News in PUR testing & recycling.

Several interesting new testing techniques for PUR foams will be presented at the Polyurethanes World Congress '93 this month in Vancouver, B.C. There will also be several papers on advances in PUR recycling and numerous reports on CFC-replacement technologies. Here are some details on topics that were not covered in our conference preview last month (p.28).

TEST METHODS & INSTRUMENTS

Dow Plastics, Midland, Mich., will report on a method for estimating the concentration of blowing agents remaining in a foam. Dow used thin-slice accelerated desorption of gases and a gravimetric methodology to determine effective diffusion coefficients of HCFC-22 and [CO.sub.2] in PUR, PUR-modified polyisocyanurate (PIR), and polyurea-modified PUR foams. (CIRCLE 7)

Weidmuller Sensor Systems, McHenry, Ill., will feature the company's new foam-height measuring system, LRS 3V3. This microprocessor-based system monitors critical process variables during development and production of all sorts of PUR foams. The system monitors foam rise through an ultrasonic signal and stores data on foam height, rate of rise, maximum height and collapse, and foam temperature characteristics. (CIRCLE 8)

A paper from Brastemp S.A. of Brazil reports on neutron activation analysis as a quick, non-destructive method for determining content of CFCs, HCFCs or HFCs in rigid foams either in the gaseous phase or dissolved in the foam cell walls. (CIRCLE 9) Manufacturers of PIR roofing insulation must recertify their products on the Factory Mutual Calorimeter as they make their transition to alternative blowing agents. Many small-scale tests are available to measure fire resistance, but their effectiveness as predictors of performance on the FM Calorimeter hasn't been fully assessed. ICI Polyurethanes, West Deptford, N.J., has developed a novel test for trimer conversion or PIR/PUR ratio, which achieves results that have a high degree of correlation with the FM Calorimeter, ICI says. (CIRCLE 10)

Arco Chemical Co., Newtown Square, Pa., is giving a paper on a new mathematical model that's said to be highly accurate in predicting the effect of major variables in slabstock formulation (water level, isocyanate index and polymer content) on end-use properties. Besides previously reported correlations of fatigue with such variables, Arco found new and unexpected correlations of other properties, especially hardness, elongation and tear strength. (CIRCLE 11)

Olin Corp., Cheshire, Conn., will recommend use of the British flammability standard (BS-5852, Part II, Source V) test method as a lower-cost alternative to the more time-consuming California TB-133 flammability test for screening fire performance of foam/fabric barrier combinations for furniture cushioning. Results from BS-5852 on a highly flame-retardant CMHR foam correlated very well with TB-133 results, Olin reports. (CIRCLE 12)

Monsanto Instruments, Akron, Ohio, will tell how its MDR2000 moving-die rheometer has been found useful in measuring PUR set times, average and peak cure rates, and state of cure. The instrument reportedly shows good repeatability and sensitivity to formulation variations. (CIRCLE 13)

RECYCLING RESEARCH PROGRESSES

In addition to those recycling papers discussed last month, a joint presentation by Bayer AG of Germany, Miles Inc., Pittsburgh, and Sumitomo Bayer of Japan will address progress toward commercializing various PUR recovery processes. Areas of progress include technology for cost-effective size reduction; blending of reground PUR powder into flexible and semi-rigid energy-absorbing foams and RIM elastomers; adhesive bonding of flexible foam regrind for sound-deadening applications and reground rigid appliance foam for construction uses; compression molding of RIM scrap into new auto parts; and reuse of glycolized RIM chemicals in new transportation parts. Furniture and bedding are some additional markets that may be able to use recycled PUR. (CIRCLE 14)

The Polyurethanes Recycle and Recovery Council (PURRC), a unit of SPI's Polyurethanes Div. in N.Y.C., will provide an update on its recycling R&D programs. Among recent findings are that adding up to 20% reground flexible foam to virgin PUR raw materials has minimal effect on foam processing or physical properties. Some recent studies concluded that used car-seat foam can be reused in applications like carpet underlay without sacrificing performance. So far, rebonded carpet underlay has used only foam manufacturing scrap, not post-consumer material.

In one pilot study, PURRC dismantled car seats and also discarded mattresses. Time to dismantle seats and extract the foam averaged close to 1 hr. Foam recovery from mattresses took 4-8 min. PURRC says designing car seats for disassembly would significantly reduce removal time and improve recovery economics. Other studies determined that some carpet-underlay grades can contain up to 100% of used foam from car seats without any discernible difference in processing or performance characteristics. Samples were measured for compression set, strength and carpet wear.

GOOD NEWS ON SPRAY FOAM

As several conference papers will attest, rigid foamers have achieved much success in replacing ozone-destroying CFCs with HCFCs, which have lower ozone-depletion potential (ODP). Now, they are feeling regulatory pressure to move from low-ODP HCFCs to zero-ODP HFCs or other alternatives. However, new research suggests HCFC blowing agents may be even more benign than previously thought.

It now looks as though atmospheric release of CFC or HCFC blowing agents from PUR foam insulation may be greatly overestimated. New studies on sprayed foams indicate that CFCs and HCFCs are absorbed in higher quantities into the foam's polymer matrix than was previously believed. According to George H. Sievert, manager of the SPI Polyurethane Foam Contractors Div., Washington, D.C., data on CFCs being dissolved into the walls of the foam were largely overlooked in earlier research. Until now, outward diffusion into the atmosphere was assumed to be the main factor in apparent loss of CFCs, he says. And new findings show the solubility of HCFCs into the polymer matrix to be far greater than that of CFCs. Better understanding of diffusion and solubility now shows that emissions of HCFCs from PUR foam is probably far less a problem than is presently perceived.

Dr. Mark Bomberg, a senior researcher at the Institute for Research in Construction, National Research Council of Canada, Ottawa, Ont., who conducted one of the new studies, says that emission depends on both the blowing agent's permeability and solubility characteristics. The higher the solubility, the more the blowing agent tends to stay within the polymer matrix. Both permeability and solubility must be measured to determine the diffusion of the blowing agent. Bomberg adds, "Findings of our much more complex approach to this issue leads us to believe that the half-life [or time for loss of half the blowing agent from the foam to the atmosphere] of CFCs and, more significantly, HCFCs in PUR foams is far longer than is currently believed. Based on our calculations, that half-life is 100 years or more, instead of 10 to 20 years." He and others hope the new research findings will have a potentially positive impact on how long the industry will be able to continue to use HCFCs in rigid foam products.