Effect of shear history on flow instability at capillary extrusion for long-chain branched polyethylene
| Autor: | Siriprumpoonthum Monchai, Vu Anh Doan, Naoya Mieda, Shogo Nobukawa, Masayuki Yamaguchi |
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| Rok vydání: | 2011 |
| Předmět: |
Materials science
Polymers and Plastics Capillary action Plastics extrusion General Chemistry Polyethylene Surfaces Coatings and Films Linear low-density polyethylene chemistry.chemical_compound Low-density polyethylene chemistry Rheology Shear (geology) Materials Chemistry Extrusion Composite material |
| Zdroj: | Journal of Applied Polymer Science. 124:429-435 |
| ISSN: | 0021-8995 |
| DOI: | 10.1002/app.35108 |
| Popis: | Effect of applied processing history on flow instability at capillary extrusion is studied using a commercially available low-density polyethylene (LDPE) having long-chain branches. It is found that processing history in an internal mixer in a molten state depresses long-time relaxation mechanism associated with long-chain branches, which is known as “shear modification.” Consequently, the onset of output rate for melt fracture increases greatly. Furthermore, it should be noted that the sample having intense shear history shows shark-skin failure without volumetric distortion, although it has been believed that LDPE exhibits gross melt fracture at capillary extrusion. The reduction of elongational viscosity by the alignment of long-chain branches along to the main chain is responsible for the anomalous rheological response. As a result, the sample shows shark-skin failure like a linear polyethylene at a lower output rate than the critical one for gross melt fracture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 |
| Databáze: | OpenAIRE |
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