DSC and DMTA study of annealed cold-drawn PET: a three phase model interpretation

Bartolotta, A.; Marco, G. Di; Farsaci, F.; Lanza, M.; Pieruccini, M.

doi:10.1016/s0032-3861(03)00589-5

Cited by 47 publications

(34 citation statements)

References 11 publications

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“…Values for PET both in isotropic form and oriented to a draw ratio of 4, using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), have been found to exhibit significant differences. 24 The Tg was measured as around 80 °C for isotropic material, with the glass transition process starting at 70 °C; however, in oriented form the onset of glass transition was lower by 15 °C, with the Tg correspondingly lower. We have investigated the effects of molecular orientation on the Dow Lighter material by TDSC, as described above.…”

Section: Peak Shrinkage Stress In Ts1 Samplesmentioning

confidence: 99%

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

Teall

Pilegis

Sweeney

et al. 2017

Smart Mater. Struct.

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The shrinkage force exerted by restrained shape memory polymers can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn Polyethylene Terephthalate (PET) shape memory polymer tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples.The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.

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Section: Peak Shrinkage Stress In Ts1 Samplesmentioning

confidence: 99%

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

Teall

Pilegis

Sweeney

et al. 2017

Smart Mater. Struct.

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“…The length of the strips increases naturally by a factor Ӎ 4 due to cold drawing. [3][4][5] On the other hand, the sample shrinks perpendicularly to the drawing direction by a factor of ϳ0.3, which can be considered negligible as compared to . The samples were then isothermally crystallized ͑annealed͒ from the glassy state at selected temperatures T a under nitrogen flux.…”

Section: Methodsmentioning

confidence: 99%

“…3 Results for the annealed colddrawn material ͑T a = 100, 140, and 180°C͒ are also taken from Ref. 3.…”

Section: Methodsmentioning

confidence: 99%

“…3 Results for the annealed colddrawn material ͑T a = 100, 140, and 180°C͒ are also taken from Ref. 3. In all cases, the DMTA measurements were carried out in bending geometry, single cantilever configuration.…”

Section: Methodsmentioning

confidence: 99%

“…3 On the contrary, a similar phenomenology, wherever present, does not show up during or after the annealing of unoriented PET. Thus, a question regarding the assessment of the role of a mean chain orientation in the vitrification of the amorphous regions during the crystallization process arises.…”

Section: Introductionmentioning

confidence: 98%

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Confinement-induced vitrification in polyethylene terephthalate

et al. 2007

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Dynamic mechanical thermal analysis performed on cold-drawn polyethylene terephthalate ͑PET͒, cold crystallized ͑annealed͒ in the temperature interval 100-140°C, reveals the presence of marginally glassy domains above the annealing temperature T a . This suggests that the thermodynamic force driving crystallization causes the structural arrest of some noncrystalline domains. The latter thus need a temperature higher than T a to completely defreeze. Differential scanning calorimetry supports this point of view. Analogous investigations on unoriented PET, cold crystallized in the same conditions, do not show the same peculiarities; thus, chain orientation is relevant to vitrification. This phenomenology is first cast in the language of thermodynamics by introducing an excess chemical potential ␦ describing the presence of structural constraints in the amorphous domains and the effect of chain orientation. For a first test of this picture, the orientation contribution to ␦ is calculated by means of the Gaussian chain model ͑this implicitly assumes that ␦ is related to the density fluctuations͒. The resulting expression is then used to discuss the structural differences between cold-drawn and unoriented PET samples reported in the literature.

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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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DSC and DMTA study of annealed cold-drawn PET: a three phase model interpretation

Cited by 47 publications

References 11 publications

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

Confinement-induced vitrification in polyethylene terephthalate

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

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DSC and DMTA study of annealed cold-drawn PET: a three phase model interpretation

Cited by 47 publications

References 11 publications

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

Confinement-induced vitrification in polyethylene terephthalate

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

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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