Discussion of “Virtual age,is it real?”

In this note, some point of views on virtual ages are presented in terms of the discussion paper written by Finkelstein and Cha, which include generalized stochastic order‐based virtual ages, system‐level virtual ages, virtual ages in Weibull distribution and repair degrees with virtual ages. Finally, some possible future researches on virtual ages are described.     

Path to achieving molecular dispersion in a dense reactive mixture

A uniform dispersion of reactants is necessary to achieve a complete reaction involving multicomponents. In this study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants: a highly crystalline hexamethylenetetramine (HMTA) and a strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to determine the role of specific intermolecular interactions necessary for the plasticizer to dissolve the highly crystalline HMTA and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of the HMTA. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1519–1526     

A post curing strategy toward the feasible covalent adaptable networks in polyacrylate latex films

The implementation of covalent adaptable networks (CANs) in general resin system is becoming attractive. In this work, we propose a simple post-curing strategy based on the core-shell structured acrylate latex for the achievement on both the improved general performance and the CANs characteristics in latex films. The building to the CANs was relied on the introduction of 4,4′-diaminophenyl disulfide as the curing agent, which cured the acetoacetoxy decorated shell polymer through the ketoamine reaction. The metathesis reaction of aromatic disulfides in the crosslinking segments enabled the thermally induced dynamic behavior of the network as revealed in the stress relaxation tests by comparison with other diamine crosslinking agents without the incorporation of disulfide. The synergism of the dynamic crosslinking of the shell polymer and static crosslinking in the core polymer contributed to the improved mechanical strength (15 MPa, strain% = 250%) and the suppressed water adsorption (~1% in 24 h of soaking) of the latex film, which exhibited above 90% of recovery in both strength and strain from a cut-off film damage within 1 h at 80°C. Moreover, the cured latex film could be recycled, and 75% of the mechanical performance was regained after three fragmentation-hot-pressing cycles. These, in addition with the feasible and environmental friendly characteristics, suggest a sustainable paradigm toward the smart thermosetting latex polymers.     

Monitoring real-time curing of epoxies in situ using single-sided NMR

Adhesively bonded joints using epoxy are widely used in aircraft and aerospace structures. Quality control and defect detection during epoxy curing in such applications is critical. We used single-sided nuclear magnetic resonance (NMR) to nondestructively probe and spatially resolve the change in the characteristic NMR relaxation time (T₂) of epoxies during curing on a substrate. Time-dependent T₂ values were fit to a Weibull function to model temporal changes in the NMR measurables. Our results demonstrate that the reduction in molecular mobility of various epoxy/curing agent mixtures occurs more rapidly at the interface than in the bulk. Further use of single-sided NMR to acquire spatially resolved T₂ data will provide a route for elucidatory epoxy curing studies. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 616–623     

Synthesis of novel thermosetting imide compounds having phenylethynyl carbonyl groups at both terminal ends and production of new network polymers based on the imide compounds

A novel thermosetting imide compound having a respective phenylethynyl carbonyl group at both terminal ends was newly synthesized from an acid anhydride having a phenylethynyl carbonyl group and various diamine compounds. The thermosetting behavior of the obtained novel thermosetting imide compound having phenylethynyl carbonyl groups was analyzed through differential scanning calorimetry measurements and infrared spectroscopic analysis. As a result, it became clear that a curing reaction of phenylethynyl carbonyl groups proceeds at approximately 200°C and that the curing reaction thereof proceeds at a temperature that is lower by 150°C or more compared with that of phenylethynyl groups. Examination of the polymerization reaction of the imide compounds having phenylethynyl carbonyl groups using model compounds revealed that a reaction that imparted an alkene C=C and polycyclic aromatic structure progressed. Moreover, a network polymer obtained from a thermosetting imide compound having respective phenylethynyl carbonyl groups at both terminal ends exhibited extremely superior heat resistance and thermal decomposition resistance. These superior thermal properties are thought to be due to the strong molecular interaction (molecular packing) that results from the polycyclic aromatic structures and alkenes produced through polymerization of the phenylethynyl carbonyl groups and to the suppression of the movement of the molecular chains.     

Logging damage and injured tree mortality in tropical forest management

Using insights from the forest ecology literature, we analyze the effect of injured trees on stand composition and carbon stored in above‐ground biomass and the implications for forest management decisions. Results from a Faustmann model with data for a tropical forest on Kalimantan show that up to 50% of the basal area of the stand before harvest can consist of injured trees. Considering injured trees leads to an increase in the amount of carbon in above‐ground biomass of up to 165%. These effects are larger under reduced impact logging than under conventional logging. The effects on land expectation value and cutting cycle are relatively small. The results suggest that considering injured trees in models for tropical forest management is important for the correct assessment of the potential of financial programs to store carbon and conserve forest ecosystem services in managed tropical forests, such as reducing emissions from deforestation and forest degradation and payment for ecosystem services. Recommendations for Resource Managers

• Considering the role of injured trees is important for managing tropical forests
• These trees can cover up to 50% of basal area and contain more than 50% of the carbon stored in above‐ground biomass
• Reduced impact logging leads to a larger basal area of injured trees and more carbon stored in injured trees than conventional logging
• Injured trees play an important role when assessing the potential for carbon storage in the context of payment for forest ecosystem services.

     

Synthesis and characterization of epoxy resins containing imine group and their curing processes with aromatic diamine

The epoxy resins containing imine bonding were prepared from hydroxyl substituted Schiff base monomers in two steps. At the first step, hydroxyl substituted Schiff base monomers were synthesized via condensation reaction. At the second step, epoxy resins were synthesized from the reaction between Schiff base monomers and epichlorohydrine (EPC). Then curing processes of epoxy resins were achieved by p-phenylenediamine compound. The structures of resulting compounds were confirmed by FT-IR, UV-Vis and ¹H-NMR. TG-DTA and DSC measurements were performed for thermal characterizations of the compounds. Chemical resistances of the cured epoxy-amine systems were determined for coating applications in acidic, alkaline and organic solvents. HCl (10%, aqueous solution), NaOH (10%, aqueous solution), DMSO, DMF, N-methylpyrrolidone, ethanol, THF and acetone were used for corrosion tests. Chemical resistance data of the synthesized epoxy resins demonstrated that they have good chemical resistance against various acid, alkaline and common organic solvents. Surface morphologies of epoxy resin and the cured epoxy resin were determined with scanning electron microscopy (SEM) measurements. Also, optical band gap (E_g) values of Schiff base monomers and epoxy resins were calculated from UV-Vis measurements.     

Sol-Gel Microspheres Doped with Glycerol: A Structural Insight in Light of Forthcoming Applications in the Polyurethane Foam Industry

Porous silica-based microspheres encapsulating aqueous glycerol can be potential curing agents for one-component foams (OCFs). Such agents have the advantage of an enhanced sustainability profile on top of being environmentally friendly materials. A synthetically convenient and scalable sol-gel process was used to make silica and organosilica microspheres doped with aqueous glycerol. These methyl-modified silica microspheres, named “GreenCaps”, exhibit remarkable physical and chemical stability. The microspheres were characterized by scanning electron microscopy, transmission electron microscopy at reduced pressure, and cryogenic nitrogen adsorption—desorption analysis. The structure of the materials was also analyzed at the molecular level by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. As expected, the degree of methylation affects the degree of encapsulation and pore structure. Microspheres similarly methylated, however, can differ considerably in surface area and pore size due to the templating effect of glycerol on the organosilica structure. The results of the structure analysis reveal that glycerol is efficiently encapsulated, acts as a template, barely leaches over time, but is released by depressurization. A proper application of these microspheres can later on enhance both the environmental and health profile, as well as the technical performance (curing speed, foam quality, and froth thixotropy) of spray polyurethane foams.     

Global dynamics of an age‐structured virus model with saturation effects

An infection‐age virus dynamics model for human immunodeficiency virus (or hepatitis B virus) infections with saturation effects of infection rate and immune response is investigated in this paper. It is shown that the global dynamics of the model is completely determined by two critical values R ₀, the basic reproductive number for viral infection, and R ₁, the viral reproductive number at the immune‐free infection steady state (R ₁<R ₀). If R ₀<1, the uninfected steady state E ⁰ is globally asymptotically stable; if R ₀>1 > R ₁, the immune‐free infected steady state E ^? is globally asymptotically stable; while if R ₁>1, the antibody immune infected steady state is globally asymptotically stable. Moreover, our results show that ignoring the saturation effects of antibody immune response or infection rate will result in an overestimate of the antibody immune reproductive number. Copyright © 2016 John Wiley & Sons, Ltd.     

Two Zn(II)‐based meta‐organic frameworks: Selective detection of antibiotics and treatment activity on age‐related macular degeneration by reducing inflammasome activation

Via utilizing the mixed‐ligand method, two novel Zn(II)‐containing meta‐organic frameworks with the chemical formula of {[Zn(L)(5‐HIP)]·H₂O}_n ( 1 ) and [Zn(L)(2,6‐NDC)]_n ( 2 ) were prepared under the solvothermal conditions by applying aromatic dicarboxylic acids ligands (5‐H₂HIP = 5‐hydroxyisophthalic acid; 2,6‐H₂NDC = 2,6‐naphthalenedicarboxylic acid) and 1,4‐bis(benzimidazol‐1‐yl)‐2‐butylene (L). Due to its good water stability as well as the strong luminescent emission around room temperature, complex 2 has the high selectivity and sensibility of fluorescence detection to the ceftriaxone sodium (a kind of antibiotic) with the detection limit up to ppm lever. The treatment activity of the compounds on age‐related macular degeneration was assessed and the specific mechanism was investigated. First of all, the inflammasome activation in the endothelial cells of retina was evaluated with western blot. In addition to this, the down‐stream production of the inflammasome activation was also measured with ELISA detection kit.