Creep and recovery of cellulose acetate microfiber bundles

Polymer microfibers are ubiquitous in modern industry, with applications ranging from textiles and filtration to environmental protection and healthcare. However, their widespread use also contributes significantly to microplastic pollution. Cigarette filters, composed of cellulose acetate microfibers (CA-μFs), are a particularly concerning source, with an estimated 4 trillion or more smoked cigarettes littered annually, presenting an opportune material testbed for mechanical characterization. This study investigates the time-dependent mechanical behavior of CA-μFs extracted from pristine and smoked cigarette filters, characterizing their creep and recovery responses under constant stress and temperature conditions. Specifically, dynamic mechanical analysis (DMA) was employed to measure the viscoelastic response at 2 MPa (within the elastic regime) and 4 MPa (after the elastic–plastic transition), as well as at 30 °C, 40 °C, and 50 °C (representing a range of environmentally relevant temperatures). A six-parameter generalized viscoelastic model was fitted to the creep-strain data, while a Prony series representation was used to capture the shear creep modulus. Scanning electron microscopy (SEM) was used to characterize the morphology of the CA-μFs before processing, after processing, and posttesting, allowing for observation of individual microfiber responses under different loading conditions. The resolved deformed geometries of CA-μFs obtained from finite-element analysis (FEA) coincided with the physically observed deformation characteristics, further elucidating the mechanical response. This research establishes a fundamental understanding of CA-μF behavior, isolating the effects of temperature, stress, and smoking on the creep and recovery properties. This work lays the groundwork for future studies to leverage the mechanical response of CA-μFs for upcycling.