Physical ageing in amorphous and crystalline polymers. Part 2. Polyethylene terephthalate

Ahmad, A.L.; Arnoux, F.; Biddlestone, F.; Hay, J. N.

doi:10.1016/0040-6031(95)02434-4

Cited by 38 publications

(20 citation statements)

References 12 publications

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“…These data yield an activation energy of 337 kJ/mole. This figure also includes data taken from the literature 14,15 to illustrate the good correlation with results reported for other amorphous PET and obtained with modulated DSC measurements.…”

Section: Resultsmentioning

confidence: 54%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Additional studies have been reported describing the behavior of semicrystalline PET. [15][16][17][18][19][20][21][22][23][24] The effects of physical aging on mechanical properties and environmental stress crack resistance have also been investigated by others 1,2,11 as well as in our laboratories. 10,12,[25][26][27][28][29][30][31][32] Previous systematic polyester studies at the Polymer Institute have included aging effects on physical properties and environmental stress cracking behaviors of amorphous homopolymers, 10,12 copolymers, 12,25,26 blends 12,27 and oriented PET.…”

Section: Introductionmentioning

confidence: 96%

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Effects of microcrystallinity and morphology on physical aging of poly(ethylene terephthalate)

Zhou

Lofgren

Jabarin

2007

J of Applied Polymer Sci

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Physical aging characteristics of poly(ethylene terephthalate) have been evaluated in relationship to volume fraction levels of crystallinity up to 25%. Changes in the enthalpies of relaxation, monitored at aging temperatures from 55 to 658C, are found to give good fits with the Cowie-Ferguson model. Overall equilibrium enthalpy of relaxation values decrease linearly with increased crystallinity. They increase with decreased aging temperature, providing extrapolated lower temperature results that are validated in terms of specific heat relationships. Activation energies for enthalpic relaxations are found to increase from 337 to 361 kJ/mole as crystallinity increases up to 25%. Overall relaxation endotherms are further resolved into contributions from interspherulitic and intraspherulitic amorphous regions. Interspherulitic, equilibrium enthalpies of relaxation decrease with increased levels of crystallinity, while intraspherulic values show corresponding increases. Characteristic relaxation times of the intraspherulic regions increase greatly, as levels of crystallinity increase; however, interspherulitic relaxation times decrease very slightly. Dynamic differential scanning calorimetry results show two glass transitions in the case of a 25% crystalline sample and a single transition for noncrystallized material.

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Section: Resultsmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 96%

Effects of microcrystallinity and morphology on physical aging of poly(ethylene terephthalate)

Zhou

Lofgren

Jabarin

2007

J of Applied Polymer Sci

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“…Growth and shift of the peak towards higher temperatures are observed when the cooling rate decreases. Such an evolution of the endothermic peak associated with the enthalpy is explained by several authors [14][15][16][17][18] as a reduction in molecular chain mobility. In fact, molecular mobility is the fundamental property strongly affected by physical aging.…”

Section: Effect Of Cooling Ratesmentioning

confidence: 98%

Contribution to the Study of the Enthalpy Relaxation of Polyesters by DSC Experiments

Khemici

Doulache

Gourari

et al. 2012

International Journal of Polymer Analysis and Characterization

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The differential scanning calorimetry (DSC) technique was used to study the enthalpy relaxation of weakly crystalline polyethylene naphatalate (PEN). The samples were examined under two different thermal histories inside the calorimeter. The first method consists in annealing samples at temperature T a below the glass transition temperature T g , for different times Dt a . The second one consists in cooling samples from a higher temperature than T g to the room temperature using following cooling ratesb. In order to highlight the effect of thermal rigidity of molecular chains on the enthalpy relaxation of polyester, a comparative study between the enthalpy relaxation of polyethylene terephtalate (PET) and PEN with very close degrees of crystallinity v c was made. This study shows that the structural relaxation (physical aging) induces a decrease in the molecular mobility of the samples, which prevents the polymer from initiating a rapid return to the equilibrium state. On the other hand, the molecular chains in PEN are stiffer than in PET and hence relax less.

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“…The embrittlement induced by physical aging can be assessed by determining of the change in the yield stress (σ y -tensile tests) [2][3][4]. Furthermore it can be characterized by measuring the enthalpy relaxation (ΔH -differential scanning calorimetry, DSC) [2,[5][6][7]. Physical aging also influences the fracture mechanical properties of the polymer but only relatively few studies have been published so far.…”

Section: Introductionmentioning

confidence: 99%

Effect of thermal and hygrothermal aging on the plane stress fracture toughness of poly(ethylene terephthalate) sheets

Bárány¹,

Földes²,

Czigány³

2007

Express Polym. Lett.

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Abstract. The in-plane (plane stress) fracture toughness of two polyester (PET, PETG) sheets were assessed using the essential work of fracture (EWF) method after thermal and hygrothermal aging performed just below glass temperature. This ensured that physical aging takes place. On the aged sheets the yield stress (σy), enthalpy relaxation (ΔH) and EWF parameters were determined. It was observed that the essential work of fracture component related to the specific yielding (we,y) is suitable for assessing physical aging -independently of the humidity content. A good linear correlations exists between we,y, σy and ΔH.

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Physical ageing in amorphous and crystalline polymers. Part 2. Polyethylene terephthalate

Cited by 38 publications

References 12 publications

Effects of microcrystallinity and morphology on physical aging of poly(ethylene terephthalate)

Effects of microcrystallinity and morphology on physical aging of poly(ethylene terephthalate)

Contribution to the Study of the Enthalpy Relaxation of Polyesters by DSC Experiments

Effect of thermal and hygrothermal aging on the plane stress fracture toughness of poly(ethylene terephthalate) sheets

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