Isothermal crystallisation and spherulite structure of partially miscible polypropylene-linear low-density polyethylene blends

Li, J, Shanks, R and Long, Y 2001, 'Isothermal crystallisation and spherulite structure of partially miscible polypropylene-linear low-density polyethylene blends', Journal of Applied Polymer Science, vol. 82, no. 3, pp. 628-639.


Document type: Journal Article
Collection: Journal Articles

Title Isothermal crystallisation and spherulite structure of partially miscible polypropylene-linear low-density polyethylene blends
Author(s) Li, J
Shanks, R
Long, Y
Year 2001
Journal name Journal of Applied Polymer Science
Volume number 82
Issue number 3
Start page 628
End page 639
Total pages 11
Publisher John Wiley and Sons
Abstract Polypropylene (PP) was blended with a linear low-density polyethylene (LLDPE, containing 5% hexene comonomer) over a composition range of 10-90% of PP. The crystallization and morphology of the PP-LLDPE blends were studied by differential scanning calorimetry (DSC), polarized optical microscopy with a hot stage (HSOM), and scanning electron microscopy (SEM). In particular, the isothermal crystallization of PP in molten LLDPE was investigated. It was observed that the crystallization and melting behavior of PP and LLDPE changed in the blends, indicating that there was some degree of miscibility between the PP and the LLDPE. A depression of the equilibrium melting temperature (T) of PP in the blends with no more than 15% of PP confirmed that PP was miscible with LLDPE at and below 15% of PP. In addition, a drastic decrease in T from the 25% PP blend to the 20% blend led us to conclude that the miscible behavior between PP and LLDPE became favorable at a PP concentration of 20%. The optical microscopic images showed that, in the blends with 10 and 15% of PP, the PP crystallized as open-armed diffuse spherulites, similar to those in the miscible blends. In contrast, the PP crystallized in a phase-separated matrix or droplets with more than 25% of PP, when obvious phase separation occurred. The SEM image revealed that the PP lamella was able to penetrate the PP and LLDPE phase boundary and grow in the LLDPE phase. The above results displayed that the PP dissolved in the LLDPE, and, particularly, when the PP concentration was below 20%, the dissolution was substantial.
Subject Polymers and Plastics
DOI - identifier 10.1002/app.1891
Copyright notice © 2001 John Wiley and Sons
ISSN 0021-8995
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