Thermoplastic interpenetrating polymer networks based on a poly(styrene-b-butadiene) copolymer and an ionically-terminated polybutadiene ionomer

Thermoplastic interpenetrating polymer networks (IPN) are mixtures of two physically crosslinked polymers. Thermoplastic IPNs were prepared by blending an SBS triblock elastomer with a 1,2-polybutadiene that was ionically-terminated at both ends. The morphologies of these IPNs were studied using differential scanning calorimetry and dynamic mechanical thermal analysis. It was concluded that the ionomer was incompatible with the SBS elastomer, since the T_gs of both the 1,2-polybutadiene from the ionomer and the essentially 1,4-polybutadiene from the SBS component were observable at temperatures that were close to those of the individual components. The addition of the polybutadiene material had, however, an influence on the relaxation processes of the polystyrene blocks. The polystyrene glass transition in the pure SBS copolymer is broadened by the interfacial region between polystyrene and polybutadiene. The low temperature shoulder was much more pronounced when the ion-terminated polybutadiene was present, indicating it has a preference to be located in these interfacial regions. © 1994 John Wiley & Sons, Inc.     

Effect of changing groundwater levels caused by land-use changes on greenhouse gas fluxes from tropical peat lands

Monthly measurements of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes in peat soils were carried out and compared with groundwater level over a year at four sites (drained forest, upland cassava,upland and lowland paddy fields) located in Jambi province, Indonesia. Fluxes from swamp forest soils were also measured once per year as the native state of this investigated area. Land-use change from drained forest to lowland paddy field significantly decreased the CO₂ (from 266 to 30 mg C m^–2 h^–1) and N₂O fluxes (from 25.4 to 3.8 g N m^–2 h^–1), but increased the CH₄ flux (from 0.1 to 4.2 mg C m^–2 h^–1) in the soils. Change from drained forest to cassava field significantly increased N₂O flux (from 25.4 to 62.2 g N m^–2 h^–1), but had no significant influence on CO₂ (from 266 to 200 mg C m^–2 h^–1) and CH₄ fluxes (from 0.1 to 0.3 mg C m^–2 h^–1) in the soils. Averaged CO₂ fluxes in the swamp forests (94 mg C m^–2 h^–1) were estimated to be one-third of that in the drained forest. Groundwater levels of drained forest and upland crop fields had been lowered by drainage ditches while swamp forest and lowland paddy field were flooded, although groundwater levels were also affected by precipitation. Groundwater levels were negatively related to CO₂ flux but positively related to CH₄ flux at all investigation sites. The peak of the N₂O flux was observed at –20 cm of groundwater level. Lowering the groundwater level by 10 cm from the soil surface resulted in a 50 increase in CO₂ emission (from 109.1 to 162.4 mg C m^–2 h^–1) and a 25% decrease in CH₄ emission (from 0.440 to 0.325 mg C m^–2 h^–1) in this study. These results suggest that lowering of groundwater level by the drainage ditches in the peat lands contributes to global warming and devastation of fields. Swamp forest was probably the best land-use management in peat lands to suppress the carbon loss and greenhouse gas emission. Lowland paddy field was a better agricultural system in the peat lands in terms of C sequestration and greenhouse gas emission. Carbon loss from lowland paddy field was one-eighth of that of the other upland crop systems, although the Global Warming Potential was almost the same level as that of the other upland crop systems because of CH₄ emission through rice plants.     

H ∞ filtering for singular bilinear systems with application to a single-link flexible-joint robot

In this paper, we consider the H _∞ filters design for singular bilinear systems. The approach is based on the parameterized solution of a set of constrained Sylvester equations. The exponential convergence and l ₂ gain attenuation problems are solved by using the bounded real lemma, which leads to linear matrix inequalities (LMI) formulation. Finally, a detailed design procedure is given for the estimation of the states of a flexible joint robot, which demonstrates the effectiveness of the proposed method.     

Synthesis of UHMW-PE by a Highly Active Homogeneous System: η5-(C5H5)2Ti(η1-OC(O)C6H5)2/MAO

Summary The complex ⁵-(C₅H₅)₂Ti (¹-OC(O)C₆H₅)₂ was synthesized and activated with MA0 for ethylene polymerization. The resultant polymer is UHMW-PE with a viscosimetric molecular weight of Mv = 6.8 x 10⁶ to 0.7 x 10⁶ g/mol dependent on the temperature of the reaction. The effects of the Al/Ti molar ratio and temperature of the reaction on the catalytic activity and polymer properties were studied.     

Physicochemical properties of irradiated and loaded LDPE films with polyfunctional monomers

Polyfunctional monomers (PFMs), namely, trimethylol propane trimethacrylate (TMPTMA), trimethylol propane triacrylate, ethylene glycol dimethacrylate, and diethylene glycol diacrylate were blended with low‐density polyethylene (LDPE) and exposed to different doses of EB irradiation. Fourier transform infrared and ultraviolet and UV–vis spectroscopy of the unirradiated, irradiated, unloaded, and PFMs‐loaded LDPE films were studied under various irradiation doses up to 300 kGy. The degree of crosslinking and oxidative degradation, as measured by the spectroscopic parameters, were dependent on both the irradiation dose and the type of loaded PFMs. For all of the loaded monomers, the extent of crosslinking increased at different rates as a function of irradiation dose. TMPTMA monomer was the most efficient in enhancing the crosslinking of LDPE films compared to the other loaded monomers. However, the unloaded LDPE film showed the least extent of crosslinking. In addition, the EB‐radiation‐induced changes, such as trans‐vinylene formation, a decrease in vinyl and vinylidene unsaturation; and carbonyl double‐bond formation and change in crystallinity were correlated. The importance of these results on the prediction of the role of polyfunctional monomers in the production of crosslinked polymers is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2025–2035, 2003     

Preparation and thermomechanical characterization of poly(vinyl chloride) blends compatible with terpolymer‐containing maleic anhydride

In this study, I aimed to change the thermomechanical characteristics of poly(vinyl chloride) (PVC), which is widely used in commercial areas. Copolymers containing maleic anhydride (MA) units are commonly used to obtain compatible polymer blends. In our study, PVC blends were also prepared with the terpolymers with and without anhydride units. I assumed that the impact of the terpolymer on the thermomechanical characteristics of the PVC material could be more effectively controlled. For this purpose, two sets of six different blends of PVC with or without MA were synthesized, among which one was pure PVC, but the other five blends contained 2, 4, 6, 8, and 10% terpolymer. In conclusion, I observed that the terpolymer with the MA unit more regularly changed the thermomechanical characteristics of PVC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1586–1589, 2004     

Synchronization in heterogeneous networks of discrete‐time introspective right‐invertible agents

This paper studies output synchronization problem, formation problem, and regulated synchronization problem for a heterogenous network of discrete‐time introspective right‐invertible agents. We first propose a decentralized control scheme to solve the output synchronization problem for a set of communication topologies. Moreover, if the synchronization trajectories are assumed to be bounded, a universal controller can be constructed for all communication topologies, which contain a directed spanning tree. The design can be applied to solve the formation problem with arbitrary formation vectors. In the regulated synchronization problem, we assume only the root receives information from exosystem. We then design a decentralized controller to solve the problem for a set of communication topologies. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and Processing Characteristics of Ba0.65Sr0.35TiO3 Powders from Catecholate Precursors

Powders of composition Ba_0.65Sr_0.35TiO₃ were prepared from catecholate precursor phases, BaTi(C₆H₄O₂)₃ and SrTi (C₆H₄O₂)₃. The physical and chemical properties of the base powders, and those doped with 0.2 wt% manganese, are reported in detail. The dimensions of the primary particles in the starting powders were of the order of 20–50 nm, but the occurrence of abnormal grain growth during sintering promoted grain sizes in the ceramic of up to ∼100 μm. In some microstructures, coarse grains coexisted with a ∼1-μm fraction to produce a characteristic bimodal grain size distribution. By contrast, under comparable sintering conditions, namely 1350° or 1400°C for 1 h, grain growth in Mn-doped samples was suppressed, leading to uniform microstructures with a grain size of only a few micrometers. The pellet densities were nevertheless similar, 97% of theoretical in both doped and undoped samples. No significant difference was observed in the dielectric permittivity of the two compositions: the peak relative permittivity occurred at ∼20°C, with a maximum value of ∼22 000.     

Eco-friendly electronics,based on nanocomposites of biopolyester reinforced with carbon nanotubes: a review

ABSTRACT

Fabrication of electronic materials from nanocomposite of biopolyesters reinforced with carbon nanotubes can be regarded as the effective alternative for conventional nanocomposites consisting of non-biodegradable polymers. Commercial availability of biopolyester-based nanocomposites is limited because of their high cost compared to other polymers, but the factor of their compostable nature is worthless for environmental protection. Such nanocomposites have potential applications in biodegradable sensors, EMI materials, etc. In this review, the current progress of biopolyester/CNTs nanocomposites in the field of biodegradable electronics is reviewed and also the impact of CNTs dispersion on electrical, thermal and mechanical properties of eco composites is stipulated.     

Synthesis,characterization, and antitumor activity of poly(maleic anhydride‐co‐vinyl acetate‐co‐acrylic acid)

The ternary copolymerization of maleic anhydride (MA), vinyl acetate (VA), and acrylic acid (AA) [P(MA‐co‐VA‐co‐AA)], which is considered to be an acceptor–donor–acceptor system, was carried out in 1,4‐dioxane with benzoyl peroxide as an initiator at 70°C under a nitrogen atmosphere. Constants of complex formation for the monomer systems in the study were determined by UV–visible (hydrogen‐bonding complex) and ¹H‐NMR (charge transfer complex) methods, respectively. The results show that polymerization of the P(MA‐co‐VA‐co‐AA) system proceeds by an alternating terpolymerization mechanism. It is shown that the synthesized copolymers have typical polyelectrolyte behavior, ability for reversible hydrolysis–anhydrization reactions, and semicrystalline structures. In these cases, including radical polymerization, and formation of semicrystalline structures, the hydrogen‐bonding effect plays a significant role. The in vitro cytotoxicities of the synthesized terpolymer and alternating copolymer were evaluated using Raji cells (human Burkitt lymphoma cell line). The antitumor activities of prepared anion‐active copolymers were studied using methyl–thiazol–tetrazolium colorimetric assay and 50% of the cytotoxic dose of each copolymer and terpolymer were calculated. Hydrolyzed P(MA‐co‐VA‐co‐AA) and P(MA‐alt‐AA) copolymers have sufficiently high antitumor activity, which depends on the amount of hydrogen‐bonding carboxylic groups and their regular distribution in the side chain of functional macromolecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3425–3432, 2006