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Effect of polymer swell in extrusion foaming of low-density polyethylene
- Publication Year :
- 2021
-
Abstract
- Insights into the effect of die swell on extrusion foam of thermoplastic polymers are presented. The die swell or Barus effect is the swelling of a viscoelastic material due to a fast elastic recovery after being subjected to stress. The elastic recovery is proportional to the energy stored in the material during the deformation that is released immediately when the material is free to expand. In extrusion foam, the elastic recovery happens at the die exit together with the foaming process (i.e., bubble nucleation and growth). Previous reports on extrusion have focused on modeling the die swell or foaming individually. We investigated the existence of a link between the die swell and foaming that is fundamental in designing the geometry of a die for extrusion foam. Simple and complex dies were used to measure the expansion ratio of a polyethylene blown with isobutane and CO2. It was found that the expansion ratio is anisotropic, the anisotropy in the expansion of the foam is due to the die swell strongly affecting the final shape of the product, and it cannot be neglected in standard application for extrusion foam. Surprisingly, it was found that the foam density changes at a high level of die swell because it is affected by the elastic recovery of the material.
- Subjects :
- Fluid Flow and Transfer Processes
Physics
business.product_category
Mechanical Engineering
Computational Mechanics
Die swell
Condensed Matter Physics
01 natural sciences
Viscoelasticity
Swell
010305 fluids & plasmas
Expansion ratio
Low-density polyethylene
Mechanics of Materials
0103 physical sciences
Die (manufacturing)
lipids (amino acids, peptides, and proteins)
Extrusion
cardiovascular diseases
Deformation (engineering)
Composite material
010306 general physics
business
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....13d9b3681f30cc3224020a5295893a17