Noncatalytic polymerization of ethylene glycol and epoxy molecules for rigid polyurethane foam applications

The study investigated an approach to incorporate modified epoxidized soy‐based vegetable oil polyol as a replacement for petroleum‐based polyether polyol and to substantially reduce the isocyanate loading in the rigid foam formulation. Noncatalytic polymerization of epoxidized bodied soybean oil and ethylene glycol (EG) was carried out in a closed batch reaction. Cleavage of the oxirane rings and hydroxyl group attachment at optimum conditions provided the desired polyol products. The polyols were characterized based on its hydroxyl numbers, acidity, viscosity, iodine number, and Gardner color index for quality purposes. Reactions of oxirane ring and EG were verified by spectroscopic FTIR. Crosslinking performance was evaluated by extractability analysis on the polyurethane (PU) elastomer wafers. Rigid foaming performed at 50 and 75% petroleum‐based polyether polyol replacements have shown excellent thermoinsulating and mechanical properties compared with epoxidized soybean oil (ESBO) alone or petroleum‐based polyether polyol alone. A reduction of up to 8% of the polymeric diphenylmethane diisocyanate was achieved using the synthesized ESBO‐EG‐based polyols. A higher average functionality polyol is key component to the reduction of isocyanate in PU synthesis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Rigid polyurethane foams made from high viscosity soy‐polyols

This study investigated the physical properties of water‐blown rigid polyurethane (PU) foams made from VORANOL®490 (petroleum‐based polyether polyol) mixed with 0–50% high viscosity (13,000–31,000 cP at 22°C) soy‐polyols. The density of these foams decreased as the soy‐polyol percentage increased. The compressive strength decreased, decreased and then increased, or remained unchanged and then increased with increasing soy‐polyol percentage depending on the viscosity of the soy‐polyol. Foams made from high viscosity (21,000–31,000 cP) soy‐polyols exhibited similar or superior density‐compressive strength properties to the control foam made from 100% VORNAOL® 490. The thermal conductivity of foams containing soy‐polyols was slightly higher than the control foam. The maximal foaming temperatures of foams slightly decreased with increasing soy‐polyol percentage. Micrographs of foams showed that they had many cells in the shape of sphere or polyhedra. With increasing soy‐polyol percentage, the cell size decreased, and the cell number increased. Based on the analysis of isocyanate content and compressive strength of foams, it was concluded that rigid PU foams could be made by replacing 50% petroleum‐based polyol with a high viscosity soy‐polyol resulting in a 30% reduction in the isocyanate content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Coordination‐Assisted Bioorthogonal Chemistry: Orthogonal Tetrazine Ligation with Vinylboronic Acid and a Strained Alkene

Bioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality that might be present. Recent developments in the field include orthogonal bioorthogonal reactions to modify multiple biomolecules simultaneously. During our research, we observed that the reaction rates for the bioorthogonal inverse‐electron‐demand Diels–Alder (iEDDA) reactions between nonstrained vinylboronic acids (VBAs) and dipyridyl‐s‐tetrazines were exceptionally higher than those between VBAs and tetrazines bearing a methyl or phenyl substituent. As VBAs are mild Lewis acids, we hypothesised that coordination of the pyridyl nitrogen atom to the boronic acid promoted tetrazine ligation. Herein, we explore the molecular basis and scope of VBA–tetrazine ligation in more detail and benefit from its unique reactivity in the simultaneous orthogonal tetrazine labelling of two proteins modified with VBA and norbornene, a widely used strained alkene. We further show that the two orthogonal iEDDA reactions can be performed in living cells by labelling the proteasome by using a nonselective probe equipped with a VBA and a subunit‐selective VBA bearing a norbornene moiety.     

SkaSim – Skalierbare HPC‐Software für molekulare Simulationen in der chemischen Industrie

This article outlines advances in molecular modeling and simulation using massively parallel high‐performance computers (HPC). In the SkaSim project, partners from the HPC community collaborated with users from science and industry. The aim was to optimize the prediction of thermodynamic property data in terms of efficiency, quality and reliability using HPC methods. In this context, various topics were dealt with: atomistic simulation of homogeneous gas bubble formation, surface tension of classical fluids and ionic liquids, multicriteria optimization of molecular models, the development of the molecular simulation codes ls1 mardyn and ms2, atomistic simulation of gas separation processes, molecular membrane structure generators, transport resistors and the evaluation of predictive property data models based on specific mixture types.     

Preparation and electrochemical characterization of LiNi<Subscript>0.8</Subscript>Co<Subscript>0.2</Subscript>O<Subscript>2</Subscript> cathode material by a modified sol–gel method

LiNi_0.8Co_0.2O₂ cathode powders for lithium-ion batteries were prepared by a modified sol–gel method with citric acid as chelating agent and a small amount of hydroxypropyl cellulose as dispersant agent. The structure and morphology of LiNi_0.8Co_0.2O₂ powders calcined at various temperatures for 4 h in air were characterized by means of powder X-ray diffraction analyzer, scanning electron microscope, thermogravimetric analyzer and differential thermal analyzer, and Brunauer–Emmett–Teller specific surface area analyzer. The results show that LiNi_0.8Co_0.2O₂ powders calcined at 800 °C exhibit the best layered structure ordering and appear to have monodispersed particulates surface. In addition, the electrochemical properties of LiNi_0.8Co_0.2O₂ powders as cathode material were investigated by the charge–discharge and cyclic voltammetry studies in a three-electrode test cell. The initial charge–discharge studies indicate that LiNi_0.8Co_0.2O₂ cathode material obtained from the powders calcined at 800 °C shows the largest charge capacity of 231 mAh g⁻¹ and the largest discharge capacity of 191 mAh g⁻¹. And, the cyclic voltammetry studies indicate that Li⁺ insertion and extraction in LiNi_0.8Co_0.2O₂ powders is reversible except for the first cycle.     

Texture and Chemical Characteristics of Soy Protein Meat Analog Extruded at High Moisture

The relationships among extruder responses, texture, and protein solubility of soy protein meat analogs were studied. Soy protein isolate and wheat starch at 9:1 ratio were extruded at 60%, 65%, and 70% moisture contents and 137.8, 148.9, and 160°C cooking temperatures. The results showed that moisture content was a more important factor on the overall product texture than cooking temperature. Lower moisture content resulted in higher die pressure, harder texture, and lower total protein solubility. At a fixed moisture content, a higher cooking temperature resulted in a softer and less chewy product but only slightly changed the protein solubility. According to partial least square regression, the data from Texture Profile Analysis, protein solubility, and extruder responses correlated well and could be used to predict each other.     

Shrinkage and warpage prediction of injection‐molded thin‐wall parts using artificial neural networks

This study demonstrates the successful use of back‐propagation artificial neural networks (BPANNs) in predicting the shrinkage and warpage of injection‐molded thin‐wall parts. The effects of structural parameters of a BPANN on the predictionaccuracy and the capability of a BPANN in determining the optimal process condition are also discussed. The training and testing data are obtained experimentally based on a Taguchi L₂₇ (3¹³) test schedule. The results show that the trained BPANN can successfully predict the shrinkage and warpage of injection‐molded thin‐wall parts. Comparing the prediction accuracies of the trained BPANN and C‐Mold software, it is noted that the trained BPANN predicts more accurately. In terms of determining the optimal process condition for minimizing the shrinkage and warpage of injected thin‐wall parts, the trained BPANN is also shown to give a better optimal process condition than Taguchi's method. Polym. Eng. Sci. 44:2029–2040, 2004. © 2004 Society of Plastics Engineers.     

Thermally reversible cross-linked polyamides and thermo-responsive gels by means of Diels-Alder reaction

Cross-linked polyamides and polyamide gels were prepared from maleimide-containing polyamides and a tri-functional furan compound and showed thermal reversibility in cross-linking behavior and in gel formation through Diels-Alder (DA) and retro-DA reactions. The rate constant k of the DA cross-linking reaction were 1.25-4.83×10⁻⁵ dm³ mol⁻¹ s⁻¹ in the temperature range of 20-60 °C with an activation energy of 32.1 kJ mol⁻¹. The cross-linking densities, thermal properties, and thermal reversibility of the polyamides/furan polymers were adjustable with the contents of maleimide groups in polyamides.     

An experimental model of Chinese textual database

Abstract

A textual database deals with retrieval and manipulation of documents. It allows a user to search on‐line complete documents or parts of documents rather than attributes of documents. Resembling a formatted database which uses a data model as its underlying structure, a textual database has to base its development upon a document model. In this paper, a document model, called the ECHO model, is proposed. The ECHO model provides a document representation, called the ECHO structure, for expressing documents and operations on the representation that serve to express queries and manipulations on documents. It has the ability to provide multiple document structures for a document, a flexible search unit for retrieving textual information, and a subrange search on a textual database. In addition, the ECHO structure is relatively easy to maintain. An architecture of a textual database based on the ECHO model is also proposed. In order to improve the query performance, a refined character inversion method, called ARCIM, is proposed as the text‐access method of the Chinese textual database. The ARCIM can retrieve texts faster than a simple inversion method and requires less space overhead.