Viscosity contrast effects on the structure – Property relationship of multilayer soft film/foams

Abstract

In this research work, multilayer soft film/foam systems based on low-density polyethylene (LDPE) have been developed. In order to improve the layer stability during processing, a viscosity contrast between film and foam layer polymers is maintained. Three different LDPE grades having different melt flow indices were used and film/foam systems with up to 32 layers were produced. High-viscosity film layer and low-viscosity foam layer in each film/foam system contributed to good layer integrity even with high foam content. Measurements of cell density and cell size distribution indicated that high viscosity film layer and increasing layer number have significant confinement effect that enhanced the cell nucleation and suppressed the cell coalescence and thus contributed to single cell arrays in foam layers. Constrained cell growth was observed in 16 and 32 layers film/foam systems. Confinement effect from the high viscosity film layer was also observed at higher foam content. In addition, uniform layer integrity resulted from high viscosity contrast between film and foam layers contributed to higher deformability.Moreover, increasing layer number also improved the tensile modulus and strength of each film/foam system.

Strategy for the preparation of lightweight polypropylene/polyethylene‐octene elastomer composite foams with different phase morphologies using supercritical carbon dioxide

“…Because the cells could grow freely in pristine POE, the cell size was large. This accords with the results of Rahman et al 59 According to the graphs of the cell size and cell density with respect to the number of layers, the increase in the number of layers increased the nucleation of the cells and limited the cell growth. Increasing the number of layers did not allow for a more pronounced reduction of the cell size.…”

“…This is because as the number of layers increased, the layer thickness gradually decreased, and the limiting effect on the cell growth increased, which increased the cell nucleation. This accords with the results of Rahman et al 59 According to the graphs of the cell size and cell density with respect to the number of layers, the increase in the number of layers increased the nucleation of the cells and limited the cell growth. .…”

Thermoformable high oxygen barrier multilayer EVOH/LDPE film/foam

“…This result was achieved because the materials were selected based on the principle of viscosity contrast and due to the use of LDPE‐ g ‐MA in the foam layer. The latter works as a compatibilizer to improve the adhesion between the film and foam layer . Furthermore, EVOH copolymer is partially compatible with LDPE, due to 44% polyethylene content.…”

“…Plastic foam is widely used in several applications due to outstanding properties such as its low density, thermal and acoustic isolation, impact and shock absorption, and low production cost . However, most common foamed products have high oxygen and water vapor transmission due to their porous structure.…”

“…A novel technique to prepare coextruded multilayer film/foam structures was recently proposed and developed by Baer and coworkers . Multilayer polymer coextrusion consists basically in a system of multiple single screw extruders with melt pumps, a coextrusion feedblock, a sequence of layer multiplier elements, and an exit die.…”