Stress and strain oscillations in syndiotactic polypropylene and in poly(ethyleneterephthalate)

Ebener, H.; Pleuger, B.; Petermann, J.

doi:10.1002/(sici)1097-4628(19990131)71:5<813::aid-app15>3.0.co;2-p

Cited by 21 publications

(11 citation statements)

References 8 publications

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“…Control experiments with commercial i PP, HDPE, and nylon-6,6 resins confirmed this effect was a consequence of the intensive properties of i PPO and not the experimental setup (Figure S52). Although this behavior is more commonly observed in metals, , stress oscillations (SOs) have been reported in a variety of common polymers such as HDPE, , i PP, syndiotactic PP, − polyethylene terephthalate, ,,− PAs, ,, polyvinyl chloride, and bisphenol A polycarbonate . While much debate has taken place on the mechanism for why SOs occur, a recent report by Hughes claims that the response is the result of crazing and formation of microcavities within their poly(butylene succinate) specimens.…”

Section: Resultsmentioning

confidence: 99%

Isotactic Poly(propylene oxide): A Photodegradable Polymer with Strain Hardening Properties

et al. 2020

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Leakage and accumulation of highly stable commercial plastics has led to substantial contamination of the environment. Highly isotactic poly(propylene oxide) (iPPO) was investigated as a potential high-strength thermoplastic with greater susceptibility toward degradation under ambient conditions. Various stereoregular forms of iPPO including enantiopure, enantioenriched, racemic, and stereoblock were synthesized with a single catalyst architecture in the presence of chain transfer agents. These materials were found to possess the same approximate ultimate tensile strength (UTS) via uniaxial tensile elongation analysis (∼75 MPa). A serrated tensile response corresponding to stress oscillations was observed in all forms of iPPO. An investigation on strain rate dependence showed that an increase in strain rate results in the decay and disappearance of the serrated response. Further evaluation of iPPO revealed its dramatic strain hardening afforded an UTS comparable to that of nylon-6,6. Exposing iPPO to UVA light (365 nm) resulted in photolytic degradation. Following 30 days of continuous exposure at 250 μW cm −2 , the M n decreased from 93 kDa to 21 kDa, while samples not exposed to UVA light remained unchanged. Through selective stabilization with antioxidant additives, we believe iPPO could be a suitable replacement for nylon-6,6 in environmentally susceptible applications.

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Section: Resultsmentioning

confidence: 99%

Isotactic Poly(propylene oxide): A Photodegradable Polymer with Strain Hardening Properties

et al. 2020

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“…Model parameters, such as E 0 , E 1 , η 0 , η 1 , ε c and ε f 0 can be calculated from Equation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). If σ 0 is known E 0 can be determined from Equation (8) and solving the Equation (18) τ 0 can be obtained: (18) and from Equation (6) η 0 can be calculated.…”

Section: Methods Of Determining the Model Parametersmentioning

confidence: 99%

“…The general solution of Equation (13) is in Equation (14), which is similar to that of Equation (5): (14) where τ 1 is a new time constant (Equation (15)): (15) Here σ(t 1 +0) = σ 0 , hence the stress-strain relationship and the initial slope for the second interval (t 1 < t ≤ t 2 ) are given by Figure 7 and it is described in Equations (16) and (17): (16) (17) It can be assumed that the phenomena in the next and further intervals are similar to those in the second interval, consequently the force process is periodical.…”

Section: Force Oscillation Responsementioning

confidence: 99%

“…According to this explanation shear bands cannot easily cross each other on the sample surface, which is in agreement with the experimental observation that cavities always appear inside the test specimen. According to Ebener et al [15] oscillation arises if the test specimen can store enough elastic energy. For this the initial length of the test specimen should be large enough.…”

Section: Introductionmentioning

confidence: 99%

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Modelling tensile force oscillation during the tensile test of PET specimens

Vas¹,

Ronkay²,

Czigány³

2009

Express Polym. Lett.

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Abstract. Force oscillation occurring during the tensile testing of poly(ethylene terephthalate) (PET), resulting in periodical cavitation of the test specimens, has been studied. A mathematical model has been developed to describe the phenomenon, wherein special fibre bundles are assigned to the amorphous molecular chains. In order to model the local periodical transformations and the rate dependent viscoelastic behaviour the coupled fibre bundle cells were supplemented with a twoelement Maxwell model. Using the parameters determined from the measurements the model was compared to the measured force-elongation diagrams and it has been concluded that the simple model can be well used to describe the phenomenon.

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“…It can be observed for both amorphous and semi-crystalline polymers too. Amorphous but crystallisable polymers like poly(ethylene terephtalate) also exhibit this effect [7]. Moreover, it was also observed in amorphous non-crystallizable polymers like polycarbonate (PC) [6].…”

Section: Introductionmentioning

confidence: 94%

Study of the stress oscillation phenomenon in syndiotactic polypropylene/montmorillonite nanocomposites

Mouzakis¹

2010

Express Polym. Lett.

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Abstract. The phenomenon of Stress Oscillation (SO) was studied in syndiotactic polypropylene and syndiotactic polypropylene nanocomposites with montmorillonite. The effect was provoked by varying the crosshead speed during tensile testing of thin stripes. The internal morphology of the stress oscillated specimens was studied by scanning electron microscopy on chemically etched samples revealing that cavitation prevails inside the opaque stripes of the yielded areas. Differential scanning calorimetry proved that there exists virtually no crystallinity differentiation between the characteristic alternating opaque/transparent stripes that mark the stress oscillation during necking. Finally a simple finite element model of the necking area of the specimens revealed non-uniform internal stress distributions of yield-point magnitudes.

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Stress and strain oscillations in syndiotactic polypropylene and in poly(ethyleneterephthalate)

Cited by 21 publications

References 8 publications

Isotactic Poly(propylene oxide): A Photodegradable Polymer with Strain Hardening Properties

Isotactic Poly(propylene oxide): A Photodegradable Polymer with Strain Hardening Properties

Modelling tensile force oscillation during the tensile test of PET specimens

Study of the stress oscillation phenomenon in syndiotactic polypropylene/montmorillonite nanocomposites

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