Synchrotronowe badania nanostruktury materialow polietylenowych

Abstract

Nanostructures of polyethylene materials were investigated, at real time in the processes of crystallization and melting, with using of SAXS (Fig. 2) or DSC (Fig. 4) methods. The following polyethylene materials (Table 1)were investigated: of ethylene/1-alkene (propene, butene, octene), standard linear polyethylene (PE-L), high-density polyethylene (PE-HD) and low-density polyethylene (PE-LD). The term homogeneous copolymers concerns obtained with using of metalocene or vanadium based catalysts. Except the narrow molecular weights distributions they show constant content of co-monomers units in the chains and statistically identical distribution of these units in the each chain. Theoretical base as well as the methodology of the calculations of the results were described in details. There were presented mathematical dependences describing: correlation function [equation (1), graphical forms in Figs. 1 and 7], invariant [i.e. full scattering power of a material - equations (2) and (3)], thickness of crystalline lamellae and amorphic layers [equation (5)] as well as mass degree of crystallinity [equation (7)]. Changes of crystallinity degree (ω c - Figs. 5, 6 and 9), invariant (Q - Fig. 3), long period values (L p ), thickness of crystalline lamellae (L c ) or amorphic layers (L a ) [Figs. 8, 10 and 11, equations (8)-(12)] proceeding in the wide range of temperature (from -40°C to +120°C) were discussed. The mechanism of lamella systems' melting was explained, taking into consideration the significant L p changes versus temperature and constant thickness of crystalline lamellae.