The role of crazes in the crack growth of polyethylene

Lustiger, A.; Corneliussen, Roger

doi:10.1007/bf01082132

Cited by 79 publications

(35 citation statements)

References 12 publications

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“…The crack starts at a craze, which is initiated at the point of stress concentration. As shown by Lustiger and Corneliussen, [3] the same process occurs in the commonly used environmental stress cracking agent known as Igepal CO-630. Igepal not only enhances craze formation, but it also reduces the time up to the onset of crack growth.…”

Section: Introductionmentioning

confidence: 93%

Environmental Stress‐Cracking Resistance of LDPE/EVA Blends

Borisova

Kreßler

2003

Macro Materials & Eng

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Blends of low‐density polyethylene with random copolymers of ethylene and vinyl acetate (PE/EVA) are studied with respect to their environmental stress‐cracking resistance (ESCR) using the Bell‐telephone test. This system shows the shortest time to failure in the ESCR test after annealing at 50 °C in a stress‐cracking agent (Igepal solution) compared with that in the tests conducted at 30 and 70 °C. The increase of the time to failure at 70 °C as compared with that at 50 °C is probably the result of the semicrystalline proportion of EVA melting. Transmission electron microscopy images (see Figure) reveal that EVA particles are molten and deformed in bending direction of the sample at 70 °C in contrast to samples annealed at 50 and 30 °C. TEM pictures of a failed sample during the test conducted at 50 °C indicate that EVA particles can stop crack propagation.TEM image of PE/EVA‐5.4 after 1 000 h in ESCR test conditions at 70 °C.magnified imageTEM image of PE/EVA‐5.4 after 1 000 h in ESCR test conditions at 70 °C.

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Section: Introductionmentioning

confidence: 93%

Environmental Stress‐Cracking Resistance of LDPE/EVA Blends

Borisova

Kreßler

2003

Macro Materials & Eng

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“…In spite of its semi-crystalline morphology, polyethylene goods in outdoor applications are also very prone to this kind of deterioration, due to various kinds of stresses such as mechanical (application of load in service or from residual processing stresses [7]), chemical (cleaning agents, oils, paints) [6] combined with environmental factors (exposure to solar irradiation, temperature variations, humidity and pollution). Moreover, ESC has been observed in polyethylenes even in the absence of harsh environment conditions [8,9]. Some molecular mechanisms have been proposed to explain ESC in polyethylenes.…”

Section: Introductionmentioning

confidence: 99%

“…Some molecular mechanisms have been proposed to explain ESC in polyethylenes. Among the controlling factors that have been considered in the literature the most relevant are interlamellar failure in a process highly influenced by the concentration of tie molecules [8], the disentanglement of the macromolecules within the crystalline regions, the number of tie molecules and the strength of the crystals that anchor them [10]. Several authors agree with the assumption that the resistance to ESC is directly related to the density of tie molecules [3,11e13], which in turn is related to the number of short branches [13,14] and the molar mass of the polymer [11].…”

Section: Introductionmentioning

confidence: 99%

Polyethylene blends: A correlation study between morphology and environmental resistance

Munaro

Akcelrud

2008

Polymer Degradation and Stability

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“…It is known that, under this deformation mode, micro-voids form inside a material which can be identified as the source of the characteristic whitening. 39,40 These micro-voids might easily be converted into cracks when the applied stress increases. This crazing is often observed in stiff and brittle materials.…”

Section: Microstructural Modificationmentioning

confidence: 99%

The toughening effect of a small amount of poly(ɛ-caprolactone) on the mechanical properties of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/PCL blend

Katsumata

Saitō

Fang

et al. 2011

Polym J

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To improve the mechanical properties of bacterial poly(3-hydroxybutyrate) [P(3HB)] and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)], the materials were blended with poly(e-caprolactone) (PCL). The P(3HB-co-7 mol% 3HH) cast film and the P(3HB-co-11 mol% 3HH) melt-pressed film show brittleness after aging, although unaged samples show ductile behavior. However, the addition of a small amount of PCL was found to greatly improve the toughness of the P(3HB-co-7 mol% 3HH) cast film and the P(3HB-co-11 mol% 3HH) melt-pressed film. Reduction in the whitening of the elongated P(3HB-co-7 mol% 3HH) film by blending with PCL indicates that a transition in the deformation mechanism of the film was induced. In P(3HB-co-11 mol% 3HH)/PCL melt-pressed films, a cloud of craze initiation created by the dispersed PCL was observed. Differential scanning calorimetry thermograms and scanning electron microscopy images of the blended films indicated that finely dispersed PCL, the crystallization of which was restricted, and/or voids formed during preparation contribute to the delocalization of the applied stress and ductile deformation of P(3HB-co-3HH) films. In conclusion, the transition in the deformation mechanisms and the delocalization of the applied stress are expected to be important for enhancing the toughness of aged P(3HB-co-3HH)s, and blending with a small amount of PCL is a simple way to improve the mechanical properties of P(3HB-co-3HH)s. Polymer Journal (2011) 43, 484-492; doi:10.1038/pj.2011.12; published online 23 February 2011Keywords: blend; mechanical property; polyhydroxyalkanoate; poly(e-caprolactone); tensile test INTRODUCTION Several kinds of polyhydroxyalkanoates (PHAs) are biosynthesized by various bacteria as energy-storage materials. 1-5 They may be produced from renewable natural resources and have biodegradability. Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)] is part of the PHA family. 6 Doi et al. 7 have found that the content of the 3HH unit greatly affected the thermal and mechanical properties of P(3HB-co-3HH), but had little effect on the crystalline structure of 3HB-rich P(3HB-co-3HH)s because of the formation of the P(3HB)-homopolymer-type crystalline phase and the exclusion of the 3HH unit from the crystalline lattice. P(3HB-co-3HH) was found to show improved mechanical properties and thermal plasticity over those of known PHAs. 8,9 One of the notable advantages of P(3HB-co-3HH)s is their adjustable mechanical properties, from soft to hard material, depending on the comonomer-unit composition; this allows for the tailoring of P(3HB-co-3HH) to various societal applications, such as in green and sustainable polymeric materials.However, P(3HB-co-3HH) becomes brittle after aging at room temperature, thus restricting its practical applications. Although

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The role of crazes in the crack growth of polyethylene

Cited by 79 publications

References 12 publications

Environmental Stress‐Cracking Resistance of LDPE/EVA Blends

Environmental Stress‐Cracking Resistance of LDPE/EVA Blends

Polyethylene blends: A correlation study between morphology and environmental resistance

The toughening effect of a small amount of poly(ɛ-caprolactone) on the mechanical properties of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/PCL blend

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