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1.
The surface molecular motion of polymeric solids was investigated on the basis of scanning force microscopic and temperature-dependent X-ray photoelectron spectroscopic measurements. The surface of the monodisperse polystyrene films was in a glass-rubber transition state even at 293 K in the case of number-average molecular weight less than ca. 30k. The surface glass transition temperature, Tgs for the symmetric poly(styrene-block-methyl methacrylate) diblock copolymer films were much lower than those for the bulk samples. A remarkable depression of Tg at the air-polymer interface was explained by the surface localization of chain end groups. 相似文献
2.
《印度化学会志》2023,100(1):100839
This paper presents the study of the chemical and physico-mechanical properties of the natural and synthetic fabrics used in extreme low-temperature (?20 °C) gloves. The essential properties, such as the weight of the gloves, cold insulation, and surface water repellency, were studied. In-depth analysis by 13C solid-state nuclear magnetic resonance spectroscopy (13C SSNMR), attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), and differential scanning calorimetry (DSC) techniques were undertaken to understand the chemical and thermal characteristics of the fabrics. The physico-mechanical properties, such as thickness, weight, softness, tear strength, abrasion resistance, blade cut resistance, and puncture resistance, of each fabric used in the gloves, were also studied. Finally, the physico-mechanical properties were correlated with the chemical nature of the fabrics and the garment's performance properties.The present study will guide in the selection of materials for designing low-temperature protective garments. The in-depth analysis presented in this work will also help the researchers in the chemical identification of natural and synthetic polymeric fabrics using solid-state NMR, ATR-FTIR, and DSC techniques. 相似文献
3.
An investigation of dynamic mechanical, thermal, and electrical properties of housing materials for outdoor polymeric insulators 总被引:1,自引:0,他引:1
The present paper reports the results about a study of mechanical, thermal, dynamic mechanical and electrical properties of housing (weather shed) materials for outdoor polymeric insulators. Silicone rubber, ethylene-propylene-diene monomer (EPDM) and alloys of silicon-EPDM are known polymers for use as housing in high voltage insulators. The result of dynamical mechanical measurement shows that the storage modulus of blends enhances with increase EPDM in formulation. It can be seen from the result of TGA measurement that initial thermal degradation of silicone rubber improves by the effect of EPDM in blends. The blends of silicone-EPDM show good breakdown voltage strength compared to silicone rubber. Surface and volume resistance of silicone rubber improve by EPDM content. The mechanical properties of EPDM such as strength, modulus and elongation at break improve by silicone. 相似文献
4.
Brillouin scattering of laser light has been used to study the temperature dependence of phonon velocity in a variety of amorphous polymeric systems, particularly internally and externally plasticized methacrylates. Discontinuities in the temperature coefficient of the hypersound velocities are observed at the glass transition temperatures (Tg). This phenomenon is related to changes in the temperature behavior of the specific volume accompanied by corresponding discontinuities in certain second-order thermodynamic quantities. This method was also used to examine the temperature dependence of the Landau-Placzek ratio. This ratio is relatively large in polymer systems and appears to be independent of temperature in the region of the glass transition, provided that there are no internal strains in the sample at the temperature of measurement. Evidence is presented which suggests that the abrupt changes in this ratio at Tg reported by earlier workers were due to kinetic effects related to the relaxation of internal strains above Tg, and the results of recent studies by other investigators, both corroborating and supplementing the present work, are reviewed. 相似文献
5.
Andrew K. Galwey 《Journal of Thermal Analysis and Calorimetry》2007,87(2):601-615
This analysis of interface
phenomena considers the alternative processes that may result from heating
a crystal, particularly including thermal decomposition, involving chemical
reactions, and melting, involving loss of long-range structural order. Such
comparisons are expected to provide insights into the factors that determine
and control the different types of thermal changes of solids. The survey also
critically reviews some theoretical concepts that are currently used to describe
solid-state thermal reactions and which provides relevant background information
to models used in a recently proposed theory of melting. Probable reasons
for the current lack of progress in characterizing the factors that control
chemical changes and mechanisms of thermal reactions in solids are also discussed.
It is concluded that some aspects of the macro properties of reaction
interfaces in crystal reactions have been adequately described, including
geometric representations of interface advance during nucleation and growth
processes. In contrast, relatively very little is known about the detailed
(micro) processes occurring within these active, advancing interfacial zones:
reactant/product contacts during chemical reactions and crystal/melt contacts
during fusion. From the patterns of behaviour distinguished, a correlation
scheme, based on relative stabilities of crystal structures and components
therein, is proposed, which accounts for the four principal types of thermal
changes that occur on heating solids: sublimation, decomposition, crystallographic
transformation or melting. Identifications of the reasons for these different
consequences of heating are expected to contribute towards increasing our
understanding of each of the individual processes mentioned and to advance
theory of the thermal chemistry of solids, currently enjoying a prolonged
quiescent phase. 相似文献
6.
V. V. Boldyrev 《Russian Chemical Bulletin》1990,39(10):2029-2044
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2228–2245, October, 1990. 相似文献
7.
J. Koberstein T. P. Russell R. S. Stein 《Journal of Polymer Science.Polymer Physics》1979,17(10):1719-1730
Presently existing theories of small-angle light scattering by polymeric materials are extended by consideration of the total integrated scattering intensity. It is shown how this quantity, known as the total integral or Porod invariant in small-angle x-ray scattering, may be used to calculate the average square of the fluctuations in refractive index and orientation. Calculations are presented using both statistical and model approaches. 相似文献
8.
Motori A. Montanari G. C. Saccani A. Peruzzotti F. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):1159-1166
Two thermal analysis techniques (isothermal differential calorimetry and isothermal thermogravimetric analysis) are used as
analytical methods for short-term thermal endurance characterization of polymeric materials, used for electrical insulation.
These techniques are applied to commercial grade ethylene-propylene rubber and polyvinyl chloride. It is shown that thermogravimetric
analysis provides very satisfactory results, independently of the degradation reactions which take place in the material.
Calorimetry proves to be effective only for polymers (such as polyolefins) in which oxidation is the largely prevailing degradation
mechanism in the test and service temperature ranges.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Birinchi Kumar Das Sanchay Jyoti Bora Monideepa Chakrabortty Laksheswar Kalita Rajesh Chakrabarty Ramakanta Barman 《Journal of Chemical Sciences》2006,118(6):487-494
Molecules in metal isonicotinate tetrahydrates, M(NC5H4-p-CO2)2.4H2O with M = Mn, Fe, Co, Ni, Cu, Zn, consisting of the hexacoordinate complexestrans-[M(NC5H4-p-CO2)(OH2)4], participate in exhaustive hydrogen-bond formation among themselves to lead to a robust 3D supramolecular network in the
solid state. Solid-state diffuse reflectance UV-Vis-NIR spectra of the complexes have been assigned to ligand field and charge
transfer transitions. Sharp weight loss due to dehydration, as shown by TGA of Cu(NC5H4-p-CO2)2.4H2O, suggests the suitability of this complex for the gravimetric estimation of copper. 相似文献
10.
11.
L. Stoch 《Journal of Thermal Analysis and Calorimetry》1987,32(6):1651-1658
Temperature-activated reactions of decomposition, the synthesis of new compounds, and reduction and oxidation, termed here intraframework reactions, take place within the structural framework of solids. They are distinguished in that they occur within the bulk volume of the substance, in the area of the influence of crystal fields. The atoms and ions participating in these reactions are displaced by diffusion, which is usually directional diffusion. The regularities governing some of these reactions are presented in the paper.
Zusammenfassung Im Strukturgefüge von Feststoffen treten sogenannte Intratexturreaktionen auf: durch Wärme hervorgerufene Zersetzungsreaktionen, Sýnthese neuer Verbindungen, Reduktion und Oxidation. Diese sind dadurch gekennzeichnet, daß sie im gesamten Volumen der Substanz, in einem vom Kraftfeld des Kristalles beeinflußten Raum ablaufen. Der Austausch der an den Reaktionen teilnehmenden Atome und Ionen wird durch eine stets gerichtete Diffusion verursacht. Es werden Gesätzmäßigkeiten beschrieben, denen einige dieser Reaktionen unterliegen.
- , , , . , , . . , . , , , . .相似文献
12.
L. Stock 《Journal of Thermal Analysis and Calorimetry》1991,37(7):1415-1429
Selected examples of dehydration, accompanied by violent disintegration or bloating of the decomposing solid substance are presented. This phenomenon has been explained as a specific case of internal decomposition of solids. A sealed box with compressed gaseous products is proposed as a model of the process. The practical applications of this phenomenon are discussed.
Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday
The work was financially supported by the Ministry of National Education, grant No P/03/257/90-z. The authors wishes to express his thanks to all who contributed to this support. 相似文献
Zusammenfassung Es werden ausgewählte Beispiele für die Dehydratation, begleitet von heftiger Zersetzung oder Aufblähen der zersetzten Feststoffe dargelegt. Diese Erscheinung wird als ein Spezialfall der internen Zersetzung von Feststoffen beschrieben. Als Modell für diesen Prozeß wird ein abgeschlossener Behälter mit unter Druck stehenden gasförmigen Produkten vorgeschlagen. Praktische Anwendungen dieser Erscheinung werden diskutiert.
Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday
The work was financially supported by the Ministry of National Education, grant No P/03/257/90-z. The authors wishes to express his thanks to all who contributed to this support. 相似文献
13.
Kinetic equations for the decay of the free radicals in polymeric solids are given for the following assumptions on which they are based: (1) two simultaneous first-order but physically separated decay reactions; (2) two simultaneous noninteracting second-order decay reactions; (3) combined simultaneous but intermingled first- and second-order decay reactions; (4) the same but for independent, i.e., not intermingled, first- and second-order decay reactions; (5) a second-order decay reaction in the presence of some free radicals that do not decay; and (6) a first-order decay reaction in the presence of some free radicals that do not decay. In all of the above physical systems the total concentration only can be measured. Hence the above kinetic equations refer to the change of the total concentration with time. It is found that the data for the decay of the free radicals in irradiated isotactic polypropylene and 61% styrene-39% butadiene block copolymer agree best with the equations for the second-order decay in the presence of a fraction of nondecaying free radicals. 相似文献
14.
15.
Practical aspects of the studies of stages of thermal dissociation of solids, of the kinetics of the stages, and of utilization of general regularities of the process for verification of kinetic studies are discussed.
Zusammenfassung Die praktischen Aspekte der Untersuchungen über die Stufen der thermischen Dissoziation von Festkörpern und ihrer Kinetik weiterhin über die Anwendungsmöglichkeiten der RegelmÄssigkeiten der Verifikation der kinetischen Untersuchungen werden erörtert.
, .相似文献
16.
《Thermochimica Acta》1986,100(1):315-338
This survey systematically considers the factors responsible for localization and autolocalization of thermal decomposition processes of solids. The specificity and complexity of nucleation and nuclei growth in topochemical processes are shown. 相似文献
17.
18.
I. V. Melikhov A. L. Nikolaev A. V. Gopin V. E. Bozhevol’nov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(1):71-76
A kinetic model of the crystallization of substances in the volume of an agglomerate of many microparticles or in a polymeric gel in solution with a given composition and temperature was formulated. The model takes into account the diffusion of the crystallizing substance from outside into the space between microparticles in an agglomerate or between polymeric globules in a gel and then from this space into the volume of microparticles (globules) with the simultaneous nucleation and growth of microcrystals of the crystallizing substance. The possibility of simultaneous diffusion of several crystallizing substances, which chemically react with each other to produce product microcrystals, heating of the gel (solid) by the heat of crystallization, pushing the solution out from the space between microparticles, and changes in the volume of the gel (solid) as a result of crystallization is considered. The model was used to develop a classification of crystallization types in gels and porous solids and interpret several phenomena described in the literature. A hypothesis was advanced concerning some unknown phenomena related to crystallization. 相似文献
19.
Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomem-branes. It refers to that glycosyl groups are introduced onto the membrane surface by various strate-gies, which combine the separation function of the membrane with the biological function of the sac-charides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the sur-face-glycosylated membranes. 相似文献
20.
Boehmite (AlOOH) sheets were synthesized via a hydrothermal method and then successfully functionalized with a bi‐functional coupling agent, γ‐aminopropyl‐ triethoxysilane (APTES), through a facile neutral solvent method. Scanning electron microscope and transmission electron microscopy images showed a uniform morphology of AlOOH sheets. APTES was found to be covalently bound with AlOOH sheets. The linked APTES can be combined with an epoxy oligomer through a ring opening addition reaction. The modified AlOOH was used as reinforcing agent to reinforce the epoxy resin cured by 4,4‐diaminodiphenylsulfone. The results of tensile and differential scanning calorimetric test revealed the tensile strength and glass transition temperature (Tg) firstly increase and then decrease with the increase of functionalized AlOOH sheets loading. When the loading of functionalized AlOOH sheets increased to 5 parts per hundred resin, the highest tensile strength and Tg were obtained. They are 100.8 MPa and 174.5 °C. Microscopic examinations revealed the presence of large plastic deformations at the micronscale in the formed composites in agreement with the observed strengthening effect of functionalized AlOOH sheets. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献