Small‐angle x‐ray diffraction studies of plastically deformed polyethylene. II. Influence of draw temperature, draw ratio, annealing temperature, and time

Abstract

Linear polyethylene drawn at 0, 110, and 120°C t o a draw ratio between 1.1 and 6 was investigated by small-and wide-angle X-ray scattering. Besides a small increase o€ meridional long period at low draw ratios one observes a decrease of diagonal (at an angle y to the meridian) and equatorial long period a t high draw temperatures. This decrease is the consequence of thinning of lamellae by chain tilt in the compressional field of the uniaxial draw deformation. The early decrease of the meridional scattering intensity indicates the rapidly increasing loss of packing order as a consequence of the disappearance of lamellae oriented perpendicular to the draw direction due to rotational motion towards parallel orientation. The intensity decrease in the equatorial scattering, however, is caused by the rapid destruction of lamellae parallel to the draw. By micronecking they are transformed into microfibrils of the new fiber structure. With increasing draw ratio the diagonal maximum *) Present address : Kalle AG, D-6202 Wiesbaden-Biebricli, W. Germany. den Mikroeinschnurungen zeigt, bis zu sehr hohen Verstreckungsgraden (18.-4) bestehen. Bei 0 O C , mit praktisch aufgehobener Langsbeweglichkeit der Ketten im Kristallgitter, tritt diese Deformation nur noch bis h -1.5 auf, ohne eine merkliche Verkleinerung von LD oder LE. I n diesem Falle werden die Lamellen schon bei kleinem h durch Gleitbewegung der Ketten in den ,,nichtkristallinen" Grenzfiachen zwischen den Mosaikblocken zerstort, ohne da8 dabei eine merkliche Kettenneigung in den Blocken stattfinden wurde. Verstrekken bei 110°C ahnelt in vieler Beziehung mehr dem Tie€-als dem Hochtemperaturfall. Eine derartige Temperaturabhangigkeit ist der des Langperiodenwachs tums sehr ahnlich : sehr schnell bei 120 'C, gerade noch beobachtbar bei 110°C und unmerklich unterhalh 80'C. Diese dhnlichkeit scheint daher zu ruhren, da13 es sich in beiden Fallen um die gleiche longitudinale Heweglichkeit der Molekulketten in Kristallgitter handelt.

A structural study on solid state drawing of solution-crystallized ultra-high molecular weight polyethylene

“…At higher draw ratios the intensity of the long period decreases drastically, whereas the value of L remains constant. These results are similar to experimental data obtained for drawn meltcrystallized commercial linear PE grades [36,37]. This implies that the molecular weight and the use of gelation has no significant influence on the behavionr of the long period upon drawing.…”

“…Clements and Ward [37] explain the observed decrease in SAXS reflection intensity at higher draw ratios by an increase in formation of crystalline bridges acting as links between oriented lamellae. Peterlin and Corneliussen [36] ascribe it to a decrease of effective electron-density difference between amorphous and crystalline components. However, the above-mentioned interpretations are not simply transferable to deformations up to extremely high draw ratios.…”

On the strain-induced fibrillar microstructure of polyethylene: Influence of chemical structure, initial morphology and draw temperature

“…together with deformation conditions [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. It was shown in some cases that these structural or experimental factors could have an impact on the mechanism of fragmentation of the crystalline lamella via the local stress distribution on the crystalline lamellae [22,25,30].…”

Plasticity of semi-crystalline polymers: crystal slip versus melting-recrystallization

“…This process should not involve significant change of the crystal block thickness, in comparison to the mother lamellae. However, the commonly reported observation that the long fibril period of various semi-crystalline polymers plastically drawn far beyond the yield point only depends on the draw temperature 1 [13][14][15] led a number of authors to conclude that the crystalline phase undergoes a strain-induced melting and subsequently recrystallizes during the drawing process. The former mentioning of melting-recrystallization upon drawing of semi-crystalline polymers by Flory and Yoon [16], more from intuition than from experimental facts, is regularly taken as testimony for the phenomenon certainty.…”