聚丙烯合金PP-c的晶相结构及形态

用偏光显微镜和广角X射线衍射研究了聚丙烯合金PP c的结晶形态.发现PP -c的晶相结构中不仅存在α-晶型聚丙烯(α- PP ) ,也存在着β-晶型聚丙烯(β-PP) .计算了不同乙烯含量PP c的结晶度和β- PP含量.表明随着乙烯含量的增加,β- PP的含量增加,而PP- c的结晶度下降.通过与同等熔融结晶条件下等规聚丙烯(iPP)的结晶形态相比较,发现乙烯组分含量的增加,改变了球晶的生长状况,降低了PP- c晶相的晶体完整性.     

稀土氧化物对聚丙烯晶型和动态力学性能的影响

本文用DSC和粘弹谱仪研究了La_2O_3,Y_2O_3和混合稀土氧化物对全同聚丙烯(iPP)的结晶行为,熔融行为和动态力学性能的影响。结果表明不同的iPP/稀土氧化物复合材料中iPP的晶型不同,Y_2O_3和稀土氧化物是iPP的α和β晶成核剂,La_2O_3是α晶成核剂。含有β晶试样同只有α晶试样相比,在T_g真松弛区其tanδ值较低,贮能模量E从-50℃～+50℃较高,从+50℃～+145℃则E值较低。     

在低频振动场中注塑成型iPP试样的结构与性能研究

利用自行研制的低频振动注塑成型装置进行等规聚丙烯(iPP)试样的结构与性能研究.实验中对常规注射和振动注射成型的试样力学性能和微观形态进行了对比实验.采用低频振动注塑成型工艺实现了IPP试样的自增强,在190℃下进行注射,强度由常规试样的41.3 MPa最大提高到振动试样的48.4 MPa(振幅PA=59.4 MPa,振频FR=0.7 Hz),强度提高了17.2%;SEM显示常规试样芯层结构主要由球晶构成,振动注射使球晶在流动方向上变形、取向,晶粒尺寸得到细化;DSC表明振动注射促进熔融峰向高温漂移,晶体结晶更加完善,结晶度最大提高了12.1%;WAXD显示低频大振幅振动注塑有利于γ晶型的生成,γ晶型有利于试样实现自增强.     

制备方法对iPP/EPR合金晶相结构的影响

用示差扫描量热仪(DSC)和广角X射线衍射仪(WAXD)研究了溶液共混法和熔融共混法制备的等规聚丙烯/二元乙丙橡胶(iPP/EPR)(85:15,W/W)合金的晶相结构.发现溶液共混法制得的iPP/EPR合金晶相中仅存在α-iPP,而熔融共混样品中则同时生成了α-iPP和β-iPP.这一结果表明,EPR并不是iPP/EPR合金中β-iPP生成的关键因素.考察了结晶温度和熔体热处理对iPP/EPR合金晶相结构的影响,发现通常的热处理并不能消除合金中β-iPP的生成.     

硅氧烷液晶共聚物作为β晶成核剂对等规聚丙烯结晶结构与形态的影响

采用广角X射线衍射(WAXD)与偏光显微镜(POM)等手段研究了硅氧烷液晶共聚物(LCP-O2)作为新型成核剂对聚丙烯(PP)共混样品结晶结构与形态的影响.结果表明,低浓度的LCP-O2在PP共混体系中起到异相成核的作用,使PP的晶核数目增多,球晶细化,并提高了结晶速度,同时也诱导出了β晶的形成.LCP-O2的成核效果主要依赖于其在PP中的相对含量、液晶的分子结构与结晶的热处理过程,且随着结晶温度或成核剂含量的增加,对应PP试样的β晶含量(Kβ)呈现先增加,后降低的趋势.当LCP-O2质量分数为1.0%,在130℃等温结晶1h,对应PP试样的Kβ最大,为58%.此外,属于单斜晶的α球晶呈现黑白颜色,晶束呈放射状生长,边界清晰;而属于三方晶的β球晶亮度要高于α球晶,其颜色艳丽多彩,束状晶片聚集体呈支化生长,内部排列比α晶疏散,边界相对模糊,且β晶与α晶的形态分别在157和171℃完全消失.     

DC26NDCA诱导聚丙烯的β晶型结晶行为及微观形态研究

研究了N,N-二环己基-2,6-萘二酰胺(DC26NDCA)诱导等规聚丙烯(iPP)的结晶行为和微观形态。用WAXD分析DC26NDCA诱导iPP晶型的变化,用DSC研究DC26NDCA对iPP的结晶和熔融行为的影响,并用偏光显微镜(POM)原位观察DC26NDCA诱导iPP的结晶生长过程。结果表明：DC26NDCA能有效地诱导iPP产生卢晶型,卢晶含量可达90％以上,使iPP非等温结晶过程的结晶温度(Tc)从110．2℃提高到126．6℃,而熔融温度由161．2℃下降至151．6℃;POM原位观察结果表明,β型成核剂DC26NDCA诱导iPP成核结晶的生长过程和方式符合附生结晶的规律。     

等规聚丙烯在混合稀释剂中结晶行为

利用偏光显微镜和扫描电子显微镜研究了等规聚丙烯(iPP)在混合稀释剂中的非等温结晶行为和由热致相分离(TIPS)法制备的iPP微孔材料的结构。iPP的质量分数固定为30%,采用不同配比的邻苯二甲酸二丁酯(DBP)/大豆油组成混合稀释剂。结果表明,混合稀释剂的配比影响体系的粘度和稀释剂与iPP的相容性,进而影响iPP球晶的生长和TIPS法制备的iPP微孔材料结构。在2K/min的降温速率的条件下,iPP球晶半径和球晶的生长速率均随时间的延长呈指数增长,iPP球晶生长速率随混合稀释剂中DBP含量的增加而降低,当iPP球晶生长时间达2min时,混合稀释剂中DBP的质量分数从0增加到60%,iPP球晶生长速率从41.9μm/min降至10.3μm/min,所制得的微孔材料断面均呈蜂窝状结构,且孔径随混合稀释剂中DBP含量的增加有明显增大的趋势。     

硅灰石填充聚丙烯复合材料性能的研究

本文研究了硅灰石填充聚丙烯(含乙烯22％)复合材料的热学、广角X-射线衍射和动态力学性质。复合材料中β晶含量随硅灰石含量增高而增加。试样的熔融及结晶行为表明,所有硅灰石填充试样均含有α和β两种晶型,4个结晶熔融转变;而未填充试样只有a晶型,2个结晶熔化转变。在DSC曲线上,β晶在升温过程中转变成α晶型。硅灰石填料对聚丙烯动态力学性能的影响表明,硅灰石起到了增强剂和β晶成核剂的双重作用,填料硅灰石已进入聚丙烯的结晶相。     

等规聚丙烯β晶形态研究

本文用正交偏光显微镜和扫描电镜观察了加成核剂βIPP的晶体形态,发现偏光下βIPP为彩色树枝状,是由弧形晶片生长成的球晶,并提出了β晶是由一个中心向相反方向枝化生长的晶体模型。     

温度对iPP和TMB-5/iPP结晶行为的影响

通过DSC和同步辐射WAXS技术测定了结晶温度对iPP和TMB-5/iPP结晶行为的影响.结果表明,随等温结晶温度升高,iPP总结晶度变化不大,但是β晶型含量降低的同时α晶型含量增加.TMB-5是一种具有温度依赖的选择性成核剂,当等温结晶温度高于140℃时,含TMB-5成核剂的iPP的β晶型的含量急剧降低.本文进一步探讨了TMB-5对iPP结晶行为影响的机理.     

β/α Transformation of β-polypropylene during tensile deformation: effect of crystalline morphology

In this work, the β/α transformation of β-nucleated iPP at different tensile strains has been analyzed. The crystalline morphology of iPP is controlled by the content of β-phase nucleating agent (β-NA), namely, well-developed β-spherulites induced by critical content of β-NA and bundle-like morphology without distinctly developed spherulites by supercritical content of β-NA. It is interesting to observe that the crystalline morphology of β-iPP exhibits great influence on the β/α transformation process during deformation. For well-developed β-spherulites, the content of β-iPP increases at relatively low tensile strain and then decreases gradually with the further increase of tensile strain. However, for bundle-like morphology, the content of β-iPP decreases monotonically with the increase of tensile strain. More important, well-developed β-spherulites, which have integrated crystalline structures, exhibit much smaller degree of β/α transformation as compared with bundle-like morphology at the same tensile strain, leading to more β-iPP maintaining and participating in the deformation process at high strain and consequently, resulting in better ductility. The results of this study further show the importance of crystalline morphology in determining the ductility of β-nucleated iPP on the one hand. On the other hand, this work provides the illuminating explanation for the reason why the well-developed β-spherulites exhibits more excellent ductility compared with the bundle-like morphology.     

Formation of β-crystal from nonisothermal crystallization of compression-molded isotactic polypropylene melt

The crystalline structures of isotactic polypropylene (iPP) subjected to compression-molding were studied by means of differential scanning calorimeter (DSC), optical microscope (OM) and wide-angle X-ray diffraction (WAXD). β-crystal can be formed from nonisothermal crystallization of the sample compression-molded at the molten state and the β-phase content increased with increasing pressure of molding. Thermal treatment of the molten sample at 200 °C could eliminate the effect of compression-molding on crystalline structure. It was suggested that the compression-molding of iPP melt plays an important role in improving the nucleation ability of β-crystal.     

Shear-induced topology changes in liquid crystals of the soybean lecithin/DDAB/water system

The viscoelastic behavior of the two different liquid crystalline lamellar phases and the liquid crystalline cubic phase of the mixed soybean lecithin/DDAB system in water was studied through rheology, with mechanical parameters studied as a function of composition. The swollen or diluted lamellar region is formed by vesicles, and its characteristic flow curve presents two-power law regions separated by a region where viscosity passes through a maximum. Yield stress and shear-dependent flow behavior were also observed. The microstructure suffers transformation under shear stress, and rheological response shifts from thixotropic to antithixotropic loops. Similar rheological behavior has been observed for samples in the collapsed or concentrated lamellar region, at the water-rich corner of the phase diagram. Vesicle formation may therefore occur by shearing the initial stacked and open bilayers. However, concentrated lamellar samples in the water-poor part of the phase diagram are less sensitive to shear effects and show plastic behavior and thixotropy. All lamellar samples manifest high elasticity. The dynamic responses of both lamellar topologies, i.e., vesicles and open bilayers, are comparable and exhibit an infinite relation time. The bicontinuous cubic, liquid crystalline phase is highly viscous. Its dynamic response cannot be modeled by a Maxwell model.     

Conformation of liquid crystalline state in interaction between chemical materials and biomembrane in terms of modern physics

Ｍａｎｙｉｍｐｏｒｔａｎｔｆｕｎｃｔｉｏｎｓｉｎｔｈｅｐｒｏｃｅｓｓｏｆｌｉｆｅａｒｅｃｌｏｓｅｌｙｒｅｌａｔｅｄｗｉｔｈｔｈｅｌｉｑｕｉｄｃｒｙｓｔａｌｌｉｎｅｓｔａｔｅｏｆｂｉｏｍｅｍｂｒａｎｅ.Ｓｏｔｈｅｓｔｕｄｙｏｎｔｈｅｃｏｎｆｏｒｍａｔｉｏｎｏｆｔｈｅｌｉｑｕｉｄｃｒｙｓｔａｌｌｉｎｅｓｔａｔｅｏｆｂｉｏｍｅｍｂｒａｎｅｈａｓｂｅｅｎｏｎｅｏｆｔｈｅｆｒｏｎｔｉｅｒｄｏｍａｉｎｓｏｆｌｉｆｅｓｃｉｅｎｃｅｓｏｆａｒ[1—4].Ｉｎｒｅｃｅｎｔｙｅａｒｓ,ｔｈｅｒｅｓｕｌｔｓｏｆａｇｏｏｄｍ…     

The use of optical microscopy to follow the degradation of isotactic polypropylene (iPP) subjected to natural and accelerated ageing

Microscopy and mechanical properties are commonly used to follow the changes in morphology and mechanical resistance, respectively, of materials before and after any type of treatment. In this work, we used light microscopy (LM), scanning electron microscopy (SEM) and measurement of the mechanical properties to assess the natural ageing of samples of isotactic polypropylene (iPP) in Campinas and after exposure to Weather-Ometer type accelerated ageing equipment. The results obtained for the mechanical properties and by light microscopy (LM) allowed us to identify the ageing time based on the amount of radiation, for a 50% loss of elongation at break. The results were similar for samples subjected to the two types of ageing processes. Although a simple technique, LM was considered efficient when compared with SEM and the measurement of mechanical properties.     

Mechanical enhancement of melt-stretched β-nucleated isotactic polypropylene: The role of lamellar branching of β-crystal

Melt-stretched isotactic polypropylene (iPP) filled with different weight fractions (0, 0.1, 0.2 and 0.4 wt %) of β-nucleating agent (β-NA) was extruded via a single screw extruder with a slit die and immediately melt-stretched at the die exit. The microstructure and mechanical properties (i.e., monotonic tensile, step-cycle and stress relaxation behavior) of these samples were analyzed. Unexpectedly, the lamellar branching of β-crystal, which is similar to lamellar branching of α-crystal, is observed in melt-stretched β-nucleated iPP. More interestingly, it is found that, compared with other samples, iPP containing 0.2 wt % of β-NA has the best mechanical properties. Through thorough analysis of various structural characterizations, the improved tensile strength obtained from step-cycle tests and viscous force obtained from stress relaxation measurements for iPP with 0.2 wt% of β-NA is ascribed to lamellar branching of β-crystal. The study is an example of preparing high performance polymers via practical polymer processing methods.     

LAMELLAR STRUCTURE OF THERMOTROPIC LIQUID CRYSTALLINE POLYMERS

The lamellar structure of a thermotropic aromatic polyester with flexible spacer has beenstudied by using transmission electron microscopy. It was found that the lamellar structure couldbe observed in the crystalline samples of this semirigid polymer crystallized from different states.The thickness of lamellae is around 10 nm, which is similar to that of the conventional polymersof flexible chain molecules. The molecular chains in the lamellae are oriented in the thicknessdirection as determined by electron diffraction. The possibility of molecular chains folding in the lamellae has been discussed.     

The electron microscope characterization of the fine structure of nylon 6: I. The supermolecular structure in melt-cast,isotropic bulk material

The application of phosphotungstic acid (PTA) as a staining agent with appropriate hardening procedures and accurate ultra-thin sectioning has enabled the direct transmission electron microscope (TEM) investigation to be carried out on the lamellar fine structure of bulk nylon 6. Details of the organization of the crystal lamellae within spherulites and other morphological structures, their shape and, especially, their dimensions were revealed and the mean structural long period was determined. Interspherulitic regions without any indication of crystalline ordering could be observed in samples which were rapidly cooled from the melt. The investigations on bulk material were completed by observations on solution-grown thin films. Optical diffraction (OD) was used for evaluating the electron micrographs; the results were compared with the data from small angle X-ray scattering (SAXS).