯的特性粘度,而熔融活性着色剂在低浓度范围内对聚酯起着明显的增粘作用,不仅可提高着色牢度,还可以抵消由于热加工而引起的聚酯的热降解。     

Rheological properties of glass bead-filled low-density polyethylene composite melts in capillary extrusion

The melt flow of glass bead-filled low-density polyethylene composites in extrusion have been observed by using a capillary rheometer to investigate the effects of temperature, shear rate, and filler content on the rheological properties of the melts. The results show that the melt shear flow obeys a power law, and the dependence of the apparent shear viscosity, η_app, on temperature is in accord with an Arrhenius equation. At the same temperature and shear rate, η_app increases slightly with increasing the volume fraction of glass beads, but the flow behavior index decreases with increasing filler content. In addition, the first normal stress difference of the melts linearly increases with increasing wall shear stress. Good agreement is shown with the N₁ calculated with the equation presented in this article and the pressured data from the sample melts. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1451–1456, 1999     

Micronization of polyethylene terephthalate via freezing of highly sheared emulsions of polyethylene terephthalate in saturated liquid tetrahydrofuran

A novel technique for micronizing polyethylene terephthalate (PET) resin (∼ 3 mm) with saturated liquid tetrahydrofuran (THF) has been developed. PET pellets were introduced to a high-pressure vessel filled halfway with THF at loadings up to ∼ 7 wt % PET. When the vessel was closed and heated, the PET pellets exhibited significant melting point depression at 190°C in saturated liquid THF at 17.1 bar. Although other organic solvents were also able to depress the melting point of PET, only THF was able to facilitate the formation of an emulsion of PET-rich liquid droplets in the saturated liquid solvent when the mixture was agitated. In an attempt to generate the smallest possible PET droplets, a high-speed (5000 rpm), close-clearance, radial flow impeller was used to shear and disperse the droplets at ∼ 200°C and 20.1 bar. Emulsion was rapidly cooled while mixing. The PET droplets froze at ∼ 190°C, and the vessel was then cooled to ambient temperature. The excess liquid THF was decanted, and the PET particles were dried in a vacuum oven to remove residual THF. The PET particle sizes ranged between 2 and 70 μm, with number, area, and volume average diameters of 6, 20, and 30 μm, respectively. A comparison between the PET resin and PET powder properties indicated that the micronization reduced the M_w from 32,700 to 22,800. DSC results suggest that the rapid quench leads to a morphology different from equilibrium, with small somewhat imperfect crystallites, a lower overall degree of crystallinity, and a suppressed ΔC_p at the glass transition. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of shear history on flow instability at capillary extrusion for long‐chain branched polyethylene

Effect of applied processing history on flow instability at capillary extrusion is studied using a commercially available low‐density polyethylene (LDPE) having long‐chain branches. It is found that processing history in an internal mixer in a molten state depresses long‐time relaxation mechanism associated with long‐chain branches, which is known as “shear modification.” Consequently, the onset of output rate for melt fracture increases greatly. Furthermore, it should be noted that the sample having intense shear history shows shark‐skin failure without volumetric distortion, although it has been believed that LDPE exhibits gross melt fracture at capillary extrusion. The reduction of elongational viscosity by the alignment of long‐chain branches along to the main chain is responsible for the anomalous rheological response. As a result, the sample shows shark‐skin failure like a linear polyethylene at a lower output rate than the critical one for gross melt fracture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

熔体流动时间法测定PBT树脂特性粘数的研究

开发了一种新的特性粘数分析方法 ,该方法采用熔体流动时间计算特性粘数 ,与经典特性粘数分析方法有很好的相关性且具有分析时间短、费用低、无污染等优点。     

Impact of organoclay and maleated polyethylene on the rheology and instabilities in the extrusion of high density polyethylene

The impact of organoclay on the rheology and extrusion of high density polyethylene (HDPE) was studied. Organoclay effect was studied at very low clay loading (≤0.1 wt %) while serving as a processing aid. A special design slit die with three transducers was used in the study of the extrusion melt instabilities. The rheological results showed that normal stress difference of HDPE was reduced during steady shear rate and stress growth tests when organoclay (≤0.1 wt %) was added. The extensional strain and stress growth of HDPE reduced with the addition of organoclay. So, organoclay (≤0.1 wt %) has an effect on the shear and extensional rheology of HDPE. The intensity of the melt instability was characterized with both a moment analysis and distortion factor (DF) from an advanced Fourier transform analysis. Both showed the same trends in the characterization of the pressure fluctuations in the die. Generally, addition of organoclay (≤0.1 wt %) to HDPE led to the reduction in DF. The ratio of first and second moment analyses became reduced as well. The results quantified the extent of elimination of gross melt fracture in HDPE by organoclay. Also, the extrusion pressure was reduced with organoclay (≤0.1 wt %) inclusion hence more throughput. There was a good correlation between rheology and extrusion. Both showed that the platy‐like organoclay streamlined the melt flow. However, the maleated polyethylene added as a compatibilizer did not give substantial synergistic effect. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

利用KH560和纳米SiO2采用“一步法”反应挤出增黏PET

以KH560（3-缩水甘油基氧基丙基三甲氧基硅烷）和纳米SiO₂颗粒复配作为扩链剂,采用“一步法”反应挤出增黏聚对苯二甲酸乙二醇酯（PET）。KH560和SiO₂的添加量均为PET质量分数的2.5%时,增黏效果最好。并且在PET不干燥的情况下,KH560和SiO₂复配也可增加PET的黏度,可用作PET的扩链剂和防水解剂。经透射电镜观察,发现SiO₂在PET中的分散状况良好。用FTIR研究了KH560、SiO₂、PET三者之间的反应机理。用TGA分析了SiO₂的接枝率,发现接枝率高达72.0%。用DSC对PET/纳米SiO₂复合材料的结晶行为进行了研究,并讨论了结晶行为对力学性能的影响。当KH560和SiO₂的添加量均为PET质量分数的2.5%时,结晶度最低,综合力学性能最好。     

Action of alkali on polybutylene terephthalate and polyethylene terephthalate polyesters

The two polyesters (polybutylene terephthalate and polyethylene terephthalate) were treated with aqueous as well as alcoholic solutions of sodium hydroxide at varying temperatures for different durations of time. The results were evaluated in terms of the loss in weight of the samples. The fabric samples of polyethylene terephthalate showed a greater degree of weight loss as compared to those of polybutylene terephthalate. The mechanism for the differences in the action of alkali on these two polyesters is explained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1097–1102, 2000