耐候改性聚丙烯

本试验讨论了滑石粉对聚丙烯性能的影响、偶联剂的作用及填充改性聚丙烯的耐候性。     

耐候聚丙烯老化性能的研究

分别研究了弹性体、成核剂DICK、BaSO4、光稳定剂UV－531、UV－770有其复合体系对耐候聚丙烯老化性能的影响。结果发现，所研制的耐聚丙烯老化后的拉伸强度保持率、伸长率保持率、冲击强度保持率均优于耐候聚丙烯的理化指标。     

低等规聚丙烯的研制Ⅰ.低等规聚丙烯的微观结构和性能

采用低等规聚丙烯催化剂制得ＬＩＰＰ,并测定其微观和性能结果表明。ＬＩＰＰ是短距有序长距无序的等规和少量间规立体嵌段均聚物,其性能与高等规聚丙烯和副产无规聚丙烯有较大的差别。     

聚丙烯的蠕变过程及微观结构变化的研究

在25℃下研究了应力、退火处理、紫外辐照等外界因素对聚丙烯(PP)蠕变行为的影响。发现PP在蠕变过程中存在临界失效现象,而且外界因素只对临界失效现象出现的时间产生影响,而不会影响临界失效应变值(εcr)的大小。PP在蠕变过程中内部微观结构发生着复杂的变化:在25 MPa下,蠕变初期随着形变的增加,分子链取向排列诱导二次结晶,导致材料的取向度和结晶度增加;自由体积尺寸增大,当自由体积尺寸达到最大值时,分子链的活动能力最强,出现临界失效现象。     

聚丙烯/稀土氧化物复合材料性能与微观结构

以稀土氧化镧(La2O3)和氧化铈(CeO2)为改性剂,聚丙烯(PP)为基体,通过熔融混合挤出制得PP/稀土氧化物复合材料。对该复合材料的力学性能、耐热性、流动性进行了测试和分析,采用扫描电镜对其微观结构进行观察,对稀土氧化物改性PP机理进行了讨论。结果表明,La2O3改性PP比PP基体力学性能、耐热性、流动性均有提升,CeO2对PP基体增韧效果明显。稀土氧化物粒子在复合材料中分散均匀、与PP相容性良好,稀土氧化物使PP得到有效增强增韧。     

流延膜专用聚丙烯的微观结构与热性能

对两个流延膜专用聚丙烯（分别记作CPP-1,CPP-2）的链结构进行表征,并研究了试样的熔融和结晶行为。结果表明：CPP-1的重均分子量略高于CPP-2,相对分子质量分布也略宽;CPP-1中的乙烯含量高于CPP-2,等规指数低于CPP-2;CPP-1中可结晶的乙烯序列较短或含量较少,而CPP-2中可能具有较长的乙烯序列结构;CPP-1的两个熔融峰均高于CPP-2;CPP-1的结晶温度高于CPP-2,而结晶度低于CPP-2;CPP-2在127.0℃左右有较强的熔融峰,说明此温度条件下熔融的结晶序列较多,而CPP-1在127.0℃处的熔融峰强度较弱,说明两个试样内部的结晶序列分布有差异。     

SEBS-g-MAH对聚丙烯/氢氧化镁纳米复合材料微观结构与流变性能的影响

以马来酸酐接枝的SEBS(SEBS-g-MAH)作为界面改性剂制备了PP/SEBS-g-MAH/氢氧化镁(MH)纳米复合材料,采用SEM、DSC和毛细管流变仪研究了SEBS-g-MAH对复合材料的微观结构、结晶行为和流动性能的影响。结果表明,SEBS-g-MAH的加入充当了MH粒子与PP基体的界面层,提高了纳米MH粒子在PP中的均匀分散性,改善了两者的界面相互作用和PP/MH复合体系的流动性能。     

聚丙烯/BA原位聚合改性MMT纳米复合材料的微观结构

通过原位聚合制备了聚丙烯酸丁酯（PBA）改性蒙脱土（MMT），再与PP熔融复合，制成PP／MMT复合材料，利用X射线衍射（XRD）、扫描电子显微镜（SEM）和电子探直表征了复合材料的微观结构。结果表明：PP／MMT复合材料为纳米复合材料，MMT的加入诱导了β－晶型PP的形成。     

原位反应增容法制备非卤阻燃聚丙烯微观结构研究

利用扫描电镜（SEM）研究了原位反应增容法制得的非卤阻燃聚丙烯的微观结构,着重探讨了反应性单体的种类和用量对其微观结构的影响,并用傅里叶变换红外光谱（FTIR）表征了反应性单体与聚丙烯树脂反应产物的结构。实验结果表明,采用此法制得的非卤阻燃聚丙烯均可显著提高阻燃剂与聚丙烯树脂的相容性,但不同的反应体系增容效果不同。     

合成和应用过程中MBS微观结构的研究

为了考察MBS微观结构与其合成工艺、产品性能之间的关系，利用电子显微镜技术对丁苯胶乳、MBS接枝胶乳、MBS粉末颗粒、PVC／MBS共混物的微观形态进行了系统的研究分析；对PVC／MBS共混物经过拉伸后内部微观结构和冲击后的断面进行分析研究，初步探讨了MBS的抗冲改性机理。     

Natural weathering of polypropylene in a tropical zone

Natural weathering of isotactic polypropylene (PP) plates (2 mm in thickness) was conducted for 15 months in the Philippines. Optical microscopy, scanning electron microscopy, and atomic force microscopy revealed that the surface layer (200–300 nm in thickness) was affected in the first month, and cracks are formed toward the deeper layer. On the basis of the microscopic observations along with FTIR, DSC, GPC, and tensile strength measurements, the following degradation mechanism of PP was proposed. At first, through oxygen introduced into the PP, only the surface layer seems to be affected. Gradually, the surface layer may be removed, exposing the inner layer. Then, molecular chains of the inner layer start to be degraded, accompanying a significant loss of tensile properties. Part of the degraded materials seems to be eroded, leading to the formation of cracks on the surface of the uncovered inner layer. Finally, the original surface layer may be totally eroded, making the structure of the inner layer (which should reflect the spherulitic texture) evident. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 931–938, 2003     

Characterization of microstructure of polypropylene alloys

Two polypropylene (PP) alloys, which have similar composition, molecular weight and molecular weight distribution, but different processing and application properties, were fractionated using a preparative temperature rising elution fractionation (TREF) technique. It was found that PP alloys are mainly composed of four components: ethylene–propylene random copolymer, block-type copolymer, transition copolymer and propylene homopolymer. However, the fractionation data show that the distribution and the composition are different for these two samples. A possible mechanism is proposed for the formation of PP alloys of different compositions. Based on this mechanism, some possible adjustment of the polymerization parameters is suggested to control the microstructure. © 1998 Society of Chemical Industry     

Natural weathering of polypropylene films. I. Exposure time and yield properties

The yield properties of about 500 h of outdoor weathering (in the rainy season) of polypropylene (PP) films have been studied. The yield strain, plastic strain, and initial modulus, work of yield attained local maxima at 48- and 240-h exposure time; elastic strain attained near double maxima at these times. The yield stress reached a local minimum for the 144-h exposed film before increasing with further exposure hours. The increase in yield strain, plastic strain, and initial modulus were explained in terms of crosslinking chemocrystallization; decreases were due to chain scission and leaching. Critical dissolution time data, interpreted in proportion to density, crystallite thickness, and percent crystallinity, increased with PP exposure time, reaching a maximum at 48 h before decreasing to values even lower than that of unexposed film from the 120-h exposure. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 667–673, 1998     

The microstructure of polypropylene welds as a guide to processing history

The well known occurrence of different crystalline forms in polypropylene and their easy recognition in the polarising microscope has provided a method of analysing the behaviour of this material during the production of hot plate welds. The different thermal behaviour of the α- and the β-forms of crystalline polypropylene allows estimation of the thermal history of the polymer in the region of the weld. In particular it is possible to estimate the amount of material actually melted by contact with the hot plate. The effect of the original crystalline microstructure of the components being welded on the microstructure of the recrystallised material forming the weld bond has also been explored. It is possible to characterise the general crystalline texture in the weld bead in terms of the shear and thermal history of the material. The influence of pre- and post-welding annealing of the polypropylene has been investigated and a difficulty is encountered in explaining an apparent ‘memory’ of β-form crystallisation which conflicts with established x-ray diffraction results.     

Effect of iron carboxylates on the photodegradability of polypropylene. II. Artificial weathering studies

The various iron carboxylates such as ferric caprate, ferric laurate, ferric myristate, ferric palmitate, and ferric stearate were synthesized to enhance the photodegradability of polypropylene (PP). The prodegradants (0.2%) synthesized were blended with virgin PP and then blown into films. All the PP films mentioned were exposed to ultraviolet (UV) radiation of 365 nm at room temperature to study the photodegradation behavior of PP with and without the prodegradants under artificial weathering conditions. The photoirradiated films were found to degrade after certain hours of UV exposure, which could be found from the steep increase of hydroxyl, carbonyl, lactone, ester, carboxylic acid, and crystallinity index. At the same time, a sudden decrease of elongation at break percentages and tensile strength; development of surface cracks indicated the scission of the main chain of the PP. The results revealed that PP containing prodegradants degraded at a faster rate than the virgin material. However, the effectiveness of the prodegradants for the photodegradation of PP was found to be in the order: ferric caprate > ferric laurate > ferric myristate > ferric palmitate > ferric stearate. The results showed that the number of carbon atoms present in the alkyl part of the various prodegradants played a vital role in the degradation phenomenon. Furthermore, it could be concluded that the mobility of the alkyl radicals formed from the decomposition of the incorporated prodegradants during artificial weathering played a prominent role in the photooxidative degradation behavior of PP films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

PE/PP共混物卷绕丝微观结构的研究

用透射和扫描电子显微镜研究PP/PE共混物在熔融纺丝时 ,PE掺入对PP结构的影响。研究结果表明 :PE与PP存在一定程度的相互作用 ,PP中加入PE能改变卷绕丝中PP结晶结构 ;PP中加入质量分数低于 10 %的PE时可以顺利纺丝 ,所得的卷绕丝断裂伸长率较大 ,具有良好的可拉伸性     

Effects of decoppering pretreatment on accelerated weathering behaviors of waste printed circuit boards powders reinforced polypropylene composites

Waste printed circuit boards powders (WPCBP), the critical by-products in the dispose process of waste electrical and electronic equipment, were selected as reinforcing fillers in polypropylene (PP) composites, which brought forward a new way to reuse WPCBP for a sustainable world. However, the multivalent metals in WPCBP could accelerate the degradation of PP molecule chains. In this study, nitric acid was selected as copper removal to pretreat WPCBP, and most of the metals were removed after decoppering pretreatment, which was evidenced by X-ray fluorescence (XRF). The ensuing compound was characterized by oxidation induction time, scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical analysis. As expected, the accelerate weathering behaviors of PP composite with nitric acid treated WPCBP were substantially improved, for instance, the notched impact strength and tensile strength of untreated PP/WPCBP composite after 21 days thermal aging were just 0.85KJ/m² and 9.3 MPa, while the PP composite with 6 wt % nitric acid-treated WPCBP was 3.47KJ/m² and 32.1 MPa. We envisage this facile strategy, that is, using proper concentration of nitric acid to pretreat WPCBP could improve the accelerate weathering properties of PP/WPCBP composites, which would broaden the potential applications of WPCBP in polymer compounds. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48224.     

The spherulitic and lamellar morphology of melt-crystallized isotactic polypropylene

A study is presented concerning the basic morphology of melt-crystallized isotactic polypropylene (iPP). Involved within, is the coordinated application of optical and electronmicroscopy on a range of commercial iPP-s, crystallized in the temperature range 100°C–150°C. For electron microscopy in particular, the permanganic etching technique has been used throughout, providing the simultaneous combination of both real space microstructures with electron diffraction information. The investigation itself has centred on the five different spherulite types, as identified optically, which were then correlated with the details of their particular lamellar morphology. It was found that each spherulite type is characterized by virtue of the arrangement of its constituent lamellae, in terms of orientation, habit type and crystal structure. Thus, specific correlations were obtained between the structural entities on all scales of the structure hierarchy.     

氢气、外给电子体及聚合温度对iPP微观结构的影响

用工业非均相Ziegler-Natta催化剂通过实验室制备和工业生产获得等规聚丙烯(i PP),利用高温凝胶渗透色谱仪、差示扫描量热仪等对i PP进行分析表征。在聚合温度分别为60,70℃条件下,研究了H2、外给电子体环己基-甲基-二甲氧基硅烷(CHMMS)对i PP相对分子质量及其分布、立构规整性及结晶性能等的影响。结果表明:H2,CHMMS对i PP微观结构的影响与聚合温度有很大关系;在不加CHMMS、聚合温度为60℃时,加入H2使i PP全同立构五单元组序列结构含量从60.16%增至77.45%;H2和CHMMS通过影响丙烯分子的"头-头"或"头-尾"结合方式对i PP的微观立体缺陷分布有调整作用。     

纳米ZnO 对 PP自然光降解的影响

在PP中添加O～1.2%的纳米ZnO粉体,通过共混熔融纺丝纺制成纤维,研究了共混纤维在自然光照射条件下的力学性能变化。结果表明,随着纳米ZnO用量的增加,共混纤维的断裂伸长率、断裂强度都迅速地降低,快速降解的起始点和断裂仲长率降低一半所需要的时间也逐步缩短。说明纳米ZnO对PP的自然光降解具有一定的催化作用,可用作PP材料可控光降解的光敏剂。