scholarly journals Preparation of Associative Polyurethane Thickener and Its Thickening Mechanism Research

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Gao Nan ◽  
Zhang Zhuo ◽  
Dong Qingzhi
Keyword(s):  
Molecular Weight ◽  
Particle Size ◽  
Soft Segment ◽  
Synthesis Process ◽  
Segment Length ◽  
Solvent Ratio ◽  
Aqueous Dispersions ◽  
Before And After ◽  
Size And Morphology ◽  
End Capping

Associative polyurethane (PU) thickener has been synthesized by preparing the prepolymer with the reaction of polyethylene glycol (PEG) and isophorone diisocyanate (IPDI), which then end-capping with long-chain alkanol. The synthesis process, as well as hydrophilic chain length, theoretical molecular weight, solvent ratio, and thickener percentages, has been researched. The results shows that it reaches the upmost thickening effect when the theoretical molecular weight is under 20000, soft-segment length is under 4000, solvent ratio is 1 : 1, and thickener percentages are controlled at 10%. Furthermore, thickening mechanism of PU thickener has been analyzed detailedly through the measurement of the critical micelle concentration (CMC) of PU thickener and analysis of the influence of PU thickener on the particle size and morphology of PU dispersions. It has been observed from the scanning electron microscopy (SEM) that the PU aqueous dispersions produce a certain degree of flocculation when the PU thickener was added, and this flocculation structure has been proved to be a thixotropic structure through the characterization of the change of particle size before and after the thickener is introduced into the PU aqueous dispersions. The CMC measurement results present that the thickening effect will be apparent when the concentration is controlled in a low range.

Role of the Hydrothermal Synthesis Conditions on the Structure and Morphology of Co-Doped Y2O3:Er3+-Yb3+ Nanostructured Materials

2010 ◽  
Vol 9 ◽  
pp. 109-116 ◽  
Author(s):  
A. Martinez ◽  
J. Morales ◽  
P. Salas ◽  
C. Ángeles-Chávez ◽  
L.A. Diaz-Torres ◽  
...  
Keyword(s):  
Particle Size ◽  
Nanostructured Materials ◽  
Precipitation Method ◽  
Cubic Phase ◽  
Solvent Ratio ◽  
Synthesis Conditions ◽  
Water Solvent ◽  
Size And Morphology ◽  
Hydrothermal Precipitation ◽  
Co Doped

This work is devoted to the structural and morphological study of co-doped Y2O3:Yb3+-Er3+ nanophosphors, with 1 mol% of Er2O3 and 2 mol% of Yb2O3, synthesized by hydrothermal precipitation method via cetyltrimethylammonium bromide (CTAB) surfactant complex for different ethanol/water solvent ratios ranging from 1:1 to 1:10. Structural characterization results showed the prevalence of cubic phase independent of the solvent ratio although particle size does depend on the solvent ratio. Concerning to morphology, microscopic characterization indicates that the content of water used in synthesis is determinant in the morphology of resulting samples: a high content of water favored the formation of nanorods/nanofibers while a low water content give rise to heterogeneous morphology with irregular particles. Also, solvent ratio determines the consistency of nanostructured materials; an intermediate solvent ratio leads to nanofibers while a high solvent ratio let to obtain nanorods with length/diameter ratio ~3-5. These results show that solvent concentration plays an important role in particle size and morphology of nanostructured materials while the annealing temperature determines the phase composition and crystallite size.

scholarly journals Microflow Nanoprecipitation of Positively Charged Gastroresistant Polymer Nanoparticles of Eudragit® RS100: A Study of Fluid Dynamics and Chemical Parameters

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2925 ◽  
Author(s):  
Cristina Yus ◽  
Manuel Arruebo ◽  
Silvia Irusta ◽  
Victor Sebastián
Keyword(s):  
Fluid Dynamics ◽  
Particle Size ◽  
Flow Rate ◽  
Physicochemical Parameters ◽  
Polymer Concentration ◽  
Critical Parameters ◽  
Synthesis Process ◽  
Size Analysis ◽  
Solvent Ratio ◽  
Microscopy Imaging

The objective of the present work was to produce gastroresistant Eudragit® RS100 nanoparticles by a reproducible synthesis approach that ensured mono-disperse nanoparticles under the size of 100 nm. Batch and micromixing nanoprecipitation approaches were selected to produce the demanded nanoparticles, identifying the critical parameters affecting the synthesis process. To shed some light on the formulation of the targeted nanoparticles, the effects of particle size and homogeneity of fluid dynamics, and physicochemical parameters such as polymer concentration, type of solvent, ratio of solvent to antisolvent, and total flow rate were studied. The physicochemical characteristics of resulting nanoparticles were studied applying dynamic light scattering (DLS) particle size analysis and electron microscopy imaging. Nanoparticles produced using a micromixer demonstrated a narrower and more homogenous distribution than the ones obtained under similar conditions in conventional batch reactors. Besides, fluid dynamics ensured that the best mixing conditions were achieved at the highest flow rate. It was concluded that nucleation and growth events must also be considered to avoid uncontrolled nanoparticle growth and evolution at the collection vial. Further, rifampicin-encapsulated nanoparticles were prepared using both approaches, demonstrating that the micromixing-assisted approach provided an excellent control of the particle size and polydispersity index. Not only the micromixing-assisted nanoprecipitation promoted a remarkable control in the nanoparticle formulation, but also it enhanced drug encapsulation efficiency and loading, as well as productivity. To the best of our knowledge, this was the very first time that drug-loaded Eudragit® RS100 nanoparticles (NPs) were produced in a continuous fashion under 100 nm (16.5 ± 4.3 nm) using microreactor technology. Furthermore, we performed a detailed analysis of the influence of various fluid dynamics and physicochemical parameters on the size and uniformity of the resulting nanoparticles. According to these findings, the proposed methodology can be a useful approach to synthesize a myriad of nanoparticles of alternative polymers.

Direct manipulation of particle size and morphology of ordered mesoporous silica by flow synthesis

RSC Advances ◽  
2015 ◽  
Vol 5 (18) ◽  
pp. 13331-13340 ◽  
Author(s):  
T. N. Ng ◽  
X. Q. Chen ◽  
K. L. Yeung
Keyword(s):  
Particle Size ◽  
Mesoporous Silica ◽  
Hollow Spheres ◽  
Ordered Mesoporous Silica ◽  
Direct Manipulation ◽  
Flow Synthesis ◽  
Precise Control ◽  
Ordered Mesoporous ◽  
Particle Size And Morphology ◽  
Size And Morphology

Flow-synthesis of mesoporous silica allows deliberate and precise control over the size and shapes and enables the preparation of complex microstructures (i.e., hollow spheres).

Effect of the rice flour particle size and variety type on water holding capacity and water diffusivity in aqueous dispersions

LWT ◽  
2021 ◽  
Vol 142 ◽  
pp. 111082
Author(s):  
Barbora Lapčíková ◽  
Lubomír Lapčík ◽  
Tomáš Valenta ◽  
Petr Majar ◽  
Kristýna Ondroušková
Keyword(s):  
Particle Size ◽  
Rice Flour ◽  
Water Holding Capacity ◽  
Aqueous Dispersions ◽  
Water Diffusivity ◽  
Water Holding

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

Effect of particle size and delignification on the rate of digestion of hemicellulose and cellulose by cellulase in mature pangola grass stems

1983 ◽  
Vol 34 (3) ◽  
pp. 241 ◽  
Author(s):  
CW Ford
Keyword(s):  
Particle Size ◽  
Cell Walls ◽  
Trichoderma Viride ◽  
Structural Features ◽  
Cell Wall Polysaccharides ◽  
Particle Size Reduction ◽  
Digitaria Decumbens ◽  
Hemicellulose Degradation ◽  
Before And After ◽  
The Difference

Stem cell walls of pangola grass (Digitaria decumbens) were ground to two particle sizes (c. 1 and 0.1 mm diameter), and incubated with cellulase (ex. Trichoderma viride) for varying times before and after delignification. Total cell walls finely ground (0.1 mm) with a Spex Shatterbox mill were initially degraded more rapidly (to 24 h) than delignified 1 mm particles. Thereafter the delignified material was solubilized to a greater extent. Subsequent specific determinations of cell wall polysaccharides indicated that delignification increased the rate of hemicellulose degradation to a greater extent than did particle size reduction, whereas the opposite was found for cellulose. The difference between delignified and Spex-ground residues, in terms of the amount of polysaccharide digested, was much greater for cellulose than hemicellulose. It is concluded that structural features play a more important role in limiting cellulase degradation of cellulose than does association with lignin, the reverse being so for hemicellulose.

scholarly journals Effect of DMPA and Molecular Weight of Polyethylene Glycol on Water-Soluble Polyurethane

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1915 ◽  
Author(s):  
Eyob Wondu ◽  
Hyun Woo Oh ◽  
Jooheon Kim
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Polyethylene Glycol ◽  
Photoelectron Spectroscopy ◽  
Water Solubility ◽  
Soft Segment ◽  
Water Soluble ◽  
Size Exclusion ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry

In this study water-soluble polyurethane (WSPU) was synthesized from isophorone diisocyanate (IPDI), and polyethylene glycol (PEG), 2-bis(hydroxymethyl) propionic acid or dimethylolpropionic acid (DMPA), butane-1,4-diol (BD), and triethylamine (TEA) using an acetone process. The water solubility was investigated by solubilizing the polymer in water and measuring the contact angle and the results indicated that water solubility and contact angle tendency were increased as the molecular weight of the soft segment decreased, the amount of emulsifier was increased, and soft segment to hard segment ratio was lower. The contact angle of samples without emulsifier was greater than 87°, while that of with emulsifier was less than 67°, indicating a shift from highly hydrophobic to hydrophilic. The WSPU was also analyzed using Fourier transform infrared spectroscopy (FT-IR) to identify the absorption of functional groups and further checked by X-ray photoelectron spectroscopy (XPS). The molecular weight of WSPU was measured using size-exclusion chromatography (SEC). The structure of the WSPU was confirmed by nuclear magnetic resonance spectroscopy (NMR). The thermal properties of WSPU were analyzed using thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).

Olfactory Training Using Heavy and Light Weight Molecule Odors

Perception ◽  
2016 ◽  
Vol 46 (3-4) ◽  
pp. 343-351 ◽  
Author(s):  
Sophia C. Poletti ◽  
Elisabeth Michel ◽  
Thomas Hummel
Keyword(s):  
Molecular Weight ◽  
Olfactory Dysfunction ◽  
Light Weight ◽  
Short Term ◽  
Olfactory Loss ◽  
Short Term Exposure ◽  
Before And After ◽  
Phenyl Ethyl Alcohol ◽  
A Prospective Study ◽  
Olfactory Training

Background Repeated short-term exposure to odors is known to improve olfaction in patients with acquired olfactory dysfunction. The aim was to find out whether differences in molecular weight of odors used for olfactory training influences olfaction. We hypothesized a greater improvement following training with light weight molecule (LWM) odors. Methods A prospective study was performed in patients with posttraumatic (PTOL) and postviral olfactory loss (PVOL). Olfactory training was performed over a period of 5 months. One group ( n = 48) used four odors containing heavy weight molecules (HWM; >150 g/mol) and another ( n = 48) containing LWM (<150 g/mol). Olfaction was tested before and after the training using the Sniffin’ Sticks test. Results Olfactory training was associated with olfactory improvement, with the improvement in PVOL patients being three times greater than that seen in the PTOL group. Compared with LWM training, HWM training was associated with a significantly greater improvement in Phenyl Ethyl Alcohol (PEA) threshold scores in PVOL patients; however, no such improvement could be shown for other subtests or in PTOL patients. Conclusion Overall, training was associated with olfactory improvement. With the exception of threshold scores in PVOL, there were no significant differences between LWM and HWM groups.

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