scholarly journals Rheokinetic study of crosslinking of α,ω-dihydroxy oligo(alkylene maleate)s with a trisisocyanate

2003 ◽  
Vol 68 (3) ◽  
pp. 147-162 ◽  
Author(s):  
Branko Dunjic ◽  
Jasna Djonlagic ◽  
Slavko Vukasinovic ◽  
Maurice Sepulchre ◽  
Marie-Odile Sepulchre ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Reaction Rate ◽  
Loss Modulus ◽  
Phase Segregation ◽  
Mechanical Analysis ◽  
Rheological Parameters ◽  
Crosslinking Reaction ◽  
Curing Process ◽  
Segmental Mobility ◽  
Time Curve

The crosslinking reaction of three series of ?,?-dihydroxy oligo(alkylene maleate)s with a trifunctional isocyanate was followed by dynamic mechanical analysis and FTIR spectroscopy. The evaluation of rheological parameters such as storage G? and loss modulus G", was recorded. A typical G?versus time curve has a characteristic "S" shape, indicating autoacceleration of the crosslinking reaction. The whole curing process starting from G?equal G", or the beginning of gelation is described by a second - order phenomenological rheokinetic equation which takes into account the autoacceleration effect, the latter being a consequence of the superposition of both the chemical reaction and phase segregation. It appears that the crosslinking reaction rate depends on the concentration of the functional groups, i.e., on the molecular weight of the polyester prepolymer and on the length of the aliphatic sequence in the repeating unit or the segmental mobility. The crosslinking rate decreases in the order: poly(octamethylene maleate) > poly(hexamethylene maleate) > poly(butylene maleate).

Studies on Curing Kinetics Parameter of TDI-PPG-MOCA Polyurethane by FTIR

2011 ◽  
Vol 328-330 ◽  
pp. 966-969 ◽  
Author(s):  
Qing Zhen Wen ◽  
Chao Yu ◽  
Jin Hua Zhu ◽  
Tian Yu Liu
Keyword(s):  
Reaction Rate ◽  
Curing Kinetics ◽  
Crosslinking Reaction ◽  
Curing Process ◽  
Second Order Reaction ◽  
Reaction Rate Constants ◽  
Curing Reaction ◽  
Different Temperatures ◽  
Measured Effect ◽  
Kinetics Parameter

The curing process of polyurethanes was investigated with FTIR method. The curves of conversion (α)VS curing reaction time (t) at different temperatures were obtained .The curing reaction of the system was found to be second order reaction. The reaction rate constants and activation energy had been measured. Effect of the use lever of curing agent and temperatures on curing reaction was discussed. The results showed that when the mole ratio of NCO/OH is smaller than 1, the crosslinking reaction take place at high temperature.

Effect of wood species and molecular weight of phenolic resins on curing behavior and bonding development

Holzforschung ◽  
2005 ◽  
Vol 59 (6) ◽  
pp. 635-640 ◽  
Author(s):  
Guangbo He ◽  
Ning Yan
Keyword(s):  
Molecular Weight ◽  
Wood Species ◽  
Weight Fraction ◽  
Mechanical Analysis ◽  
Gel Point ◽  
High Molecular Weight Fraction ◽  
Curing Process ◽  
Phenolic Resins ◽  
Curing Behavior ◽  
Bonding Performance

Abstract In this study, dynamic mechanical analysis (DMA) was used to investigate the curing behavior and bonding performance of phenolic resins with different molecular weights as a function of three wood species. The curing process of the resin was characterized by both gel point and tanδ. The change in storage modulus before and after curing was used to characterize the bonding development. Resin molecular weight was found to significantly influence the curing process, while the effect of wood on the curing behavior among the three species was not clear. The resin should contain a low-molecular-weight fraction and a high-molecular-weight fraction to achieve the best bonding performance. The optimum molecular weight and molecular weight distribution was found to be different among the different wood species studied.

scholarly journals The transition nanoreactor-nanoparticle in epoxy polymers curing process

2008 ◽  
Vol 2 (4) ◽  
pp. 281-284
Author(s):  
Georgiy Kozlov ◽  
◽  
Musa Bashorov ◽  
Abdulakh Mikitaev ◽  
Gennady Zaikov ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Euclidean Space ◽  
Reaction Rate ◽  
Typical Feature ◽  
Reaction Rate Constant ◽  
Conversion Degree ◽  
Curing Process ◽  
Epoxy Polymers ◽  
Curing Reaction ◽  
Fractal Space

It has been shown that for curing reaction in fractal space the reaction rate constant reduction is typical. Another typical feature of this reaction is the formation of a large number of microgels with smaller molecular weight in comparison with reaction in Euclidean space at the same conversion degree. The dimensional border between nanoreactor and nanoparticle for the curing reaction under consideration has been obtained.

Monitoring Polymer-Assisted Mechanochemical Cocrystallisation Through in Situ X-Ray Powder Diffraction

2020 ◽  
Author(s):  
Luzia S. Germann ◽  
Sebastian T. Emmerling ◽  
Manuel Wilke ◽  
Robert E. Dinnebier ◽  
Mariarosa Moneghini ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Powder Diffraction ◽  
Reaction Rate ◽  
Polymer Additives ◽  
Time Resolved ◽  
X Ray

Time-resolved mechanochemical cocrystallisation studies have so-far focused solely on neat and liquid-assisted grinding. Here, we report the monitoring of polymer-assisted grinding reactions using <i>in situ</i> X-ray powder diffraction, revealing that reaction rate is almost double compared to neat grinding and independent of the molecular weight and amount of used polymer additives.<br>

scholarly journals Ginsenoside Absorption Rate and Extent Enhancement of Black Ginseng (CJ EnerG) over Red Ginseng in Healthy Adults

Pharmaceutics ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 487
Author(s):  
Saebyul Yoo ◽  
Bom-I Park ◽  
Do-hyun Kim ◽  
Sooyoung Lee ◽  
Seung-hoon Lee ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Molecular Weight ◽  
Absorption Rate ◽  
Systemic Exposure ◽  
Red Ginseng ◽  
Double Blind ◽  
Time Curve ◽  
Concentration Time ◽  
Black Ginseng ◽  
Clinically Significant

Red ginseng (RG) and black ginseng (BG, CJ EnerG) were prepared from fresh ginseng using one and nine cycles of steaming and drying, respectively. This process reduces the molecular weight (MW) of ginsenoside-active compounds in ginseng by removing sugar moieties from their dammaranes. We compared the pharmacokinetic characteristics of ginsenosides between BG comprising mainly low-MW ginsenosides (Rg3, Rg5, Rk1, and Rh1) and RG that predominantly contains high-MW ginsenosides (Rb1, Rb2, Rc, Rd, Re, and Rg1). The safety profiles and tolerability were also studied using a randomized, double-blind, single-dose, crossover clinical trial. A combination of Rb1, Rg1, and Rg3, well-known representative and functional RG components, exhibited a 1-h faster absorption rate (Tmax) and 58% higher exposure (24-h area under the concentration–time curve, AUC24) in BG than in RG. Furthermore, the combination of Rg3, Rg5, and Rk1, the major and most efficient components in BG, displayed 824% higher absorption (AUC24) in BG than in RG. The total ginsenoside showed a 5-h rapid intestinal absorption (Tmax) and 79% greater systemic exposure (AUC24) in BG than in RG. No clinically significant findings were observed in terms of safety or tolerability. Thus, BG extract was more effective than RG extract.

scholarly journals Certain Rheological Aspects of Functionalized Guar Gum

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Meenu Kapoor ◽  
Dhriti Khandal ◽  
Ruchi Gupta ◽  
Pinklesh Arora ◽  
Geetha Seshadri ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Guar Gum ◽  
Loss Modulus ◽  
Industrial Applications ◽  
Green Technology ◽  
Low Molecular Weight ◽  
Radiation Processing ◽  
Industrial Sectors ◽  
Wide Acceptance

Guar gum and its derivatives are highly important industrial hydrocolloids as they find applications in various industrial sectors. Guar is a polymer of high molecular weight and its aqueous solutions exhibit unique rheological properties, which has led to its wide acceptance by the industry. In certain industrial applications low molecular weight guar and its derivatives are needed, and conventionally chemical depolymerisation of guar is carried out for this purpose. Radiation processing is a novel and green technology for carrying out depolymerization and can be an ideal substitute for chemical depolymerisation technique. In order to study the effect of radiation on guar derivatives, three types of derivatives have been taken in the present study: carboxymethyl, hydroxyethyl, and methyl guar. The effect of 1–50 KGy radiation dose on the rheological behavior of these derivatives has been studied, and the results have been described in the present paper. The effect on storage and loss modulus with respect to frequency and effect on viscosity with respect to shear rate have been discussed in detail.

scholarly journals Oxazoline-based crosslinking reaction for coatings

2021 ◽  
Author(s):  
Philipp Knospe ◽  
Patrick Böhm ◽  
Jochen Gutmann ◽  
Michael Dornbusch
Keyword(s):  
Mechanical Properties ◽  
Loss Modulus ◽  
New Technology ◽  
Sol Gel ◽  
Polymer Network ◽  
Time Dependent ◽  
Crosslinking Reaction ◽  
Coating Materials ◽  
Rheological Measurements ◽  
Excellent Adhesion

AbstractNowadays, coating materials must meet high demands in terms of mechanical, chemical and optical properties in all areas of application. Amongst others, amines and isocyanates are used as crosslinking components for curing reactions, meeting the highly demanding properties of the coatings industry. In this work, a new crosslinking reaction for coatings based on oxazoline chemistry is investigated with the objective to overcome disadvantages of established systems and fulfill the need for sustainable coating compounds. The oxazoline-group containing resin, synthesized from commercially available substances, undergoes cationic self-crosslinking polymerization to build up a network based on urethane and amide moieties. NMR-, IR- and ES-mass spectroscopy are suitable techniques to characterize the synthesized oxazoline monomers, which are linked to polyisocyanates and polymerized afterwards via self-polymerization. The progress of crosslinking is followed by changes in IR spectra and by rheological measurements to calculate time dependent values for storage and loss modulus. The glass transition temperature of the resulting coating is determined, too. Furthermore, sol–gel-analysis is performed to determine the degree of crosslinking. After application on steel and aluminium panels, application tests are performed. In addition to excellent adhesion to the substrate, the polymer network shows promising mechanical properties and with that it could represent a new technology for the coatings industry.

Dynamic Mechanical Analysis of Bio-Based and Synthetic Petroleum Based Polymer Foams with Powder Type Organic Filler at Prolonged Ultra-Violet Exposure

2020 ◽  
Vol 01 (01) ◽  
Author(s):  
M A Zulhakimie ◽  
◽  
Anika Zafiah M. Rus ◽  
N S S Sulong ◽  
A Syah Z A ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Epoxy Polymer ◽  
Loss Modulus ◽  
Ultra Violet ◽  
Mechanical Analysis ◽  
Uv Exposure ◽  
Polymer Foams ◽  
Polymer Foam ◽  
Powder Filler ◽  
Tan Δ

Wood powder filler applied to the bio-based and epoxy polymer foams has the potential to reinforce the polymer foam structure. The 'Meranti' wood filler type was used as the filler in this analysis. In order to observe the pore size of each sample when exposed to different hours of UV exposure using optical microscopy (OM), this study was made.This analysis was conducted to compare the mechanical properties of each sample with different filler ratios of 0 wt%, 5 wt%, 10 wt%, 15wt% and 20 wt% at different UV exposure hours, which is 0 hour to 6000 hours with a 2000 hour rapid increase. Using the DMA Q800 TA unit, the mechanical properties were studied. In order to obtain the product of their mechanical properties, samples having a scale of 40 x 10 x 5 mm were clamped into the machine. The results will show the value of tan δ, loss modulus and storage modulus from the DMA test.The tan δ value shows that the high tanδvalue will be produced by the higher ratio filler. In contrast to bio-based polymer foams, epoxy polymer foams with powder fillers have the highest tan δ value. It shows that the higher filler ratio can be reported with the lower tan δ value. As the filler ratio filler in the polymer foams increased, the consequence of storage and loss modulus was found to increase. The greater the modulus of loss and the modulus of storage, the lower the temperature. As energy is lost as heat during UV irradiation exposure, bio-based polymer foams with a high powder filler ratio can dissipate more energy.

Processes for coating surfaces with a copolymer made from sulfur and dicyclopentadiene

2021 ◽  
Author(s):  
Maximilian Mann ◽  
Bowen Zhang ◽  
Samuel J. Tonkin ◽  
Christopher T Gibson ◽  
Zhongfan Jia ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight ◽  
Curing Process ◽  
Shelf Stable

The reaction between sulfur and dicyclopentadiene was optimised to form a shelf stable and soluble low molecular weight oligomer. After a simple curing process at 140 °C the material was...

scholarly journals Dynamic Mechanical Properties of Hybrid Layered Silicates/Kaolin Geopolymer Filler in Epoxy Composites

2017 ◽  
Vol 54 (3) ◽  
pp. 543-545 ◽  
Author(s):  
Yusrina Mat Daud ◽  
Kamarudin Hussin ◽  
Azlin Fazlina Osman ◽  
Che Mohd Ruzaidi Ghazali ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Speed ◽  
Hybrid Composites ◽  
Loss Modulus ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Layered Silicates ◽  
Epoxy Composites ◽  
Damping Factor ◽  
Dynamic Mechanical

Preparation epoxy based hybrid composites were involved kaolin geopolymer filler, organo-montmorillonite at 3phr by using high speed mechanical stirrer. A mechanical behaviour of neat epoxy, epoxy/organo-montmorillonite and its hybrid composites containing 1-8phr kaolin geopolymer filler was studied upon cyclic deformation (three-point flexion mode) as the temperature is varies. The analysis was determined by dynamic mechanical analysis (DMA) at frequency of 1.0Hz. The results then expressed in storage modulus (E�), loss modulus (E�) and damping factor (tan d) as function of temperature from 40 oC to 130oC. Overall results indicated that E�, E�� and Tg increased considerably by incorporating optimum 1phr kaolin geopolymer in epoxy organo-montmorillonite hybrid composites.

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