Pure Hydrolysis of Polyamides: A Comparative Study

Brette, Mathis Mortensen; Holm, Allan Hjarbæk; Drozdov, Aleksey D.; Christiansen, Jesper de Claville

doi:10.3390/chemistry6010002

Cited by 8 publications

(2 citation statements)

References 99 publications

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“…The isoelectric point (IEP) was approximately 4.39. Presumably, chargeable carboxylate and amine groups exist within the membrane from either mild hydrolysis of the amide groups or the presence of end groups. − At pH less than the IEP, the carboxylate and amine groups would be predominately protonated to give the membrane a net positive charge. At a pH greater than the IEP, a net negative charge is present from the deprotonated carboxylic groups.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of a Porous Membrane as a Mass-Transfer Efficient Structure for the Adsorption of Per- and Polyfluoroalkyl Substances from Drinking Water

Kim,

Chernysheva,

et al. 2024

ACS EST Eng.

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With drinking water regulations forthcoming for per-and polyfluoroalkyl substances (PFAS), the need for costeffective treatment technologies has become urgent. Adsorption is a key process for removing or concentrating PFAS from water; however, conventional adsorbents operated in packed beds suffer from mass transfer limitations. The objective of this study was to assess the mass transfer performance of a porous polyamide adsorptive membrane for removing PFAS from drinking water under varying conditions. We conducted batch equilibrium and dynamic adsorption experiments for perfluorooctanesulfonic acid, perfluorooctanoic acid, perfluorobutanesulfonic acid, and undecafluoro-2-methyl-3-oxahexanoic acid (i.e., GenX). We assessed various operating and water quality parameters, including flow rate (pore velocity), pH, ionic strength (IS), and presence of dissolved organic carbon. Outcomes revealed that the porous adsorptive membrane was a mass transfer-efficient platform capable of achieving dynamic capacities similar to equilibrium capacities at fast interstitial velocities. The adsorption mechanism of PFAS to the membrane was a mixture of electrostatic and hydrophobic interactions, with pH and IS controlling which interaction was dominant. The adsorption capacity of the membrane was limited by its surface area, but its site density was approximately five times higher than that of granular activated carbon. With advances in molecular engineering to increase the capacity, porous adsorptive membranes are well suited as alternative adsorbent platforms for removing PFAS from drinking water.

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Section: Resultsmentioning

confidence: 99%

Evaluation of a Porous Membrane as a Mass-Transfer Efficient Structure for the Adsorption of Per- and Polyfluoroalkyl Substances from Drinking Water

Kim,

Chernysheva,

et al. 2024

ACS EST Eng.

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“…The mechanical properties of PA fibers in the long term decrease due to chemical aging, and they can undergo hydrolysis when in contact with aqueous media for a long time [ 25 ]. On the other hand, PA can be mechanically or chemically recycled through thermal depolymerization, which makes it a sustainable material [ 26 ].…”

Section: Introductionmentioning

confidence: 99%

Waterless Dyeing of Polyamide 6.6

Eren,

Özyurt

2024

Polymers

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Waterless dyeing of polyamide 6.6 using scCO2 (supercritical carbon dioxide) was investigated. PA (polyamide) fibers can be dyed with various dyes, including disperse dyes. The conventional aqueous dyeing process uses large amounts of water and produces polluted water. Considering these environmental issues, waterless dyeing of fibers is a forefront issue, and utilization of supercritical carbon dioxide (scCO2) is a commercially viable technology for waterless dyeing. This study tested PA6.6 (polyamide 6.6) dyeing in scCO2 at 100 °C 220 bar pressure for 45 min. Color measurements and color fastness tests were performed, as well as tensile strength, scanning electron microscope (SEM) analysis, and Fourier transform infrared spectroscopy (FTIR) analysis. PA6.6 fabrics yielded higher K/S (color strength, the Kubelka–Munk equation) values with larger molecular weight dye and almost the same color strength with medium and small-sized dyes, demonstrating the ability of dyeing in a supercritical environment without water as a more environmentally friendly dyeing option compared to conventional dyeing.

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Utilizing a combination of experimental and machine learning methods to predict and correlate between accelerated and natural aging of CFRP/AL adhesive joints under hygrothermal conditions

Karimi,

2024

Polymer Composites

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This study investigates how carbon fiber reinforced polymer (CFRP)‐to‐aluminum adhesive joints behave under accelerated aging conditions with hygrothermal exposure and compares these findings against naturally aged samples to evaluate material reliability in challenging environments. The CFRP‐to‐aluminum adhesive joints were manufactured and subjected to natural aging for durations ranging from 1 to 3 years with 6‐month intervals, as well as accelerated aging (hygrothermal) for periods ranging from 100 to 1200 h, with intervals of 50 h. Subsequently, the mechanical properties of the joints were evaluated using a three‐point bending test. To forecast natural aging times from accelerated aging data, five machine learning models were utilized: artificial neural network, support vector regression, linear regression, polynomial regression, and random forest regression. Hygrothermal aging significantly degraded the matrix, causing a shift in failure modes from cohesive to mixed types (cohesive, adhesive, and fiber tear failures), leading to a notable decline in bending strength. The study observed a 23.13% strength reduction in samples aged naturally for 3 years and a 24.33% decrease in those subjected to 1000 h of accelerated aging. The random forest regressor demonstrated superior accuracy in predicting natural aging times across different accelerated aging periods. Through the application of machine learning models, this study introduces a novel approach to forecast natural aging durations using data from accelerated aging experiments. This method shows potential for optimizing joints and composite structures, ultimately improving their durability and minimizing the likelihood of failures during operational use.Highlights Studied hygrothermal effects on accelerated aging of carbon fiber reinforced polymer/Aluminum (AL) adhesive joints. Noted strength reduction from hygrothermal aging. Used five machine learning models; random forest regression had the highest accuracy. Analyzed correlation between natural and accelerated aging of dissimilar adhesive joints.

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Pure Hydrolysis of Polyamides: A Comparative Study

Cited by 8 publications

References 99 publications

Evaluation of a Porous Membrane as a Mass-Transfer Efficient Structure for the Adsorption of Per- and Polyfluoroalkyl Substances from Drinking Water

Evaluation of a Porous Membrane as a Mass-Transfer Efficient Structure for the Adsorption of Per- and Polyfluoroalkyl Substances from Drinking Water

Waterless Dyeing of Polyamide 6.6

Utilizing a combination of experimental and machine learning methods to predict and correlate between accelerated and natural aging of CFRP/AL adhesive joints under hygrothermal conditions

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