Journal of Cellular Plastics

Sprayed rigid foam is a significant segment of the polyurethane industry, and as in other rigid foam segments, spray foam formulators need to find ways to meet current product requirements when the use of HCFC-141b is phased out in January 2003. Due to some of the unique characteristics of the spray foam industry, though, the choice of a replacement blowing agent is perhaps more complex than in any other rigid foam sector. The alternatives receiving the most consideration today are HFC-245fa, hydrocarbons, and water.

All of these potential blowing agents have significant hurdles to overcome before they could serve as satisfactory replacements for HCFC-141b in the spray foam market. As of May 1999, a firm commitment to commercialize HFC-245fa has not been made. The use of hydrocarbons in spray would require significant improvements in safe handling procedures and modifications to spray equipment due to flammability issues. And with water-blown systems, dimensional stability and adhesion are two technical hurdles that must be overcome. It is conceded as well that insulation performance (as measured by initial k-factor) will not be as good for a water-blown foam as with HCFC-141b.

It was because of the lack of an obvious HCFC-141b replacement for the spray foam industry that Huntsman Polyurethanes decided to investigate possible solutions. Any alternative would need to meet the processing and handling requirements that are currently met with HCFC-141b systems.

The objective of this work is to develop zero-ODP (ozone depletion potential) technology that meets the performance characteristics that are currently achieved with HCFC-141b spray foam roofing systems. The focus of this paper is on the development of water-blown technology for roofing systems. Foams were processed via high-pressure spray equipment in a controlled environment. The study looked at the effect of polyol, catalyst, blowing agent, and processing variables on foam quality.

This fundamental study investigates the blowing agent (isopentane) on the extensional viscosity of LDPE at appropriate strain rates and then correlates to the foaming process. The main purpose was to calculate extensional viscosity growth function as a function of extrusion rate and time with and without the presence of isopentane in LDPE. A simple theological technique using the Haake capillary rheometer with pulling attachments was used in the study. The experimental technique is simple and cost effective, but a powerful tool to screen new resins for foam processing applications.

A number of rear-seat-to-back-window trim panels (CHMSL covers) were manufactured by thermoforming ground polyurethane-cored headliner (UROCOR) scrap with PMDI as a binder with and without water as a component of the composite mixture utilizing industrial equipment at a Lear plant in Holland, Michigan. Unexpectedly, it was found that UROCOR scrap which contains a significant amount of flexible and semi-rigid polyurethane foam can be thermoformed without addition of PMDI. In order to confirm that the polyurethane scrap can be used as a binder, the polyurethane seating foam scrap was successfully recycled as the sole scrap and in 75/25 and 50/50 mixtures with resinated fibers.

INSITE** Technology from The Dow Chemical Company has enabled the production of ethylene-styrene Interpolymers (ESI) by copolymerization of ethylene and styrene monomers. The properties of interpolymers vary significantly with copolymer styrene content. Interpolymers with up to about 45 weight percent copolymer styrene are semicrystalline and exhibit good low temperature toughness. Interpolymers with greater than about 45 weight percent copolymer styrene are essentially amorphous and range from those that have low modulus and high elongation to those that have higher modulus with unique stress relaxation and dead fold properties. Interpolymers have both aromatic and aliphatic functionality. Hence, they are compatible with a variety of other thermoplastics. Interpolymers have been commercially launched under the trademark "INDEXt Interpolymers" and are classified as E-Series (up to about 45 weight percent styrene) or S-series (greater than about 45 weight percent styrene). This paper describes the properties of blends of interpolymers with low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS), as well as the novel and unique foams made by expanding some of these blends with physical blowing agents.