Synthesis and properties of polyesterimides and their isomers

A new type of polyesterimide has been synthesized by polycondensation of a dicarboxylic acid containing an internal imide group with ethylene glycol. The dicarboxylic acid was synthesized by reacting aminobenzoic acid with trimellitic acid anhydride in N, N-dimethylformamide solution. Three isomeric (ortho, meta, and para) polyesterimides were prepared from the respective isomer of the dicarboxylic acid. The solubility characteristics, solubility parameters, solution viscosity behavior, density, crystallinity, and thermal properties of these three isomeric polyesterimides were discussed. Some generalizations about structure–property relationship in polyesterimides were also made. It was found that while the ortho and meta isomers of the polyesterimide are amorphous, the para isomer tends to be somewhat crystalline and consequently less soluble, even in polar solvents. The thermal behavior of the meta isomer resembles closely that of the para isomer. The thermal stability of these isomers follows the order para ≥ meta > ortho.     

Investigation in thermal endurance of polyesterimide used in electrical machines

The purpose of this investigation is to evaluate thermal lifetime of polyesterimide using Weibull statistics. Thermal aging was performed on twisted pair specimens of copper wire insulated by a polyesterimide layer. The study shows that breakdown voltage varies versus aging time. Its increase is allotted to a crosslinking inducing a diminution of mean‐free path of charge carriers leading thereby to a mobility decrease, whereas its decrease is attributed to the viscosity diminution expressing a weakening of molecular bonds and a mobility increase of charge carriers. Shape parameter changes in function of aging time. Its increase is ascribed to an arrangement of the molecular structure, whereas its decrease is due to an augmentation in the size of defects. The thermal endurance graph is a straight line indicating that the degradation is governed by a first‐order chemical reaction. Activation energy and temperature index were determined. The degradation is governed by the dissolution of copper into the polymer and accelerates its degradation occurring at the polyesterimide–copper interface. Oxygen can diffuse into the insulation and attack copper resulting in the formation of copper oxide. The degradation is caused by the scission of imide and ester bonds. The process is followed by a change in color and a presence of cracks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal decomposition kinetics of thermotropic liquid crystalline polyesterimides

We investigated the thermal decomposition behavior of three groups of polyesterimides that had been synthesized from different compositions of monomers that were added in different. We characterized these polymers with thermogravimetric analysis (TGA) and calculated the apparent activation energy (E_a) associated with the thermal decomposition process by the Ozawa method. The results showed that the E_a of the polyesterimides was correlated with the length of the methylene spacer and the content of the 4,4′‐dihydroxybenzophenone monomer. The polyesterimide with four methylene spacers in the main chain had a higher E_a than that with six methylene spacers. The polyesterimide with a higher 4,4′‐dihydroxybenzophenone content provided better thermal stability. The E_a of the polyesterimides also depended on the sequence in which the monomers were added during the copolycondensation process. The E_a of these polyesterimides followed the order: p‐hydroxybenzoic acid added first > p‐hydroxybenzoic acid mixed 4,4′‐dihydroxybenzophenone adding > 4,4′‐dihydroxybenzophenone added first. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2467–2472, 2005     

超支化聚酯改性聚酯亚胺不饱和树脂

合成了一种带柔性链的芳醚型聚酯亚胺不饱和树脂(AEPUR),采用红外光谱技术对其结构进行了表征。研究了端羧基超支化聚酯(HTM-4)对AEPUR/环氧树脂E-44共混体系的弯曲性能、冲击性能和热性能的影响。结果表明,HTM-4能显著提高AEPUR/E44共混物的冲击强度和弯曲性能,表现出明显的增韧/增强作用,体系的热分解温度变化不大,残碳率明显增加。     

Tribological properties of polyesterimide and its composites

Polyesterimide (PEI) and phenol formaldehyde (PF) samples were synthesized, and composites of the two polymers, as well as composites with carbon, were prepared. Using a pinon-disc machine, the friction and wear properties of the following samples were studied in the load range of two to eight bars:

• Phenolformaldehyde vs. steel
• Phenol formaldehyde cured with hexamethylenetetramine vs. steel
• Polyesterimide vs steel
• Polyesterimide and carbon composite vs steel
• Phenol formaldehyde vs polyesterimide
• Phenol formaldehyde and polyesterimide composite vs. phenol formaldehyde
• Phenol formaldehyde and polyesterimide composite vs. steel.

The data obtained from these experiments were compared with literature data on poly(tetrafluoroethylene) and nylon, conventionally used for tribological applications. It is seen that, in terms of thermal stability, friction, and wear, PEI and PF are promising for tribological applications.     

F级聚酯酰亚胺浸渍漆组成分析

通过光谱和化学方法对聚酯酰亚胺浸渍漆结构和组成进行了分析,为合成提供了有价值的数据。分析结果为：该聚酯酰亚胺由对苯二甲酸、偏苯三甲酸、４,４’－二氨基二苯甲烷和三（β－羟乙基）异氰尿酸合成;溶剂为混合甲酚和乙二醇单乙基醚;催化剂为含钛的化合物     

Thermal transition behaviors in a liquid crystalline polyesterimide

The crystallization and melting behaviors of the polyesterimide, derived from N,N′-hexane-1,6-diylbis(trimellitimides), 4,4′-dihydroxybenzophenone and p-hydroxybenzoic acid, were investigated by using polarized light microscopy (PLM), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The nematic texture of the polyesterimide was observed on raising temperature to 265 °C, and the nematic phase was found to convert to isotropic melt beginning from about 300 °C, the ordered nematic micro-domains still surviving after 320 °C. Isothermal crystallization of the samples was performed at 180 °C after heating samples at various temperatures in the range of 265-360 °C, and a completed crystallization peak can appear on DSC curves up to the heating temperature of 360 °C in the presence of the nematic phase and the ordered nematic micro-domains. Non-isothermal crystallization of the samples at different cooling rate was carried out, and the melting of the resulting crystals exhibits double endotherms. It is indicated that a fast crystallization in the nematic phase forms relatively more ordered crystals, which melt at higher temperature, and a slow crystallization in the isotropic phase or in the biphasic melt produces poor crystals, which melt at lower temperature. The crystallized polyesterimide was annealed, which has a minor effect on the high-melting peak but leads to a continual shifting of the low-melting peak to higher temperature with increasing annealing temperature or annealing time. WAXD patterns indicated that the structural transform was not found during annealing process.     

Weibull statistics in electrical aging of polyesterimide under AC voltage

This article is aimed at the investigation of electrical aging of polyesterimide under AC voltage using Weibull statistical analysis. It's shown that the time to breakdown characteristic (V–t) of polyesterimide includes two zones (segments of straight line). The first zone characterizes a statistical dispersion of the intrinsic defects of material. The second zone expresses the real aging of polymer. The variation of the slope of lifetime curve is attributed to the change in the degradation mechanism. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

N-(carboxymethyl) trimellitimide–based polyesterimides as film formers for air-drying protective coatings

N-(carboxymethyl) trimellitimide, the imidodicarboxylic acid, was prepared by the reaction between trimellitic anhydride and glycine. This was subsequently condensed in N-methyl-2-pyrrolidone with the alcoholysis products obtained from linseed oil and glycerine to get different oil length polyesterimide resins. The drying characteristics of the resins and the physicochemical properties of the clear and the iron oxide pigmented coatings were evaluated. The results indicate that these materials form a promising class of film—formers for coatings of good durability and protective properties.     

聚酯酰亚胺及其应用

本文介绍了聚酯酰亚胺树脂的基本合成方法。重点介绍了其在柔性印刷电路领域的应用。以及在液晶显示、新型绝缘电线涂料、太阳能电池与感光树脂中的应用。阐明为了适应高速发展的现代经济与科技发展的需要,信息记录材料与现代影像技术领域应加速对上游产品中相关基础材料与技术的研发与应用。     

Thermal degradation of polymers. Part I. Thermogravimetric and differential thermal analysis studies of atactic poly-m-aminostyrene and related polymers

Thermogravimetric and differential thermal analysis have been employed to study the thermal degradation patterns of poly-m-aminostyrenes and poly-m-acetamidostyrenes of different molecular weights and also the corresponding 2:1 copolymers with styrene. The thermal degradation routes have also been compared and contrasted with that of polystyrene. Experiments have been carried out in static air and dynamic nitrogen, and the different behavior exhibited by these polymers has been reconciled in terms of their differing structures and different mechanisms for pyrolytic degradation.     

Kinetic model for thermal dehydrochlorination of poly(vinyl chloride)

In this paper, a novel method for calculating degradation kinetics is presented. The method has been applied to the thermal dehydrochlorination of two different samples of PVC. It has been observed that this dehydrochlorination is complex and involves two different processes. A model that accounts for the entire dehydrochlorination is proposed. This model involves nucleation and growth and diffusion controlled mechanisms. The kinetic parameters are obtained from linear heating rate, isothermal and sample controlled thermal analysis experiments. Kinetic results obtained from the macroscopic thermal analysis measurements demonstrate the correlation between the kinetics of the thermal dehydrochlorination of PVC and the structure of this macromolecule.     

Universal calibration for thermal field-flow fractionation

Experiments have shown that the thermal diffusion coefficient of a polymer is independent of the sample's molecular weight. According to the relationship between the ordinary diffusion coefficient and polymer molecular weight, a universal calibration method for thermal field-flow fractionation (FFF) has been created. This method has been examined experimentally by three polymers of different chemical composition with different molecular weight in three organic solvents. It is shown that this method is useful both in terms of calibrating a thermal FFF system with some readily available polymer standard, for use with unknown samples of known thermal diffusivity, and in terms of determining the thermal diffusion coefficient of the unknown sample under conditions where its molecular weight can be measured by other methods.     

二维氮化铝材料传热性能的模拟研究

二维氮化铝材料是一种新型Ⅲ-Ⅴ族二维材料,具有与石墨烯相似的分子结构和材料性能,受到了广泛的关注,然而其导热性能尚未被充分探讨。应用分子动力学模拟的方法研究了单层二维氮化铝在不同温度的热稳定性和导热性能,并分析了其声子频谱。结果表明,单层二维氮化铝材料可以在极高温度（3500 K）下保持结构稳定性,同时在常温情况热导率可达264.2 W·m^-1·K^-1;在500 K以上温度时,声子色散现象使得该材料热导率明显降低。为二维氮化铝材料导热过程的调控和高温导热材料的应用提供了理论指导。     

Study on the Thermal Stability and Stabilization Mechanism of a Novel Thermal Stabilizer for Rigid Poly (Vinyl Chloride)

A novel thermal stabilizer for rigid poly (vinyl chloride) has been examined. Its high stabilizing efficiency is detected by the extent of discoloration and the mass loss rate of the degraded samples when compared with some of reference stabilizers. A higher stabilizing efficiency is produced as the novel thermal stabilizer is mixed with different co-stabilizers. The study results for thermo oxidative stability of the degraded samples with novel thermal stabilizer have shown that the novel thermal stabilizer can prevent or delay the thermal oxidative degradation of PVC. A probable stabilization mechanism for the novel thermal stabilizer has been proposed.     

Comparison of symmetric and asymmetric energy conversion cycles in PZT plates

The pyroelectric response dependence of direct energy conversion on thermal cycling conditions has been studied using PZT (97/3) plates. A comparison has been made between different thermal cycles resulting in symmetric or asymmetric voltage outputs. We have found that the latter give better results.     

Thermophysical properties of densified pitch based carbon/carbon materials—I. Unidirectional composites

Unidirectional carbon/carbon composites were developed using high-pressure impregnation/carbonization technique with PAN and pitch based carbon fibers of varying microstructure as reinforcements and different types of pitches as matrix precursors. The composites have been given final heat treatment to 2500-2700 °C. Microstructure of these composites has been evaluated using scanning electron microscope and polarized light optical microscope. Thermophysical properties, i.e., thermal conductivity, coefficient of thermal expansion and specific heat have been evaluated. It is found that the type of fibers and matrix present in the composites influences the absorption (specific heat) and transmission (conductivity) of thermal energy. The temperature dependence of thermal diffusion, specific heat, thermal conductivity and coefficient of thermal expansion has been studied and correlated with microstructure of carbon/carbon composites.     

ZrO_2相变设计改善耐火材料抗热震性的设想

ＺｒＯ２的马氏体相变是陶瓷学界广泛研究的重要课题之一,并在结构陶瓷的增韧和强化中得到成功应用。耐火材料一般在热循环条件下服役,与常温下使用的结构陶瓷不同,其抗热震性是一个重要的性能指标。本文根据ＺｒＯ２的相变特征提出了利用ＺｒＯ２相变改善锆质耐火材料抗热震性的设想。     

Effect of the polymer shell in imidazole microencapsulation by solvent evaporation method

In this paper, the microencapsulation of imidazole derivatives (1-methylimidazole and 2-phenylimidazole, 1-MIm and 2-PhIm, respectively) as core materials into polymeric shells has been studied. Imidazoles are used as latent curing agents for epoxy resins with application for example in the manufacturing of electronic devices. Microencapsulation of imidazoles has been carried out by solvent evaporation and different experimental parameters (e.g. type of polymer for the shell) have been analyzed and the final properties of the capsules obtained (particle size, morphology or thermal properties). Characterization has been carried out using differential scanning calorimetry (DSC) and thermal gravimetry analysis (TGA) for the thermal properties and determination of the imidazole content (%) into the capsules, and scanning electron microscopy (SEM) for the morphological characterization. Using infrared spectroscopy (IR), chemical characterization of the capsules has been carried out, confirming the presence of both components imidazole and polymer in the case of the microcapsules prepared with 2-PhIm. The reaction mechanism of the curing process of a standard epoxy resin with the different microencapsulated imidazoles has been also studied. Results have shown that the thermal stability of the capsules and the weight losing rate of the imidazole in the capsules depend on the polymer used for the shell.