FTIR INVESTIGATION ON CRYSTALLINITY OF HYDROXYPROPYL METHYL CELLULOSE-BASED POLYMERIC BLENDS

Two series of polymeric blends have been prepared based on hydroxypropyl methyl cellulose (HPMC)/polyacrylic acid (PAA) (1:1, 1:2, 1:3, 1:4) and HPMC/sodium alginate (SA) (1:30, 2:30, 3:30, 4:40) and investigated by Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR-FTIR). IR analysis confirmed the interaction between the polymeric components in the blend and the degree of structural organization. Crystallinity changes in the blends were observed as a function of a number of experimental parameters, such as temperature, composition and HPMC concentration, by determining the quantitative crystallinity indexes: Total Crystallinity Index (TCI), Lateral Order Index (LOI) and Hydrogen Bond Index (HBI).

Interactions of primaquine and chloroquine with PEGylated phosphatidylcholine liposomes

This study aimed to analyze the interaction of primaquine (PQ), chloroquine (CQ), and liposomes to support the design of optimal liposomal delivery for hepatic stage malaria infectious disease. The liposomes were composed of hydrogenated soybean phosphatidylcholine, cholesterol, and distearoyl-sn-glycero-3-phosphoethanolamine-N-(methoxy[polyethyleneglycol]-2000), prepared by thin film method, then evaluated for physicochemical and spectrospic characteristics. The calcein release was further evaluated to determine the effect of drug co-loading on liposomal membrane integrity. The results showed that loading PQ and CQ into liposomes produced changes in the infrared spectra of the diester phosphate and carbonyl ester located in the polar part of the phospholipid, in addition to the alkyl group (CH2) in the nonpolar portion. Moreover, the thermogram revealed the loss of the endothermic peak of liposomes dually loaded with PQ and CQ at 186.6 °C, which is identical to that of the phospholipid. However, no crystallinity changes were detected through powder X-ray diffraction analysis. Moreover, PQ, with either single or dual loading, produced the higher calcein release profiles from the liposomes than that of CQ. The dual loading of PQ and CQ tends to interact with the polar head group of the phosphatidylcholine bilayer membrane resulted in an increase in water permeability of the liposomes.

Effect of Sulfuric Acid Baking and Caustic Digestion on Enhancing the Recovery of Rare Earth Elements from a Refractory Ore

To improve the recovery of rare earth elements (REEs) from a refractory ore, this study investigated two different chemical decomposition methods, namely sulfuric acid baking and caustic digestion, with their respective leaching processes. The studied lateritic ore contained goethite (FeOOH) as a major constituent with REEs scattered around and forming submicron grains of phosphate minerals, such as apatite and monazite. Therefore, despite the substantially high content of REEs (3.4% total rare earth oxide), the normal acidic leaching efficiency of REEs reached only 60–70%. By introducing sulfuric acid baking and caustic digestion, the REE-leaching efficiency was significantly improved. After sulfuric acid baking at 2.0 acid/solid ratio and 200 °C for 2 h, the leaching efficiency reached 97–100% in the subsequent water-leaching. When the ore was digested with a solid/liquid ratio of 100 g/L in a 30 wt% NaOH solution at 115 °C and 300 rpm for 3 h, the REE-leaching efficiency of 99–100% was attained at 80 °C using a 3.0 M HCl solution. The correlation between the REE and the Fe-leaching was determined. The improvements in REE-leaching in both methods were mostly attributed to the mineral phase and crystallinity changes of Fe-bearing minerals due to the ore pretreatments. Such findings were also supported by X-ray diffraction and scanning electron microscopy analyses.

Effect of Friction Stir Welding Process on Crystallinity and Degradation of Polypropylene

The aim of this study was to investigate the crystallinity changes and degradation of polypropylene due to heat generated by friction stir welding, i.e., heat generated by friction between the rotation tool and the welded materials. The tool pin was rotated at 620 rpm in the welding process. The travelling speed was varied between 7.3 mm/minute and 13 mm/minute. A cylindrical tool pin, 4.5 mm in diameter and 5.7 mm in length, was used in this experiment. The shoulder dimension was 18 mm in diameter and 90 mm in length. A conventional milling machine was used in the friction stir welding process. The crystallinity test was carried out with X-ray diffraction, hardness was observed using a Shore Type-D durometer, and polymer degradation data was obtained by thermogravimetry analysis. The areas compared were base material, weld nugget area, and thermomechanical affected zone. The results showed that there was a change in the percentage of crystallinity in areas that had undergone friction stir welding, and that the change was inversely proportional to the traveling rate of the friction stir welding process. The friction stir welding process was affected by the initial degradation temperature and hardness property of the polypropylene. This result shows that it is possible to choose specific parameters of friction stir welding in order to obtain good weld joint properties.

Thermo-Oxidative Behavior of Carbon Black Composites for Self-Regulating Heaters

The composite materials for self-regulating heaters are conductive composites based on a polymer matrix and a dispersed conductive filler consisting in either carbon black or another carbon material, such as graphite or nanotubes. Similar materials are suitable for sensors and current limitations. As these materials used in heating applications work usually at elevated temperatures in presence of air, the ageing processes would be an important limiting factor of their lifetime. Therefore, thermal oxidation processes and crystallinity changes during the service of these products are of major interest in durability studies. The potential interference of carbon-based materials with the oxidation and ageing of polymer matrix shall be known in order to correctly estimate the durability of such materials. The effect of radiation exposure is studied taking into account the potential use of such materials in radiation environments. In this work, the activation energies of some initial, unaged and aged products at elevated temperatures are compared in order to characterize the effect of thermo-oxidative ageing and hence to evaluate their durability. The effect of some antioxidants is also discussed. The crystallinity, calculated from DSC was used for evaluation of the physical changes induced within the aged materials, following the procedures described in previous work. FTIR-ATR technique was used for characterization of chemical changes induced by ageing.

Cryogenic Treatment of Polymer/MWCNT Nano-Composites for Mechanical and Tribological Applications

The cryogenic treatment of material has been known to motivate structural stability by rearranging its crystallographic structure in metals and by promoting intermolecular as well as intramolecular rearrangements in polymers. Additionally, in case of polymers reinforced with micro fillers, the structural changes brought about by cryogenic treatment are still largely governed by the polymer matrix itself. Thus, when investigated for their mechanical and tribological properties, the response of polymer/MWCNT nano-composites after cryogenic treatment was found to be depending on the cryo-structural modifications in the polymer matrix, followed by the MWCNT interaction to some extent. The enhancement in the mechanical properties of the polymer/MWCNT nano-composites is attributed to the increasing % crystallinity, changes in crystal structure, conversion of less stable phases into more stable phases, change in the nature of bonding and strengthening of interphase between polymer and MWCNT. Thus, for the cryogenic treatment temperature of -185 °C, the optimum soaking period for PA and PA/MWCNT nano-composite was 24 hrs, whereas for PBT and PBT/MWCNT nano-composite it was 12 hrs and 16 hrs, respectively. This agrees well with the popular claim that each polymer has a specific functional group and/or structural characteristic that readily responds to the cryogenic treatments conditions (irrespective of the filler type, content and/or interaction), thereby, modifying the structure and giving superior properties, which makes cryogenic treatment a material specific process.