超临界CO2辅助PTFE/PP挤出的研究

研究了超临界CO2辅助聚四氟乙烯(PTFE)/聚丙烯(PP)共混体系的挤出成型过程。结果表明,超临界CO2辅助挤出成型过程中,超临界CO2对PTFE/PP体系能起到一定的增韧作用,并且超临界CO2作为一种增塑剂,能降低PTFE/PP体系的粘度,改善体系的流动性和加工性。     

超临界二氧化碳辅助PP/UHMWPE挤出成型的研究

研究了超临界二氧化碳对超高摩尔质量聚乙烯(UHMWPE)挤出成型的影响规律。首先将纯UHMWPE样条放到超临界二氧化碳中浸泡,研究对其力学性能的影响;然后在UHMWPE中加入一定量的聚丙烯(PP)进行共混,以改善UHMWPE的加工性能,并在通入超临界二氧化碳的条件下进行挤出成型。结果表明:超临界二氧化碳确能有效改善UHMWPE的加工性能,有利于UHMWPE成型加工;在超临界二氧化碳通入量一定条件下PP加入量对UHMWPE的加工性能和力学性能都有一定的提高。     

聚丙烯/超高相对分子质量聚乙烯共混物的结晶动力学及发泡性能研究

采用差示扫描量热仪（DSC）对含有不同含量超高分子量聚乙烯（UHMWPE）的聚丙烯进行测试和表征,采用Ozawa方法、莫志深方法和Kissinger方法分析了该体系的非等温结晶动力学。利用自行研制的超临界流体挤出发泡实验装置,对含有UHMWPE的PP进行了超临界二氧化碳挤出发泡实验研究。结果表明：超高分子量聚乙烯的加入降低了PP的结晶活化能,含有UHMWPE的PP在较高的温度下开始结晶,且由于超高分子量聚乙烯大分子链的存在,与聚丙烯分子链发生缠结,阻碍聚丙烯分子链排入晶格,降低了结晶速率,结晶温区拓宽,有利于聚丙烯挤出发泡成型;加入UHMWPE后,PP的发泡效果明显改善,泡孔平均直径减小,泡孔尺寸分布更加均匀,PE-UHMW的含量为5份时,表观密度达到0.038g/cm-3。     

PP/超临界CO2连续挤出发泡成型

以超临界CO2为发泡剂,在连续挤出发泡过程中研究了超临界CO2用量对高熔体强度均聚聚丙烯(PP)发泡成型过程的影响.随着超临界CO2用量的增加,发泡挤出机口模压力降低,试样发泡倍率降低,泡孔尺寸变小,泡孔密度提高.在w(CO2)为3%,5%时,得到发泡倍率最高为13左右的PP发泡材料.w(CO2)为7%,发泡温度为12...     

基于超临界CO2制备熔体微分静电纺聚丙烯纤维

通过密封的压力容器将聚丙烯（PP）和超临界CO2混合,形成气固均相体系,采用熔体微分静电纺丝法制备PP和超临界CO2均相体系纤维;研究超临界CO2混合以及混合后形成的均相体系进行升温处理对制备纤维的影响。结果表明,纯PP、PP和超临界CO2混合后形成的均相体系以及对均相体系升温处理后,制备的纤维平均直径分别为12.8、8.02、5.08 μm;PP和超临界CO2混合后,聚合物的黏度得到降低;PP和超临界CO2混合后,制备的纤维结晶度得到降低。     

超高分子量聚乙烯/聚丙烯共混改性研究进展

超高分子量聚乙烯(UHMWPE)的加工一直是一个世界性难题。采用聚丙烯(PP)改性UHMWPE可显著提高UHMWPE的加工性能并保持较好的力学性能,因而UHMWPE/PP共混体系的研究受到广泛关注。本文首先介绍了限制UHMWPE加工成型的主要原因,其次从相态结构、流动性能、力学性能及耐磨性能等方面综述了近年来UHMWPE/PP共混改性的研究进展,最后对其发展方向进行了展望。     

用于超临界CO_2辅助挤出PP多相体系的双螺杆构型优化

为优化自制的可进行超临界CO_2辅助挤出的双阶挤出机组的双螺杆构型,采用不同双螺杆构型(即输送螺杆、剪切螺杆和混合螺杆),以不同类型的分散相为研究对象,制备了聚丙烯(PP)/乙烯-辛烯共聚物(POE)共混体系、PP/纳米CaCO_3和PP/纳米蒙脱土(MMT)复合体系。采用扫描电子显微镜和透射电子显微镜对不同分散相粒子在PP基体中的分散进行了分析。结果表明:混合螺杆能使弹性体POE粒子在PP基体中分散更均匀;而3种双螺杆构型对无机纳米粒子在PP中的分散效果相近,即无机纳米粒子均难以达到纳米级均匀分散。在超临界CO_2辅助挤出制备PP多相体系中,可选择混合螺杆为双螺杆构型。     

UHMWPE/PP共混改性体系研究(Ⅰ)

制备了UHMWPE/PP合金材料,研究了UHMWPE/PP共混体系的流动性和力学性能及相容剂对共混体系的增容作用,研究表明:PP能有效地改善UHMWPE流动性,但与UHMWPE为不相容体系,相容剂D能够有效提高UHMWPE/PP体系的相容性,提高了材料的拉伸强度和冲击强度,达到一定的增强和增韧效果。     

可进行超临界CO_2辅助挤出的双阶挤出机组的设计

为进行超临界CO2辅助挤出成型制备聚丙烯多相体系,通过对双螺杆构型、单螺杆以及温控系统的选择和设计,自行设计了一套啮合同向双螺杆挤出机串接单螺杆挤出机的双阶挤出机组。在该机组的双螺杆挤出机机筒开有注气口,可进行超临界CO2计量注入。通过改变注气口对应处的双螺杆构型,设计了3种不同类型的螺杆构型用于实验研究。     

UHMWPE/PP共混改性体系研究(Ⅱ)

制备了UHMWPE/PP合金材料,研究了UHMWPE/PP共混体系的流动性和力学性能及相容剂对共混体系的增容作用,研究表明:PP能有效地改善UHMWPE流动性,但与UHMWPE为不相容体系,相容剂D能够有效提高UHMWPE/PP体系的相容性,提高了材料的拉伸强度和冲击强度,达到一定的增强和增韧效果.     

Reactive extrusion of polypropylene with supercritical carbon dioxide: Free radical grafting of maleic anhydride

A reactive extrusion process for the functionalization of polypropylene with maleic anhydride in the presence of supercritical carbon dioxide was studied. Supercritical carbon dioxide was used in this reactive extrusion system to reduce the viscosity of the polypropylene melt phase by forming a polymer–gas solution in order to promote better mixing of the reactants. Subsequently, the effect of supercritical carbon dioxide on the level of grafting, product homogeneity, and molecular weight was evaluated. Analysis of the products revealed that the use of supercritical carbon dioxide led to improved grafting when high levels of maleic anhydride were used. The experimental results showed no evidence of an improvement in the homogeneity of the product, while melt flow rate measurements showed a reduction in the degradation of polypropylene during the grafting reaction when low levels of maleic anhydride were employed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1116–1122, 2003     

Influence of poly(ethylene glycol)‐containing additives on extrusion of ultrahigh molecular weight polyethylene/polypropylene blend

The influence of poly(ethylene glycol) (PEG)‐containing additives on the extrusion behavior of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blend was studied. It was found that the addition of small amounts of PEG to UHMWPE/PP blend resulted in significant reduction of die pressure and melt viscosity, and obvious increase of the flow rate at a given die pressure, while PEG/diatomite binary additives enhanced the improvement in the processability of UHMWPE/PP blend. When pure HDPE was extruded with the die through which UHMWPE/PP/PEG blend was previously extruded, the extrusion pressure of HDPE increased with the extrusion time gradually. This meant that PEG might migrate to the die wall surface and coat it in the extrusion of UHMWPE/PP/PEG blend. FTIR spectra and SEM micrographs of the UHMWPE/PP/PEG extrudates indicated that PEG located not only at the surface but also in the interior of the extrudates. So, the external lubrication at the die wall, combined with the internal lubrication to induce interphase slippage of the blend, was proposed to be responsible for the reduction of die pressure and viscosity. In addition, an ultrahigh molecular weight polysiloxane and a fluoropolymer processing aid were used as processing aids in the extrusion of UHMWPE/PP as control, and the results showed that only minor reduction effects in die pressure and melt viscosity were achieved at their suggested loading level. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1282–1288, 2006     

Synchronous toughening and reinforcing of polypropylene with ultrahigh‐molecular‐weight polyethylene via melt blending: Mechanical properties,morphology, and rheology

Blending systems based on polypropylene (PP) and ultrahigh‐molecular‐weight polyethylene (UHMWPE) were prepared via a melt extrusion by the four‐screw and the twin‐screw extruders, respectively. The mechanical evaluation demonstrated that the synchronous toughening and reinforcing effects could be achieved from the combination of the PP and the UHMWPE, in which the toughness and the tensile properties could be improved with increasing the UHMWPE content, and achieved optimal values at a weight ratio of PP/UHMWPE (85/15). EPDM can be used as a compatibilizer to improve the compatibility and the interfacial adhesion between the PP and the UHMWPE. This resulted in more effective toughening and reinforcing effects. In contrast, for the PP/UHMWPE blends prepared by the normal twin‐screw extruder, the poor dispersion capacity for the UHMWPE resulted in a deterioration of all mechanical parameters. Morphological observation revealed that the UHMWPE domain was well distributed as tiny particles in the PP matrix, which was confirmed by the differential scanning calorimetry analysis. The toughening effect was attributed to the energy dissipation caused by these rigid tiny particles that detached from the matrix to initiate the local matrix shear yield and formed the void. Rheological investigation demonstrated that there was an interesting composition dependence of viscosity, for which the melt viscosities of the PP/UHMWPE blends decreased when 5 wt % UHMWPE was added, and then began to increase as the UHMWPE content continued to increase. However, this dependence on composition became weaker because of the compatibilization of the EPDM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3498–3509, 2006     

超临界CO_2预处理对UHMWPE纤维电子束辐照效果的影响

采用正交试验,研究了超临界CO_2预处理工艺(压力、温度、时间)对辐敏剂三羟甲基丙烷三甲基丙烯酸酯(TMPTMA)渗入率及超高相对分子质量聚乙烯(UHMWPE)纤维凝胶含量和蠕变率的影响,并利用Minitab软件分析UHMWPE纤维凝胶含量和蠕变率与TMPTMA渗入率之间的关系,最后通过对UHMWPE纤维各项性能的测定,进一步优化超临界CO_2预处理工艺。研究结果表明:处理温度对TMPTMA的渗入率及UHMWPE纤维凝胶含量和蠕变率影响最大,其次为压力,时间的影响最小;确定了最佳工艺为处理压力30 MPa、温度80℃、时间50 min;TMPTMA渗入率是引起各个影响因素不同水平之间凝胶含量和蠕变率出现差别的重要因素;超临界CO_2预处理对UHMWPE纤维的辐照交联起到了重要的促进作用,使其抗蠕变性能得到很大程度的改善。     

Open‐cell polypropylene/polyolefin elastomer blend foams fabricated for reusable oil‐sorption materials

The fabrication of high‐performance oil sorbents is of great significance for oil spill cleanup. The main objective of this study was to prepare open‐cell polypropylene/polyolefin elastomer (PP/POE) blend foams for fabrication of reusable sorbents for oil sorption. Open‐cell PP/POE blend foams were prepared via continuous‐extrusion foaming using supercritical carbon dioxide as the blowing agent. The interconnected open‐cell structure was characterized by scanning electron microscopy. The hydrophobicity and lipophilicity of PP/POE open‐cell foams were revealed by tests of contact‐angle measurement, water and cyclohexane sorption on the foam surface, CCl₄ and cyclohexane sorption in water, and oil/water separation. Further, the sorption tests indicated that PP/POE blend foams showed larger oil‐uptake capacities than pure PP foams. In addition, cyclic compression tests showed that PP/POE open‐cell foams had excellent ductility and significantly improved recoverability compared to pure PP foams. In cyclic sorption–desorption tests, the sorption kinetics was studied in terms of capacity and saturation time, showing that PP/POE foams kept larger sorption capacities for 10 cycles, with larger sorption rates and good reusability. Based on the high open‐cell content, the good hydrophobic and oleophilic properties, the high oil‐sorption capacity, the improved recoverability, the large sorption rate, and the good reusability in cyclic oil‐sorption performance, the PP/POE open‐cell foams have shown promise as potential oil sorbents in applications for oil spill cleanup. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43812.     

Characterization of PP/Mg(OH)2 and PP/Nanoclay Composites with Supercritical CO2 (scCO2)

In this article, supercritical carbon dioxide (scCO₂) is used to form a high density microcellular foam structure to reduce the polymer use and facilitate dispersion of Mg(OH)₂ and Nanoclay fillers. A twin-screw extruder system was used to predistribute the inorganic filler from the PP polymer, resulting composite PP/filler pellets. This followed by the use of a single-screw extruder wherein supercritical carbon dioxide is introduced in the formulation. Finally the resulting foam PP/filler/CO₂ pellets are injection molded into test samples. The structure and properties of the composites are characterized using a scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), and density measurements. Furthermore, PP/Clay/Mg(OH)₂ polymer composites are subjected to examinations to obtain their yield and tensile strengths, elasticity modulus, % elongation, Izod impact strength, hardness, Heat deflection temperature (HDT), Vicat softening point and Melt flow index (MFI).     

不同协助技术固相接枝改性聚丙烯的研究

分别采用有机分散剂、溶液浸渍和超临界二氧化碳(SC CO2)协助技术对聚丙烯(PP)进行固相接枝改性。通过自由基聚合制备了PP与马来酸酐(MAH)、丙烯酸(AA)的接枝共聚物(PP-g-MAH/AA),考察了单体投料量、反应时间、反应温度对接枝反应的影响,用傅里叶变换红外光谱(FTIR)对PP-g-MAH/AA进行了表征,并测试了接枝产物的水接触角、热稳定性、熔体流动速率和力学性能。实验结果表明,当单体投料量为6%,100℃下反应2h时,三种协助方法的接枝效率均达到最大值,SC CO2协助技术对PP接枝改性的接枝率和接枝效率较最高,可达5.33%和88.83%。测试结果表明,SC CO2协助技术制得PP接枝产物热稳定性最好、水接触角最小。     

Dynamic rheology–morphology relationship of PP/EPDM blends prepared by melt mixing under Sc-CO2

It was demonstrated that the high mixing efficiency of twin screw extruder (TSE) helped to disperse the ethylene–propylene–diene terpolymer (EPDM) domains in polypropylene (PP) matrix, but could not lead to the uniform distribution of EPDM phase with small sizes because of the thermodynamical immiscibility between PP and EPDM. So supercritical carbon dioxide (Sc-CO₂) was environmentally and economically introduced to the twin screw extrusion to assist the melt mixing of PP and EPDM. The scanning electron microscopy photographs showed that co-continuous phase morphology was formed to some extent for the PP/EPDM 60/40 blend prepared with Sc-CO₂, especially with 2.5 wt% Sc-CO₂. This was the one important reason for that the complex viscosity and storage modulus of PP/EPDM 60/40 blend increased with the increase of Sc-CO₂ concentration.