Multilayer sheets for thermoforming non thermoformable polymers
| Autor: | Lisa-Maria Wittmann, Dietmar Drummer |
|---|---|
| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Journal of Plastic Film & Sheeting. 38:225-244 |
| ISSN: | 1530-8014 8756-0879 |
| DOI: | 10.1177/87560879211037387 |
| Popis: | Multilayer sheets were used for thermoforming non thermoformable polymers in order to face the challenge of semi-crystalline polymers like low melt-stiffness. Mono- and 2-layer sheets consisting of different polypropylene (PP) homopolymers were extruded on a twin screw extruder. The PP viscosity as was measured by melt flow rate (MFR) 3 g/10 min., 12 g/10 min., 22 g/10 min. and 50 g/10 min. The layer ratio was varied between the equal layer ratio (A50/B50) of the individual layers and the low (A30/B70) or high viscosity ratio (A70/B30). The extrusion results show that for extreme viscosity differences (MFR3 and MFR50), the critical layer ratios known from the literature are only valid to a limited extent. The critical viscosity ratio The investigation of thermoformability on laboratory scale of the extruded PP sheets with different viscosities showed that the low viscous layer position has only a marginal influence on the general thermoformability. Thermoforming of materials that are not thermoformable, with a storage modulus of less than 10³ Pa and a ratio between storage and loss modulus (tan δ) greater than 1, becomes possible using a multilayer sheet independant of the layer ratio. If the layer with higher viscosity acts as a stabilizing layer, thermoforming is possible. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|