On the crystalline nature of poly(di-isopropyl fumarate)

Summary Molecular order of poly(di-isopropylfumarate) (PDIPF), obtain ed by free-radical initiation, is investigated by calorimetric measurements and X-ray diffraction analysis. It is found that the polymer decomposes without melting at temperatures above 200°C while displaying two endothermic transitions, probably of the solid-solid type, at 65 and 126°C respectively. Further evidence of crystalline order and orientability is provided by the X-ray experiments which show one equatorial (11.16 Å) and two meridional (4.81 and 2.40 Å) reflections respectively. The corresponding stereoselective nature of the polymerization reaction is interpreted as resulting from the steric influence of the bulky isopropyl substituents of the monomer.     

Drying Schedules for Canelo Wood

Canelo wood is a highly valued native species in Chile that shows delicate marbling patterns with a pinkish soft silver luster. Due to its decorative qualities, canelo wood is dried for the manufacture of furniture and musical instruments. However, canelo wood lacks vessels cells that typically transport the water in hardwoods. Per its drying behavior, canelo wood is considered a transition species between hardwoods and softwoods. Therefore, this article reports drying schedules that were developed for drying 25-mm and 50-mm canelo lumber. In addition, this article reports experimental overall mass transfer coefficients, so that drying times for each of the drying stages can be easily estimated.     

Climate Change and Drying of Agricultural Products

Global warming is affecting the world and will continue to affect humans and the ecosystem in the future, in different regions of the earth in diverse ways: air temperature rise, modifications in the precipitation and snow/ice melting rates, sea level rise, changes in geographical distribution, and even extinction of some plants and animals. In particular, the predictions presented in the 2007 Report of the Intergovernmental Panel on Climate Change, Working Group 1 (available at www.ipcc.ch) for the mean temperature increase in the present century is about (3 ± 1)°C/century for a middle range scenario of human behavior. Mitigation measures need to be taken urgently in all aspects of activities in order to reduce the future impact of the temperature augmentation. In particular, the drying process (as well as the pre- and post-drying operations) needs to be reanalyzed, in order to try to participate in this world effort to reduce the impact of anthropogenic activities that introduce in the atmosphere an excess of greenhouse gases (GHG). The energy savings, use of renewable energies, optimization of each part of the drying process, and use of control devices for detecting and minimizing the atmospheric injection of GHG are some of a large number of possible actions to be taken in this respect. A nice example of how a planetary problem can be solved with the global participation of scientists, professionals, authorities and general public is the stopping of the destruction of the ozone layer and its possible recuperation in the near future, as discussed in the WMO related report (“Scientific Assessment of Ozone Depletion: 2006”, that can be obtained at http://www.wmo.int/pages/prog/arep/gaw/ozone2006/ozoneasstreport.html).^{[ 10} World Meterorological Organization . Scientific Assessment of Ozone Depletion: 2006 ; Cambridge University Press : 2007 , Chapter 7 . [Google Scholar] ^]     

Amphiphilic antidepressant drug amitriptyline hydrochloride under the influence of ionic and nonionic hydrotropes; micellization and phase separation

Herein we report the micellization and cloud point of an amitriptyline hydrochloride (AMT) under the influence of cationic, anionic and nonionic hydrotropes. Anionic hydrotropes were employed to know the micellar and surface behaviors, besides studying the clouding behavior of AMT drug with cationic, anionic and nonionic hydrotropes. Tensiometric study has been performed and the properties studied include the critical micelle concentration (cmc), maximum surface excess at the air/water interface (Γ_max), the minimum area per of amphiphilic molecule at air/water interface (A_min), and the different thermodynamic parameters, besides clouding phenomenon. Interaction parameters of micelles (β^m) and monolayer (β^σ) indicate that drug-hydrotrope systems show better interaction at the interface than in micelles.     

Environmentally friendly copolymeric beads of Chlorella vulgaris and poly(methacrylamide) grafted aliginic acid di‐block copolymers for biosorption of zinc ions

The synthesis of biodegradable environmentally friendly copolymeric beads for water treatment biosorption processes is demonstrated. The synthesized poly(methacrylamide) grafted aliginic acid copolymers were characterized using ¹H NMR, Fourier transform infrared spectroscopy, TGA and SEM. The di‐block copolymers showed a morphological change from two‐dimensional layer‐by‐layer structures to three‐dimensional well‐compacted wrinkles as grafting efficiency increased. The copolymeric beads were formed from the di‐block copolymer and algae crosslinked with 5% calcium ions (w/w). These copolymeric beads were then subjected to biosorption investigations for zinc ions as a model heavy metal ion at different pH values and stirring time periods. Batch adsorption experiments showed that the copolymeric beads were effective in zinc ion removal from aqueous solutions with maximum uptake exceeding 89.0 mg g^–1 using higher grafting efficiency copolymeric beads at pH 5.5. Equilibrium pH studies revealed that zinc biosorption was pH dependent and maximum uptake was obtained at pH 5.5. Dynamics studies showed that the biosorption of zinc was rapid with equilibrium attained within 40 min and the data followed pseudo‐second‐order kinetics. The equilibrium biosorption of zinc ions on the copolymeric beads exhibited a Freundlich isotherm fit. © 2012 Society of Chemical Industry     

Vapor‐Liquid Equilibrium of MTBE‐Methanol,MTBE‐Methanol‐Calcium Chloride and MTBE‐Methanol‐Lithium Chloride Mixtures

Isobaric vapor‐liquid equilibria of methyl tert‐butyl ether (MTBE)‐methanol, MTBE‐methanol‐calcium chloride, and MTBE‐methanol‐lithium chloride mixtures were measured at 93.57 kPa using a Malanowski equilibrium still which circulates both the vapor and liquid phases. The experimental results of the salt‐free system showed that MTBE‐methanol forms a minimum boiling azeotrope of 69.80 mol.‐% MTBE at 93.57 kPa and 322.67 K. The experimental results of the salt‐free system were predicted using the original UNIFAC and the UNIFAC‐Dortmund methods, where the vapor‐phase compositions were predicted with root‐mean‐square deviations (RMSD) of 0.0046 and 0.0091, respectively, and the bubble point temperatures were predicted with RMSD of 0.36 and 0.71 K, respectively. The Wilson and the nonrandom two‐liquid (NRTL) models could satisfactorily correlate the experimental data of the salt‐free mixtures with RMSD in the vapor‐phase compositions calculation of 0.0047 and 0.0059, respectively and in bubble‐point temperatures calculation of 0.20 and 0.40 K, respectively. Addition of either calcium chloride or lithium chloride to the MTBE‐methanol mixtures resulted in salting‐out the MTBE and shifting the azeotropic point to a vapor composition of 76.5 mol.‐% and 93.0 mol.‐% MTBE, respectively. Both the Tan‐Wilson and Tan‐NRTL models could satisfactorily predict the bubble‐point temperatures of the MTBE‐methanol‐calcium chloride mixtures with RMSD of 0.143 and 0.130 K, respectively, and the vapor phase compositions with RMSD of 0.0055 and 0.0041, respectively.     

Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Study

The interaction of cationic gemini and cationic conventional surfactants by conductivity was systematically overviewed, paying attention to synergism observed in micellization. These mixed systems were found to show remarkable synergism in micelle formation. The experimental critical micelle concentration values being lower than the value predicted by ideal solution theory indicate that the mixed micellization is due to attractive interaction between the two components. Gemini/conventional systems form mixed micelle due to attractive interactions (negative β values). The values of micellar mole fraction of constituent 1 (X ₁) in surfactant mixtures are more than in the ideal state (X ₁ ^ideal ), which means that, the mixed micelles are rich in conventional surfactants in comparison to that in the ideal state.     

Rotational molding of compatibilized PA6/LLDPE blends

In this work, rotational molding was used to produce parts based on a blend of linear low-density polyethylene (LLDPE) and polyamide 6 (PA6). In particular, the concentration of PA6 (0, 10, 20, and 30% vol) with and without a compatibilizer (Surlyn 9020) was investigated via two methods: dry blending in a high-shear mixer and melt compounding in a twin-screw extruder followed by pulverization. To determine the efficiency of the rotomolding process, similar parts were produced via compression molding. For rotational molding, dry ice (solid CO₂) was used to create an inert atmosphere in the mold and the processing conditions were followed by the mold internal air temperature traces. From the samples produced, thermal, morphological, and mechanical properties were measured. The results showed that the rotomolded parts of the melt blended compounds generated smaller and better dispersed PA6 particles in the LLDPE matrix. This finer morphology led to improved mechanical properties, especially when the compatibilizer was present. But the latter was found to be more effective on the compression-molded samples.