Degradation of Polyurethane Foam

Determination of 4,4/-methylenedianiline (5a) in hydrolyzed human urine may serve as a biomarker for exposure to methylenebis(4-phenyl isocyanate) produced on thermal degradation of polyurethane foam. The urine is hydrolyzed with H2SO4 and 4,4 -methylenedianiline (5a) is derivatized to the corresponding pentafluoropropionamide. 

Modesti, M. Lorenzetti, A. Recent trends in flame retardancy of polyurethane foams. In Progress in Polymer Degradation and Stability Research, Moeller, H.W., Ed. Nova Science Publisher New York, 2008 pp. 115-148. 

Mahoney et a/.87 have described the reaction of polyurethane foam and superheated water at 200 °C for 15 min, which leads to toluene diamines and polypropylene oxide. Hydrolysis of polyurethane and rubber mixtures has been used as a method not only of recovering valuable chemicals from the polyurethane fraction, but also to separate the polymers because rubber is inert to hydrolysis.89 The degradation takes place by contact with saturated steam at 200 °C for 12 h. This process may find particular applications in the treatment of rubber/polyurethane laminations. 

A good example of such a continuous moulding process that incorporates Foam Film technology is a system developed for the production of industrial vehicle carpets. These products are usually made out of a sandwich of two or more layers of different materials. Individually, they provide different features aesthetics and function (a textile carpet or a synthetic mat), sound deadening (a layer of polyurethane foam) and protective (a cheap layer to protect the foam from moisture and degradation). 

Antiscorch additives for the prevention of degradation in polyurethane foam... 

Zhu et al. studied polyurethane foams from soy reinforced with cellulose microfibers. They found an increase on the onset degradation temperature of the thermal degradation of polyurethane with the addition of 2 wt % cellulose fibers. They attributed this fact to the insulator effect of cellulose fibers [52]. Navarro-Baena et al. studied shape memory PU based on PLA-PCL-PLA block copolymer and reinforced with both CNCs and PLA grafted CNCs [72]. Aside the increment on the shape memory behavior of the polyurethane-based nanocomposites, they reported an increase on the thermal stability of the PU matrix in particular, they reported that, although CNCs improved the thermal stability of both PCL and PLEA blocks, in particular the thermal stability of the PCL block was improved in the nanocomposites increasing the maximum degradation temperature of about 40 with respect to the PCL block of the neat PU-matrix [72]. 

Borda J, Pasztor G and Zsuga M (2000) Glycolysis of polyurethane foams and elastomers, Polym Degrad Stabil 68 419-422. 

During the past year, several new studies have been published on -D-glucosidase IME systems that attempt to fulfill these process-relevant criteria. Immobilization of -D-glucosidase by attachment to polyurethane foam (40) has shown some promise as an economical IME system due to the support s resistance to enzymatic and microbial degradation, advantageous physical properties, and improved kinetics. However, the potential for fouling by particulate matter exhibited by foams renders these supports... 

Domingo et al. evaluated immobilization of trichloroethylene-degrading Burkholderia cepacia bacteria using hydrophilic polyurethane foam. The influences of several foam formulation parameters upon cell retention were examined. Surfactant type was a major determinant of retention a lecithin-based compound retained more cells than Pluronic- or silicone-based surfactants. 

Work at the EPA Gulf Breeze Laboratory has demonstrated the potential usefulness of encapsulation in the bioremediation of PAHs. A model system has been developed in which a pure culture capable of degrading fluoranthene (strain EPA505) has been successfully encapsulated in polyurethane foam and polyvinyl alcohol (Baker et al., 1988). The capsules can be stored for several months at 4 °C with only minimal loss of viability. Upon addition of the capsules to moist soil, fluoranthene mineralization commenced in approximately the same way as observed when fresh bacterial cells were added to the soil. These results are shown in Figure 5.7a. Since the same inoculation size was used in all flasks during this experiment, the results suggest that the immobilization process does not significantly affect microbial activity. 

Thermal degradation of foams is not different from that of the solid polymer, except in that the foam structure imparts superior thermal insulation properties, so that the decomposition of the foam will be slower than that of the solid polymer. Almost every plastic can be produced with a foam structure, but only a few are commercially significant. Of these flexible and rigid polyurethane (PU) foams, those which have urethane links in the polymer chain are the most important. The thermal decomposition products of PU will depend on its composition that can be chemically complex due to the wide range of starting materials and combinations, which can be used to produce them and their required properties. Basically, these involve the reaction between isocyanates, such as toluene 2,4- and 2,6-diisocyanate (TDI) or diphenylmethane 4,3-diisocyanate (MDI), and polyols. If the requirement is for greater heat stability and reduced brittleness, then MDI is favored over TDI. 

The first step of the degradation process, as shown in Figure 3.12, corresponds to the different magnitudes of the net heat flux imposed onto the material. A typical ignition plot is presented in Figure 3.13 for polyurethane foam. If the net heat flux is weak (i.e., for polyurethane foam <6 kW/m2... 

---