John Eric Benson

Foamed and Oriented Polypropylene Films

Foamed polypropylene films that are made by extruding mixtures of polypropylene (PP) and a chemical blowing agent are described in this study. The films are prepared by a cast extrusion process, followed by machine direction orientation. This article describes the structure–property relationships of the resultant foamed PP films and the varied applications of the foamed films.

IMPROVED ELECTROSTATIC PINNING USING A BIASED, CONDUCTIVE SHIELD

Abstract Electrostatic pinning is a technology used to improve the intimacy of contact of an extruded resin onto a casting wheel in the process of producing plastic films such as polyethylene terephthalate (PET). This improvement is achieved by spraying electrical charge onto the resin just prior to contact with the casting wheel, creating an electrostatic force of attraction between the resin and wheel. This work focuses on altering the electrostatic pinning hardware, rather than resin formulation, for improved performance. A biased, semicircular, conductive shield is placed around the pinning wire to increase its resin-charging efficiency. This results in a pinning system having increased latitude with respect to resin formulation. It is shown that a spectral analysis of the profilometry of pinned resin samples provides a method for quantifying pinning quality. This method is used to demonstrate a direct correlation between pinning quality and net current deposited on the extruded resin by the pinning hardware. Another important result is the existence of an optimal shield bias voltage that depends upon the pinning wire voltage. This apparatus is shown to perform well for a variety of PET resin formulations incorporating various levels of metal additives.