Study of structural changes and mesomorphic transitions of oriented poly(ethylene therephthalate) fibers in supercritical CO2

Baseri, Somayeh; Karimi, Mohammad; Morshed, Mohammad

doi:10.1016/j.eurpolymj.2012.01.017

Cited by 21 publications

(8 citation statements)

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“…It has been introduced to modify the microstructure of a polymer, such as the crystal structure [21,23,24,25,26]. The microstructures of polyethylene terephthalate (PET) fibers treated in scCO 2 , which aids in dyeing and improves the crystallinity, were studied, and the rearrangement of polymer chains in the amorphous phase was induced by cold drawing and exposure to scCO 2 [27,28]. Luo studied the surface modification of aramid fiber in scCO 2 with glycidyl-POSS to improve the surface adhesion of aramid fiber/epoxy resin [29].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Kong

2019

Polymers

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High modulus aramid fiber, such as Kevlar 49, is conventionally prepared by the heat annealing of high strength aramid fiber under a suitable tension at high temperature, especially higher than 500 °C. This enables the mobility of a rigid molecule chain to be rearranged into a more perfect crystalline or orientation structure under tension. However, annealing decreases the tensile strength, since the thermal degradation of the molecular chain at high temperature cannot be avoided. Kevlar 49 fibers treated in supercritical carbon dioxide (scCO2) under tension could improve their mechanical properties at a low temperature. The effects of the tension on the mechanical properties and structure of the Kevlar 49 fibers were studied by mechanical testing, wide-angle and small-angle X-ray scattering (WAXS, SAXS), and scanning electron microscopy (SEM). The results show that the mechanical properties, crystallinity and orientation of the fiber can be improved when the tension is less than 0.6 cN/dtex, which may be due to the increasing of the mobility of a rigid segment with the help of the plasticization of scCO2 and re-arrangement of macromolecular chain into crystalline and orientation structure under tension. What’s more, the amorphous region also was enhanced by crosslinking reaction of toluene 2,4-diisocyanate (TDI) with the chain end groups of the macromolecules in the amorphous regions. However, a decrease of tenacity was found when the tension was higher than 0.6 cN/dtex, which is because the tension was so high that the microfibril was broken. The results indicated that treating the Kevlar 49 fiber in scCO2 under a suitable tension with TDI as a crosslink agent can simultaneously improve both the tenacity and modulus of the fiber.

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Section: Introductionmentioning

confidence: 99%

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Kong

2019

Polymers

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“…Along these lines, a brief study of these parameters was carried out using the density and birefringence measurements. These parameters for the samples exposed under tension have been reported in our previous work . The objective of the present study is to focus on certain observations concerning the molecular dynamics of exposed samples in an attempt to enhance the current understanding of the effects of scCO 2 on structural changes and mesomorphic transitions in the preparation of new PET materials with improved properties.…”

Section: Introductionmentioning

confidence: 71%

“…In our previous work, we used DSC, FTIR, and WAXD (Wide angle x‐ray diffraction) methods to examine the mesomorphic transitions of PET fibers when treated under scCO 2 with tension . Here, we are going to report the results obtained from DMA (a method more sensitive than DSC to transitions in polymers) of cold‐drawn PET fibers exposed to scCO 2 with and without tension.…”

Section: Introductionmentioning

confidence: 99%

Effect of CO₂on Mesomorphic Structure of Cold-Drawn Poly(ethylene therephthalate) Fibers by Dynamic Mechanical Analysis

Baseri

Karimi

Morshed

2015

Adv. Polym. Technol.

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Dynamic mechanical analysis (DMA) provides interesting information about the dynamic viscoelastic properties and molecular scale motions. This article presents the results of an investigation into the effects of draw ratio and supercritical CO 2 (scCO 2 ) exposure on structural changes and mesomorphic transitions in cold-drawn poly(ethylene terephthalate) (PET) fibers by focus on DMA. Samples of partially oriented yarn PET fibers were uniaxially drawn below the glass transition temperature (T g ) using various draw ratios to obtain filaments with different structures for subsequent exposure to scCO 2 in the presence and absence of tension at a temperature of 80°C and under a pressure of 220 bar. Microstructural investigation of the samples was carried out by combining the results obtained from DMA, differential scanning calorimetry, as well as density and birefringence measurements, all of which exhibited a good correlation. The rigid amorphous region in the PET samples was considered for interpreting structure-property relations. Results showed that increasing draw ratio leads to increased values of rigid amorphous regions and distribution of molecular orientation in the amorphous regions followed by an increase in the relaxation time distribution. Depending on sample conditions, exposure to scCO 2 was found to have a strong effect on the transformation of the transient structure into crystalline or amorphous regions. PET fibers exposed to scCO 2 under tension yielded higher values of crystallinity and orientation compared to those under no tension. In the case of PET fibers exposed to scCO 2 under no tension, CO 2 molecules released from the structure possibly caused a metastable structure to form in the amorphous phase. Therefore, rearrangement of molecular chains during the dynamic mechanical test in the temperature sweep mode is expected to increase the storage modulus of the sample before its glass transition temperature is reached. As a result, an increment is observed in the storage modulus of samples exposed to scCO 2 without tension that can be related to the release of stress stored during the depressurization process. scCO 2 exposure can be, therefore, claimed to be an environmentally friendly method for inducing structural changes and enhancing crystallinity in PET samples. C 2015 Wiley Periodicals, Inc. Adv Polym Technol 201 , , 21578; View this article online at wileyonlinelibrary.com.

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“…The polyester yarn has three sharp peaks derived from the crystalline domain of polyester. Generally polyester has a type of triclinic crystals that appear in completely different angles 32 . The crystallinity is obtained by calculating the ratio of the area under the crystal peaks to the area under the whole curve (Table 4).…”

Section: Resultsmentioning

confidence: 99%

Study of thermomechanical properties of hybrid tire cord

Mahdavipour

Karimi

Hoseini³

2020

Polymers for Advanced Techs

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Thermomechanical properties of tire cords, which have a considerable influence on tire functions, were investigated in the current research. The nylon and polyester cords are the most commonly used polymers in the tire. Many efforts have been made to produce a new tire cord having the capability of integrating the desired properties of these two polymers into one cord. In this study, a new cord structure was developed using nylon 6,6 and polyester tire yarns. The effect of thermal treatment was studied at the temperatures of 180°C, 200°C, and 220°C under two different loads of 600 and 1800gf on thermomechanical properties of the nylon 6,6/polyester hybrid tire cord. Shrinkage and shrinkage force as thermal properties, as well as static and dynamic mechanical properties, were investigated. The relationship between the aforementioned properties and variation in the crystal structure and fiber orientation obtained from Differential scanning calorimetry (DSC) and Wide‐Angle X‐Ray Scattering (WAXS) analysis were examined too. The results showed that the higher tension leads to the higher initial modulus and storage modulus due to the crystallization of polymers during heat treatment. The shrinkage and shrinkage force also increased, as the tension increased. In addition, a decrease in residual shrinkage and shrinkage force were acquired because of an enhancement in the temperature.

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Study of structural changes and mesomorphic transitions of oriented poly(ethylene therephthalate) fibers in supercritical CO2

Cited by 21 publications

References 35 publications

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Effect of CO₂on Mesomorphic Structure of Cold-Drawn Poly(ethylene therephthalate) Fibers by Dynamic Mechanical Analysis

Study of thermomechanical properties of hybrid tire cord

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Study of structural changes and mesomorphic transitions of oriented poly(ethylene therephthalate) fibers in supercritical CO2

Cited by 21 publications

References 35 publications

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Effect of CO2on Mesomorphic Structure of Cold-Drawn Poly(ethylene therephthalate) Fibers by Dynamic Mechanical Analysis

Study of thermomechanical properties of hybrid tire cord

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Product

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Effect of CO₂on Mesomorphic Structure of Cold-Drawn Poly(ethylene therephthalate) Fibers by Dynamic Mechanical Analysis