THERMOFORMING EVALUATION OF COEXTRUDED MULTILAYER EVOH/LDPE FILM/FOAM

摘要

A multi-layered film/foam system having 16,32,and 64 alternating foam and film layers has been developed using multilayer coextrusion technology.The film layer was based on ethylene-vinyl alcohol (EVOH) copolymer and foam layer on low-density polyethylene (LDPE).The cellular structure was characterized by scanning electron microscopy investigating the effect of the number of layers and layer composition on the film/foam structure.The film/foam materials produced exhibited variable properties,such as density,cell size,cell density,and mechanical properties by changing the layer number and composition.The stress-strain behavior of these film/foam materials at several temperatures was examined.The stress strain curves obtained were referenced to understand the influence of temperature on the uniaxial deformation process.This information provides insight into the material properties and process conditions influencing thermoforming behavior and performance.The thermoformability of the film/foam materials were evaluated.Optimum forming capacity was achieved at 60°C.These film/foam materials showed a lower reduction of thickness in the sidewalls,as well as a higher dimensional uniformity in the thermoformed product.