Engineering plastics from lignin. VI. Structure–property relationships of PEG-containing polyurethane networks

Hydroxypropyl lignin-based thermosetting polyurethanes were synthesized with excess hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI) by solution casting. Four polyethylene glycols (PEG) of molecular weight 400, 600, 1000, and 4000 were mixed with lignin polyol to incorporate different proportions of soft segment into the network prior to crosslinking. Neither thermal nor mechanical and limited small angle x-ray scattering (SAXS) analysis provided distinct evidence for phase separation and microstructure formation. The study examines the effect of the soft segment in relation to chain length and weight contribution on the thermal and mechanical properties of the final networks. A significant sensitivity of glass transition temperature (T_g), of swelling in DMF, and of the mechanical properties to soft segment content was observed. Some of this sensitivity must, however, be attributed to differences in crosslink density since the polyol to diisocyanate weight ratio was kept constant throughout the synthesis series. The magnitude of the change of the different properties was found to be influenced by both glycol content and glycol molecular weight. The T_g of the network decreased from 105°C to as low as 38°C (HDI), and from 158°C to 70°C (TDI), with incorporation of up to 17.8% glycol, and it was greater with lower molecular weight glycols than with higher ones at any weight fraction. Swelling in DMF increased as expected with soft segment content. Mechanical properties were affected most if HDI and lower molecular weight glycols were used. The uniformity in structure, reduction in brittleness, and considerable improvement in mechanical properties with inclusion of minor PEG contents indicates that lignin-based network polyurethanes can be synthesized with controllable performance characteristics.     

How does organisational absorptive capacity matter in the assimilation of enterprise information systems?

Extant literature offers two mostly distinct perspectives on enterprise systems assimilation – driven either by internal expertise and learning capability or by external institutional pressures. This study combines the two perspectives and subscribes to the view that organisations’ learning capability moderates their acquiescence to institutional pressures. The study then anchors organisational learning capability to the concept of absorptive capacity and proposes that its two dimensions – potential absorptive capacity (PACAP) and realised absorptive capacity (RACAP) – affect enterprise systems assimilation through different pathways. Our survey‐based empirical study of Enterprise Resource Planning (ERP) systems in the post‐implementation stage reveals that while both PACAP and RACAP have a positive direct impact on assimilation, PACAP positively moderates the impact of mimetic (institutional) pressures, but not normative (institutional) pressures, on assimilation; whereas RACAP positively moderates the impact of normative pressures, but not mimetic pressures, on assimilation. Thus, our theoretical contribution lies in understanding the distinct ways in which PACAP and RACAP moderate the influence of external institutional pressures on enterprise systems assimilation.     

Magnetic field-assisted photochemical machining (MFAPCM) of SS316L

In this paper, a new technique of photochemical machining (PCM) process has been described. The objective of this study is to investigate the effect of applying a magnetic field on the PCM of AISI 316?L stainless steel. The experiments were planned and conducted using a Full Factorial Design (FFD) approach. The control parameters selected were magnetic field, temperature, concentration and time. The analysis of the results shows significant improvement in the etch rate due to the application of a magnetic field. The highest etch rate was achieved at a concentration of 700?g/l, at the temperature of 60°C in a static magnetic field. The improvement of the etch rate is 2.5 times with the application of magnetic field as compared to the conventional PCM process.     

Classifying the Geometric Dilution of Precision of GPS satellites utilizing Bayesian decision theory

The errors resulting from satellite configuration geometry can be determined by Geometric Dilution of Precision (GDOP). Considering optimal satellite subset selection, lower GDOP value usually causes better accuracy in GPS positioning. However, GDOP computation based on complicated transformation and inversion of measurement matrices is a time consuming procedure. This paper deals with classification of GPS GDOP utilizing Parzen estimation based Bayesian decision theory. The conditional probability of each class is estimated by Parzen algorithm. Then based on Bayesian decision theory, the class with maximum posterior probability is selected. The experiments on measured dataset demonstrate that the proposed algorithm lead, in mean classification improvement, to 4.08% in comparison with Support Vector Machine (SVM) and 9.83% in comparison with K-Nearest Neighbour (KNN) classifier. Extra work on feature extraction has been performed based on Principle Component Analysis (PCA). The results demonstrate that the feature extraction approach has best performance respect to all classifiers.     

DNA immobilization and SAW response in ZnO nanotips grown on LiNbO3 substrates.

DNA immobilization enhancement is demonstrated in a structure consisting of ZnO nanotips on 128 degrees Y-cut LiNbO3. The ZnO nanotips are grown by metalorganic chemical vapor deposition (MOCVD) on the top of a SiO2 layer that is deposited and patterned on the LiNbO3 SAW delay path. The effects of ZnO nanotips on the SAW response are investigated. X-ray diffraction and scanning electron microscopy are used to analyze the ZnO nanotips, which are of single crystalline quality, and they are uniformly aligned with their c-axis perpendicular to the substrate surface. The photoluminescence (PL) spectrum of the ZnO nanotips shows strong near bandedge transition with insignificant deep level emission, confirming their good optical property. DNA immobilization enhancement is experimentally validated by radioactive labeling tests and SAW response changes. The ZnO nanotips enhance the DNA immobilization by a factor of 200 compared to ZnO film with flat surface. DNA hybridization with complementary and noncomplementary second strand DNA oligonucleotides is used to study the selective binding of the structure. This device structure possesses the advantages of both traditional SAW sensors and ZnO nanostructures.     

Hydroxy Propylated Lignin-Isocyanate Combinations as Bonding Agents for Wood and Cellulosic Fibers

Lignin and hydroxy propylated lignin derivatives were reacted with diisocyanates in the presence of cellulose fibers and wood particles. The attachment of lignin and lignin derivates to hydroxyl-rich surfaces of lignocellulosic materials proved to be a convenient way for increasing strength properties of reconstituted fiber and particle materials. Results indicate that hydroxypropylated lignin derivatives are capable of contributing equal or even greater strength increases to relignified fiber composites than do monomeric or polymeric diisocyanates alone. With reinforced fiber mats, it was found that strength properties were virtually unaffected up to a level of approximately 50% replacement of diisocyanates by lignin-based materials. This beneficial contribution by lignin to bonding properties could not be verified for reconstituted wood products, the strength and swelling properties of which suffered in relation to lignin content. Thftse differences are explained with differences in method of adhesive preparation and application. Lignins were obtained from the spent pulping liquor of the Kraft process, and by alkaline extraction of steam exploded Aspen wood chips. These lignins were, for the most part, reacted with propylene oxide.     

Investigation of the Process of Hardening of Diglycidyl Ether Bisphenol a by Phosphate Binders

The interaction between diglycidyl ether bisphenol A and conventional and waterdeficient phosphate binders has been investigated. The data of chemical analysis, IR spectroscopy, and differentialthermal analysis point to the formation of a spatially crosslinked epoxy polymer under the influence of the phosphate binders. It has been shown that conventional binders can be used as hightemperature hardeners of epoxy oligomers. When waterdeficient binders are used, the formation of a threedimensional polymer structure is observed at room temperature.     

Structural and Optical Properties of ZnO Nanotips Grown on GaN Using Metalorganic Chemical Vapor Deposition

ZnO nanotips are grown on epitaxial GaN/c-sapphire templates by metalorganic chemical vapor deposition. X-ray diffraction (XRD) studies indicate that the epitaxial relationship between ZnO nanotips and the GaN layer is (0002)ZnO||(0002)GaN and (101̄0)ZnO||(101̄0)GaN. Temperature-dependent photoluminescence (PL) spectra have been measured. Sharp free exciton and donor-bound exciton peaks are observed at 4.4 K with photon energies of 3.380 eV, 3.369 eV, and 3.364 eV, confirming high optical quality of ZnO nanotips. Free exciton emission dominates at temperatures above 50 K. The thermal dissociation of these bound excitons forms free excitons and neutral donors. The thermal activation energies of the bound excitons at 3.369 eV and 3.364 eV are 11 meV and 16 meV, respectively. Temperature-dependent free A exciton peak emission is fitted to the Varshni’s equation to study the variation of energy bandgap versus temperature.