Role of Functional Groups in the Monomer Molecule on the Radical Polymerization in the Presence of Graphene Oxide. Polymerization of Hydroxyethyl Acrylate under Isothermal and Non-Isothermal Conditions

Functional groups in a monomer molecule usually play an important role during polymerization by enhancing or decreasing the reaction rate due to the possible formation of side bonds. The situation becomes more complicated when polymerization takes place in the presence of graphene oxide since it also includes functional groups in its surface. Aiming to explore the role of functional groups on polymerization rate, the in situ bulk radical polymerization of hydroxyethyl acrylate (HEA) in the presence or not of graphene oxide was investigated. Differential scanning calorimetry was used to continuously record the reaction rate under both isothermal and non-isothermal conditions. Simple kinetic models and isoconversional analysis were used to estimate the variation of the overall activation energy with the monomer conversion. It was found that during isothermal experiments, the formation of both inter- and intra-chain hydrogen bonds between the monomer and polymer molecules results in slower polymerization of neat HEA with higher overall activation energy compared to that estimated in the presence of GO. The presence of GO results in a dissociation of hydrogen bonds between monomer and polymer molecules and, thus, to higher reaction rates. Isoconversional methods employed during non-isothermal experiments revealed that the presence of GO results in higher overall activation energy due to the reaction of more functional groups on the surface of GO with the hydroxyl and carbonyl groups of the monomer and polymer molecules, together with the reaction of primary initiator radicals with the surface hydroxyl groups in GO.

The Investigation of Viscometric Properties of the Most Reputable Types of Viscosity Index Improvers in Different Lubricant Base Oils: API Groups I, II, and III

Four commercial viscosity index improvers (VII) have been used to investigate the behavioral differences of these compounds in three types of universally applicable base oils. The used VIIs are structurally three types of co-polymer: ethylene-propylene, star isoprene, and two di-block styrene-isoprene. After dissolving of different amounts of VIIs in different base oils, the kinematic viscosities at two standard temperatures were determined and the intrinsic viscosities were calculated according to Huggins method, then the effects of changes in base oil and polymer type were investigated. Intrinsic viscosities as criteria for polymer molecules sizes were found to be higher at lower temperature than at higher temperature. Dependence of intrinsic viscosity on the polymer molecular weight was observed. In the previous works, one or two types of VIIs were studied in only one type of base oil and/or solvent, not different base oils. Furthermore, different ranges of temperatures and concentrations not necessarily applied ranges were selected, but in this work, common base oils and most commercial VIIs were used and the viscometric properties were compared at two temperatures. Viscosities at these temperatures are used for determining VI and definition of lubricant’s viscosity grades. VI improvement is the main cause of VII usage.

EFFECTS OF OV-POSS NANOPARTICLES ON THE VULCANIZATION KINETICS OF NATURAL RUBBER COMPOUNDS

Polyhedral oligomeric silsesquioxanes (POSSs) are new-generation additives, which can provide improved properties in polymer matrices by physical and/or chemical interactions between the polymer molecules and their reactive sites. In the case of rubber-based polymeric systems, POSSs are also able to accompany with the vulcanization reaction. In this study, it was aimed to investigate the effect of octavinyl functionalized POSS (OV-POSS) on sulphur vulcanization of a model natural rubber (NR) based compound. The reaction kinetics was studied by using various kinetic approaches based on Moving Die Rheometry and Differential Scanning Calorimetry. Rheometric data was evaluated by using a common non-linear cure kinetic model, which is called Isayev and Deng Model. Kissinger, Flynn-Wall-Ozawa, and Crane Models were used to process thermal data for curing reactions. All the models were found to be able to analyze vulcanization kinetics of OV-POSS containing NR-based rubber compounds as well as the effect of OV-POSS incorporation.

The Soft and High Actuation Response of Graphene Oxide/Gelatin Soft Gel

The high actuation response of soft gel from a graphene oxide/gelatin composite was prepared as an alternative material in soft robotics applications. Graphene oxide (GO) was selected as the electroresponsive (ER) particle. GO was synthesized by modifying Hummer’s method at various ratios of graphite (GP) to potassium permanganate (KMnO4). To study the effect of ER particles on electromechanical properties, GO was blended with gelatin hydrogel (GEL) at various concentrations. The electrical properties of the ER particles (GO and GP) and matrix (GEL) were measured. The capacitance (C), resistance (R), and dielectric constant of the GO/GEL composite were lower than those of the GO particles but higher than those of the GEL and GP/GEL composite at the given number of particles. The effects of external electric field strength and the distance between electrodes on the degree of bending and the dielectrophoresis force (Fd) were investigated. When the external electric field was applied, the composite bent toward electrode, because the electric field polarized the functional group of polymer molecules. Under applied 400 V/mm, the GO/GEL composite (5% w/w) showed the highest deflection angle (θ = 82.88°) and dielectrophoresis force (7.36 N). From the results, we conclude that the GO/GEL composite can be an alternative candidate material for electromechanical actuator applications.

Effectiveness of Thermal Stimulation of Superplasticizers on Fresh Properties of Cement Mortar

Polycarboxylic acid-based superplasticizers are used in various types of concrete work. Wide variations in environmental temperatures are known to affect how well chemical admixtures perform as superplasticizers, influencing the properties of the concrete. However, little has been reported on changes in performance caused by thermal variations. Previous studies have reported that heating superplasticizers change the polymer structure, improving and sustaining cement particles' dispersibility. Moreover, the improved fluidity from thermal stimulation is not temporary. The effect has been observed to remain for about seven days, with the residual characteristics differing depending on the superplasticizers used. Therefore this study evaluates mortar stiffness when using thermally stimulated superplasticizers and evaluates how the stimulation affects construction performance using measures such as the flow and rheological properties (plastic viscosity) of fresh mortar, vane shear tests, blade viscometer tests, and mortar vibration box tests. Mortar's fluidity was found to improve by about 25% when using thermally stimulated additives, with plastic viscosity dropping by up to 45% and the stress likely to be needed for pumping also being reduced by about 16%. Filling speed was also found to increase by about 26%. Thus, thermal stimulation improves mortar and concrete construction performance, and it may be possible in the future to carry out the construction with fewer workers utilizing this technology’s benefits. The study indicates a need for further investigation of how thermal stimulation affects polymer molecules’ adsorption efficiency with cement to elucidate the mechanism at full scale and propose ways to adopt thermal stimulation at actual construction sites.

Overview of methods in Oil spill technology

Over the decades oil spills have been the biggest threat to the aquatic life and to a nation’s economy. Many methods were suggested in the literature to remove the oil that is present on the surface of sea water after the spill. Hydrogel formation is one of the best technique that could be adopted to handle oil spills. Since the oil spill is a oil and water emulsion, formation of hydrogels with these emulsions could lead to the recovery of oil. The formation of hydrogels can be either physically crosslinking the polymer molecules or covalent bonding among the entangled polymer molecules. The methods of making the hydrogels conceivable to acquire surface hydrophobicity and oleophilicity. Hydrogel technology could be more cost effective and efficient in recovering the oil from the spill, eco-friendly and easy to use. It is proposed that the hydrogels could be potential candidates for handling the oil spills. The methods described in this review explains the various hydrogels that could be utilized for oil spill recovery.

Sol Gel Technique to Prepare Composite Material of Glass-Dye-Polymers

Herein we describe the synthesis and in-depth characterization of chemically blended hybrid glasses in which polymer molecules are uniformly distributed and covalently bonded to inorganic matrices. This approach uses a monomer with double bonds, which are hydrosilylated with triethoxy silane and co-condensed with silicon tetraalkoxide to afford a molecular composite of SiO2 glass and the polymer. The generated coposites were characterized using SEM, TGA and XRD as well as a host of stability tests. They showed increased stability and uniform distribution of the blend. <br>

Sol Gel Technique to Prepare Composite Material of Glass-Dye-Polymers

Herein we describe the synthesis and in-depth characterization of chemically blended hybrid glasses in which polymer molecules are uniformly distributed and covalently bonded to inorganic matrices. This approach uses a monomer with double bonds, which are hydrosilylated with triethoxy silane and co-condensed with silicon tetraalkoxide to afford a molecular composite of SiO2 glass and the polymer. The generated coposites were characterized using SEM, TGA and XRD as well as a host of stability tests. They showed increased stability and uniform distribution of the blend. <br>