Kreyenschmidt, Martin
We present a new method for investigating the oxidation and emission behavior of air-permeable materials.
Employing this method, a differentiated statement can be made about the extent to which critical volatile organic
compounds (VOCs) such as formaldehyde, acetaldehyde, and acrolein are contained in the material as impurities or
formed by thermo-oxidative degradation of the polymer matrix in the use phase. The parameters affecting methods
of VOC analysis are reviewed and considered for the developed method. The molecular mechanisms of VOC formation
are discussed. Toxicological implications of the reaction kinetics are put into context with international
guidelines and threshold levels. This new method enables manufacturers of cellular materials not only to determine
the oxidative stability of their products but also to optimize them specifically for higher durability.
Environmental Implication: Cellular materials are ubiquitous in the technosphere. They play a crucial role in
various microenvironments such as automotive interiors, building insulation, and cushioning. These materials
are susceptible to oxidative breakdown, leading to the release of formaldehyde, acetaldehyde, and acrolein. The
ecotoxicological profiles of these compounds necessitate monitoring and regulation. The absence of reproducible
and reliable analytical methods restricts research and development aimed at risk assessment and mitigation. This
work significantly enhances the toolbox for optimizing the oxidative stability of any open-cell cellular material
and evaluating these materials in terms of their temperature-dependent oxidation and emission behavior.
Polyurethane (PUR) soft foams release malodorous and potentially toxic compounds
when exposed to oxidative conditions. Current chamber test methods cannot distinguish between
pre-existing volatiles and those formed during oxidation, nor can they assess the formation rates
of oxidation products. We subjected PUR soft foam to oxidative treatment in a continuous air
flow at 120 ◦C. Emissions were convectively transferred from the foam to an exhaust port and
analyzed using a thermodesorption–gas chromatography–mass spectrometry (TD-GC-MS) system,
with external calibration employed for the quantification of selected analytes. The study identified
hydroperoxide formation and degradation as key mechanisms in the breakdown of the polyether soft
segments. This process predominantly produces volatiles, such as carboxylic acids, formates, acetates,
alpha-hydroxy-ketones, (unsaturated) aldehydes, substituted dioxolanes and dioxanes, glycols,
and allyl ethers. Volatiles associated with the degradation of the hard segments include aniline,
benzoxazole, 2-methylbenzoxazole, and benzaldehyde. This experimental setup enables reproducible
qualitative and quantitative analysis of volatiles formed during the oxidative degradation of PUR
soft foams, providing new insights into the segment-dependent chemical pathways of the polymer’s
molecular breakdown.
VOC EMISSIONS FROM PARTICLE FILTERING HALF MASKS – METHODS, RISKS AND NEED FOR FURTHER ACTION
(2021)
Investigations into volatile organic compound (VOC) emissions from polymer fleeces used in particle filtering
half masks were conducted and evaluated against the German hygienic guide value for total volatile organic com-
pounds and the “Lowest Concentration of Interest” for construction products. All masks showed emission of Xy-
lene. In 94 % of samples, up to 24 additional aromatic compounds were found. 17 % of samples showed terpenes,
53 % emitted aldehydes, 77 % exhibited caprolactam and 98 % released siloxanes. All masks exceeded the TVOC
hygienic guidance value level 5 of 10 mg/m³. Emission levels were investigated for masks immediately after their
packages were opened and for masks that were “vented” for two weeks. Further, the emissions were repeatedly
measured to investigate the decrease of emissions. An exponential decline was observed and a fitting function was
calculated. The influence of the two commonly gas chromatograph (GC) hyphenated detectors, mass spectrometer
(MS) and flame ionization detector (FID) on the VOC quantification, as well as the influence of temperature on
the emission of VOCs were investigated. A statistical analysis of emission value differences for Notified Bodies
was conducted and CE 2163 and 2020-1XG proved to be outliers.
A new approach to determine the elements carbon, hydrogen, nitrogen and oxygen (CHNO) in polymers by wavelength-dispersive X-ray fluorescence analysis (WDXRF) in combination with partial least squares (PLS) regression was explored. The quantification of CHNO was achieved by using the Rayleigh and Compton scattering spectra of an Rh X-ray tube from 84 different polymers. Concealed differences of the corresponding scattering spectra could be utilized to quantify CHNO in a multivariate manner. It was shown that the developed model was capable of determining these commonly non-measurable matrix elements in polymers using WDXRF. Furthermore, the influence of spectral resolution, which is given by the collimator and the crystal, on the prediction of CHNO was explored in this study. It was found that minimal spectral resolution led to the most accurate CHNO predictions. Information about matrix composition could be used to improve so-called semi-quantitative XRF methods based on fundamental parameters (FP) for the analysis of plastics, soil or other samples with high organic content.
Background
During shortages of filtering face pieces (FFP) in a pandemic, it is necessary to implement a method for safe reuse or extended use. Our aim was to develop a simple, inexpensive and ecological method for decontamination of disposable FFPs that preserves filtration efficiency and material integrity.