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1.
The epoxy–POSS hybrid networks with POSS bound as pendant cages or with untethered POSS dispersed in the matrix were prepared and their structure was controlled. Formation of the hybrid network was followed by chemorheology. In situ development of physical crosslinks in the pregel stage of the network build-up was observed in case of the hybrids with tethered POSS. The complex effect of POSS on mechanical properties is manifested by either increase or decrease in rubbery modulus of different hybrids. This behavior reflects (a) reinforcement due to POSS hard aggregates, (b) diminishing of crosslinking density of the epoxy network by tethered monofunctional POSS and (c) physical crosslinking via POSS domains. Theories of network formation and rubbery elasticity as well as the model of mechanical behavior of particulate composites were applied to interpret the mechanical properties of the hybrids. 相似文献
2.
The effect of SKN-30KTRA low molecular weight rubber on the elastic and strength properties of adhesive compositions made with epoxy-rubber composition, is shown. The data on the effect of rubber on curing of adhesive compositions are presented. 相似文献
3.
The influence of Jeffamine T-403 polyoxypropylenetriamine on the physico-mechanical, adhesion, and relaxation properties of polymeric compositions based on the products of preliminary thioesterification reaction of epoxy resin with liquid thiokol was studied. It was shown that the introduction of polyoxypropylenetriamine leads to a significant increase of the adhesive and cohesive strength, the elongation at break, and the work of destruction of the material. 相似文献
4.
The cure behavior of diglycidyl ether of bisphenol A with a simple ether amine (4,7,10, trioxa -1,13, tridecane diamine), system I and a polyether amine (polypropylene glycol block polyethylene glycol block polypropylene glycol bis 2 amino propyl ether), system II was compared by Differential Scanning Calorimetry. The exothermicity of the curing reaction of system I is higher than that of system II (316 ± 15 J g ?1 for System I and 230 ± 15 J g ?1 for system II). Kinetic parameters viz., activation energy, pre-exponential factor, and rate constant for curing were evaluated by Kissinger method and Kissinger–Akahira–Sunose isoconversion method. Both systems showed low glass transition temperatures and System II shows a much lower T g (?38 °C) than system I (26 °C). The thermogravimetric analysis of the two cured epoxy amine systems showed comparable thermal stability. 相似文献
5.
Hot-cured epoxy compound based on ED-20 resin and isomethyltetrahydrophthalic anhydride was modified with alkanolamines of different structures. The influence exerted by the structure of alkanolamines on the structure and operation characteristics of modified epoxy–anhydride compounds was examined. Introduction of alkanolamines decreases the gel and cure times and enhances the operation properties of cured epoxy–anhydride compounds. The best products were obtained with alkanolamines derived from ethylenediamine. Their introduction into epoxy–anhydride compounds enhances by a factor of 1.5–2 the elasticity, tensile strength at uniform extension, and impact resilience of the cured formulations. 相似文献
6.
This article describes the test results of thermal properties and flammability of the unconventionally cross-linked blends
of chlorosulfonated polyethylene (CSM) and butadiene–styrene rubber (SBR) by means of zinc oxide or nano-zinc oxide. The thermal
curves have been interpreted from the point of view of the chemical transitions of elastomers and their blends. It has been
found that the content of combined chlorine in CSM exerts a significant influence on the cross-linking kinetics of CSM/SBR
blends, their thermal properties and flammability. 相似文献
7.
Products of sorption of uranyl ions on HDTMA-red clay in the presence of phosphates were characterized by thermal analysis. It was established on the basis of DTG curves of the sorption products and FTIR spectra of the gaseous phase of sorption products decomposition that the thermal stability of the mineral increased when P(V) ions were sorbed along with U(VI) ions, i.e., the temperature of defragmentation/oxidation of surfactant increased when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay to P(V)–HDTMA-clay. The DSC curves of the sorption products showed that defragmentation/oxidation was an exothermic process and dehydration and dehydroxylation had an endothermic character. The investigated sorption system has practical importance, since an evident increase in U(VI) sorption over the entire pH range is observed when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay. 相似文献
8.
In the present work, we report the preparation and characterization of a new family of thermosets based on off-stoichiometric anhydride–epoxy formulations in the presence of an anionic initiator. Diglycidyl ether of bisphenol A (DGEBA) and hexahydro-4-methylphthalic anhydride (HHMPA) have been used as epoxy and anhydride comonomers, respectively, and 1-methylimidazole (1MI) has been used as anionic initiator. The isothermal curing kinetics and the thermal properties of the stoichiometric and the off-stoichiometric systems have been compared. The kinetics of the isothermal curing has been analyzed by differential scanning calorimetry (DSC) using an isoconversional method and the ?esták–Berggren equation to determine the activation energy, the frequency factor and the reaction orders. The materials obtained were characterized by DSC and dynamic mechanical analysis. Gelation during epoxy–anhydride condensation was determined by thermomechanical analysis. At the same curing temperature, the reaction is faster in the system with excess of epoxy groups. However, the glass transition temperatures of the partially cured stoichiometric system are greater. The gelation time of the off-stoichiometric system is shorter than that of the stoichiometric one. The results indicate that the dual-curing character of off-stoichiometric DGEBA/HHMPA thermosets with 1MI as anionic initiator makes them suitable for multistage curing processes with easy control of degree of cure and material properties in the intermediate stage and enhanced final material properties. 相似文献
9.
Investigations of montmorillonite (MMT) clay mineral modification effects on electro‐optical properties of nanocomposites, based on the nematic liquid crystal 4‐pentyl‐4′‐cyanobiphenyl (5CB) and MMT have been carried out. Only the composite with MMT modified by an organic surface‐active substance, dioctadecyldimethylammonium chloride, has been shown to manifest electro‐optical memory effect and contrast. A polar dopant (acetone), added to the mixture, significantly increases composite homogeneity. Results of IR spectroscopy measurements lead to the conclusion, that there is a mutual influence of components on each other in organoclay systems, which appears as an alignment of near‐surface layers of both the organic and inorganic components of the composite. Due to such interactions these systems show electro‐optical contrast and memory effect. A composite with organophobic Na‐MMT does not show these electro‐optical properties, due to the absence of component interactions, as shown by IR spectroscopic data. 相似文献
10.
Poly(lactide)/halloysite nanotubes (PLA/HNT) nanocomposites with crystalline matrix were obtained by cold crystallization and examined. Neat HNT and HNT treated with N,N′- ethylenebis(stearamide) (EBS) were used as nanofillers. Reference materials, PLA and PLA/EBS blend, prepared in the same way, were also considered. The influence of HNT and/or EBS content on the crystallinity and morphology of PLA matrix, as well as on the dynamic mechanical and optical properties of the materials, was determined.The nanocomposites contained well-distributed HNT, with only occasional agglomerates. HNT, EBS-treated HNT and EBS influenced the morphology of the crystalline PLA matrix and the amounts of the disorder α’ (termed also δ) and order α crystallographic forms of PLA. Crystallinity increased stiffness of the materials compared to their counterparts with the amorphous matrix. Owing to the crystallinity and the presence of the nanofillers, the storage modulus at 20 °C and 60 °C increased by up to 30 and 60%, respectively, compared to neat amorphous PLA. Interestingly, at lower nanofiller content the crystalline nanocomposites with EBS were more transparent than neat crystalline PLA. 相似文献
11.
The powder injection molding (PIM) process has an advantage of near net shaping of homogeneous micro structure and density at the complicate form. This study was investigated for microstructure and mechanical properties of WC–10%Co insert tool alloy fabricated by PIM process. The WC–10%Co feedstock mixed with wax binder was fabricated by two blade mixer. After WC–10%Co feedstocks were injection molded, debinding process was carried by two-steps methods with solvent extraction and thermal debinding. The binder was eliminated with normal hexane for 12 h at 50 °C by solvent extraction, and subsequently thermal debinding was examined for 1 h at the temperature 900 °C. After debinding process, the specimens were sintered at vacuum or N 2/H 2 mixed gas atmosphere at 1380 °C. The microstructure and phase were observed by FE-SEM. In the case of sintered at 1380 °C in vacuum atmosphere, the hardness was 1600 Hv, and the relative density of WC–10%Co was 92.5%. The density of WC–10%Co sintered at 1380 °C in mixed gas atmosphere was 87.5% and the hardness was lower than 1400 Hv. Residual carbon contents of sintered at vacuum and mixed gas atmosphere were 5.4 wt%. 相似文献
12.
Nylon 66–clay (polyamide 66 (PA66)–organophilic montmorillonite (OMT)) exfoliated nanocomposites were synthesized based on nylon 66 salt and organoclay (OMT) modified by hydro-aminocaproic acid via condensation polymerization. And the nanocomposites were characterized by X-ray diffraction and transmission electronic microscopy. Exfoliated morphology with different clay content was obtained. The effects of cation exchange capacity and organic modified agent of OMT on the formation of exfoliated nanocomposites were investigated. It was shown that only suitable cation exchange capacity and organic modified agent could result in the formation of exfoliated morphology under the condition of condensation polymerization. The thermal and flammability properties of the nanocomposites were investigated through thermogravimetry and cone calorimetry experiments. Results indicate that the exfoliated nanocomposites have enhanced thermal stability and flame retardant properties compared with pure PA66. 相似文献
13.
Biological nanocomposites are a valuable addition to the existing nanocomposite materials and eventually can substitute petroleum-based composite materials in numerous applications due to their inherent advantages such as biodegradability, eco-friendliness, low cost, and easy availability to name a few. Recently, polymer–clay nanocomposites have achieved much more attention due to their enhanced properties such as size dispersion and significant enhancement in physicochemical and mechanical properties in comparison to the pure polymer systems. Among various biopolymers, starch is one of the most abundant natural polymers on the earth and is highly valuable due to its chemical and physical properties. Starch polymer has highly increased potential as an alternative to petroleum-based materials. However, starch cannot be used alone and starch–clay nanocomposite has emerged as a new potential green sustainable material. This article focuses on recent progress in starch-based nanocomposites with particular emphasis on starch–clay nanocomposite preparation, properties, and applications. 相似文献
15.
The effect of ß-cyclodextrin (ß-CD) on cetyltrimethylammonium bromide (CTAB) micellar properties was studied by the determination of the diffusion coefficient, D. When the CTAB micelles have a spherical structure, D firstly increased and then remained unchanged, while the micellar aggregation number, N, decreased with the addition of ß-CD. When the CTAB concentration was less than the first critical micellar concentration, CTAB molecules could be included into ß-CD cavities with the molar ratio of CTAB to ß-CD being about 1:1. However, when the CTAB concentration was higher than the first critical micellar concentration, mixed spherical micelles were formed with the molar ratio of CTAB to ß-CD being 9:1. 相似文献
16.
Fe-pillared bentonite clay-based nanoadsorbent was synthesized by the thermal aging technique. The characteristics of the nanocomposite were detected by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), electron dispersive X-ray spectrometer (EDX), reflectance spectrophotometer (RS), and electromagnetic transition instrument (ETI). The TGA result demonstrated that the Fe particles generated on the clay surface can significantly improve the thermal stability of clay particles. The SEM and EDX results showed the presence of chemical elements of Fe, Al, and Si on the surface of clay. In this research, the successful synthesis of Fe-pillared clay nanocomposite can be concluded from the FTIR spectra. 相似文献
17.
Journal of Thermal Analysis and Calorimetry - Artificial aggregates, such as fly ash lightweight aggregates, can be used as eco-friendly alternatives to natural aggregates. This work aims to... 相似文献
18.
The influence of polyvinyl alcohol (PVA) adsorption on the structure of the diffuse layer of silica (SiO 2) in the temperature range 15–35 °C was examined. The microelectrophoresis method was used in the experiments to determine
the zeta potential of the solid particles in the absence and presence of the polymer. The adsorption of PVA macromolecules
causes the zeta potential decrease in all investigated SiO 2 systems. Moreover this, decrease is the most pronounced at the highest examined temperature. Obtained results indicate that
the conformational changes of adsorbed polymer chains are responsible for changes in electrokinetic properties of silica particles.
Moreover, the structure of diffuse layer on the solid surface with adsorbed polymer results from the following effects: the
presence of acetate groups in PVA chains, the blockade of silica surface groups by adsorbed polymer and the shift of slipping
plane due to macromolecules adsorption. 相似文献
19.
Different thermal analysis techniques were used to study the effect of fillers and ionic liquids (ILs) on the vulcanization process, thermal and dynamic mechanical properties of acrylonitrile–butadiene elastomer (NBR). The products of the studies were composites of NBR filled with hydrotalcite, nanosized silica or carbon black. ILs such as 1-butyl-1-methylpyrrolidinium (BMpyrrolBF4), 1-butyl-4-methylpyridinium (BMpyrBF4) or 1-butyl-1-methylpiperidinium (BMpipBF4) tetrafluoroborates were applied to improve the dispersion degree of the curatives and filler particles in the elastomer and to increase the efficiency of vulcanization. The differential scanning calorimetry results indicated that ILs reduced the vulcanization temperature of NBR compounds and increased the homogeneity of cross-link distribution in the elastomer network. NBRs filled with carbon black or silica exhibited similar thermal stabilities, whereas hydrotalcite reduced the temperature of thermal decomposition. The lowest mechanical loss factors were determined for vulcanizates filled with nanosized silica. 相似文献
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