热分析技术及其在高分子材料研究中的应用

简要介绍了热分析技术——热重法、差热分析、差示扫描量热法、热机械分析法和动态机械热分析法等及其在高分子材料领域的广泛应用。热分析技术的方法具有快速、方便等优点,在高分子材料的研究中发挥着重要作用。     

示差扫描量热法进展及其在高分子表征中的应用

示差扫描量热法(DSC)是表征材料热性能和热反应的一种高效研究工具,具有操作简便、应用广泛、测量值物理意义明确等优点.近年来DSC技术的发展大大拓展了高分子材料表征的测试范围,促进了对高分子物理转变的热力学和动力学的深入研究.温度调制示差扫描量热法(TMDSC)是DSC在20世纪90年代的标志性进展,它在传统DSC的线性升温速率的基础之上引入了调制速率,从而可将总热流信号分解为可逆信号和不可逆信号两部分,并能测量准等温过程的可逆热容.闪速示差扫描量热法(FSC)是DSC技术近年来的创新性发展,它采用体积微小的氮化硅薄膜芯片传感器替代传统DSC的坩埚作为试样容器和控温系统,实现了超快速的升降温扫描速率以及微米尺度上的样品测试,使得对于高分子在扫描过程中的结构重组机制的分析以及对实际的生产加工条件的直接模拟成为可能.本文从热分析基础出发,依次对传统DSC、TMDSC和FSC进行了介绍,内容覆盖其发展历史、方法原理、操作技巧及其在高分子表征中的应用举例,最后对DSC未来的发展和应用进行了展望.本文希望通过综述DSC原理、实验技巧和应用进展,帮助读者加深对DSC这一常用表征技术的理解,进一步拓展DSC表征高分子材料的应用.     

Role,effect, and influences of micro and nano‐fillers on various properties of polymer matrix composites for microelectronics: A review

Ever since the discovery of polymer composites, its potential has been anticipated for numerous applications in various fields such as microelectronics, automobiles, and industrial applications. In this paper, we review filler reinforced polymer composites for its enormous potential in microelectronic applications. The interface and compatibility between matrix and filler have a significant role in property alteration of a polymer nanocomposites. Ceramic reinforced polymeric nanocomposites are promising candidate dielectric materials for several micro‐ and nano‐electronic devices. Because of its synergistic effect like high thermal conductivity, low thermal expansion, and dielectric constant of ceramic fillers with the polymer matrix, the resultant nanocomposites have high dielectric breakdown strength. The thermal and dielectric properties are discussed in the view of filler alignment techniques and its effect on the composites. Furthermore, the effect of various surface modified filler materials in polymer matrix, concepts of network forming using filler, and benefits of filler alignment are also discussed in this work. As a whole, this review article addresses the overall view to novice researchers on various properties such as thermal and dielectric properties of polymer matrix composites and direction for future research to be carried out.     

Polymer Composites for Thermoelectric Applications

This review covers recently reported polymer composites that show a thermoelectric (TE) effect and thus have potential application as thermoelectric generators and Peltier coolers. The growing need for CO₂‐minimizing energy sources and thermal management systems makes the development of new TE materials a key challenge for researchers across many fields, particularly in light of the scarcity or toxicity of traditional inorganic TE materials based on Te and Pb. Recent reports of composites with inorganic and organic additives in conjugated and insulating polymer matrices are covered, as well as the techniques needed to fully characterize their TE properties.     

Dynamic dielectric analysis. A new thermal analysis technique

Applications of dynamic dielectric analysis (DDA) in studies on the thermal decomposition and phase transformations of solid materials are discussed. Three illustrative examples are presented for (a) a system undergoing a chemical reaction or thermal alteration on application of heat, (b) a system undergoing a crystallographic transformation and (c) detection of moisture in naturally occurring materials. The advantages derived by applying a combination of DDA and a conventional thermal analysis technique such as DTA to studies on thermal processes are demonstrated. It is shown that the information obtained from techniques such as DTA or TG is limited in scope unless used in conjunction with a method which sheds light on the mechanistic aspects of the physical or chemical process of interest.     

Applications of some thermo-analytical techniques to glasses and polymers

Thermal characterization of materials provides conclusions regarding the identification of materials as well as their purity and composition, polymorphism, and structural changes. Analytical experimental techniques for thermal characterization comprise of a group of techniques, in which physical properties of materials are ascertained through controlled temperature program. Among these techniques, traditional differential scanning calorimetry (DSC) is a well-accepted technique for analyzing thermal transitions in condensed systems. Modulated DSC (MDSC) is used to study the same material properties as conventional DSC including: transition temperatures, melting and crystallization, and heat capacity. Further, MDSC also provides unique feature of increased resolution and increased sensitivity in the same measurement. “Hot disk thermal constant analyzer”, based on Transient Plane Source (TPS) technique, offers simultaneous measurement of thermal transport properties of specimen, which are directly related to heat conduction such as thermal conductivity (λ) and thermal diffusivity (χ). This method enables the thermal analysis on large number of materials from building materials to materials with high thermal conductivity like iron. The temperature range covered so far extends from the liquid nitrogen point to 1000 K and should be possible to extend further. This review also presents some interesting results of phase transition temperature of miscible (CPI/TPI) and immiscible (PS/PMMA) polymeric systems carried out through dynamic mechanical analyzer along with the thermal transport properties obtained for cis-polyisoprene (CPI), trans-polyisoprene (TPI), and their blends determined by TPS technique.     

Contribution of size exclusion chromatography and thermal analysis methods in the study of the radiochemical behavior of plastic materials

Sterilization by irradiation techniques is considered to be an improved method to treat polluted products of human consumption. Secondary effects, that may be generated in the components of packaging materials, could induce organoleptic damage and some physico-chemical modifications, observed especially in plastic materials. In order to demonstrate any such secondary changes, we have investigated the effects of beta-irradiation (a treatment which could induce either a reticulation or a cleavage in a polymeric sequence) on three polymers; namely, low density polyethylene, polystyrene and polyvinyl chloride. The techniques used to identify irradiation-induced modifications of these polymers were size exclusion chromatography and thermal analysis. Thermal analysis showed a decrease in the percentage of crystallinity of polyethylene after its radiosterilization. Exclusion chromatography highlighted a reticulation for irradiated polyvinyl chloride and polystyrene.     

Tunable Thermoelastic Anisotropy in Hybrid Bragg Stacks with Extreme Polymer Confinement

Controlling thermomechanical anisotropy is important for emerging heat management applications such as thermal interface and electronic packaging materials. Whereas many studies report on thermal transport in anisotropic nanocomposite materials, a fundamental understanding of the interplay between mechanical and thermal properties is missing, due to the lack of measurements of direction‐dependent mechanical properties. In this work, exceptionally coherent and transparent hybrid Bragg stacks made of strictly alternating mica‐type nanosheets (synthetic hectorite) and polymer layers (polyvinylpyrrolidone) were fabricated at large scale. Distinct from ordinary nanocomposites, these stacks display long‐range periodicity, which is tunable down to angstrom precision. A large thermal transport anisotropy (up to 38) is consequently observed, with the high in‐plane thermal conductivity (up to 5.7 W m^?1 K^?1) exhibiting an effective medium behavior. The unique hybrid material combined with advanced characterization techniques allows correlating the full elastic tensors to the direction‐dependent thermal conductivities. We, therefore, provide a first analysis on how the direction‐dependent Young's and shear moduli influence the flow of heat.     

Thermophysical properties of polypropylene/aluminum composites

This article is dedicated to the study of the thermal parameters of composite materials. A nonlinear least‐squares criterion is used on experimental transfer functions to identify the thermal conductivity and the diffusivity of aluminum‐polymer composite materials. The density measurements were achieved to deduce the specific heat and thereafter they were compared to values given by differential scanning calorimetry measurement. The thermal parameters of the composite material polypropylene/aluminum were investigated for the two different types of aluminum filler sizes. The experimental data were compared with several theoretical thermal conductivity prediction models. It was found that both the Agari and Bruggeman models provide a good estimation for thermal conductivity. The experimental values of both thermal conductivity and diffusivity have shown a better heat transport for the composite filled with large particles. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 722–732, 2004     

The degradation of new thermally degradable thermosets obtained by cationic curing of mixtures of DGEBA and 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione)

The thermal degradation of thermosetting materials prepared by cationic copolymerization of mixtures of different proportions of diglycidylether of bisphenol A (DGEBA) with 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione) (MCP) initiated by ytterbium or lanthanum triflate or using a conventional initiator, BF₃·MEA was investigated. To study the thermal degradation, several techniques were used such as thermogravimetry (TGA), infrared spectroscopy (FTIR) and calorimetry (DSC) and the volatiles evolved during degradation were identified by mass spectrometry. The materials prepared possess the characteristics of thermally degradable thermosets, due to the presence of ester groups in the polymer chain, which are broken at the beginning of degradation. The degradability increased when lanthanide triflates were used in the curing, especially the ytterbium salt and when the proportion of MCP in the material increased.     

Photothermal applications to the thermal analysis of solids

Major application of optically-induced thermal waves to the thermal and thermodynamic analysis of solids are reviewed. The spectrum of available techniques,from the conventional photoacoustic detection to novel photothermal laser probing and frequency multiplexing is discussed, and their utilization for the measurement of thermophysical thermal transport-related parameters of solids is presented. These include the thermal diffusivity, effusivity, conductivity and specific heat. The ability of photothermal methods to perform thermal analysis on large classes of solids, including conducting and insulating bulk materials, crystals, layered porous and coated structures, thin films and inhomogeneous thermal profiles is highlighted. Finally, special capabilities of photothermal analysis, such as the monitoring of surface thermodynamic phenomena and phase transition studies, including high-T _c superconductors, are described in order to give a complete overview of the rich potential of photothermal-based methodologies.     

溶胶-凝胶法制备壳聚糖/SiO2杂化材料

以正丁酐（Butyric anhydride)、壳聚糖(Chitosan）、甲基丙烯酰氧基丙基三甲氧基硅烷（MPTMS）、正硅酸乙酯（TEOS）为原料,采用迈克尔加成反应合成了丁酰壳聚糖-MPTMS,配合酸催化sol-gel过程,制备了透明的壳聚糖/SiO2杂化材料,FTIR表征了杂化材料的结构。TGA,SEM以及力学性能测试结果表明,杂化材料的成型工艺对材料的表面形貌、热分解温度以及力学性能的影响显著。     

Polyolefin,olefin copolymers and polyolefin polyblend nanocomposites

This paper reviews recent studies done in academia or industrial laboratories on polymer nanocomposites based on various type of polyolefins like homopolymers, copolymers and polyblends reinforced with various mineral (montmorillonite, bentonite, closite, laponite, layered double hydroxide, etc.) carbon based (graphite, carbon nanotubes, carbon nanofibers, exfoliated graphite, graphene, carbon black, etc.) nanofillers. The review covers their preparation, their mechanical, thermal, flammability, gas barrier capability, electrical, dielectrical, antibacterial characteristics and their potential applications like low weight structural materials, part of optical devices, thermal interface materials, electric and electromagnetic components, absorption, antibacterial materials, etc.     

导电高分子及其纳米复合材料的热电性质

与无机热电材料相比, 有机热电材料具有资源丰富、 成本低、 质量轻、 柔韧性好及热导率低等优点, 成为热电研究领域关注的热点. 理论和实验结果表明, 低维化和小尺度化是热电材料研究和开发的发展方向. 本文对低维有机热电材料的合成、 器件组装及热电性质的影响因素等进行简要评述, 并对低维有机热电材料的研究方向进行了讨论.     

Thermal desorption characterisation of molecularly imprinted polymers. Part I: a novel study using direct-probe GC-MS analysis

A novel thermal desorption technique using a direct-probe device (Chromatoprobe) attached to a gas chromatograph–mass spectrometer is presented for the thermal pretreatment, characterisation and analysis of molecularly imprinted polymers. The technique is demonstrated as effective for the removal of volatile materials, including template and unreacted monomers, from methacrylic acid–ethylene glycol dimethacrylate copolymers imprinted with 2-aminopyridine. Mass spectrometry is a powerful technique for polymer bleed characterisation. Thermal desorption studies on reloaded template and related compounds are reported as a means of assessing polymer morphology, specific binding by imprinted polymers compared with reference non-imprinted polymers and selective binding by an imprinted polymer for its template. Calibration studies on the thermal desorption technique using an internal standard are presented with R ² > 0.999. The technique provides a novel method for assessment of polymer thermal stability, composition and morphology.     

Diffusion in gas separation membrane materials: A comparison and analysis of experimental characterization techniques

Typically, materials with high-performance transport properties such as zeolites, carbon molecular sieves, or hyper rigid polymers are inherently difficult or impossible to characterize by steady-state membrane permeation experiments used for conventional polymers. Diffusion coefficients determined by transient sorption, a measurement easily performed on brittle media, are analyzed here and compared to those determined by steady-state permeation/sorption and transient permeation for a glassy polymer and a carbon molecular sieve. Average and local diffusion coefficients are extrapolated to zero upstream partial pressure to eliminate effects caused by concentration dependence. Good agreement between the techniques was observed for the glassy polymer. On the other hand, carbon molecular sieves, possessing a more complex morphology, exhibit a greater difference in diffusion coefficients determined by the various techniques. Nevertheless, comparison of the analysis techniques is shown to provide potentially valuable insights into the morphological features of such carbon molecular sieves. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1747–1755, 1998     

Thermal stability of polypropylene-clay nanocomposites subjected to laser pulse heating

Polypropylene based nanocomposites filled with montmorillonite nanoclay prepared by twin screw extrusion have been studied for thermal stability at high heating rates. In contrast to traditional thermal stability and flammability studies of polymer nanocomposites using heating rates on the order of tens of degrees per minute, this study achieves heating rates that are six orders of magnitude higher. This was accomplished using laser pulse heating. The results show that the nanoclay increases thermal stability of the polymer, as measured by a decrease in the mass loss for a laser pulse at a given energy and intensity. Electron microscopy and various spectroscopic techniques show that a silicate-rich char layer may provide the mechanism for protection of the polymer and decreased degradation rates. The results of the study are compared to the typical results found in traditional thermal stability testing.     

Methods for the determination of water in polymers

Water may be “weakly” or “strongly” bound to other substances by physical or chemical forces. Knowledge of the amount of water and the type of bonding in polymeric materials is very important in control of many polymerization processes and in the physical behavior of the polymer. Hundreds of methods have been proposed for the determination of water in concentrations ranging from p.p.b. to high percentages. Some are direct; others require preliminary concentration or chemical reaction. The most useful methods of analysis for water in polymers are based on chemical, spectroscopic, gravimetric, thermal, electrical, and physical techniques. Chemical methods are represented by Karl Fischer titration, acylation, and nitride reactions. Infrared, nuclear magnetic resonance, and mass spectrometry are the principal spectroscopic approaches. Other useful methods include direct weight loss, thermogravimetry, differential thermal analysis, thermal evolution analysis, dielectric constant, conductance, coulometry, chromatography, azeotropic distillation, piezoelectric, manometric, and volumetric procedures. Recent developments are described with emphasis on applications of these techniques.     

Thermal stability of structurally related polymers containing carborane and phthalocyanine groups

These studies were undertaken to determine the thermal behavior of structurally related polymers having a carborane nucleus in the recurring unit. Three of these products also contained phthalocyanine rings in their molecules. Results of thermal analysis studies show generally that the relative heat stability of the polymers conforms closely with indications given by similar investigations of structurally related intermediate and model compounds. A polymer with dimethylsiloxane units exhibited more resistance to thermal decomposition than similar products having urethane groups in their molecules. The urethane polymers derived from tolylene diisocyanate were found to be somewhat less heat-stable than analogous materials synthesized from methylenebis-(p-phenyl isocyanate). The relative order of thermal resistance of these materials follows that of more conventional polyurethane elastomers.     

Assessment of nanoparticle loading and dispersion in polymeric materials using oscillatory photon correlation spectroscopy

The inclusion of small concentrations of nanoparticles in polymeric materials (≤5 wt. %) can significantly enhance material properties and functionality. However, poor or non-uniform particle dispersion resulting in particle clustering (agglomeration) in polymer nanocomposites (PNCs) limits the potential for property enhancement in these materials. Achieving good dispersion is considered essential for successful commercialization of PNCs. Hence, reliable and accurate measurement techniques for characterizing particle loading and dispersion would significantly contribute towards understanding and optimizing the material performance of PNCs, and consequently play a pivotal role in product development. This paper, the last of three papers on optical techniques, presents the results of a study using a dynamic light scattering technique, oscillatory photon correlation spectroscopy (Os-PCS), for discriminating between different particle loadings and levels of dispersion. The technique has been applied to two epoxy-based resin systems reinforced with either nanoclay platelets or silica microspheres.