Cigarette filters: a benchmarking investigation of thermal and chemical attributes

Cellulose acetate (CA) has been extensively studied with minimal regard to end-of-life analysis. Cigarette filters predominantly comprise CA fibers and chemical additives for filtration and manufacturing, altering their physicochemical and thermal properties and influencing their interactions with the environment upon disposal. This research established and employed multifaceted analyses to determine the physicochemical and thermal properties of cellulose acetate sourced from unsmoked cigarette filters and pristine CA powder, including Fourier transform infrared spectroscopy (FTIR), optical and electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). FTIR analysis ascertained the structure of CA by resolving spectral peaks while pointing out the effects of additives, processing conditions, and the degree of substitution. An increase in the latter indicates reduced biodegradability and potentially longer persistence after disposal. The morphology was examined using electron and optical microscopies, revealing insights into FTIR results. TGA elucidated the decomposition response, evidencing moisture and volatile retention in the CA fibers extracted from unsmoked cigarette filters, suggesting unique decomposition behavior due to the reactivity of the additives with the surrounding environment. The thermal decomposition of unsmoked cigarette filters is insensitive to inter- and intra-filter variability. DSC analysis identified the thermal transitions of the CA fibers and powder, accentuating the effects of morphology, entanglements, and plasticizers on the structural stability of cellulose acetate. Our research establishes a baseline characterization of cigarette filters, laying the scientific foundations for further investigations into this pervasive pollutant.