Melting Temperature Characteristics for Polyethylenes from Crystal Size Distribution

Abstract

Semi-crystalline polymers exhibit broad and multiple peaks in their melting traces. Thus, the melting temperature characteristics of polymers should consider both melting peak positions and melting temperature polydispersity. In this work, the effective melting temperature and temperature polydispersity are defined and calculated from DSC traces, using the crystal size number distribution and the melting temperature equation. Three methods are proposed for calculating melting temperature characteristics. These methods are based on: (i) average crystal size, (ii) the crystal stem number distribution function, and (iii) the monomer structural unit distribution function. They were employed to analyze the isothermal and non-isothermal experimental results for polyethylene polymers, especially linear low-density polyethylene copolymers. The first method, based on the value of average crystal size, gives the most reasonable results, taking into consideration agreement with experimental observations and structural data.

Primary Chemical Sequence Ultimately Determines Crystal Thickness in Segmented All-Aliphatic Copolymers

“…Processing conditions are known to affect crystallinity of thermoplastic elastomers. For example, change in the crystallization temperature during cooling from the polymer melt and structural defects of different nature typically result in crystal size polydispersity. − Physical properties of semicrystalline polymers are strongly dependent on crystallinity and therefore processing conditions. , The design of novel TPEs with predefined properties which are also independent of the processing conditions is an important challenge.…”