This paper deals with ultra-high-strength monofilaments of linear polyethylene that are produced by solution spinning and subsequent hot drawing at 120° C. The influence of the draw ratio on the mechanical and thermal properties of the fibres was investigated. Some salient features of a polyethylene filament with a draw ratio of 31.7 are: tensile strength at break=3.0 GPa, Young's modulus=90 GPa and DSC-melting point at a scan speed of 10° C min−1=145.5° C. The modulus was found to depend linearly on the draw ratio. The tensile strength tended, by contrast, to approach an upper limit at high draw ratios. Additional morphological and X-ray studies revealed an extremely good orientation of the macromolecules in the fibre direction of the highly drawn polyethylene monofilaments.

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Ultra-high-strength polyethylene filaments by solution spinning/drawing

The effects of “short term shearing” on the subsequent crystallization of a polydisperse Ziegler−Natta isotactic polypropylene are observed using in situ optical measurements and ex situ microscopy. Imposition of brief intervals of shear (0.25−20 s, less than a thousandth of the quiescent crystallization time) can reduce the crystallization time by 2 orders of magnitude (e.g., at 141 °C with a wall shear stress of 0.06 MPa). With increasing shearing time, the crystallization time saturates and highly anisotropic growth ensues. This transition to oriented growth correlates with changes in the transient behavior during flow and the semicrystalline morphology observed ex situ. During flow, we observe the generation of long-lived, highly oriented structures (evident in the transient birefringence) under all conditions that induce subsequent growth of highly oriented crystallites. In turn, the development of oriented crystallites observed in situ after cessation of flow correlates with development of a “skin-core” morphology (highly oriented skin on a spherulitic core) observed ex situ. Interestingly, the long-lived structures generated during flow appear at shorter times with increasing temperature (at fixed shear stress), the opposite of the trend one would expect on the basis of the temperature dependence of quiescent crystallization.

Shear-Enhanced Crystallization in Isotactic Polypropylene. 1. Correspondence between in Situ Rheo-Optics and ex Situ Structure Determination

One polymer composite materials have been prepared using a difference in melting points between the components. This depends on the fact that aligned and extended chains provide thermodynamically more stable crystals, which thus will have higher melting points than conventionally crystallized melts. The growth of transcrystalline regions in the melt matrix at the interface plus an observed partial melting between fibre and matrix are indications of a strong and intimate interfacial bond with a gradient in morphologies for the system studied, high-density polyethylene. The pull-out test is a simple and adequate method for evaluating the interfacial shear strength of one polymer composites. The value for the high-density polyethylene composite falls between the strengths for glass-reinforced polyester and epoxy resins. However, the interfacial strength in the polyethylene composites is due mainly to the unique epitaxial bonding rather than the radial forces from compressive shrinkage. The low critical aspect ratio for the filaments in these polyethylene composites suggests possible advantageous uses as short fibrereinforced materials where the interfacial strength is a controlling factor.

The concept of one polymer composites modelled with high density polyethylene

A new method for the preparation of high modulus thermoplastic films

The validity of interpreting measured rotating frame relaxation times, T1ρC*, in terms of molecular motion is investigated for crystalline, oriented, linear polyethylene (PE) as a representative rigid organic solid with reasonably strong dipolar couplings. T1ρC* data are presented at three temperatures, −100, 28, and 100 °C and for 13C rf fields, ν1C, in the range 35<ν1C<90 kHz, for the orientation where B0 is parallel to the PE chain axes. With the exception of the T1ρC* data taken at ν1C≳80 kHz and T=100 °C, all T1ρC* data observed were determined not by molecular motion, but rather by spin–spin effects in which the spin‐locked carbon system seeks to equilibrate with the proton dipolar system with a characteristic time constant TCHD(ν1C), while at the same time the proton dipolar system is equilibrating with the lattice with a time constant T1D. The TCHD values deduced from T1ρC* support existing theory which predicts that TCHD(ν1C) ∝ exp(2πν1CτD) where τD is the correlation time for dipolar fluctuation...

13C NMR rotating frame relaxation in a solid with strongly coupled protons: Polyethylene

High-density commercial polyethylenes have been crystallized under the combined orientation and pressure effects available in the Instron capillary rheometer. The samples so formed were found to have a high degree of crystal perfection and crystal orientation in combination with the unusual property of transmitting visible light. The procedure for forming the crystal structure is elucidated. X-Ray and differential scanning calorimetry techniques were utilized to initiate a study of the structure. Evidence is presented that is consistent with the presence of an extended chain component in the crystal structure.

The properties of polyethylene crystallized under the orientation and pressure effects of a pressure capillary viscometer

High-density commercial polyethylenes have been crystallized under the combined orientation and pressure effects available in the Instron capillary rheometer. The samples so formed were found to ha...

Polyethylene crystallized under the orientation and pressure of a pressure capillary viscometer. Part I

A commercial high‐density polyethylene has been crystallized in the Instron Capillary Rheometer under the combined influence of pressure and orientation. A transparent high‐modulus, and highly oriented filament structure was produced. In order to determine quantitatively the degree of orientation, azimuthal x‐ray scans of the 002 reflection plane were used to obtain the orientation function of the orthorhombic unit cell relative to the flow axis in the rheometer (identified with the filament axis). A value of +0.996±0.002 was measured for this orientation function indicating that the backbones of the crystalline polyethylene chains were virtually aligned perfectly parallel to the flow axis of the rheometer. This report is concerned with the high‐resolution techniques required to measure such highly oriented samples. In conjunction with the x‐ray study, birefringence measurements are included which permit the determination of the orientation of the amorphous component as well as the crystalline component.

Orientation and Structure of Polyethylene Crystallized under the Orientation and Pressure Effects of a Pressure Capillary Viscometer

The general properties of a novel process for producing high modulus polyolefins are discussed. The technique is an extrusion drawing involving a crystal-crystal transformation. The principal tests have been made on polyethylene and the guidelines have been established for extending the technique to other polyolefins. The characterization of such materials is extensively discussed, particularly in the light of the concept of continuous crystals.

Polymer modulus and morphology: The tensile properties of polyethylene

Unusual morphologies have been shown to be produced in high density polyethylene near its melting point and under selective conditions of orientation and pressure existing in an Instron capillary extrusion rheometer. Points of study involve the remarkably high optical clarity and tensile moduli for the morphologies produced in these filaments. Details of the crystallization procedure are provided. The morphologies resulting from the Instron procedure have been analyzed by several different techniques. X-ray, calorimetry, microscopy and modulus data are discussed. The transparent filaments are composed of a large number of microfibers having a high degree of crystalline orientation parallel to the capillary axis. Electron diffraction and calorimetric studies indicate that a portion of the strands have an unusually high degree of order. Structural models for the strands are also proposed.



Es wurde gezeigt, das sich in Hochdruck-Polyathylen in der Nahe der Schmelztemperatur und unter bestimmten Bedingungen in bezug auf Orientierung und Druck, wie sie im Instron-Extrusions-Kapillar-Rheometer vorliegen, ungewohnliche morphologische Strukturen ausbilden. Die bemerkenswert hohe optische Transparenz und die Spannungsmoduln der in diesen Faden vorliegenden morphologischen Gebilde waren Gegenstande der Untersuchungen. Einzelheiten des Kristallisationsverfahrens werden beschrieben. Die morphologischen Strukturen, die sich bei dem „Instron-Verfahren” herausbilden, wurden mit Hilfe von rontgenographischen, kalorimetrischen, mikroskopischen und mechanischen Messungen untersucht. Die transparenten Fasern setzen sich aus einer grosen Zahl von Mikrofibrillen, die einen hohen kristallinen Orientierungsgrad parallel zur Kapillarachse bestizen, zusammen. Elektronenbeugung und kalorimetrische Untersuchungen zeigen, das ein Teil der Fasern einen ungewohnlich hohen Ordnungsgrad besitzt. Es werden Strukturmodelle fur die Fasern vorgeschlagen.

John H. Southern

Papers

The properties of polyethylene crystallized under the orientation and pressure effects of a pressure capillary viscometer

Polyethylene crystallized under the orientation and pressure of a pressure capillary viscometer. Part I

Orientation and Structure of Polyethylene Crystallized under the Orientation and Pressure Effects of a Pressure Capillary Viscometer

Polymer modulus and morphology: The tensile properties of polyethylene

Unique polyethylene morphologies produced under extrusion conditions