Dow Chemical (Brasil)

We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of alpha-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.

Ethylene/ethane separation via cryogenic distillation is extremely energy‐intensive, and membrane separation may provide an attractive alternative. In this paper, ethylene/ethane separation performance using polymeric membranes is summarized, and an experimental ethylene/ethane polymeric upper bound based on literature data is presented. A theoretical prediction of the ethylene/ethane upper bound is also presented, and shows good agreement with the experimental upper bound. Further, two ways to overcome the ethylene/ethane upper bound, based on increasing the sorption or diffusion selectivity, is also discussed, and a review on advanced membrane types such as facilitated transport membranes, zeolite and metal organic framework based membranes, and carbon molecular sieve membranes is presented. Of these, carbon membranes have shown the potential to surpass the polymeric ethylene/ethane upper bound performance. Furthermore, a convenient, potentially scalable method for tailoring the performance of carbon membranes for ethylene/ethane separation based on tuning the pyrolysis conditions has also been demonstrated. © 2013 American Institute of Chemical Engineers AIChE J , 59: 3475–3489, 2013

Abstract Poly(3,4-ethylene dioxythiophene) (PEDOT) is a chemically stable, conjugated polymer that is of considerable interest for a variety of applications including coatings for interfacing electronic biomedical devices with living tissue. Here, we describe recent work from our laboratory and elsewhere to investigate the morphology of PEDOT in the solid state. We discuss the importance of oxidative chemical and electrochemical polymerization, as well as the critical role of the counterion used during synthesis and film deposition. We have obtained information about the morphology of PEDOT from a number of different complimentary techniques including X-ray diffraction, optical microscopy, scanning electron microscopy, transmission high-resolution electron microscopy, and low-voltage electron microscopy. We also discuss results from ultraviolet-visible light spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). PEDOT is a relatively rigid polymer that packs in the solid state at a characteristic face-to-face distance (010) of ∼0.34 nm, similar to graphite. These sheets of oriented PEDOT molecules are separated from one another by ∼1.4 nm laterally, with the (100) distance between layers quite sensitive to the choice of counterion used during sample preparation. The order in the films is typically modest, although this also depends on the counterion used and the method of film deposition. The films can be organized into useful structures with a variety of nanoscale dissolvable templates (including fibers, particles, and lyotropic mesophases). When PEDOT is electrochemically deposited in the presence of bromine counterions, highly ordered crystalline phases are observed. It is also possible to deposit PEDOT around living cells, both in vitro and in vivo. Keywords: conjugated polymerspolymer morphologypoly(thiophene)polymer microscopy Acknowledgements The authors gratefully appreciate funding from the National Science Foundation, the National Institute of Health, the Army Research Office, the University of Michigan College of Engineering GAP funding program, Biotectix LLC, the Michigan University Commercialization Initiative, and the Defense University Research Instrumentation Program. The assistance of Dr. John Mansfield and Dr. Haiping Sun at the Electron Microscopy and Analysis Laboratory (EMAL) is appreciated. The support of Ying Qi in the Materials Science and Engineering J. D. Hanawalt X-ray Microanalysis Laboratory (XMAL) is acknowledged. Andre Pergeron, a summer student from Greenhills High School in Ann Arbor, assisted in the LVEM of PEDOT. Dotty Sorenson from the Medical Imaging Laboratory (MIL) in the Medical School provided technical support in the embedding, microtoming, and TEM imaging of alginate and PEDOT-coated alginate hydrogels. DCM, JLH, and SRB are cofounders of Biotectix, a University of Michigan spin-off company interested in the commercialization of materials for interfacing electronic biomedical devices with living tissue.

Abstract Polymerization of anhydrous ethylenimine proceeds to completion with destruction of the terminal 1-aziridinyl group at relatively low molecular weight. In the absence of evidence for end groups, it is suggested that the chain terminating process is the formation of large rings composed of repeating CzHs N units. Information is given on the various intermediates present in the early stages of polymerization of ethylenimine and on analytical techniques for determining the degree of branching in polyethylenimine.

ABSTRACT: Pesticides are considered the first line of defense for the control of pests and diseases. At least in the short and medium term, the use of pesticides will remain an important strategy for pest management, allowing growers to produce crops of sufficient quality at low costs. A broad approach known as Integrated Pest Management (IPM) combines several different pest-control strategies, among which the combination of chemical and biological control stands out. It requires pesticides that achieve optimal control of target pests with minimal impact on the activity of biological control agents. Because of the dynamics of pest infestations, IPM routines are continuously adjusted by growers, requiring comprehensive information about pesticide effects on natural enemies. However, this information is not always available and often contradictory, which constrains the design of field recommendations. In this review, we focused on the importance of selective pesticides in IPM programs, and the effects of chemical pesticides on parasitoids, predators, and entomopathogenic fungi. We provided a detailed discussion of the challenges and constraints for research on pesticide effects on natural enemies, as well as for the resulting field recommendations.

Abstract This study reports 6FDA:BPDA‐DAM polyimide‐derived hollow fiber carbon molecular‐sieve (CMS) membranes for hydrogen and ethylene separation. Since H 2 /C 2 H 4 selectivity is the lowest among H 2 /(C 1 ‐C 3 ) hydrocarbons, an optimized CMS fiber for this gas pair is useful for removing hydrogen from all‐cracked gas mixtures. A process we term hyperaging provides highly selective CMS fiber membranes by tuning CMS ultramicropores to favor H 2 over larger molecules to give a H 2 /C 2 H 4 selectivity of over 250. Hyperaging conditions and a hyperaging mechanism are discussed in terms of an expedited physical aging process, which is largely controlled by the hyperaging temperature. For the specific CMS material considered here, a hyperaging temperature beyond 90 °C but less than 250 °C works best. Hyperaging also stabilizes CMS materials against physical aging and stabilizes the performance of H 2 separation over extended periods. This work opens a door in the development of CMS materials for the separation of small molecules from large molecules.

Abstract The use of agricultural-based biofuels has expanded. Discussions on how to assess green house gas (GHG) emissions from biofuel policies, specifically on (non-observed) land-use change (LUC) effects involve two main topics: (i) the limitations on the existing methodologies, and (ii) how to isolate the effects of biofuels. This paper discusses the main methodologies currently used by policy-makers to take decisions on how to quantify LUCs owing to biofuel production expansion. It is our opinion that the concerns regarding GHG emissions associated with LUCs should focus on the agricultural sector as a whole rather than concentrating on biofuel production. Actually, there are several limitations of economic models and deterministic methodologies for simulating and explaining LUCs resulting from the expansion of the agricultural sector. However, it is equally true that there are avenues of possibilities to improve models and make them more accurate and precise in order to be used for policy-making. Models available need several improvements to reach perfection. Any top model requires a concentration of interdisciplinary designers in order to replicate empirical evidence and capture correctly the agricultural sector dynamics for different countries and regions. Forgetting those limitations means that models will be used for the wrong purposes.

Various types of polyethylene homopolymers and copolymers, including linear high-density polyethylene (HDPE), branched low-density polyethylene (BLDPE), poly(ethylene vinyl acetate) copolymer (EVA), heterogeneous linear poly(ethylene/α-olefin) copolymer (het-LEAO) or commonly known as linear low-density polyethylene, homogeneous linear poly(ethylene/α-olefin) copolymer (hom-LEAO), and homogeneous branched poly(ethylene/α-olefin) copolymer (hom-BEAO), were evaluated for their melt rheological and thermodynamic properties with emphasis on their molecular structure. Short-chain branching (SCB) mainly controls the density, but it has little effect on the melt rheological properties. Long-chain branching (LCB) has little effect on the density and thermodynamic properties, but it has drastic effects on the melt rheological properties. LCB increases the pseudo-plasticity and the flow activation energy for both the polyethylene homopolymer and copolymer. Compared at a same melt index and a similar density, hom-LEAO has the highest viscosity in processing among all polymers due to its linear molecular structure and very narrow molecular weight distribution. Small amounts of LCB in hom-BEAO very effectively reduce the average viscosity and also improve the flow stability. Both hom-LEAO and hom-BEAO, unlike het-LEAO, have thermodynamic properties similar to BLDPE. © 1996 John Wiley & Sons, Inc.

Abstract Overload phenomena in GPC are investigated with samples of narrow polystyrenes and short but efficient columns packed with Styragel. Viscous fingering is shown to be a leading cause of peak skewing and broadening. A correlation is proposed to define a safe operating range in terms of sample concentration, volume, and the average intrinsic viscosity of the solute polymer.

The marine dinoflagellate, Glenoclinium foliaceum Stein, has been shown to contain fucoxanthin, instead of peridinin, as the major xanthophyll. In addition, 2 carotenes-β-carotene and a compound with spectral properties reminiscent of isomerized y-carotene-and 2 xanthophylls-diadinoxanthin and an unidentified compound-were also isolated. These results support an earlier work that indicated the possible presence of fucoxanthin in some members of the Pyrrophyta.

The viability of recycling post-industrial packaging waste, compounded from multilayer laminated PET-PE films, for production of polymer blends with good physico-mechanical performance is analyzed. Initially, several PET-PE model-blends were prepared from fresh polymers and were compounded with different formulations, based on design of experiments (DOE). Polymer compatibilizers based on maleic anhydride (PE-g-MA) and glycidyl methacrylate (E-GMA) have been used to promote the compatibilization reaction. The physico-mechanical properties of the model-blends were evaluated by response surface methodology (RSM). Finally, the post-industrial waste was compounded with the same concentration of compatibilizers in the previous set of model-blends. The DOE methodology showed to be a useful tool for assessing the recycling, since it helped to produce recycled materials with acceptable physico-mechanical properties. Between both compatibilizers studied, PE-g-MA showed to be the best additive for compatibilization due to the presence of a polyamide component in the waste, which undergoes a kinetically favorable compatibilization reaction.

Abstract Block copolymer surfactants, made from 1,2‐butylene oxide (BO), propylene oxide (PO) and ethylene oxide (EO), exhibit wide ranges of properties and performance. In particular, BO/EO block copolymers exhibit improved surfactant performance with respect to PO/EO analogs. One interesting difference between these two classes of surfactants is the EO capping efficiency of polyoxypropylene (POP) vs. polyoxybutylene (POB) hydrophobe secondary hydroxyl groups. In this regard, nuclear magnetic resonance measurements have shown that POP secondary diols react more readily with EO than POB diols. For the case of ethoxylated POB polymers, the amount of unethoxylated secondary hydroxyl is proportional to the average length of the polyoxyethylene (POE) blocks. Differential scanning calorimetry was used to observe crystallinity of POE blocks. For a given POB hydrophobe molecular weight and weight percentage EO, surfactant performance properties can be augmented by affecting POE block length in the ethoxylation process.

Five graphite/epoxy composites containing toughened epoxies prepared at Dow Chemical and AS-4 graphite fibers from Hercules have been studied in Mode I, mixed mode, and Mode II to determine their delamination fracture toughnesses Gc and the controlling micromechanism of fracture. The Gc values were determined using split laminate specimens. The delamination fracture process was observed in real time in the scanning electron microscope. To increase delamination fracture toughness, both an improved interface as well as higher resin toughness were found to be required. Increasing Mode II loading, particularly of the more brittle systems, gives a significantly greater resistance to crack propagation as measured by the total energy release rate required to propagate the crack.

Genetically modified soybean with transgenic event DAS-81419-2 (Conkesta™ technology), expresses two Bacillus thuringiensis (Bt) derived proteins, Cry1Ac and Cry1F. Event DAS-81419-2 is a proposed new Integrated Pest Management (IPM) tool with demonstrated high efficacy for controlling the primary lepidopteran pests affecting soybean production in South America. Studies were conducted in Brazil from 2011 to 2016 to assess the efficacy of DAS-81419-2 against secondary lepidopteran pests including Elasmopalpus lignosellus, Agrotis ipsilon and Helicoverpa armigera, using artificial infestations to ensure uniform pest pressure. Results from research trials across nine localities showed that compared to a non-Bt isoline, DAS-81419-2 significantly reduced the seedling stage plant mortality caused by E. lignosellus and the feeding damage caused by H. armigera during both vegetative and reproductive crop growth stages. Event DAS-81419-2 showed moderate activity on A. ipsilon, and additional control tactics such as a chemical insecticide applied as a seed treatment or spray during early crop stages may be needed against this pest to provide consistently higher levels of protection in fields that are at risk of infestation. Collectively, the efficacy of soybean transgenic event DAS-81419-2 for the control of secondary lepidopteran pests, added to its high efficacy on primary lepidopteran pests suggest this new, dual protein technology will be an important tool where primary and secondary pests affect soybean production.

Abstract Zeolitic membranes synthesized using organic structure‐directing agents (SDAs) require an activation step to remove the SDA and open their porosity. Activation is typically achieved by high‐temperature (>673 K) calcination. This process has multiple disadvantages, including coke formation due to incomplete removal of the SDA as well as the formation of cracks and other defects due to differential thermal expansion of the membrane layer and the underlying support material. Here we report that high‐performance hollow fiber membranes of the small‐pore (0.38 nm) zeolite SSZ‐13 can be produced via UV irradiation to decompose and remove the SDA. Remarkably, UV irradiation allowed complete removal of the bulky SDA (trimethyladamantylammonium hydroxide) from the pores at near‐ambient conditions, whereas membranes activated by calcination exhibited severe cracking. The UV‐activated SSZ‐13 membranes showed excellent H 2 /C 3 H 8 and CO 2 /CH 4 mixture selectivities (up to 810 and 110 whereas the conventionally activated membranes showed poor selectivity (<5). The combined demonstration of hollow fiber membrane synthesis and low‐temperature membrane activation of small‐pore zeolite membranes is a significant step in the effort to create reliable, scalable, and low‐cost fabrication processes for zeolite membranes for gas separations.

Bacillus thuringiensis (Bt) event DAS-81419-2 (Conkesta technology) in soybean, Glycine max (L.) Merrill, expresses Cry1F and Cry1Ac proteins to provide protection from feeding by several lepidopteran pests. A total of 27 field experiments across nine locations were conducted from 2011 to 2015 in southern and central Brazil to characterize the efficacy of DAS-81419-2 soybean infested with Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae), Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), Heliothis virescens (F.) (Lepidoptera: Noctuidae), and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) during vegetative (V4) and reproductive (R2 and R4) crop developmental stages. The efficacy of DAS-81419-2 was compared to that of a non-Bt isogenic variety managed with or without applications of commercial foliar insecticides for lepidopteran control. DAS-81419-2 soybean consistently experienced defoliation levels of 0.5% or less (compared with 20.05-56.74% in the non-Bt, nonsprayed treatment) and larval survival of < 0.1% in all four species across the vegetative and reproductive plant stages evaluated. The efficacy of DAS-81419-2 was significantly higher than commercial foliar insecticides applied to the non-Bt variety. DAS-81419-2 soybeans containing two highly effective Bt proteins are expected to be a more robust IRM tool compared to single-trait Bt technologies. The consistent efficacy of DAS-81419-2 soybeans across years, locations, and crop stages suggests that it will be a valuable product for management of hard-to-control key lepidopteran pests in South American soybean production.

The requirements of the Texas State Implementation Plan of the U.S. Clean Air Act for the Houston-Galveston Ozone Nonattainment Area stipulate large reductions in oxides of nitrogen (NO(x)) emissions. A large number of sources at Dow Chemical Co. sites within the nonattainment area may require the addition of continuous emission monitoring systems (CEMS) for online analysis of NO(x), CO, and O2. At the outset of this work, it was not known whether the analyzers could accurately measure NO(x) as low as 2 ppm. Therefore, NO(x) CEMS analyzers from five different companies were evaluated for their ability to reliably measure NO(x) in the 2-20 ppm range. Testing was performed with a laboratory apparatus that accurately simulated different mixtures of flue gas and, on a limited basis, simulated a dual-train sampling system on a gas turbine. The results indicate that this method is a reasonable approach for analyzer testing and reveal important technical performance aspects for accurate NO(x) measurements. Several commercial analyzers, if installed in a CEMS application with sampling conditioning components similar to those used in this study, can meet the U.S. Environmental Protection Agency's measurement data quality requirements for accuracy.

BACKGROUND: The ability of sirolimus (SRL), in combination with reduced exposure of cyclosporine, was investigated to prevent acute rejection and associated side effects. METHODS: Between June 1999 and February 2000, 70 recipients of primary one-haplotype living-related donor renal allografts were randomized to receive SRL (2 mg/d) or azathioprine (AZA) (2 mg/kg/d) combined with cyclosporine and prednisone. The primary end-point was a composite of first occurrence of biopsy-confirmed acute rejection, graft loss, or death during the first 3 months after transplantation. RESULTS: From week 4 to month 12, SRL patients received lower cyclosporine (week 4: 364 mg/d vs. 455 mg/d, p = 0.004; month 12: 195 mg/d vs. 255 mg/d, p = 0.038) doses and showed lower cyclosporine concentrations (week 4: 247 ng/mL vs. 309 ng/mL, p = 0.04; month 12: 143 ng/mL vs. 188 ng/mL, p = 0.045). Compared with AZA, SRL patients showed reduced 3-month primary end point (0% vs. 17.1%, p = 0.025), and reduced incidence of biopsy-confirmed acute rejection at 3 months (0% vs. 14.3%, p = 0.01) but not at 12 months (11.4% vs. 14.3%, NS). Mean creatinine at 12 months were not different (1.8 +/- 0.6 vs. 1.6 +/- 0.6, p = 0.23). Hyperlipidemia was the only adverse event more frequent among SRL patients (49% vs. 17%, p = 0.01). There were no differences in infections and no malignancies in both groups. CONCLUSIONS: The combination of 2 mg fixed doses of SRL, reduced cyclosporine exposure and prednisone was associated with a low incidence of acute rejection and did not result in significantly impaired graft function compared with patients receiving AZA, standard doses of cyclosporine and prednisone.

Abstract Aqueous solutions of alkanolamines such as monoethanolamine (MEA) have been used for years to separate carbon dioxide and hydrogen sulfide from other gases in continuous absorption/desorption processes to meet very low treated gas specifications. However, MEA can undergo side reactions with CO2 which produce various types of degradation compounds. These by-products reduce performance of the solvent leading to increased energy consumption and corrosion. This can be a serious problem in applications such as the removal of CO2 in synthesis gas and natural gas treating with down stream cryogenic equipment. Formulated alkanolamine products based on methyldiethanolamine (MDEA) have made significant advances in energy efficiency, but are still susceptible to degradation and decreased performance. A next generation product, GAS/SPEC∗ CS-PLUS, has now been developed and shown to be even more energy efficient. In addition, it improves separation and overall capacity while maintaining long term performance.

This work applies a multi-scale approach to the microencapsulation by interfacial polymerization. Such microencapsulation is used to produce fertilizers, pesticides and drugs. In this study, variations at three different scales (molecular, microscopic and macroscopic) of product design (i.e., product variables, process variables and properties) are considered simultaneously. We quantify the effect of the formulation, composition and pH change on the microcapsules' properties. Additionally, the method of measuring the strength of the microcapsules by crushing a sample of microcapsules' suspension was tested. Results show that the xylene release rate in the microcapsules decreases when the amine functionality is greater due to a stronger crosslinking. Such degree of crosslinking increases the compression force over the microcapsules and improves their appearance. When high levels of amine concentration are used, the initial pH values in the reaction are also high which leads to agglomeration. This study provides a possible explanation to the aggregation based on the kinetic and thermodynamic controls in reactions and shows that the pH measurements account for the polyurea reaction and carbamate formation, which is a reason why this is not a suitable method to study kinetics of polymerization. Finally, the method used to measure the compressive strength of the microcapsules detected differences in formulations and composition with low sensibility.