DETERMINATION OF CRYSTALLINE LAMELLAR THICKNESS IN POLY(ETHYLENE TEREPHTHALATE) USING SMALL-ANGLE X-RAY SCATTERING AND TRANSMISSION ELECTRON MICROSCOPY*

The crystalline lamellar thickness of semicrystalline poly(ethylene terephthalate) (PET) was evaluated using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Both SAXS onedimensional (1D) correlation function and interface distribution function analyses were utilized to determine the crystalline lamellar thickness. The two-dimensional fast Fourier transformation (2D-FFT) of the TEM image and the Gaussian-like lamellar thickness distribution determined from the TEM image were also performed. Results indicate that the larger value of the two correlation lengths calculated from the SAXS analysis should be assigned to the crystalline lamellar thickness in PET. Discussions and comparison among different methods for characterizing the lamellar thickness of semicrystalline polymers are made.

     

POLY(3-HYDROXYBUTYRATE)-BASED COPOLYMERS AND BLENDS: INFLUENCE OF A SECOND COMPONENT ON CRYSTALLIZATION AND THERMAL BEHAVIOR*

Isotactic poly(3-hydroxybutyrate) (P3HB) is an aliphatic polyester obtained by bacterial fermentation. This truly biodegradable polymer has been widely investigated, mainly with the aim to replace conventional plastics, which cause environmental pollution. To improve its properties, extensive studies have been conducted to modify it properly by copolymerization or blending with other polymers. Macroscopic properties of polymers, particularly of polymer blends, are strongly affected by their microstructure, especially by the allocation of different phases and their level of dispersion and adhesion. In nonreactive blends, the adhesion level is mainly determined by the similarity between the chemical structure of the components, and the arrangement of the phases is remarkably controlled by the crystallization conditions. The superstructure of the crystalline phases accounts for the mechanical resistance of the blend, but the composition and the distribution of the amorphous phases also play an important role, especially with respect to toughness properties. This article reviews data on thermal properties and the crystallization process of P3HB and its copolymers, both alone and in the presence of other polymers. In particular, copolymers of 3-hydroxybutyrate with 3-hydroxyvalerate and with 4-hydroxybutyrate and blends of P3HB and the copolymers with atactic poly(3-hydroxybutyrate), poly(vinyl acetate), poly(vinyl alcohol), poly(ethylene oxide), poly(methylene oxide), poly(epichlorohydrin), and poly(methyl methacrylate) are considered. Major attention is directed toward the influence of miscibility and composition on solidification kinetics and crystal structure with the objective to provide an overview of the current state of the art.

     

半结晶聚酯(PET)的二相共存结构的表征

采用X射线衍射对称反射法,对半结晶聚酯PET₂试样收集粉末X射线衍射全图(XDWP)数据,用Rietveld方法和Fourier过滤技术,对XDWP拟合并分离成结晶衍射峰之和CR₂和非晶散射峰之和AM₂两部分,与此同时获得PET₂试样的结晶相CR₂的三斜晶系晶胞参数:a=0.445,b=0.592,c=1.072nm,α=99.6,β=116.9,γ=111.9(°),结晶密度d_{c关键词： 聚对苯二甲酸乙二醇酯 二相共存结构 径向分布函数 Rietveld方法 Fourier过滤技术}     

COMPATIBILIZATION OF POLY(ETHYLENE OXIDE)/POLY(STYRENE) BLENDS: EFFECT OF THE MOLECULAR WEIGHT OF THE COMPATIBILIZER

The effect of the molecular weight and concentration of the compatibilizer maleic acid-alt-styrene copolymer (MAaS) on the compatibility behavior of incompatible poly(ethylene oxide)/poly(styrene) (PEO/PS) blends was studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEO with [Mbar] _w = 100,000 (PEO₁₀₀) and PS with [Mbar] _w = 225,000 (PS₂₂₅) were used for this study. DSC measurements showed two T _g values that were shifted relative to those of the pure components. This result should be indicative that MAaS acts as a compatibilizer for the blend. Diminishing of the spherulitic growth rate G was observed as the content and molecular weight of MAaS increased in the blend. This result was confirmed by morphological analysis, by which it was possible to observe that the amorphous component diminished its droplike domains. Contact angle measurements suggest that the wettability of PEO drops on a PS/MAaS surface are larger in the system containing MAaS as the compatibilizer.     

Rheological,thermal, and mechanical properties of poly(ethylene naphthalate)/poly(ethylene terephthalate) blends

Structural, Theological, thermal, and mechanical properties of blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) obtained by melt blending were investigated using capillary rheometry, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) observation, tensile testing. X-ray diffraction, and ¹H nuclear magnetic resonance (NMR) measurements. The melt Theological behavior of the PEN/PET blends was very similar to that of the two parent polymers. The melt viscosity of the blends was between that of PEN and that of PET. Thermal properties and NMR measurement of the blends revealed that PEN is partially miscible with PET in the as molded blends, indicating that an interchange reaction occurs to some extent on melt processing. The blend of 50/50 PEN/PET was more difficult to crystallize compared with blends of other PEN/PET ratios. The blends, once melted during DSC measurements, almost never showed cold crystallization and subsequent melting and definitely exhibited a single glass transition temperature between those of PEN and PET during a reheating run. Improvement of the miscibility between PEN and PET with melting is mostly due to an increase in transesterification. The tensile modulus of the PEN/PET blend strands had a low value, reflecting amorphous structures of the blends, while tensile strength at the yield point increased linearly with increasing PEN content.     

结晶PMMA/SAN共混体系的相容性和PMMA结晶行为的NMR研究

我们用固体NMR方法研究了SAN与结晶PMMA的相容性,并提出了可能的相容性机理;同时我们也研究了PMMA的结晶行为,发现它不同于SMA/PMMA中只存在少量结晶区的PMMA的行为.SAN/结晶PMMA是部分相容的体系,由于PMMA中的羰基与SAN中的苯基的相互吸引才导致共混物相容,且SAN只与无定形PMMA区相容,结晶区可用NMR方法检测到,这说明SAN/PMMA的相容性比SMA/PMMA差,主要原因是SAN与PMMA的相互作用弱于SMA与PMMA的相互作用.交替共聚利于相容.     

TIME-RESOLVED SAXS/WAXS STUDY OF PHASE BEHAVIOR AND CRYSTALLIZATION IN POLYMER BLENDS

Real-time SAXS and WAXS patterns have been simultaneously obtained during isothermal melt-crystallization of blends of low-molecular-weight poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA). The analysis of results shows that the originally homogeneous, single-phase polymer blend separates into two phases. The PMMA molecules diffuse from the blend and form completely segregated regions while PEO starts to crystallize. The first and dominating effect at the beginning of crystallization is the formation of unstable lamellae of nonintegrally folded chains (NIF). The real-time crystallinity and density of the PEO crystalline phase in absolute units were obtained from the time-resolved SAXS/WAXS results. The structure development proceeds in two steps. A very fast evolution of PEO crystals from the melt starts to crystallize in disordered NIF lamellae with thick amorphous interlayers and with a lower density of crystalline phase. The steep growth of crystallinity and crystalline density mean quick thickening of crystalline part of lamellae and improvement of their crystalline structure. In the second step, the structure of the crystalline phase gradually improves and crystallinity grows very slowly. The recrystallization of NIF lamellae into extended chain lamellae (EC) and lamellae with once folded chains (1F) proceeds during both stages of crystallization.     

Miscibility, Crystallization, and Rheological Behavior of Solution Casting Poly(3-hydroxybutyrate)/poly(ethylene succinate) Blends Probed by Differential Scanning Calorimetry, Rheology, and Optical Microscope Techniques

应用差示扫描量热、流变及偏光显微镜等方法研究了聚3-羟基丁酸酯/聚丁二酸乙二醇酯(PHB/PES)共混体系的相容性、结晶和流变行为．相图显示该共混体系有两个玻璃化转变,但PHB的熔点随其含量的减少而降低,这个结果证明该共混体系是部分相容的,同时应用偏光显微镜观察体系结晶形态的发展证实了这个结论．依赖于结晶温度和组成,PHB和PES能同时结晶,也能分步结晶,且PHB的球晶生长速率随PES含量的增加而增大．对于部分相容的聚合物共混体系,共混组成对球晶生长速率的影响也做了详细地讨论．     

聚对苯二甲酸丁二醇酯/聚(对苯二甲酸丁二醇酯-e-己内酯)二元结晶共混体系的相容性和结晶行为

聚对苯二甲酸丁二醇酯(PBT)/聚(对苯二甲酸丁二醇酯-e-己内酯)(PBT-PCl)是一个新制备的具有分子间排斥相互作用的A/AxB1?x型两元结晶共混体系. 根据两元平均场模型,报道对苯二甲酸丁二醇酯(BT)与"-己内酯(CL)结构单元的相互作用参数为0.305. DSC研究发现,此共混物呈现了与典型的共聚物/均聚物共混物不同的结晶特征. PBT-PCL影响PBT链的活动力和晶片堆积;同时PBT-PCL的结晶受到先期结晶的PBT晶粒的阻滞. 尽管拥有相同的BT单元,共混的两组分在组成变化范围内仍没有形     

Miscibility,Morphology, and Thermal Properties of Poly(Trimethylene Terephthalate)/Polycarbonate

Abstract

Poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends were prepared by melt blending and rapid quenching in ice water. The miscibility and thermal properties were investigated using differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA). The blend's morphologies were investigated using scanning and transmission electron microscopies. Both DSC and DMA results suggested that PTT and PC were very limited, partially miscible pairs. The melting point, melt crystallization, and cold crystallization exotherms in the blends of PTT were depressed by the presence and amount of PC. When the PC content was <50 wt%, PC spherical particles were found to distribute evenly in the PTT matrix; at 50–60 wt%, the two‐phase structures were close to being bicontinuous. At higher PC content, PTT formed a string‐like texture in the PC matrix. The PTT spherulitic morphologies in PTT/PC blends were found to be very sensitive to PC and PC content. When the PC content was ≥60 wt%, the blends crystallized as an agglomeration of tiny PTT crystals.     

Transmission Electron Microscopic Investigation of the Morphology of High-Speed Spun Poly(Ethylene Terephthalate) Fibers

Permanganic etching was performed on high-speed spun (HSS) and regular fibers of poly(ethylene terephthalate) (PET), and their surface morphologies were investigated via the two-stage carbon replica method using a transmission electron microscope (TEM). The HSS PET fibers, with disordered amorphous regions, showed peculiar surface morphology; many small warts corresponding to the pits of etched disordered amorphous regions were observed. Such unevenness, however, was hardly observed on the surface of the permanganic-etched regular PET fibers, with well-oriented amorphous regions, or on the surface of alkali-etched HSS PET fibers. The permanganic etchant removed the disordered amorphous regions more preferentially compared with the alkali etchant.     

DYNAMICS IN POLY(OXYMETHYLENE) AND POLY(OXYMETHYLENE-CO-OXYETHYLENE) AS STUDIED VIA A COMBINED CREEP RATE SPECTROSCOPY/DIFFERENTIAL SCANNING CALORIMETRY APPROACH

The peculiarities and kinetics of segmental dynamics in a few semi-crystalline poly(oxymethylene) (POM) samples and in poly(oxymethylene-co-oxyethylene) with 1.5% ethylene oxide units were studied over the temperature range from 110 to 430K. Differential scanning calorimetry (DSC) and laser-interferometric creep rate spectroscopy (CRS) were used. The latter was operated under uniaxial tension or compression. A number of dynamic anomalies were observed. These included a suppressed glass transition (T _g) with its transformation into segmental relaxations below and above T _g, and a pronounced dynamic heterogeneity, with the dispersion of activation energies of segmental motion ranging from 60 to 500 kJ mol^?1. Formation of anomalous long folds in POM and the copolymer structure is assumed from DSC data, indicating a predominant contribution of “straightened out” tie chains to the structure of disordered regions in these isotropic polymers. Discrete high-resolution CRS analysis showed that numerous peaks (separate types of segmental motion) constituted dynamics in the interlamellar layers of the polymers under study. Considerable influence of comonomer or small additives, or preliminary treatments (quenching, small pre-straining) on discrete CR spectra was observed and are discussed in the text. All the anomalies observed could be treated in terms of the concept of the common segmental nature of α and β relaxations in flexible-chain polymers; as the breakdown of intermolecular motional cooperativity due to nanoscale confinement effect, and as a different constraining influence of crystallites on dynamics in the intercrystalline layers.     

具有分子取向的拉伸高聚物(PET)中13C-NMR化学位移值的估算

本文从已知的聚对苯二甲酸乙二醇酯(PET)的X-射线原子坐标和化学位移张量主值出发,计算了拉伸的PET样品,相对于外磁场不同放置方位下的¹³C-NMR谱峰的化学位移值,很好地解释了实验结果,并得到了拉伸条件下,高聚物中分于取向的信息。     

STUDIES ON THE RELATIONSHIPS BETWEEN THE STRUCTURE AND THE LOCALIZED ENERGY STATES OF POLY (ETHYLENE TEREPHTHALATE) ELECTRETS

A series of poly(ethytene terephthalate) (PET) films with different degrees of planar orientation [Δ(xy)z], crystallinity (X_c) and molecular weights were prepared by drawing biaxially, annealing at 110℃ and γ-imadiation of 0.5-4MGy. The peaks of localized energy states were separated from the detrapping cur-rent curves by means of poling temperature scanning method of themally stimulated current. The depth of localized energy levels enlarged with the rise of Δ(xy)z, X_c and γ-inadiation dose. The kinds of structural defects increased because of the changes of orientation structure of chains, crystalline structure and molecular chain structure, which caused the number of localized states to increase from 2 to 6 and the distribution width of the depth of localized levels to broaden.     

具有分子取向的拉伸高聚物(PET)中~(13)C—NMR化学位移值的估算

本文从已知的聚对苯二甲酸乙二醇酯(PET)的X-射线原子坐标和化学位移张量主值出发,计算了拉伸的PET样品,相对于外磁场不同放置方位下的~(13)C-NMR谱峰的化学位移值,很好地解释了实验结果,并得到了拉伸条件下,高聚物中分于取向的信息。     

Exclusive attributes of undoped poly (ethylene terephthalate) for alpha particle detection

Poly (ethylene terephthalate) (PET) is available worldwide and has a broad range of applications. However, its basic properties as a scintillation material that is undoped with fluorescent guest molecules are not completely known. Here, we optically characterise undoped PET for use in radiation detection. Light absorption is primarily below 350 nm, with an emission maximum at 385 nm. An effective refractive index, determined from the emission spectrum and the wavelength dependence of the refractive index, is 1.62, which is greater than that for the sodium D line (N_D = 1.57). The density of PET is 1.33 g/cm³, and its stopping power for 1-MeV electrons is 1.72 MeV cm²/g. Distinct peaks generated by alpha particles from ²¹⁰Pb and ²⁴¹Am radioactive sources appear in PET light-yield distributions. The PET response to 5-6-MeV alpha particles is approximately one-eighth that for electrons. These results demonstrate that undoped PET has special attributes for alpha particle detection. This knowledge will enable better performance of radiation equipment based on PET and its blends with other aromatic ring polymers.     

On the molecular mechanism of the crystal transformation (tetragonal-hexagonal) in polybutene-1

The phase transformation from the tetragonal to the hexagonal crystal modification in highly oriented lamellae of poly-butene-1 has been followed by transmission electron microscopy (TEM). It is found that the reaction-controlling step is the nucleation process. No lattice orientation relationship (besides the [001]-direction, which is parallel in both crystal modifications) exists between non-transformed and transformed crystals. The nucleation is strongly enhanced by thermal or external stresses. Crystal growth, nucleated by external stresses, was observed at temperatures as low as — 150°C. The molecular mechanisms of the transformation are discussed.     

Electroless plating of nickel–phosphorous on surface-modified poly(ethylene terephthalate) films

Chemical surface preparation for Ni–P electroless metallization of poly(ethylene terephthalate) (PET) films without using Chromium-based chemicals, was studied. The applicability of this method was verified by a subsequent metallization process. Thermal analysis was conducted to observe the main thermal transitions and stability of the polymer and metallized films. Contact angle analysis was performed to assess the surface hydrophilicity so as to optimize the substrate preparation process. X-ray diffraction, EDAX and SEM analysis were used to understand the composition and morphology of the polymeric substrate and Ni–P coat growing process. Adherence strength, contact sheet resistivity and optical diffuse reflection were measured on the metallized films. The time of chemical etching affects the polymer surface hydrophilicity, polymer/metal adherence strength, surface resistance and optical diffuse reflection, while Ni coating morphology is controlled by the pH of the electroless bath. High wettability of the polymer surface, adherence strength of 800 N cm⁻², high optical diffuse reflection and low surface resistivity of the Ni coating, were found for films etched for 60 min. Metallizations performed at pH 7.5 produce Ni–P coatings with 12.0 wt.% phosphorous content, which were amorphous and flexible. The contact sheet resistivity of the plated films is sensitive to roughness variations of the substrate. The method proposed in this work allows the production of metallized films appropriate for the fabrication of flexible circuits.