β-PP在国内典型气候条件下的自然老化行为研究

采用熔融挤出法制备了β晶犁聚丙烯(β-PP),将纯聚丙烯(PP)和β-PP在国内四个典型气候带进行自然老化试验,通过立体显微镜、傅里叶变换红外光谱仪和广角X射线衍射仪研究了自然老化对材料表面形貌、微观结构和晶型的影响.结果表明:纯PP和β-PP在海南三亚市最易老化,新疆若羌县次之,西藏拉萨市和内蒙古海拉尔市作用效果相似...     

聚丙烯复合材料光老化研究进展

综述了国内外近年来聚丙烯复合材料光老化研究方面的进展,并着重讨论了硅酸盐类无机填料以及多种纳米填料,天然纤维,高聚物共混组分,稳定助剂以及染色剂等对聚丙烯光老化的影响及其机理。     

β晶型聚丙烯的研究进展

对近年来在β晶型聚丙烯(PP)形态结构，影响β晶型含量的因素，β晶型成核剂，β晶型转变及β晶型PP性能等方面的研究工作进行了综述。添加成核剂可得到高含量的β晶型。与α晶型相比，β晶型PP的球晶尺寸大幅度减小，晶粒细化，具有良好的抗冲击性能和较高的热变形温度。     

氮氧基键合型聚丙烯的光氧老化研究

考察了受阻胺类,受阻酚类以及键合氮氧改性型等助剂对聚丙烯熔体状态的影响,较全面地分析了聚丙烯的耐候性行为及含氮氧基团助剂对增进聚丙烯耐候性行为方面的作用。从研究结果可以看出键合型聚丙烯不仅可行,而且耐候性和耐溶剂抽提性能非常优越。     

聚丙烯轿车专用料的光老化和光稳定

介绍了用于轿车保险杠的ＰＰ／ＰＥ／ＥＰＤＭ共混物的氙灯人工加速老化及户外暴露实验结果，分析了不同抗老化体系对ＰＰ／ＰＥ／ＥＰＤＭ共混物光老化后拉伸性能、冲击性能及外观变化的影响。     

聚丙烯光老化性能变化研究综述

为了更好的对聚丙烯材料进行广泛应用,延长内饰用聚丙烯类材料的使用寿命,就聚丙烯材料光老化机理及其光老化前后性能变化相关内容进行了研究,并对相关问题提出了可行性建议     

聚丙烯光氧老化研究(Ⅱ)聚丙烯材料环境适应性行为规律

研究了通过稳定剂改性后的聚丙烯材料的熔体状态与在热或光照环境条件下的老化行为规律。研究结果表明，当聚丙烯熔体中仅掺入抗氧剂时，熔体稳定性只说明材料的可加工性，并不能完全代表它的长期耐热效果；当熔体中掺入了光稳定剂和抗氧剂的协同组合体系，不仅熔体状态稳定，且长期耐光老化效果优良，所以聚丙烯从树脂——加工——材料——老化行为是一个整体过程，不仅取决于配合体系的协同效应，还取决于材料加工时的熔体状态。在聚丙烯光氧老化过程中羰基含量随老化时间增长而增加，所以选取羰基指数来表征聚丙烯材料光氧老化程度准确又可靠。本研究系统跟踪了4组试样在进行人工光(氙灯)加速试验过程中羰基指数变化与试样所接受的紫外辐射累积能量值之间的关联性，得到线性回归方程式：Y=α bx(Y—羧基指数；X——紫外辐射累积能量值，MJ／m^2；a和b为实验常数，随试样类别而异)，这4条回归线的相关系数。都在0．9以上，结果令人满意。     

不同聚丙烯在典型自然条件下的老化行为研究

选择性选取几个典型气候地区对共聚聚丙烯(PP1)与均聚聚丙烯(PP2)进行自然曝晒实验,利用光学测试仪和扫描电子显微镜(SEM)等手段对老化前后两种PP的光学性能和表面形貌进行分析,研究其在不同自然条件下的老化性能。结果表明,PP1和PP2在不同自然条件的老化程度由大到小顺序为:湿热地区(三亚、琼海和广州)>干热地区(吐鲁番和若羌)>温带地区(北京和青岛)>高原地区(拉萨和海拉尔);其中PP2的耐候性比PP1差,更容易发生老化。     

聚丙烯的光氧老化研究(Ⅰ)

未经稳定化的聚丙烯在自然环境中受光和热的影响。极易自动光氧化降解破坏而不能使用，人们常借助于添加稳定剂的措施来增进它的耐候性。通过受阻胺类，受阻酚类以及键合氮氧改性型等对聚丙烯熔体状态的研究。较全面的分析了聚丙烯的耐候性行为及含氮氧基团助剂对增进聚丙烯耐候性行为方面的作用。从研究结果可以看出键合型聚丙烯不仅可行。而且耐候性和耐溶剂抽提性能非常优越。     

不同晶型成核剂在聚丙烯改性中的应用

本文介绍了聚丙烯成核剂的种类及其不同晶型成核剂在聚丙烯改性中的应用。重点介绍了山梨醇苄叉衍生物类成核剂在聚丙烯透明改性中的应用及通过实验对比研究分析了α、β两大晶型成核剂对聚丙烯力学性能及加工性能的影响。     

Photodegradation of talc-filled polypropylene

Injection-molded talc-filled polypropylene (PP) composites have been exposed to ultraviolet (UV) radiation in the laboratory for periods up to 26 weeks. The extent of chemical degradation has been assessed by means of Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), and the results correlated with the mechanical properties. In the early stages of exposure, the photo-oxidation is faster in the talc-filled composites than in the unfilled polymer, but this trend is reversed for exposures longer than ∼12 weeks. Scanning electron microscopy (SEM) inspection has revealed that surface cracks caused by photodegradation in the filled PP occur in the surface exposed to the UV source only, resulting in much less deterioration in tensile properties when compared with the unfilled polymer which degrades significantly at the unexposed surface also. Measurements of melting temperatures by differential scanning calorimetry (DSC) gave a consistent picture of degradation with that obtained by FTIR and GPC studies. DSC analyses have also shown that an increase in the melting enthalpy for both the unfilled and filled grades occurs during exposure.     

Aging behavior of oxygen plasma-treated polypropylene with different crystallinities

Oxygen plasma-treated quenched and annealed polypropylene (PP) films with different crystallinities were investigated to characterize the surface rearrangement behavior during aging using contact-angle measurements and X-ray photoelectron spectroscopy. Optimum plasma conditions were examined by varying the power, time and pressure. Less crystalline quenched PP showed a larger increase in water contact angle and a larger decrease of oxygen atomic concentration during aging than the more crystalline annealed PP, since the oxygen species, such as hydroxyl groups, introduced by oxygen plasma treatment, oriented towards or diffused faster into the bulk with lower crystallinity. The degree of crosslinking on the surface was enhanced after plasma treatment and, in addition to increased crystallinity, the crosslinked structure induced by plasma treatment restricted chain mobility and lowered the aging rate of the PP surface.     

Photodegradation of polypropylene containing a nucleating agent

The effect of including 0.5 wt % talc on the photodegradation behavior of polypropylene (PP) was investigated in injection-molded samples exposed to ultraviolet radiation (UV) in the laboratory for periods of up to 24 weeks. The structure of the talc-nucleated samples was characterized by X-ray diffraction and light microscopy and compared with that of nonnucleated PP, and the information was used to explain the differences in their photodegradation behavior. Measurements of the extent of chemical degradation were made by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), and they showed that there is no significant effect of a nucleating agent on the kinetics of photooxidation. PP bars containing a nucleating agent showed a larger reduction in mechanical properties with UV exposure and a partial recovery in properties after prolonged exposure was observed with both types of samples. An increase in crystallinity during UV exposure (chemicrystallization) was detected by X-ray diffraction and differential scanning calorimetry (DSC) and the dependence with exposure time was similar in nucleated and nonnucleated samples. DSC was also used to determine the melting behavior and transition temperatures of the specimens during exposure and after recrystallization from the melt. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2505–2517, 1997     

Photodegradation of partially oriented and drawn polypropylene filaments

The effects of fiber structure on the process of photodegradation are controversial in the field. We tested polypropylene fibers of various form for their effects on photodegradation. Fiber grade polypropylene granules were spun into partially oriented multifilament yarns at a spinning speed of 2000 m min^?1. The yarns were drawn using a draw‐twist unit. Yarns were exposed to ultra‐violet radiations in a covered open air chamber for different periods of time under two different sources of emissions (UVA; λ > 300 nm and UVC; λ = 254 nm). The samples were examined by Fourier transform infrared spectroscopy, mechanical testing, differential scanning calorimetry, microscopy, and density measurements. In photodegradation process, the drawn filaments had a longer induction time than undrawn ones. The mechanical properties of the undrawn yarns deteriorate faster than the drawn yarns. During the early periods of degradation helical content increases considerably, while the density fluctuates and increases. The degradation rate under UVC radiation was faster than under UVA radiation because of the higher energy of the UVC radiation. The upper photostability of the drawn yarns compared to the undrawn ones was due to the higher crystalline fraction and greater molecular orientation in the drawn yarn. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45716.     

不同结构PP熔体的高速挤出畸变行为

采用恒速型双毛细管流变仪对比研究了均聚聚丙烯(PPH)T30S,嵌段共聚聚丙烯AP3N,无规共聚聚丙烯(PPR)2400和PP-R4220熔体在高速挤出流场中的流变特性。PPR在较低速率下,短口模挤出物即出现规则螺纹畸变。相对分子质量相对较小的PPH T30S在高挤出速率下也出现螺纹畸变。分析表明,螺纹畸变的发生源于口模入口区的应力集中效应和次级环流。PPR熔体黏度高,弹性大,入口流动应力集中效应显著,且黏流活化能高,分子链柔性和结构规整性差,这些是导致其容易发生螺纹畸变的因素。     

Surface modifications of polypropylene with nonylphenol ethoxylates melt additives

Nonylphenol ethoxylated (NPE) additives were melt blended in polypropylene (PP) films and characteristics of the modified films were investigated. It was found that melt blending of NPE additives improved hydrophilicity of PP films through additive surface segregation. Surface specific techniques, such as X‐ray photoelectron spectroscopy (XPS) and Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) were used to study surface compositions of samples modified with NPE additives at different aging time after extrusion. We found that surface enrichment of additives lead to hydrophilic surfaces. Hydrophilic chain length in NPE affected surface composition and hydrophilicity of NPE containing PP polymer. The effect of water immersion and aging were also reported. POLYM. ENG. SCI., 52:1920–1927, 2012. © 2012 Society of Plastics Engineers     

Photodegradation of polypropylene in the presence of ferric chloride

The effect of ferric chloride (FeCl₃) on photodegradation of isotactic polypropylene (PP) was investigated using mainly ESR spectrometry. PP powder, its oxidized samples, and FeCl₃-adsorbing PP samples were irradiated under a nitrogen atmosphere at 77°K with ultraviolet light from a high-pressure mercury lamp and a superhigh-pressure mercury lamp modified by various filters. Methyl, polymerci alkyl, and peroxy radicals were observed in the ESR spectra of the irradiated samples, and it was found that FeCl₃ depresses the formation of alkyl radicals and accelerates the formation of peroxy radicals catalyzing the reaction. From infrared study of UV-irradiated film samples, it was also inferred that FeCl₃ accelerates the photodegradation the hydroperoxide and carbonyl groups.     

主链型液晶高分子改善聚丙烯熔体高速挤出的流变行为

采用恒速型双毛细管流变仪研究了主链型热致液晶对无规共聚聚丙烯(PPR)熔体高速挤出流变性能的影响.PPR熔体螺纹状畸变是由口模入口区的应力集中效应和横向环流造成的;利用原位成纤法制备PPR/热致液晶聚合物(TLCP)试样,TLCP在拉伸场中明显取向,随拉伸速率增大,取向程度先增大后减小;取向的TLCP明显减弱熔体挤出物...     

Structural modifications induced by recycling of polypropylene

The effect of numerous reprocessing cycles on transport properties of isotactic polypropylene (iPP) films was studied and related to the change of molecular weight and molecular weight distribution occurring during the recycling. Sorption curves of dichloromethane vapor in different samples of iPP were analyzed at 25°C to investigate the effect of structure modifications on the sorption mode. Moreover, gas permeability measurements were performed to evaluate the influence of reprocessing on the gas transport properties. The results obtained were attributed to modifications in the molecular structure of the polymer, evidenced from gel permeation chromatography (GPC), and to a different morphology of the films, as results from X-ray diffractograms and dynamic-mechanical thermal analysis (DMTA).     

Investigation on the structure and crystallization behavior of controlled-rheology polypropylene with different stereo-defect distribution

Understanding concerning the influence of peroxide degradation on the stereo-defect distribution and related crystallization kinetics of controlled-rheology polypropylene are of great importance. In this study, two iPP samples (PP-A, PP-B) with similar molecular weights and average isotacticities, but different stereo-defect distributions and their degradation productions after the addition of dicumyl peroxide (DCP) were prepared. Their melt flow indexes (MFI), stereo-defect distributions, crystallization behaviors and kinetics were studied using MFI measurement, differential scanning calorimetry, wide-angle X-ray diffraction, non-isothermal crystallization kinetics and successive self-nucleation and annealing fractionation. The results showed that as the content of DCP increased, the MFI, the crystallization temperature and crystallization rate of PP increased gradually, the crystallization peak width became narrower, and the crystallite size decreased. Meanwhile, the addition of DCP greatly restrained the formation of thick lamellae and narrowed its stereo-defect distribution [meso-sequence length (MSL) distribution]. On the other hand, results showed that PP resins with different stereo-defect distribution have similar MFI variations after degradation. PP-A (whose stereo-defect distribution was less uniform than PP-B) and its degradation products still possess higher crystallization rate, stronger crystallizability, smaller crystallite size and higher fractions of long MSL, compared with their counterparts of PP-B.