Unique polyethylene morphologies produced under extrusion conditions

Abstract

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 orienlation 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. ZUSAMMENFASSUNG:Es wurde gezeigt, daB sich in Hochdrnck-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 Jnstron-Verfahren" herausbilden, wurden mit Hilfe von rontgenographischen, kalorimetrischen, mikroskopischen und mechanisbhen Messungen untersucht. Die transparenten Fasern setzen sich aus einer groBen Zahl von Mikrofibrillen, die einen hohen kristallinen Orientierungsgrad parallel zur Kapillarachse besitzen, zusammen. Elektronenbeugung nnd kalorimetrische Untersuchungen zeigen, daB ein Teil der Fasern cinen ungewohnlich hohen Ordnungsgrad besitzt. Es werden Strukturmodelle fur die Fasern vorgeschlagen.

Extrusion of highly oriented polyolefin fibers

“…That is, at higher extensional flows (higher 2, the increased melt entropy causes the effective melting point of the flowing polymer to increase; therefore the free energy change upon crystallization, (i.e., the thermodynamic driving force for crystallization) also in-& creases with increasing -4 Furthermore, since the dz extensional flow is causing the polymer chains to be extended and to develop parallel alignment, the major resistance (alignment of chains) to crystallization is dramatically reduced. Increasing the driving force for crystallization and decreasing the resistance leads to the probability of extremely rapid crystallization as noted in strain induced and in pressure induced crystallization (1)(2)(3)(4)(5)17).…”

“…Th rheometer by Southern and Porter (1)(2)(3)(4)(5) has created BACKGROUND The change in Gibb's free energy in a system undergoing change in state is defined by Ey 1 (1) where AF = F , -F , is the change in Gibbs free energy, LW is the change in enthalpy, T is the absolute temperature, and AS is the entropy change. At a first order thermodynamic transition (melting, crystallization, boiling, etc.)…”

Thermodynamics and kinetics of orientational crystallization of flexible-chain polymers

“…refs. [17][18][19]. Although similar conclusions on the final structure of flexible-chain superfibres (i.e.…”

Different Types of Extruders

“…These machines are used in specialty operations, such as melt removal directly from a polymerization reactor. In Europe, the standard extruder sizes are 20,25,30,35,40,50,60,90,120,150,200,250,300,350,400,450, 500, and 600 millimeters. Most extruders range in size from 1 to 6 inches or from 25 to 150 mm.…”

“…The fluid can be supplied to the extrusion device by high-pressure tubes. [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64], University of Leeds, England [65][66][67][68][69][70][71][72], Fyushu University, Fukuoka, Japan [73][74][75][76], Research Institute for Polymers and Textiles, Yokohama, Japan [77][78][79], Battelle, Columbus, Ohio [80][81][82][83], and Rutgers University, New Brunswick, New Jersey [84][85][86]. As mentioned earlier, publications from other sources are considerably less plentiful [87][88][89][90].…”