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Michael R. Van De Mark Ameya M. Natu Sagar V. Gade Minghang Chen Catherine Hancock Cynthia Riddles 《Journal of Coatings Technology and Research》2014,11(2):111-122
The formation of colloidal unimolecular polymer (CUP) particles from single polymer strands was investigated as a function of molecular weight. The CUP particle size was correlated with the absolute molecular weight and its distribution. The characteristics of the particles were evaluated with respect to viscosity, acid number, size distribution, and stability. The particle size varied from less than 3 nm to above 8 nm representing polymers with molecular weight in the range of 3000–153,000. Lower molecular weight polymers were found to be unstable. Particle size measurements using dynamic light scattering technique indicated a normal distribution which corresponded to the molecular weight distribution of the copolymer. The statistical distribution of the acid groups in the polymer chains played a significant role in the stability of low molecular weight polymers. 相似文献
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Sankalp Kota Louisiane Verger Varun Natu Maxim Sokol Michel W. Barsoum 《Journal of the American Ceramic Society》2021,104(2):733-739
The thermal stability and decomposition mechanisms of Fe2AlB2 powders, synthesized by reactive powder metallurgy, were studied under nitrogen (N2) or argon (Ar) atmospheres. The effects of using different FeB precursors to synthesize the Fe2AlB2 and hydrochloric acid (HCl) purification treatments on the thermal stability were also investigated. When as-synthesized Fe2AlB2 powders are treated in dilute HCl to dissolve impurity phases, decomposition in N2 atmospheres occurs readily above 1200 K. The decomposition reaction involves β-FeB precipitation and the liberated Al atoms reacting with the ambient N2 to form AlN. Under Ar environments, HCl-treated Fe2AlB2 powders decompose and precipitate β-FeB, by the out-diffusion of Al from the nanolaminated structure. Interestingly, isothermal annealing under N2 atmospheres revealed that Fe2AlB2 was more thermally stable when synthesized from lab-synthesized, instead of commercially available, FeB precursors and when the HCl treatment was avoided. The effects of the various factors on the decomposition temperature and decomposition mechanisms are discussed herein. 相似文献
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The crystallization behavior, modification of crystalline form, and orientation in polypropylene processed by blow film extrusion was studied as a function of processing parameters as well as different types of additives. The isothermal crystallization rate was greatly enhanced in the presence of certain additives, especially CaCO3. The crystalline form was predominantly α type in both compression molded or blow extruded films. However, there was an unusually large intensity of the α040 peak in the X-ray diffraction of the latter case films. The variation of the peak intensities and the increase of birefringence with increase of take-up speed has been explained on the basis of orientation induced by uniaxial stress in the machine direction. This orientation contained two components, namely the orientation of the b axis of the crystallites and the orientation of loosely bound polymer chains in the amorphous regions. © 1995 John Wiley & Sons, Inc. 相似文献
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Synthesis and application of acrylic colloidal unimolecular polymers as a melamine thermoset system
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Acrylic polymers were synthesized with a ratio of 1 : 7 or 1 : 8 of acrylic acid to acrylic ester monomers to produce an acid‐rich resin. The polymers were water reduced and solvent was stripped to produce colloidal unimolecular polymers (CUPs). These particles were typically 3–9 nm in diameter depending on the molecular weight. They were then formulated into a clear coating with melamine as the crosslinker with thermal curing. Compared to commercial latex films, these melamine‐cured acrylic CUPs had a distinct advantage of having a near‐zero volatile organic compound, better availability of surface functional groups , and improved water resistance. The coatings were evaluated for their methyl ethyl ketone resistance, adhesion, hardness, gloss, flexibility, abrasion , and impact resistance properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40916. 相似文献
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Probe Station Placement for Robust Monitoring of Networks 总被引:1,自引:0,他引:1
We address the problem of selecting probe station locations from where probes can be sent to monitor all the nodes in the
network. Probe station placement involves instrumentation overhead. Hence, the number of probe stations should be minimal
to reduce the deployment cost. Also, probe station placement should be such that the network can be monitored even in the
presence of failures. We present algorithms to select locations of probe stations so that the entire network can be monitored
for computing various performance metrics. We aim to find a minimal set of probe station nodes so as to minimize the instrumentation
overhead. The algorithm presented provides robust monitoring in presence of node failures. We then present algorithms to make
the solution resilient to probe station failures, and to deal with weakly connected nodes. We provide an experimental evaluation
of the proposed algorithms through simulation results.
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Adarshpal S. SethiEmail: |
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S. Radhakrishnan M. Tapale N. Shah E. Rairkar V. Shirodkar H. P. Natu 《应用聚合物科学杂志》1997,64(7):1247-1253
The structure development and mechanical properties of blow extruded polypropylene containing β-phase nucleating additives was studied. Quinacridone red and cadmium red were both found to nucleate the β phase in polypropylene, the former being a much more efficient nucleator than the latter. The β-phase spherulites formed in the presence of these nucleating agents were small and extensively volume filled, yielding high crystallinity. The modulus increased 2–3 times, elongation at break decreased, and there was a sharp break point without much yield when the β-phase nucleating agents were added as compared to the pure α-phase polypropylene. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1247–1253, 1997 相似文献
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Chlorocarboxylated polyethylene (CCPE) is produced by simultaneous reaction of chlorine and maleic anhydride (MA) with polyethylene (PE). Hydrogen atoms on the PE chain are substituted either by chlorine atoms or by maleic anhydride moieties. The reaction mechanism involves creation of an active site, i.e. a radical on the PE chain. There is competition between chlorine and MA molecules for the reaction with this macroradical. Chlorine reacts to give chlorinated polyethylene (CPE) type segments, while MA reacts as a single unit (as chloro derivative) without forming any graft copolymer. There is a marked reduction in the rate of chlorination of PE due to the presence of MA. This is probably due to the competitive nature of the process and the radical scavenging action of MA. 相似文献