Mechanism of submicrocrack generation in stressed polymers

Zhurkov, S. N.; Zakrevskyi, V. A.; Korsukov, V. E.; Kuksenko, V. S.

doi:10.1002/pol.1972.160100808

Cited by 158 publications

(69 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Only a very small increase of the equatorial intensity is observed limited to the smaller angles which points to no or very little void formation. This differs considerably from the results of Zhurkov et al [14] who found a high increase of the intensity over the entire angular range for films of oriented polyethylene strained to breakage. Similar results during straining were observed for unoriented polyoxymethylene [15,16] and hard elastic fibres [17,18] and were attributed to extensive void formation.…”

Section: Saxs Of Mechanically Stressed Gel-spun Polyethylene Fibrescontrasting

confidence: 99%

See 1 more Smart Citation

SAXS experiments on voids in gel-spun polyethylene fibres

1990

View full text Add to dashboard Cite

The morphology and properties of extracted gel-spun polyethylene fibres depend on the spinning conditions. The main structures in the extracted fibre are shish-kebabs and lamellae. Equatorial small-angle X-ray scattering (SAXS) experiments show that the former structure is very porous due to the presence of lamellar overgrowth preventing a close package of the backbone fibrils, whereas the latter structure is relatively dense. After hot-drawing, due to melting/recrystallization, both structures are transformed on a 100 nm scale into a dense structure consisting of shish-kebabs or fibrils containing a void volume fraction of about 1%, as revealed by the scattering power of equatorial SAXS experiments. Moreover, a slight decrease of the equatorial intensity especially at the smallest angles after treating the hot-drawn fibres with paraffin oil, points to a small contribution of multiple scattering to the equatorial scattering. This implies the presence of a superstructure of not too closely packed macrofibrils. SAXS measurements of strained ultra-high-strength polyethylene fibres show that no or very little void formation is involved in the fracture mechanism. Most probably this is due to the (partly) fibrillar structure.

show abstract

Section: Saxs Of Mechanically Stressed Gel-spun Polyethylene Fibrescontrasting

confidence: 99%

“…Another type of void is found in crystalline polymer fibres/films subjected to mechanical stresses. Examples are oriented polyethylene [14], unoriented polyoxymethylene [15,16] and hard elastic fibres [17,18]. These voids are more or less rotational ellipsoids with the smallest axis parallel to the draw direction.…”

Section: Introductionmentioning

confidence: 99%

SAXS experiments on voids in gel-spun polyethylene fibres

1990

View full text Add to dashboard Cite

show abstract

“…A recent paper for example [Parpal, et aL (1997)] proposes a model to describe a Wde range of experimental observations that were described in an earlier paper [Dang, et aL(1996)]. In this paper they state "Ahe proposed model described relies on simple thermodynamic arguments (Crine 1990), on part of the free-volume breakdovm theory of Artbauer (1996) on the formation of sub-micron sized cavities observed by Zhurkov (1972) during the, mechanical ageing of polymers and on the molecular ageing model of Crine and Vijh (1985) 3-34 3.3. The Electro-mechanical Model of Breakdown.…”

Section: -33mentioning

confidence: 99%

Investigation of the structural changes in LDPE and XLPE induced by high electrical stress

Sayers¹

2000

Eighth International Conference on Dielectric Materials, Measurements and Applications

View full text Add to dashboard Cite

SummaryHigh voltage electrical cables play an immensely important, although largely unseen, part in the lives of everybody in the world today. They are mostly buried underground and provide trouble free operation for the majority of their operational lives. However, the polymer based insulation that is used for a large number of high voltage cables is subject to long term ageing which can eventually lead to electrical breakdown. This ageing manifests itself as the appearance of tree like structures in the bulk polymer insulator. The growth of a tree frequently starts on the boundary of the polymer at the so-called "polymer-semicon" interface.This thesis is concerned, however, with the changes that must take place in the polymer before the tree is formed.Previous investigations of field induced changes occurring within polymer insulation have involved cutting the polymer to expose the region of interest: this is not a satisfactory as the cutting process can produce changes in the polymer. To avoid this a novel technique was developed whereby the polymer-semicon interface can be exposed without cutting the polymer.The interface region of the polymer in contact with the plane electrode was examined and even though the field in this region is less than at the point, it can be sufficiently large to induce structural change in the polymer, readily detectable by Raman spectroscopy.In studies of both LDPE and XLPE, we find evidence of structural change within the polymer and most significantly of considerable Raman fluorescence which is indicative of defect states in the polymer. The latter becomes modified as the polymer structure approaches electrical failure.The observations reported are set in context by the examination of the work of relevant authors and some conclusions deduced. The evidence supports a model in which the forces induced by the electrical field lead to failure by the mechanisms of local yield, microvoid craze and crack formation commonly invoked for the mechanical fracture of polymeric solids. Acknowledgments I would like to thank the School of Informatics, University of Wales, Bangor for all the help and assistance provided not only through the period of this PhD but also during my degree course. I would like to thank the people who worked at BICC Cables Limited before it became BICC General and then was sold to Pirelli Cables who closed BICC down. I would also like to thank the EPSRC for funding this work through a Co-operative Award in Science and Engineering (CASE) studentship.As a result of these connections I have had the pleasure and honour of working with Professor T. J. Lewis and Doctor J. P. Llewellyn both of whom continue to astound me with their ability to absorb new ideas, generate original ideas and furthermore to critically review those ideas and theories. Doctor Carl. Griffiths, previously of BICCGeneral provided invaluable critical appraisal of the work, results and interpretations presented here. I would also like to thank Dr Steven Befteridge, also previously of BICCGeneral, for h...

show abstract

“…Electrons can then move without scattering within the submicrocavities and this may lead to further degradation. The formation of free radicals and end-groups of scission molecules formed in polyethylene, polypropylene and polycaprolactam under axial tension was already investigated many years ago, and their asso-ciation with sub-microcrack generation in stressed polymers was well established (Zhurkov et al 1972). The number of scission chains may reach 10 19 cm -3 , three orders of magnitude larger than the number of free radicals detected in the stressed polymer, which is in turn about of the same order of magnitude as the detected sub-microcracks.…”

Section: Electrostatic Phenomenamentioning

confidence: 99%

Supramolecular ionics: electric charge partition within polymers and other non-conducting solids

Galembeck

Costa

Galembeck

et al. 2001

An. Acad. Bras. Ciênc.

View full text Add to dashboard Cite

Electrostatic phenomena in insulators have been known for the past four centuries, but many related questions are still unanswered, for instance: which are the charge-bearing species in an electrified organic polymer, how are the charges spatially distributed and which is the contribution of the electrically charged domains to the overall polymer properties? New scanning probe microscopies were recently introduced, and these are suitable for the mapping of electric potentials across a solid sample thus providing some answers for the previous questions. In this work, we report results obtained with two of these techniques: scanning electric potential (SEPM) and electric force microscopy (EFM). These results were associated to images acquired by using analytical electron microscopy (energy-loss spectroscopy imaging in the transmission electron microscope, ESI-TEM) for colloid polymer samples. Together, they show domains with excess electric charges (and potentials) extending up to hundreds of nanometers and formed by large clusters of cations or anions, reaching supramolecular dimensions. Domains with excess electric charge were also observed in thermoplastics as well as in silica, polyphosphate and titanium oxide particles. In the case of thermoplastics, the origin of the charges is tentatively assigned to their tribochemistry, oxidation followed by segregation or the Mawell-Wagner-Sillars and Costa Ribeiro effects.

show abstract

Mechanism of submicrocrack generation in stressed polymers

Cited by 158 publications

References 8 publications

SAXS experiments on voids in gel-spun polyethylene fibres

SAXS experiments on voids in gel-spun polyethylene fibres

Investigation of the structural changes in LDPE and XLPE induced by high electrical stress

Supramolecular ionics: electric charge partition within polymers and other non-conducting solids

Contact Info

Product

Resources

About