Stabilization High Molecular Weight High Density Polyethylene for Blown Film Applications, 1996 Polymers, Laminations & Coatings Conference Proceedings

As a supplier of additive systems and technical support, different approaches can be used to identify a suitable stabilizer package for film grade high molecular weight high density polyethylene. One approach might be to evaluate competitive stabilizer packages by systematically altering the stabilization system while running blown film experiments, typically on a commercial scale film line, followed by measuring physical properties of the film product such as tensile strength, elongation, Elmendorf tear, melt flow rate retention, haze and color development. Invaluable information regarding film processing stability such as output rates, line speeds, back pressures and bubble stability can also be obtained. While time consuming and resource intensive, this approach can give realistic feedback on the impact of the stabilization system on the polymer and the film blowing process. Another approach, which is more customary for an additive supplier, might be to perform simple, expedient and less resource intensive extrusion experiments in the laboratory as a function of melt processing temperature, residence time and shear rates, and then monitor maintenance of melt flow rates, color development, and thermo-oxidative stability of the polymer. No film is produced, but this approach can be used as a qualitative tool to identify promising stabilization systems. Realistically, there is no comparison between the two approaches. The utility of the blown film experiments far exceeds the type of information typically obtained from laboratory melt compounding extrusion experiments. Still, the data from the lab scale extrusion experiments may help to get headed in the right direction regarding a better understanding of the basic stabilization requirements of the polymer, and how that polymer responds to the additives. A comparison of these two approaches will be recounted in this paper.