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61.
The mechanical properties and post-thermal aging properties of natural rubber (NR) and polybutadiene rubber (BR) blends at
different blending ratios are investigated herein. The experimental results show that both tensile and tear strengths of NR/BR
blends increase with increasing NR content. BR has a higher compression stiffness than NR. The deformation of BR is less than
that of NR under the same load conditions. With regard to aging properties, both tensile stress and strain of NR/BR blends
decrease after prolonged aging. In addition, the stress loss of BR is lower than that of NR, meaning that the aging resistance
property of BR is superior to that of NR. Furthermore, accumulated thermal history has shifted the glass transition temperature
(T
g) of NR/BR blends toward lower temperatures while the loss tangent (tan δ) value increases with prolonged thermal aging. 相似文献
62.
The relations between coke yields and the volatile matter content of 30 individual and 30 blended coals were investigated. Coke yields and deposited carbon related to volatile matter content can be expressed in the following equations: CY (%) = 97.89?0.86 VMch+VMc; and DC (%)= ?2.24+0.16 VMch; where: CY=real coke yield; VMch = volatile matter content of charging coal; VMc=volatile matter content of coke, and in the case of <2%; DC = deposited carbon. The test results show excellent correlation with practice. 相似文献
63.
The pitting behaviour of type 321 stainless steel in sulfide-containing chloride aqueous environments was studied using cyclic potentiodynamic polarization. A well-established correlation between H2S and Na2S2O3 in the study of corrosion was applied, that is, H2S was simulated by Na2S2O3. The major factors affecting the pitting corrosion of type 321 stainless steel are the Cl- concentration, solution pH and temperature. The results clearly indicate that both Epit and E
pp decrease with increasing Cl- concentration and temperature, while I
pass is more sensitive to temperature variation. E
pit decreased with decreasing pH in the range 2 < pH < 7.5. The surface morphology and chemistry of the corroded type 321 stainless steel resulting from anodic polarization in 0.01 M S2O
3
2-
-containing Cl- solution were analysed by XRD, SEM and EPMA. A higher concentration of sulfur was found in the pits, and the dark surface film was mainly composed of FeS and -Fe2O3. The results describe the pitting behaviour of type 321 stainless steel in sulfide-containing Cl- aqueous environments. 相似文献
64.
Curing behavior and mechanical behavior of fully and semi-interpenetrating polymer networks based on polyurethane and acrylics 总被引:1,自引:0,他引:1
Polyurethane (PU) was made by reacting stoichiometric equivalent of trimethylol propane (TMP) and desmodur L. Fully interpenetrating polymer networks (fully IPN's) of various compositions based on PU and poly(ethylene glycol) diacrylate (PEGDA) were prepared by blending various ratios of PU/PEGDA, and cured by benzoyl peroxide (BPO). Semi-interpenetrating polymer networks based on PU and poly(ethylene glycol) monomethyl ether of acrylate (PEGMEA) were prepared in a similar way. Shift of exothermic peaks during IPN formation were examined with dynamic DSC. Viscosity increases were investigated with a Brookfield RVT type viscometer. Dynamic mechanical properties were probed via a rheometric dynamic spectroscopy (RDS).Expermintal results revealed a good compatibility of both IPN systems, as evidenced from the single damping peak of the RDS curves for each composition. Shifts of exothermic peaks to higher temperatures during the formation of fully IPN were observed, especially for the composition of PU/PEGDA = 50/50, which showed an exothermic peak at the highest temperature. Experimental results also revealed delayed viscosity increases and decreased gel fractions for all fully IPN's. On the contrary, the semi-IPN did not exhibibt similar phenomena. All these findings supported an effect of network interlock during fully IPN formation. The existence of a network not only provided a sterically hindered environment, but also restrained the chain mobility of the growing network, and vice versa, thus retarding the curing rates of both networks. Network interlock also broadened the width of the half damping peak, T1/2, and subsequently led to improved mechanical properties such as the impact resistance and Young's modulus of fully IPN material. 相似文献
65.
Blending is an effective method for improving polymer properties. However, the problem of phase separation often occurs due to incompatibility of homopolymers, which deteriorates the physical properties of polyblends. In this study, isotactic polypropylene was blended with low-density polyethylene. Crosslinking agent and copolymers of propylene and ethylene (either random copolymer or block copolymer) were added to improve the interfacial adhesion of PP/LDPE blends. The tensile strength, heat deflection temperature, and impact strength of these modified PP/PE blends were investigated. The microstructures of polyblends have been studied to interpret the mechanical behavior through dynamic viscoelasticity, wide-angle X-ray diffraction, differential scanning calorimetry, picnometry, and scanning electron microscopy. The properties of crosslinked PP/PE blends were determined by the content of crosslinking agent and processing method. For the material blended by roll, a 2% concentration of peroxide corresponded to a maximum tensile strength and minimum impact strength. However, the mechanical strength of those products blended by extrusion monotonously decreased with increasing peroxide content because of serious degradation. The interfacial adhesion of PP/PE blends could be enhanced by adding random or block copolymer of propylene and ethylene, and the impact strength as well as ductility were greatly improved. Experimental data showed that the impact strength of PP/LDPE/random copolymer ternary blend could reach as high as 33.3 kg · cm/cm; however, its rigidity and tensile strength were inferior to those of PP/LDPE/block copolymer blend. 相似文献
66.
Polymeric composites with conductivities ranging from 10–4 to 1 S cm–1 were prepared by electrochemically polymerizing pyrrole in a matrix of polyurethane. The polypyrrole/polyurethane alloy films obtained were characterized by element analysis, electron microscopy and electrical conductivity measurements. The morphology of the films depended on the solvent, the electrolyte and the current density. The mechanism of the electrochemical polymerization showed that PPy grew in a treelike structure, with molecular chains extending from the electrode surface into the solution. The transition temperature of the PPy/PU increased with the PPy content. 相似文献
67.
This work was undertaken to discuss in depth the vital differences in the morphological development during synthesis, and properties of starch‐g‐poly‐(vinyl acetate) copolymers using two different initiators, potassium persulfate (KPS) and ceric ammonium nitrate (CAN). KPS‐initiated system gave relatively low values of grafting ratio and grafting efficiency, indicating a great tendency for the formation of poly(vinyl acetate) homopolymer (PVAc). Yet, higher values were seen for the CAN‐initiated system. Transmission electron microscope observations indicated a relatively broad distribution of latex particles for the KPS‐initiated system. The surface potential of latex particles was about ?3.5 mV, which turned out to be insufficient to maintain stability of latex particles. On the other hand, a uniform particle size distribution was found for the CAN‐initiated system, as the surface potential of latex particles was 21.5 mV. Moreover, radicals on starch molecules were generated directly through a redox reaction with positively charged ceric ion. The hydrophobic PVAc chains were thus grafted on starch, resulting in an amphiphilic graft copolymer, which provides a sufficient stabilization degree as a role of surfactant to render a relatively uniform distribution of latex particles. The synthesized starch‐g‐poly(vinyl acetate) copolymers were further converted to starch‐g‐poly(vinyl alcohol) through saponification, which were subjected to evaluations regarding the biodegradation and cell culture capability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3017–3027, 2006 相似文献
68.
Blends of poly(ethylene terephthalate) (PET) and polypropylene (PP) at composition 80/20 with and without a compatibilizing
agent were studied. Both materials are widely used in the soft drink bottle industry. The compatibilizing agent was a maleic
anhydride grafted polyethylene-octene elastomer (POE-g-MA). The olefinic segment of POE is compatible with PP, whereas the maleic anhydride is affined with PET carbonyl groups.
The effectiveness of the compatibilizing agent was evaluated using different techniques, such as Fourier transform IR spectroscopy,
mechanical analysis, scanning electron microscopy, dynamic mechanical analysis, and rheological analysis. The results show
that the addition of POE-g-MA promotes a fine dispersed-phase morphology, and improves process ability and toughness of these blends. Shifts in the
glass-transition temperature of the PET phase and the increase in the melt viscosity of the compatibilized blends indicated
enhanced interactions between the discrete PET and PP phases induced by the functional compatibilizer. 相似文献
69.
Wen‐Bin Liau Yu‐Ting Sun Ling‐Yueh Yang Lee‐Yih Wang Wen‐Yen Chiu Kuo‐Huang Hsieh Sheng‐Mao Tseng 《应用聚合物科学杂志》2006,102(6):5406-5413
The polyaniline (PANI)‐coated polystyrene (PS) latexes were synthesized, and the electrically conductive films were prepared thereafter. The weight ratio of PANI was 5%. Thermal analysis of the latices was performed using DSC and TGA. In this study, the electrically conductive films were prepared above the PS glass transition temperature (Tg). During the film formation, the effects of the annealing temperature and atmosphere (air or N2) on the film resistance were investigated. In addition, the film morphology was observed utilizing scanning electron microscopy. The film resistance decreased in the initial heating stage due to the increasing temperature and the compaction of film. Then the film resistance increased with further annealing due to the aging of PANI. Typically, the film resistance was about 6000 Ω/sq, and the conductivity was 0.3 S/cm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5406–5413, 2006 相似文献
70.
Ralph H. Cullen Chiu Shun Dan Wendy A. Rogers Arthur D. Fisk 《International journal of human-computer interaction》2014,30(7):533-546
Operators and users interacting with computer environments often have to deal with multiple tasks at once, responding to each in series. Diagnostic automation, that is, automation that alerts users when and where to look, has been suggested to support the unique challenges of multiple task environments: activating tasks, switching between tasks, and tasks interfering with each other. Automation is not always reliable, however. Because of the common interaction with novel systems and the importance of training, the Simultaneous Task Environment Platform program—a multiple-task environment—was developed to understand the effects of experience on interaction with these automation-supported systems, as well as what strategies were developed. It was found that participants became more efficient with experience only when they interacted with higher reliability automation. Furthermore, the strategies participants developed focused on the differences between tasks and patterns across those tasks. Automated systems training should be sure to employ these findings. 相似文献