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Analyzing the Effect of Moisture in Transparent Polyamide and Its Composites.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Analyzing the Effect of Moisture in Transparent Polyamide and Its Composites./
作者:	Venoor, Varun.
面頁冊數:	1 online resource (277 pages)
附註:	Source: Dissertations Abstracts International, Volume: 83-09, Section: B.
Contained By:	Dissertations Abstracts International83-09B.
標題:	Plastics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28862412click for full text (PQDT)
ISBN:	9798790657245

Analyzing the Effect of Moisture in Transparent Polyamide and Its Composites.
Venoor, Varun.

Analyzing the Effect of Moisture in Transparent Polyamide and Its Composites. - 1 online resource (277 pages)

Source: Dissertations Abstracts International, Volume: 83-09, Section: B.

Thesis (Ph.D.)--University of Massachusetts Lowell, 2022.

Includes bibliographical references

Transparent polyamide (TPA) is a promising material for applications requiring high impact and transparency. This dissertation investigates the dynamics of moisture in transparent polyamide (Trogamid™ CX) and its biofiber reinforced composites with a view of better understanding the polymer structure, processing, and properties. In order to evaluate the influence of the environment under isothermal time sweeps, time-resolved rheological (TRR) measurements were conducted under oxidative (air) and inert (nitrogen) atmosphere. The implemented TRR technique elucidates structural changes occurring in PA melt under oxidative environment undergoing two concurrent phenomena's namely post-condensation and thermo-oxidative degradation. At temperatures above 255 °C, a dual-stage growth in viscoelastic properties is observed, with the exponential post-condensation leading to logistic-shaped oxidative degradation. The thermo-oxidative degradation at 270 °C is shown to initiate at the sample edge, which reduces the effective radius of the bulk melt by 6.4 % from the initial value of 12.5 mm. A new rheological analysis methodology is developed and validated to determine the viscoelastic properties of such transient materials. Time-dependent structural changes in the presence of water were also investigated using multiwave rheology. Multiwave test was conducted on transparent polyamide at 0.6 % and 0.9% H2O with frequencies from 0.25 to 64 rad/sec. Isochronal data obtained at 0, 900, 1800, 3600, 5400, and 7200 seconds for TPA with 0.6 % moisture exhibited a gradual shift in complex viscosity (η*) curves due to molar mass growth associated with melt post-condensation. The drop in magnitude for extrapolated data at 0 seconds demonstrated water-induced plasticization. At 0.9 % water content, the formation of bubbles was apparent from the collected samples. Storage (G') and loss (G'') moduli both portrayed exponential increase in time, with the magnitude higher than for the medium wet sample (0.6 % H2O). It is believed the presence of bubbles improved the mass transfer coefficient for moisture transport rising melt post-condensation rate. This article presents process modeling of twin-screw extrusion for dry and wet TPA using a combination of in-line, offline, and one-dimensional flow simulation. Increased vacuum and low initial moisture content caused a substantial increase in apparent viscosity due to the effective removal of water content from the melt through devolatilization. An empirical model based on temperature, shear rate, and residence time was predicted. Incorporation of such model in simulation package such as Ludovic® can provide valuable information on wet and dry processing of polymers. This research also investigated the effect of incorporating hydrophilic eco-friendly filler (soy flour) as reinforcement on the thermo-mechanical, mechanical and thermal stability of the composites. Two methodologies were implemented to incorporate 5 and 15 weight percent soy flour (SF) in TPA: (i) dry pellets (0.1 % water) and dry SF, (ii) wet pellets (0.6 % water) and dry SF, were processed in a twin-screw extruder. The compounding of SF/TPA composites was followed by injection molding into standard AS™ tensile specimens. The results indicate improved storage modulus (E'), mechanical properties (Young's modulus (MPa), and stress at break (MPa)) for 15 % SF/TPA produced using method two. These improved properties were attributed to better dispersion and reduction in fiber agglomerates with water-assisted extrusion.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798790657245Subjects--Topical Terms:

649803
Plastics.
Subjects--Index Terms:

Cycloaliphatic polyamideIndex Terms--Genre/Form:

542853
Electronic books.

Analyzing the Effect of Moisture in Transparent Polyamide and Its Composites.
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520 $a Transparent polyamide (TPA) is a promising material for applications requiring high impact and transparency. This dissertation investigates the dynamics of moisture in transparent polyamide (Trogamid™ CX) and its biofiber reinforced composites with a view of better understanding the polymer structure, processing, and properties. In order to evaluate the influence of the environment under isothermal time sweeps, time-resolved rheological (TRR) measurements were conducted under oxidative (air) and inert (nitrogen) atmosphere. The implemented TRR technique elucidates structural changes occurring in PA melt under oxidative environment undergoing two concurrent phenomena's namely post-condensation and thermo-oxidative degradation. At temperatures above 255 °C, a dual-stage growth in viscoelastic properties is observed, with the exponential post-condensation leading to logistic-shaped oxidative degradation. The thermo-oxidative degradation at 270 °C is shown to initiate at the sample edge, which reduces the effective radius of the bulk melt by 6.4 % from the initial value of 12.5 mm. A new rheological analysis methodology is developed and validated to determine the viscoelastic properties of such transient materials. Time-dependent structural changes in the presence of water were also investigated using multiwave rheology. Multiwave test was conducted on transparent polyamide at 0.6 % and 0.9% H2O with frequencies from 0.25 to 64 rad/sec. Isochronal data obtained at 0, 900, 1800, 3600, 5400, and 7200 seconds for TPA with 0.6 % moisture exhibited a gradual shift in complex viscosity (η*) curves due to molar mass growth associated with melt post-condensation. The drop in magnitude for extrapolated data at 0 seconds demonstrated water-induced plasticization. At 0.9 % water content, the formation of bubbles was apparent from the collected samples. Storage (G') and loss (G'') moduli both portrayed exponential increase in time, with the magnitude higher than for the medium wet sample (0.6 % H2O). It is believed the presence of bubbles improved the mass transfer coefficient for moisture transport rising melt post-condensation rate. This article presents process modeling of twin-screw extrusion for dry and wet TPA using a combination of in-line, offline, and one-dimensional flow simulation. Increased vacuum and low initial moisture content caused a substantial increase in apparent viscosity due to the effective removal of water content from the melt through devolatilization. An empirical model based on temperature, shear rate, and residence time was predicted. Incorporation of such model in simulation package such as Ludovic® can provide valuable information on wet and dry processing of polymers. This research also investigated the effect of incorporating hydrophilic eco-friendly filler (soy flour) as reinforcement on the thermo-mechanical, mechanical and thermal stability of the composites. Two methodologies were implemented to incorporate 5 and 15 weight percent soy flour (SF) in TPA: (i) dry pellets (0.1 % water) and dry SF, (ii) wet pellets (0.6 % water) and dry SF, were processed in a twin-screw extruder. The compounding of SF/TPA composites was followed by injection molding into standard AS™ tensile specimens. The results indicate improved storage modulus (E'), mechanical properties (Young's modulus (MPa), and stress at break (MPa)) for 15 % SF/TPA produced using method two. These improved properties were attributed to better dispersion and reduction in fiber agglomerates with water-assisted extrusion.
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