超硬铝合金LC9的超塑性效应

本文采用了简单的预处理工艺,开发超硬铝合金LC9的超塑性;并以等温拉伸试验和等温压缩试验相互对照、相互补充的试验方法,考察LC9的超塑性唯象学特性。结果表明,该合金的最高延伸率可达220％,m值为0.4,流动应力最低可达10MPa;最佳超塑性变形条件为:温度420℃,应变速率1.67×10~(-3)s~(-1)。     

论轴的疲劳计算判据

本文综合了转轴疲劳强度校核中影响计算安全系数的各项因素,从而推导出弯扭合成强度条件满足后无需进行疲劳强度计算的判据。同时还给出判断危险截面准确的定量标准。     

钢筋混凝土构件抗剪强度研究的新进展

本文扼要地阐述了近十几年来我国在钢筋混凝土构件抗剪强度研究方面所取得的新进展,包括:剪跨比和间接加载对抗剪强度的影响,连续粱、约束粱、预应力混凝土粱、弯筋粱、压杆和拉杆的抗剪强度等。     

明胶蛋白质基可降解塑料薄膜的研究

将分散均匀的明胶、无机填料和复合增塑剂的水溶液用流延法成膜,制得了蛋白质基可降解塑料薄膜。用拉伸实验、吸水实验和降解实验表征了蛋白质基可降解塑料薄膜的性能。结果表明:薄膜的拉伸强度和断裂伸长率随增塑剂用量的增加而增加,随无机填料用量的增加而减小;薄膜的耐水性随增塑剂用量的增加而变差;蛋白质基塑料薄膜具有生物降解性,在20天内降解度为10%左右。     

高熔体强度聚丙烯的生产及应用进展

高熔体强度聚丙烯(HMSPP)是聚丙烯的一种重要改性产品,具有广泛的用途。本文综述了高熔体强度聚丙烯的性能特点、用途、制备方法,以及国内外研究和开发情况。     

Effect of iron content on the wear behavior and adhesion strength of TiC–Fe nanocomposite coatings on low carbon steel produced by air plasma spray

In this study, the effect of Fe content on the abrasion behavior of TiC–Fe nanocomposite coatings applied on the CK45 steel substrate by air plasma spray method was investigated. For this purpose, milled TiC powder was prepared at 1, 2, 3 and 4 h milled TiC powder for 4 h was selected as the suitable sample. In the next step, a suitable sample mixture with different iron powder concentrations of 5, 10, 15, 20 and 25% was prepared by mechanical milling. The granulated mixture was applied to the substrate using air plasma spray technique. Microstructural and phase analyzes were performed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). According to the results of Williamson-Hall calculations, the TiC crystallites' size decreased by 49 nm–29 nm, and network strain reached 0.16% by increasing milling time from 1 h to 4 h. Studies have shown that the coatings contain titanium carbide, iron oxide, and titanium oxide, with the number of phases formed depending on the amount of iron in the chemical composition. Investigation of the tribological properties of the coating layer showed that with increased iron content in the coating, the wear resistance of the samples is reduced. Hardness tests on coatings indicate that adding iron to nanocomposite from 5 to 25% reduces hardness from 1025 to 699 Hv. It can be argued that a slight increase in the adhesion strength of the coating to the substrate is due to increased wettability because of the formation of molten iron in the coating.     

聚醋酸乙烯酯共聚乳液的改性研究

以醋酸乙烯酯为原料,聚乙烯醇为保护胶体,丙烯酸、丙烯酸丁酯为改性单体,研究了单体配比、引发剂、乳化剂用量和温度对醋酸乙烯酯共聚乳液性能的影响。研究表明,当丙烯酸丁酯与醋酸乙烯酯的质量比为12/30,引发剂的质量分数为0.15%,乳化剂的质量分数为0.3%,在反应温度为75℃时,可制得性能优异的聚醋酸乙烯酯胶粘剂,其T型剥离强度和耐水性能可达105 N/25mm和67 N/25mm。     

Effects of spinning speed and heat treatment on the mechanical properties and biodegradability of poly(lactic acid) fibers

We undertook this study to suggest the optimal spinning process conditions that provide a proper range of tenacity and biodegradability in textile fibers. The effect of melt‐spinning speed and heat treatment on the mechanical properties and biodegradability of poly(lactic acid) (PLA) fibers were investigated. PLA was spun at a high spinning speed of 2000–4000 m/min, and each specimen was heat‐treated. Mechanical properties were estimated by measurement of the breaking stress, and the degree of crystallinity was evaluated with wide‐angle X‐ray scattering. Biodegradability was estimated from the decreases in breaking stress, weight loss, and degree of crystallinity after soil burial. The results of the experiment reveal that heat treatment of the PLA fibers increased the breaking stress and crystallinity. With increasing spinning speed, breaking stress and crystallinity also increased. An increase in spinning speed was more effective than an increase in heat treatment for enhancing the breaking stress within the range of this study. From the soil burial test, it was revealed that an increase in spinning speed and heat treatment decreased the biodegradability of the fibers. X‐ray analysis of the soil‐buried fibers showed that fibers with higher crystallinities began to degrade more slowly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3099–3104, 2007     

A novel PEO-based composite polymer electrolyte with absorptive glass mat for Li-ion batteries

A novel PEO (polyethylene oxide)-based composite polymer electrolyte (CPE) using absorptive glass mat (AGM) as filler was prepared and characterized. Scanning electronic micrograph (SEM) images showed that the addition of Li salt and modified AGM may improve the surface morphology of CPE. The results of Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeters (DSC) indicated that the inclusion of LiClO₄ salt and the addition of AGM filler can reduce the crystallinity of PEO. It was concluded that the addition of AGM plays two roles in PEO-based CPEs, namely, interruption of the PEO recrystallization and reinforcement of CPEs, accordingly enhancing room temperature ionic conductivity of CPEs and improving its mechanical strength and electrochemical stability at high temperatures.     

Broadband dielectric spectroscopy of nanostructured maleated polypropylene/polycarbonate blends prepared by in situ polymerization and compatibilization

The miscibility and molecular dynamics of nanostructured maleated polypropylene (mPP)/polycarbonate (PC) blends prepared by in situ polymerization of macrocyclic carbonates with polypropylene modified with 0.5 wt% of maleic anhydride-reactive groups were investigated over a wide range of frequencies (10⁻²-0.5 × 10⁷ Hz) at different constant temperatures using broadband dielectric spectroscopy and scanning transmission electron microscope (STEM). The molecular dynamics of the glass relaxation process of the blend (α-relaxation process) appeared at a lower temperature range compared with that of the pure PC. This shift in the molecular relaxation process is attributed to the partial miscibility of the two polymer components in the blends as previously confirmed by the morphology via STEM. Nanoscale morphologies with average domain diameters as small as 50 nm were obtained for the different blend compositions studied. The STEM photographs show that the graft mPP-g-PC prefers to locate at the interfaces as previously reported. The relaxation spectrum of pure PC and mPP/PC blends was resolved into α- and β-relaxation processes using the Havriliak-Negami equation and ionic conductivity. The dielectric relaxation parameters, such as relaxation peak broadness, maximum frequency, f_max, and dielectric strength, Δ? (for the α- and β-relaxation processes), were found to be blend composition dependent. The kinetics of the α-relaxation processes of the blends were well described by Vogel-Fulcher-Tammann (VFT) equation. The local process of PC was resolved into two relaxation processes β₁ and β₂, associated with the carbonyl groups' motion and the combined motions of carbonyl and phenylene groups, respectively. Only β₂ shifted to lower frequency in the blend while β₁ was relatively not affected by blending. The electric modulus of the blends was used to get a sufficient resolution of the different relaxation processes in the samples, i.e., α-, β-relaxation processes, ionic conductivity, and interfacial polarization. In addition, the blending method used was found to increase the d.c. conductivity without affecting the charge carrier transport mechanism, making it possible to develop novel polymer blends with tunable dielectric properties and morphology from existing polymers.