Dynamic Mechanical Behavior of PP/PET/MAPP Blends Filled with Glass Beads

PP/PET/MAPP blends have been filled with 50 wt% of glass beads. The orientation of the PP crystalline phase, the crystallization behavior and the dynamic mechanical response of these materials have been analyzed. The dynamic mechanical response is strongly affected by the presence of the glass beads, being possible to detect the effect of PET and MAPP on the storage modulus and loss factor values. Moreover, the alpha relaxation of the composites is visibly affected by thermal treatments.     

Dynamic mechanical properties of epoxy/novolac system modified with reactive liquid rubber and carbon filler

This paper reports on the work carried out to evaluate the frequency dependent viscoelastic properties of epoxy/novolac compositons modified with a liquid reactive rubber and carbon filler. For epoxy systems modified with elastomer, three typical transitions were observed: the α-relaxation deeply related to the glass transition of epoxy, the β-transition of epoxy, and the glass transition of rubber appeared near to the β-relaxation of epoxy resin. Considering an Arrhenius equation, the activation energies of β-relaxation were estimated. In the region of glass transition and rubbery state the temperature dependence of the shift factor (α_T) was determined through Williams-Landel-Ferry (WLF) equation.     

Thermal Degradation of Tetrafunctional/Phenol Novalac Epoxy Mixture Cured with a Diamine

The effect of thermal degradation on the mechanical behaviour of a system containing both tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether (EPN) resins, cured with 4,4′-diaminodiphenylsulphone (DDS) has been studied using dynamic mechanical analysis (DMA) and tensile tests. Different curing paths using the isothermal time-temperature-transformation (TTT) diagram for this system were designed, obtaining thermosetting materials with different conversions. The influences of the degree of cure and of the aging temperature were also studied. The results showed different trends in the dynamic mechanical properties and an increase in the stiffness of the material with increasing aging time. Changes were faster and more intense with the higher temperature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Simulation of Electrical and Thermal Behavior of Poly(propylene) / Carbon Filler Conductive Polymer Composites

PP-carbon CPC show interesting thermo-electrical properties, smooth resistivity increase with temperature up to 150°C and consequently high power dissipation on a wide temperature range. The addition of short carbon fibers to PP already formulated with carbon black increases sharply the electrical conductivity of the CPC but does not have much influence on thermal conductivity as it could have been expected from the favorable aspect ratio of the fibers. The simulations of the thermo-electrical behavior of the CPC under tension put into evidence a temperature gradient at high heat flux due to the low thermal conductivity, which may damage the material itself.     

Thermal conductivity and properties of cyanate Ester/nanodiamond composites

The aim of this study was to improve thermal conductivity, thermal stability, and mechanical properties of bisphenol A dicyanate ester with the addition of nanodiamond. Cyanate ester/nanodiamond composites containing various ratios of nanodiamond were prepared. Thermal stability and thermal conductivity of the samples were evaluated by thermogravimetric analysis, differential scanning calorimetry, and laser flash method, respectively. The samples were characterized with the analysis such as gel content, water absorption capacity, and stress–strain test. Hydrophobicity of the samples was determined by contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy. The obtained results prove that the cyanate ester/nanodiamond composites have good thermal and mechanical properties and can be used in many applications such as the electronic devices, materials engineering, and other emergent. Copyright © 2014 John Wiley & Sons, Ltd.     

Al2O3/PDMS复合材料热传导的分子动力学模拟

采用分子动力学模拟方法研究了Al2O3/聚甲基二硅氧烷(PDMS)复合材料在300 K时的传热行为,通过分析热传导、温度梯度以及导热增强等理论数据,讨论了不同半径以及不同浓度的Al2O3填料粒子对PDMS传热的影响.结果 表明随着体积分数的增大,Al2O3/PDMS复合材料的热传导先减小后增加.并且当Al2O3填充粒子...     

Changes in the Mechanical Properties and Thermal Behaviour of LDPE in Response to Accelerated Thermal Aging

The accelerated thermal degradation of low-density polyethylene (LDPE) was studied in air at atmospheric pressure and temperatures of 70, 80, 90 and 100°C. The changes in elongation at break, traction resistance and density as a result of accelerated thermooxidative degradation were followed. Thermal analysis curves (TG, DTG and DTA) of non-aged and thermally aged LDPE were recorded, and the thermal analysis results were compared with those relating to the variations in the elongation at break, the traction resistance and the density as a consequence of accelerated thermal aging. This revised version was published online in July 2006 with corrections to the Cover Date.     

差示扫描量热法研究丙烯腈-衣康酸共聚物的热稳定化

应用差示扫描量热法(DSC)研究了衣康酸(IA)、气氛、升温速率对丙烯腈-衣康酸共聚物[P(AN-IA)]热稳定化的影响. IA能够显著降低放热峰起始温度、放热量和放热速率. P(AN-IA)共聚物的放热峰起始温度受气氛影响不大, 却随着IA含量的增加而明显降低, 表明在热稳定化过程中它可能首先以离子机理发生氰基环化反应, 再发生氧化反应. 提高升温速率会导致放热峰向高温偏移和放热速率加快. 采用Kissinger法计算了不同IA含量共聚物的热稳定化活化能, 结果表明IA可以有效降低活化能.     

Thermal stability and dynamic mechanical thermal analysis of epoxy thermosets possessing N,N′-disubstituted pyromellitimide units

Abstract

In this work, three epoxy resins including diglycidyl ethers of N,N′-bis(2-hydroxyethyl)pyromellitimide (DIDGE), bisphenol-A (BADGE), and polyethylene glycol (PEDGE) were isothermally cured by an amine curing agent possessing N,N′-disubstituted pyromellitimide units (denoted by DIDAM). DIDGE resin was synthesized from the reaction of N,N′-bis(2-hydroxyethyl)pyromellitimide with an excess of epichlorohydrin. Also, DIDAM curing agent was prepared from the reaction of pyromellitic dianhydride with an excess of ethylene diamine. Completion of the isothermal curing processes was approved by both Fourier transform-infrared spectroscopy and non-isothermal differential scanning calorimetry (DSC). The DSC traces showed only the phase transitions related to the thermal degradation of the resulting thermosets. According to the thermogravimetric analyses, the DIDGE/DIDAM thermoset showed higher thermal stability at temperatures above 425?°C than the other two thermosets. While BADGE/DIDAM and PEDGE/DIDAM thermosets showed about 70% weight loss in the thermal range of 400–850?°C, DIDGE/DIDAM thermoset was encountered with only about 40% weight loss. The glass transition temperatures (T_g ) of the resulting thermosets were determined using tan δ vs temperature plots obtained from dynamic mechanical thermal analysis. The T_g values of BADGE/DIDAM, DIDGE/DIDAM, and PEDGE/DIDAM thermosets were found to be 211?°C, 189?°C, and 81?°C, respectively.     

EGA/MS Investigations on the Thermal Degradation of Diammoniumhexachloroplatinate

The thermal degradation of diammoniumhexachloroplatinate (NH₄)₂PtCl₆ is used in technical scale for the production of the pure platinum metal [1] and for this reason of great interest. Our investigations have been focused on the influence of the different atmospheres (oxidizing, inert or reducing) used in the technical processes towards the degradation mechanism and the evolved volatile degradation products. The second main aspect of our investigations was the evolution of volatile platinum species. Regarding the different frequencies of platinum allergies related to the different technical processes, the evolution of volatile platinum species is of great importance, due to the supposed allergic potential of this substances [2–4]. This revised version was published online in August 2006 with corrections to the Cover Date.     

DTA中升温速率及样品热导率对T_g测量值影响的模拟研究

就不同升温速率和实际样品的不同热导率对差热分析 (DTA)中高分子材料的玻璃化转变曲线的影响进行了MonteCarlo模拟研究 ,发现当所有样品刚完成玻璃化转变时 ,在Tg 曲线中该特征点要低于Tg 的转变中点。转变中点所对应的样品温度肯定要高于实际的玻璃化转变温度。如果以玻璃化转变曲线的转变中点所对应的样品温度作为该材料的玻璃化转变温度 ,那么 ,升温速率越快、样品的热导率越小 ,所测得的玻璃化转变温度就越大 ,反之亦然。DTA测得的玻璃化转变温度与升温速率间有很好的线性依赖关系 ,但与样品热导率间的关系是非线性的     

Synthesis of polyurethane from cashew nut shell liquid (CNSL), a renewable resource

A novel thermoplastic polyurethane was prepared from cardanol, a renewable resource and a waste of the cashew industry. Cardanol was recovered from cashew nut shell liquid (CNSL) by double vacuum distillation. It was characterized by CHN analysis and IR, ¹H-NMR, and ¹³C-NMR spectroscopy techniques. Cardanol is a meta-substituted long chain phenol. The long aliphatic chain unit substituent was found to be a monoene. The monomer, 4-[(4-hydroxy-2-pentadecenylphenyl)diazenyl]phenol was prepared from cardanol. It was a dihydroxy compound as characterized by CHN analyzer, UV, and ¹H-NMR spectroscopy. The polyurethane was synthesized from this dihydroxy compound by the treatment with 4,4′-diphenylmethane diisocyanate (MDI) in dimethylformamide (DMF) solvent at 80–90°C under nitrogen atmosphere. The polymer was characterized by ¹H-NMR, FTIR, and UV spectroscopy. The elemental analysis was done for determining the percentage content of C, H, and N, and the intrinsic viscosity [η] of polymer showed 1.85 dL/gm. Thermogravimetric investigations (TGA) of the cardanol, the dihydroxy compound, and the polyurethane were performed to study their decomposition. The semicrystalline nature of the PU was confirmed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analyzer (DMTA). The wide-angle X-ray diffraction (WAXS) study of PU shew a broad amorphous halo indicative of absence of crystallinity in the polymer, which has been explained as due to strong hydrogen bonding in the hard phase. PU may possibly be useful as a telecommunication and as a nonlinear optical material. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36 : 391–400, 1998     

Thermal decomposition of β-cyclodextrin and its inclusion complex with vitamin E

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同步热分析技术在煤炭品质评价和分类鉴别的应用研究

采用经典法(GB/T 212-2008)、常量热重法(Marco-TG)和同步热分析三种方法分析了多种产地的煤炭产品,结果表明,在煤炭样品制备良好的条件下,常量热分析法与经典法的煤炭工业分析值基本吻合,同步热分析(STA)法的结果波动相对较大,可作为半定量的快速评价煤炭品质检测方法;根据褐煤、烟煤和无烟煤燃烧时的差示扫描量热曲线热力学特征,初步探讨了三种煤炭的分类鉴别技术,促进煤炭产品的进出口贸易。     

Influence of glass transition temperature of crosslinked unsaturated polyester resin/styrene formulations on the final conversion after an isothermal curing at 100°C

SMC (sheet molding compound) is a composite based on fibers‐reinforced unsaturated polyester (UP) resin molded usually at 140°C to 170°C under a pressure of 60 to 100 bars. In order to develop new SMC formulations that can be molded at lower temperature (100°C) for economic and environmental reasons, the formulation of the composite had to be completely modified, both to allow a rapid reaction at 100°C, but also to avoid a vitrification phenomenon due to the fact that the glass transition temperature (Tg) of the SMC parts becomes, during the molding process, higher than the mold temperature. In this paper, the relation between the molding temperature, the glass transition temperature, and the final conversion of UP resin/styrene formulations has been underlined. The Tg of the cured resin was decreased by two different ways. The first way involved the reduction of the crosslinking density of the UP resin by using a blend of two resins, a pure maleic and a more flexible one. This blend allows to adjust the Tg over a temperature range from 197°C (Tg of the pure UP resin) to 75°C (Tg of the pure flexible resin). The second way consisted in the addition of butyl methacrylate (BuMA), a reactive plasticizer, to the formulation, allowing a decrease of the final material's Tg from 197°C to 130°C by replacing 35 wt% of styrene by BuMA. These two methods allow to obtain a final conversion of 99% after 8 minutes of molding at 100°C.     

Thermal transitions in and structures of dried polyelectrolytes and polyelectrolyte complexes

Dynamic mechanical analysis (DMA) was used to explore the thermomechanical properties of dried polyelectrolytes and polyelectrolyte complexes (PECs) with different thermal and humidity histories. Although differences in the amount of water remaining in polyelectrolytes and PECs were small for ambient versus dessicator storage, the properties of polyelectrolyte‐based materials were drastically different for different humidity histories. Glass transition temperatures (T_gs) of poly(diallyldimethylammonium chloride) (PDADMAC) were shown to vary by 100 °C, depending on humidity and thermal histories. These parameters also change glassy storage modulus values by 100%. Furthermore, we observe that dried PDADMAC is highly lossy. DMA of dried poly(styrene sulfonate) (PSS) was more complex and did not exhibit a glass transition in the tested range. DMA of a PEC of PDADMAC and PSS revealed a humidity history‐dependent water melt in the first heating cycle, as well as storage modulus values of dried and annealed PECs that only varied by 17–26% over a 275 °C temperature range. Based on these results, we report for the first time humidity history as controlling structure and properties of polyelectrolyte‐based materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 684–691     

丙烯酸化环状磷腈/环氧丙烯酸酯光固化体系热降解动力学研究

以TGA为手段, 进行了丙烯酸化环状磷腈/环氧丙烯酸酯光固化体系热降解动力学的研究, 同时与加入粉末状环状磷腈混合体系进行了对照. 采用Kissinger, Flynn-Wall-Ozawa和Friedman三种方法计算了固化膜降解反应活化能, 证明了磷腈结构的引入, 使得体系在高温阶段的活化能有所提高, 表明降解变得困难, 热稳定性得到提高. 而反应型丙烯酸化环状磷腈相对粉末状环状磷腈混合体系具有更高的降解活化能.     

Thermal Decomposition Kinetics of High Impact Polystyrene/Organo Fe‐montmorillonite Nanocomposites

In this article, high impact polystyrene/organo Fe‐montmorillonite (HIPS/Fe‐OMT) nanocomposites were prepared by melting intercalation. The thermal stability of HIPS/Fe‐OMT nanocomposites increased significantly compared to that of HIPS examined in thermal degradation conditions. Kinetic evaluations were performed by Kissinger, Flynn‐Wall‐Ozawa, Friedman methods and multivariate nonlinear regression. Apparent kinetic parameters for the overall degradation were determined. The results showed that the activation energy of HIPS/Fe‐OMT nanocomposites was higher than that of HIPS. A very good agreement between experimental and simulated curves was observed in dynamic conditions. Their decomposition reaction model was a single‐step process of an nth‐order reaction.