Emission and time-resolved migration rates of aromatic diamines from two flexible polyurethane foams

Abstract

Performing risk assessments (RA) on household use of flexible polyurethane (PU) foams requires access to reliable data about emission and migration of potential diamine impurities. A toluene diisocyanate (TDI) and a methylene diphenyl diisocyanate (MDI) based foam were thermally treated to enable measurements on samples with defined concentrations of the corresponding diamines, toluene diamine (TDA), and methylene dianiline (MDA). The thermally treated foams used for emission testing contained up to 15 mg.kg−1 of TDA and 27 mg.kg−1 of MDA. Those used for migration testing contained 5.1 mg.kg−1 of TDA and 14.1 mg.kg−1 of MDA. Stability of the thermally generated diamines was sufficient for testing over a 37-day period. Analytical techniques that did not decompose the polymer matrix were applied. Emission rates for TDA and MDA isomers were less than the limit of quantitation (LOQ) of 0.008–0.07 μg.m−2.h−1. Migration was studied using samples of the same thermally treated foams over a 35-day period. Quantifiable migration of MDA from the MDI-based foam was only observed on Days 1 and 2. From Day 3 onward, migration rates were less than the LOQ. Quantifiable migration of TDA from the TDI-based foam rapidly decreased with time and was only observed on Days 1 thru 3. From Day 4 onward, migration rates were less than the LOQ. Theoretically, the migration rate should be inversely proportional to the square root of time (t) as t−0.5. This relationship was confirmed by the experimental data and enables extrapolating migration values to more extended time periods to conduct RAs.

Risk assessment—based verification of the CertiPURTM limit values for toluene diamine and methylene dianiline in flexible polyurethane foam

“…The respective aggregate LOQ were 1.7 μg.m −2 .d −1 for each of the TDA-isomers and 3.4 μg.m −2 .d −1 for ΣMDA 1 . Migration rates matched with a theoretical model based on Fick’s diffusion law ( Karlsson et al, 2023 ; OECD, 2009 ), whereby migration rates were linear in the initial concentration of the substance and evolved with the inverse square root of time (t −0.5 ). This theoretical basis allowed for a well-founded extrapolation of the experimental data to the anticipated period of use of a mattress.…”

“…The results of Karlsson et al (2023) showed that migration occurred primarily during Day 1 and that little to no replenishment of TDA and MDA from the interior to the surface of the foam took place. Average daily migration rates were calculated as shown in Table 1 .…”

“…To link the emission (inhalation) and migration (dermal) exposure potentials with the CertiPUR TM quality limit ( EUROPUR, 2021 ), data are required from foams that have defined concentrations of TDA or MDA. This exposure assessment made use of the consistent set of emission and migration data generated by Karlsson et al (2023) .…”

“…This limit was based on risk assessment (RA) work done in the early 2000s. Analytical methodology has been developed that enables establishing relationships between the diamines content and emission and migration rates from PUF ( Karlsson, 2023 ; Karlsson et al, 2023 ).…”

Sampling chamber with minimal wall surface for simultaneous emission testing of diisocyanates and diamines from polyurethane products

“…The limit of quantification (LOQ) was defined as the lowest calibration point for all analytes. By lowering the calibration range, the LOQs could be lowered further to 0.3 ng for the diisocyanates and 2,4-TDA, and to 1 ng for 2,6-TDA and MDA ( Karlsson et al, 2022a , 2022b ).…”