(276a) Nucleation and Bubble Growth Dynamics in Polymer Foaming on Paper Board

Polymer foamed paper board is a commercially important product for the consumer products industry and has recently found increased demand. Paper board foaming can be described as the process in which the board is sandwiched between extruded polymeric layers on both sides. One side of the board is foamed with heat to produce a uniform insulating surface with good tactile properties. The moisture inside the board vaporizes, nucleates at the interface and traverses in the thickness direction. The current study is a directed at understanding the fundamentals of the foaming process on paper board surface. The paper discusses results from a high speed photography technique used to determine the nucleation and bubble growth rates of the foaming process. Some effects of paper/polymer interfacial properties on the foaming process are also discussed. Results show that the nucleation process is more influenced by the properties of paper board than the properties of the polymeric layer. The effects of coalescence and collapse on bubble growth and final cell size distribution are also studied. Different size bins of the bubbles formed are identified and factors influencing the formation of these bins are discussed.