Nature Of Polyols Research Articles

Protection effect of polyols on Rhizopus chinensis lipase counteracting the deactivation from high pressure and high temperature treatment.

The influence of polyols on Rhizopus chinensis lipase (RCL) was investigated under high pressure. The poor stability of RCL was observed at 500 MPa at 60 °C without polyols which protected RCL against the loss of activity. The lipase is more stable in phosphate buffer than in tris buffer despite the protection of polyols. The activity was maintained 63% by the sorbitol of 2 mol/L in Tris-HCl buffer but 73% in phosphate buffer after the treatment at 500 MPa and 60 °C for 25 min. The same protective effects could be observed at 1 mol/L of sorbitol, erythritol, xylitol, and mannitol. However, further increase of hydroxyl group number could not significantly improve the enzyme stability. The protection of polyols on RCL appears to depend on both of the polyol nature and the hydroxyl group number. Together with fluorescence spectra, circular dichroism spectra indicated that the chaotic conformation of RCL under high pressure became more ordered with 1 mol/L sorbitol. The results showed that sorbitol effectively stabilized the lipase conformation including the hydrophobic core under extreme conditions. It might be attributed to the interaction of polyols with RCL surface to modify intra-/intermolecular hydrogen bonds, maintaining the hydrophobic interactions within RCL.

Green metal organic coating from recycled PETs and modified natural rubber for the automobile industry

Abstract Novel elastomeric polyurethane coating precursors from renewable natural rubber and waste bottle PET were prepared for metal coating applications. The elastomeric PU was synthesized from; modified natural rubber with hydroxyl functional groups (HLNR), modified NR grafted with polysiloxane (PDMS-g-LENR) and modified PETs (P-ET-PA and P-T-PA) such as a polyol/polyacid; a commercial MDI (Millionate MR-200) as an isocyanate. The physical properties such as film-thickness, gloss, hardness, adhesion (cross-cut and scratch-adhesion), impact test, Erichsen, bending and chemical resistance of the coated film were investigated by following the industry standards for automobile coatings. The properties of the coated films were influenced by the ratio of polyol/polyacid and the polyol nature. It was found that the coated film prepared from both of modified NR presented good adhesion with the metallic substrate by absence the surface treatment. Single layer of PU elastomer film prepared from both modified PETs with HLNR35 and MDI with mole ratio of 0.1:0.3:0.75 showed good physical properties following the industry standards for automobile coatings. The presence of PDMS-g-LENR in the coatings improved the thermal stability when compared to HLNR35. Furthermore, salt spray test and electrochemical impedance spectroscopy (EIS) were used to examine the corrosion behavior of the coated steel. It could be concluded that the best anticorrosive behavior was shown by the PDMS-g-LENR and P-T-PA formulas.

Synthesis of dimorphic MR fluid containing NiCo nanoflowers by the polymer assisted polyol method and study of its magnetorheological properties

Flower-like nanostructures of NiCo (1:1) in the presence of Jeffamine was synthesized by homogeneous nucleation in 1, 2-propanediol for 3h. Morphological characterizations performed by scanning and transmission electron microscopy (FESEM and TEM) revealed the average size distribution of 700nm containing 2D nanosheets of ~30nm thickness. The nanoflowers crystallize exclusively in face-centered cubic structures and were confirmed by x-ray diffraction studies. Various factors, including nature of polyol, concentrations of base and metal salts in precursor proved to affect the geometry of nanoflowers. Magnetic studies revealed the ferromagnetic nature of NiCo nanoflowers with high saturation magnetization and low coercivity (108.6emu/g and 78.4Oe). The enhanced shear properties and yield stress of dimorphic MR fluid containing nanoflowers of NiCo in ferrofluids can be attributed to stronger microstructure formation in the presence of magnetic field.

Incidence of the polyol nature in waterborne polyurethane dispersions on their performance as coatings on stainless steel

Three waterborne polyurethane dispersions derived from polyester, polyether and polycarbonate diols with molecular weight of 1000Da were synthesized by the acetone method and used as coatings on stainless steel 304 plates. The properties of the dispersions and the polyurethane films were influenced by the polyol nature. The polyurethanes obtained with polyether or polyester showed higher degree of phase separation between the soft and the hard segment. The higher adhesive strength under shear stresses was obtained in the joints produced with the waterborne dispersion obtained with polycarbonate diol. The properties of the polyurethane coating obtained with polycarbonate diol on stainless steel 304 were significantly higher as compared with the others. Improved performance of coatings obtained with polycarbonate diol was ascribed to the higher polarity of the carbonate groups that contributed to additional hydrogen bond formation between soft segments with respect to those obtained with polyether or polyester

Photochemical synthesis of silver and gold nanoparticles in polyhydric alcohols

A procedure was developed for the synthesis of gold and silver nanoparticles in the presence of polyols like ethylene glycol, diethylene glycol, triethylene glycol, and 1,2-propylene glycol. Spectral characteristics of the obtained nanocomposites were mesured and kinetics of the formation of the colloidal phase was studied. The influence of the polyol nature and concentration on the photoinitiated formation of silver and gold nanoparticles was studied. The 1,2-propylene glycol is shown to exhibit maximal stabilizing effect.

Synthesis of pharmacologically active hydrogels based on combined silicon and titanium polyolates

The target synthesis of new biologically active hydrogels based on combined silicon and titanium polyolates was carried out. The optimum conditions for hydrogel formation and their composition were determined. The type of hydrogels and mechanisms of gelation depend on the nature of polyols: gels based on combined silicon and titanium polyethylene glycolates are polymeric and formed via the polycondensation mechanism, whereas gels based on combined silicon and titanium glycerolates are colloidal and formed via the coagulation-condensation mechanism. The combined hydrogels based on silicon dimethyl glycerolates and titanium tetraglycerolate exhibit enhanced transcutaneous, wound healing, and regenerating activity.

Solubilities and Transfer Free Energies of Hydrophobic Amino Acids in Polyol Solutions: Importance of the Hydrophobicity of Polyols

The purpose of this work was to investigate the difference in the hydrophobicities of various polyols and the nature of interactions between hydrophobic amino acid side chains and polyols. The interactions were explored by conducting solubility studies of three amino acid derivatives, N-acetyl tryptophanamide (NATA), N-acetyl leucinamide (NALA), and N-acetyl glycinamide (NAGA), in the solutions of sorbitol, sucrose, trehalose, glycerol, ethylene glycol, ribose, and deoxyribose. Hydrophobicity index of polyols was calculated using molecular modeling. An increase in the solubility of the hydrophobic side chains of tryptophan and leucine was observed with an increase in the hydrophobicity index of polyols. Transfer free energies of NATA from water to polyols solutions were negative, whereas those for NALA were positive for all polyols except glycol. This study shows that the hydrophobic nature of polyols plays an important role in polyol-side chain interactions. Solubility behavior observed for NATA and NALA in different polyols indicates that polyols can interact differently with the same side chain depending on the nature of the polyol and the side chain.

Thermoplastic polyurethane nanocomposites of reactive silicate clays: effects of soft segments on properties

This paper addresses the effects of soft-segment on clay particle exfoliation and resultant mechanical and thermal properties of nanocomposites of reactive layered silicate clay and thermoplastic polyurethanes (TPU). The composites were synthesized via a two-step bulk polymerization scheme from polyether- and polyesterpolyols of molecular weight 2000, diphenylmethanediisocyanate, butanediol, and up to 5 wt% reactive layered silicate clay. It was found that the extent of tethering reactions between polymer chains carrying residual –NCO groups and reactive clay particles was significant, although did not depend on the nature of polyol used. Nanocomposites were obtained only in the case of polyesterpolyol, which can be attributed to both clay–polymer reactions and higher viscosity in the clay–polymer mixing step. These nanocomposites showed 125% increase in tensile stress, 100% increase in elongation, and 78% increase in tensile modulus along with 130% increase in tear strength and a 60% reduction in volume loss in abrasion test. It was observed that hydrogen bonding did not influence the properties and the extent of hydrogen bonding was not affected by the clay particles.

End‐Grained Wood‐Polyurethane Composites, 2

AbstractSummary: This paper is the second of a two‐part series devoted to the preparation and the characterization of end‐grained WPCs. WPCs were obtained by polycondensation and reactive grafting of PEG or PPG with diisocyanate derivatives within the wood structure. In this part of the study, the improvement of both the dimensional stability and mechanical properties were investigated. It came out that dimensional stability was influenced by the polyol nature, functionality, and content in wood. Both PEG and PPG appeared to be efficient to improve dimensional stabilization, especially at higher weight fraction in wood. A tuning of the impregnation conditions allowed to reach a dimensional stabilization as high as 70%. Performing compression and bending tests evidenced that the mechanical properties of the WPCs were not negatively affected by the reactive impregnation process. Moreover, it could be shown that the WPCs prepared starting from PPG displayed higher stiffness than PEG‐based WPCs.Schematic representation of the three‐layered wood cell wall.magnified imageSchematic representation of the three‐layered wood cell wall.

Comparative thermostability of glucose dehydrogenase from Haloferax mediterranei. Effects of salts and polyols

The effect of temperature and pH on thermoinactivation kinetics of glucose dehydrogenase from Haloferax mediterranei has been studied in the presence of different monovalent salts (LiCl, LiBr, NaCl, NaBr, KCl, KBr, NH 4Cl, and NH 4Br) and polyols (glycerol, erythrytol, xylitol, and sorbitol) concentrations. The stabilization degree of salts followed the rank of the Hofmeister series, and the product of the Setchenov constant ( K s) times the concentration of solute ( C s) was useful to predict the enzyme stability in the presence of salt solutions. Polyols stabilized the halophilic enzyme as much as salts. For an equal polyol concentration, the thermostability increased in the range glycerol < erythritol < xylitol < sorbitol. The overall hydroxyl group concentration proved to be a good parameter for correlating the protective effect of polyols with the polyol nature. Thermoinactivation of the halophilic glucose dehydrogenase in the presence of NaCl and sorbitol was compared with that of a nonhalophilic glucose dehydrogenase in terms of the transition state theory. The free activation energy was, in all cases, enthalpy driven, and hydrogen-bond and/or ionic-binding interactions are the main forces involved in protein stabilization. The halophilic enzyme showed, in general, lower free activation energies for the deactivation process. The adaptation of the enzyme to a halophilic environment led to an enzyme with higher activity at high salt concentrations, but such an increase in enzyme activity was not related to an enhancement in enzyme thermostability.

Effect of the type of polyol on the soft segment crystallinity in polyurethane based on methylene bis(cyclohexyl diisocyanate)

To reveal the influence of the nature of polyols on the soft segment morphology, polyurethanes based on three polyols (polypropylene glycol 2000, polyethylene glycol 2000 and polytetramethylene glycol 2000), Methylene bis( p-cyclohexyl diisocyanate) and 1,4-butanediol were synthesized. These materials were characterized using wide angle X-ray diffraction and differential scanning calorimetry. Polytetramethylene glycol based polyurethane showed soft segment crystallinity while the other two were amorphous. This feature has been connected with the specific nature of the polyols.

Some Effects of Molecular Structure on the Production of Flexible Urethane Foams

Modifications to the chemical nature of polyols, catalysts, and surfactants which give easier foaming conditions are presented. Two new series of activated polyols are described. Their surface-active properties, efficiency as co-solvents for urethane inter mediates, and gelation rates are discussed and means of separating the control of these phenomena outlined. Results are given on the use of a number of new catalyst and surfac tant systems, some of which have shown out standing promise, particularly in the areas where catalyst balance has previously been difficult. Formulations and physical properties of the foams produced are presented and discussed.