Development of a methodology for characterizing reaction kinetics, rheology, and in situ compaction of polyimide prepregs during cure

2019 ◽  
Vol 54 (6) ◽  
pp. 835-843
Author(s):  
James Magato ◽  
Donald Klosterman
Keyword(s):  
Reaction Rate ◽  
Reaction Rates ◽  
Void Content ◽  
Heating Rates ◽  
Pressure Application ◽  
Composite Fabrication ◽  
Novel Approach ◽  
Panel Thickness ◽  
Volatile Generation

PMR-type polyimide prepregs are challenging to fabricate into high quality composites due to volatiles that are generated and must be removed in situ during processing. The current work was conducted to develop accurate, reliable, and practical characterization techniques of the prepreg rheology, volatile generation, and subsequent volatile removal from the prepreg during composite fabrication. Thermal analysis was used to characterize volatile generation, reaction rates, and rheology. A novel approach was used to measure the thickness of the prepreg in situ during vacuum bag/oven processing using a high-temperature LVDT. Experimental results are presented for the commercially available RM-1100 polyimide/carbon prepreg system, including the reaction rate, rheology, and panel thickness results for a series of heating rates and ply counts. The results show the key interrelationships in these coupled phenomena and how that information can be used to select the optimum temperature of pressure application to minimize the final void content.

scholarly journals Monitoring the Interfacial Polymerization of Piperazine and Trimesoyl Chloride with Hydrophilic Interlayer or Macromolecular Additive by in-situ FT-IR Spectroscopy

2019 ◽  
Author(s):  
Xi Yang
Keyword(s):  
Ir Spectroscopy ◽  
Reaction Rate ◽  
Interfacial Polymerization ◽  
Reaction System ◽  
Reaction Rates ◽  
Water Permeation ◽  
Ft Ir ◽  
Trimesoyl Chloride ◽  
Ft Ir Spectroscopy

The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize the nanofiltration (NF) membrane. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies are applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer; (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in-situ FT-IR spectroscopy was firstly used to monitor the IP reaction of PIP/TMC reaction system, with hydrophilic interlayers or macromolecular additives. Moreover, we study the formed polyamide layer growth on the substrate, in a real-time manner. The in-situ FT-IR experimental results confirm that the IP reaction rates are effectively suppressed and the formed polyamide thickness reduces from 138±24 nm to 46±2 nm. Furthermore, the optimized NF membrane with excellent performance are consequently obtained, which include the boosted water permeation flux about 141~238 (L·m2·h/MPa) and superior salt rejection of Na2SO4 > 98.4%.

Modelling Oxidative Dissolution of Spent Fuel

1996 ◽  
Vol 465 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Redox Reaction ◽  
Uranium Oxide ◽  
Reaction Rate ◽  
Spent Nuclear Fuel ◽  
Large Fraction ◽  
Reaction Rates ◽  
Spent Fuel ◽  
First Case ◽  
Rate Of Movement

ABSTRACTSpent nuclear fuel will, by the radiation, split nearby water into oxidizing and reducing compounds. The reducing compounds are mostly hydrogen that will diffuse away. The remaining oxidizing compounds can oxidize the uranium oxide of the fuel and make it more soluble. The oxidised uranium will dissolve and diffuse away. The nuclides previously incorporated in the spent fuel matrix can then be released and also migrate away from the fuel.A model is proposed where the produced oxidizing species compete for reaction with the fuel and for escaping out of the system. The chemical reaction rate of oxygen and fuel is taken from literature values based on experiments. The escape rate of oxidants to a receding redox front in the backfill is modelled assuming a redox reaction of oxidizing component and reducing component in the surrounding. The rate of movement of the redox front is determined from the rate of production of oxidants. This is estimated using a previously devised model that has been calibrated to in situ observed radiolysis.Three cases are modelled. In the first case it is assumed that the reducing compound is insoluble and that the reaction between oxygen and reducing mineral is very fast. In the second case it is assumed that the reducing component has a known solubility and that it can migrate to meet the oxygen and quickly react. In a third case a finite reaction rate is modelled between the oxygen and the reducing species.The sample calculations show that if the reducing mineral has to be supplied from the backfill a large fraction of the spent fuel could be oxidised. If the corrosion products of a degraded steel canister can supply the reducing species and the redox reaction is fast, very small amounts of the fuel could be oxidised. Literature data indicate that the redox reaction rate may not be so fast that it can be considered instantaneous and then a considerable fraction of the fuel could be oxidised. The model gives a means of exploring which mechanisms and data may be of most importance for radiolytic fuel dissolution, but the realism of the data and the model must be tested further. There is a lack of understanding and data on reaction rates, heterogeneous as well as homogeneous. This is crucial to the results.

scholarly journals Monitoring the Interfacial Polymerization of Piperazine and Trimesoyl Chloride with Hydrophilic Interlayer or Macromolecular Additive by In Situ FT-IR Spectroscopy

Membranes ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 12 ◽  
Author(s):  
Xi Yang
Keyword(s):  
Aqueous Solution ◽  
Ir Spectroscopy ◽  
Reaction Rate ◽  
Interfacial Polymerization ◽  
Reaction Rates ◽  
Water Permeation ◽  
Ft Ir ◽  
Trimesoyl Chloride ◽  
Ft Ir Spectroscopy

The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize nanofiltration (NF) membranes. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies were applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer, and (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in situ Fourier transform infrared (FT-IR) spectroscopy was firstly used to monitor the IP reaction of PIP/TMC with hydrophilic interlayers or macromolecular additives in the aqueous solution of PIP. Moreover, the formed polyamide layer growth on the substrate was studied in a real-time manner. The in situ FT-IR experimental results confirmed that the IP reaction rates were effectively suppressed and that the formed polyamide thickness was reduced from 138 ± 24 nm to 46 ± 2 nm according to TEM observation. Furthermore, an optimized NF membrane with excellent performance was consequently obtained, which included boosted water permeation of about 141–238 (L/m2·h·MPa) and superior salt rejection of Na2SO4 > 98.4%.

scholarly journals Monitoring the Interfacial Polymerization of Piperazine and Trimesoyl Chloride with Hydrophilic Interlayer or Macromolecular Additive by in-situ FT-IR Spectroscopy

2020 ◽  
Author(s):  
Xi Yang
Keyword(s):  
Aqueous Solution ◽  
Ir Spectroscopy ◽  
Reaction Rate ◽  
Interfacial Polymerization ◽  
Reaction Rates ◽  
Water Permeation ◽  
Ft Ir ◽  
Trimesoyl Chloride ◽  
Ft Ir Spectroscopy

The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize nanofiltration (NF) membranes. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies were applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer, and (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in situ Fourier transform infrared (FT-IR) spectroscopy was firstly used to monitor the IP reaction of PIP/TMC with hydrophilic interlayers or macromolecular additives in the aqueous solution of PIP. Moreover, the formed polyamide layer growth on the substrate was studied in a real-time manner. The in situ FTIR experimental results confirmed that the IP reaction rates were effectively suppressed and that the formed polyamide thickness was reduced from 138 ± 24 nm to 46 ± 2 nm according to TEM observation. Furthermore, an optimized NF membrane with excellent performance was consequently obtained, which included boosted water permeation of about 141–238 (L/m2·h·MPa) and superior salt rejection of Na2SO4 > 98.4%.

scholarly journals Monitoring the Interfacial Polymerization of Piperazine and Trimesoyl Chloride with Hydrophilic Interlayer or Macromolecular Additive by in-situ FT-IR Spectroscopy

2019 ◽  
Author(s):  
Xi Yang
Keyword(s):  
Ir Spectroscopy ◽  
Reaction Rate ◽  
Interfacial Polymerization ◽  
Reaction System ◽  
Reaction Rates ◽  
Water Permeation ◽  
Ft Ir ◽  
Trimesoyl Chloride ◽  
Ft Ir Spectroscopy

The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize the nanofiltration (NF) membrane. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies are applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer; (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in-situ FT-IR spectroscopy was firstly used to monitor the IP reaction of PIP/TMC reaction system, with hydrophilic interlayers or macromolecular additives. Moreover, we study the formed polyamide layer growth on the substrate, in a real-time manner. The in-situ FT-IR experimental results confirm that the IP reaction rates are effectively suppressed and the formed polyamide thickness reduces from 138±24 nm to 46±2 nm. Furthermore, the optimized NF membrane with excellent performance are consequently obtained, which include the boosted water permeation flux about 141~238 (L·m2·h/MPa) and superior salt rejection of Na2SO4 > 98.4%.

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>

A novel approach for preparing in-situ nitrogen doped carbon via pyrolysis of bean pulp for supercapacitors

Energy ◽  
2021 ◽  
Vol 216 ◽  
pp. 119227
Author(s):  
Yan Ding ◽  
Yunchao Li ◽  
Yujie Dai ◽  
Xinhong Han ◽  
Bo Xing ◽  
...  
Keyword(s):  
Nitrogen Doped ◽  
Novel Approach ◽  
Nitrogen Doped Carbon

Location-thinking, value-thinking, and graphical forms: combining analytical frameworks to analyze inferences made by students when interpreting the points and trends on a reaction coordinate diagram

2021 ◽  
Author(s):  
Alexander P. Parobek ◽  
Patrick M. Chaffin ◽  
Marcy H. Towns
Keyword(s):  
Reaction Rate ◽  
Research Study ◽  
Reaction Rates ◽  
Reaction Coordinate ◽  
Structured Interviews ◽  
Chemistry Students ◽  
Qualitative Research Study ◽  
The Impact ◽  
Analytical Frameworks ◽  
Chemical Representations

Reaction coordinate diagrams (RCDs) are chemical representations widely employed to visualize the thermodynamic and kinetic parameters associated with reactions. Previous research has demonstrated a host of misconceptions students adopt when interpreting the perceived information encoded in RCDs. This qualitative research study explores how general chemistry students interpret points and trends on a RCD and how these interpretations impact their inferences regarding the rate of a chemical reaction. Sixteen students participated in semi-structured interviews in which participants were asked to interpret the points and trends along provided RCDs and to compare relative reaction rates between RCDs. Findings derived from this study demonstrate the diversity of graphical reasoning adopted by students, the impact of students’ interpretations of the x-axis of a RCD on the graphical reasoning employed, and the influence of these ideas on inferences made about reaction rate. Informed by analytical frameworks grounded in the resources framework and the actor-oriented model of transfer, implications for instruction are provided with suggestions for how RCDs may be presented to assist students in recognizing the critical information encoded in these diagrams.

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