【Basic Knowledge of Glossary Definitions for “Polymers and Materials”-004】Glossary definitions related to polymers
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This post was last edited by ljtjbx on 2015-8-5 07:28. 1. Free volume: The space in a polymer that is not occupied by the polymer itself; it is the area where the macromolecular segments can move through diffusion. 2. Die swell: The cross-sectional area of the polymer melt after extrusion is larger than that of the die opening; this phenomenon is known as the Barlow effect. 3. Melt fracture: refers to the general term for uneven surfaces on the extruded product, as well as deformities and breaks. 4. Screw compression ratio: The ratio of the volume of the first screw groove in the screw feeding section to the volume of the last screw groove in the homogenization section. It indicates the degree to which the plastic is compressed as it passes through the screw. 5. Calendring effect: During the calendring process, thermoplastic plastics are subjected to high shear and tensile stresses, causing the polymer macromolecules to align in the direction of calendring. As a result, the physical and mechanical properties of the product become anisotropic.
The Basler effect is the molding expansion, the extrudate expansion effect. In extrusion molding, it is the phenomenon in which the extrudate expands, resulting in dimensions larger than those of the corresponding die opening. It is caused by stress changes in the viscoelastic polymer melt when it comes into contact with the mold, and it is a phenomenon unique to polymer melts.