Non-linear tensile creep of polypropylene: Time-strain superposition and creep prediction

Kolařı́k, Jan; Pegoretti, Alessandro

doi:10.1016/j.polymer.2005.11.013

Cited by 75 publications

(49 citation statements)

References 54 publications

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“…1. For larger stress values, that is to say r 0 [ 0.1 MPa, the creep behavior is more affected by the value of the applied stress: the viscoelastic response of the original HDPE is now nonlinear as often reported in the literature [9][10][11][12].…”

Section: Resultsmentioning

confidence: 81%

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Creep behavior of high density polyethylene after aging in contact with different oil derivates

Habas-Ulloa¹,

d’Almeida²,

Habas³

2010

Polymer Engineering & Sci

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The creep behavior of a high density polyethylene (HDPE), currently used as raw material for pipe manufacture, was evaluated before and after exposure to oil derivates using transient rheometry. The creep behavior of the original HDPE was satisfactorily described using a generalized Kelvin-Voigt model based on two retardation times. The values of these critical times were quite different from each other, indicating a large distribution of macromolecular weight. The aging procedure was performed by immersing the polymer in two model fluids chosen to discriminate and understand the action of aromatic and paraffinic fractions of fuel derivatives (white oil, gas-oil). The batch operation was also carried out at two different temperatures to investigate the thermal activation of plausible degrading mechanisms. In the case of the aging performed in the paraffinic fluid, the polymer compliance continuously increased with the immersion duration. This behavior was attributed to a plasticization induced by the diffusion of the liquid in the polymer matrix. The same phenomenon was observed in the early stage of the HDPE aging carried out with the aromatic fluid.

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Section: Resultsmentioning

confidence: 81%

“…This approach considers that the creep response is controlled by an internal time of the polymer which differs from laboratory observation time. The discrepancy between both times is due to the current state of the material and is dependent on several quantities such as free volume, strain or stress [12].…”

Section: Introductionmentioning

confidence: 99%

Creep behavior of high density polyethylene after aging in contact with different oil derivates

Habas-Ulloa¹,

d’Almeida²,

Habas³

2010

Polymer Engineering & Sci

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“…Besides experimental observation, highly developed creep modeling can also be applied to PBT processed at different mold temperatures to develop comprehensive understanding of the creep deformation. In the past half-century, numerous creep models [11,[19][20][21] have been proposed and applied to describe the creep behavior of viscoelastic materials. Various materials of the same geometry may respond differently under identical external effects.…”

Section: Resultsmentioning

confidence: 99%

Effect of mold temperature on short and long-term mechanical properties of PBT

Banik¹

2008

Express Polym. Lett.

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Abstract. In this work, the effect of mold temperature variation on the short-term mechanical properties obtained from the tensile and Charpy impact tests, and the long-term mechanical properties obtained from dynamic mechanical loading and flexural creep of injection molded polybutylene terepthalate (PBT) are reported. It has been observed that the effect of changing the processing condition viz. mold temperature on the viscoelastic properties are more pronounced when their long-term behavior is tested. The tensile and impact properties showed only a negligible effect to the change in mold temperature. Further, analysis of the creep curves by applying a four-element Burger model presented a comprehensive understanding of their long-term viscoelastic behavior with respect to the change in mold temperature.

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“…As generally known, an enhancement of the applied stress produces a noticeable increase in the creep compliance of semicrystalline polymers above their glass transition temperature [72]. This nonlinear viscoelastic effects have been associated to a straininduced increase in the free volume in the amorphous phase of the material [17,20,46,72].…”

Section: Creep Behaviourmentioning

confidence: 92%

Linear low density polyethylene/cycloolefin copolymer blends

Dorigato¹,

Pegoretti²,

Fambri³

et al. 2011

Express Polym. Lett.

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Abstract. Linear low density polyethylene (LLDPE) was melt compounded with various amounts of a cycloolefin copolymer (COC). Scanning and transmission electron microscopy evidenced, at qualitative level, some interfacial adhesion between LLDPE and COC. Another indication of interactions between the components was the increase of crystallinity degree with rising COC content and the enhancement of COC glass transition temperature with the LLDPE fraction. In order to explain this behaviour, the incorporation of ethylene segments of COC into the LLDPE crystalline phase, leading to an increased number of norbornene units in the remaining COC component undergoing the glass transition, was hypothesized. The thermo-oxidative degradation stability of LLDPE was substantially enhanced by COC introduction for filler contents higher than 20 wt%, especially when an oxidative atmosphere was considered. An increasing fraction of COC in the blends was responsible for an enhancement of the elastic modulus and of a decrease in the strain at break, while tensile strength passed through a minimum, in agreement with the model predictions based on the equivalent box model and equations provided by the percolation theory. The introduction of a rising COC amount in the blends increased the maximum load sustained by the samples in impact tests, but decreased the blend ductility. Concurrently, a significant reduction of the creep compliance of LLDPE was observed for COC fractions higher than 20 wt%.

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Non-linear tensile creep of polypropylene: Time-strain superposition and creep prediction

Cited by 75 publications

References 54 publications

Creep behavior of high density polyethylene after aging in contact with different oil derivates

Creep behavior of high density polyethylene after aging in contact with different oil derivates

Effect of mold temperature on short and long-term mechanical properties of PBT

Linear low density polyethylene/cycloolefin copolymer blends

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