Towards Sustainable Textiles: Microplastics, Coffee, and Closing the Loop

Abstract

It is increasingly becoming clear that the way textiles are currently produced and consumed can be unsustainable and negatively impact human and environmental health. In this study both textile production, sourcing, and use-phase related pollution were considered. In the first section of this dissertation, microplastic (MP) pollution is investigated using pressure-sensitive adhesive (PSA)-coated substrates as adsorbents. In the following two sections, coffee fruit (cascara) waste is assessed as a raw material for human-made cellulosic-fibers using ionic liquid (IL) solvents.

PSAs were identified as an effective adsorbent for MPs under aqueous conditions.To better explore PSA-MP interactions, simple glass-slide substrates were made to allow rapid optical quantification. Three formulations of poly(2-ethylhexyl acrylate) PSA were considered including 92k molecular weight (MW), 950k MW, and a 50:50 wt% bimodal distribution (BD) of the 92k and 950k. The BD yielded the most robust adhesive films after 30 min under aqueous shaking conditions while 92k and 950k films degraded after 1 and 5 min respectively. The BD samples captured 50% more nylon particles than the 950k, with maximum slide coverage achieving 25% after 30 min shaking. The broad effectiveness of PSA-based capture was demonstrated through an assessment of 10 aqueous conditions including solid, chemical, and temperature modifications. Although capture was suppressed under all non-deionized water conditions, capture remained viable except at 0.1% w/v surfactant loadings. Finally, a comparison of five MP species of different size revealed an inherent bias to MP quantification. It was found that number counts of particles bias towards smaller particles and size based assessment biases towards larger particles. I propose that future MP reporting should present both count and size based quantification to control for this bias.

ILs are expected to be greener and safer biomass solvents than more conventional fiber-making systems like the viscose and lyocell processes. In conventional fiber processes and most current IL research, purified cellulose is the primary feedstock, which requires caustic alkaline or acidic treatments for isolation. Herein, the IL, Diazabicyclo[5.4.0]undec-7-inium acetate ([DBUH][OAc]) was assessed for the dissolution and shaping of unrefined lignocellulosic biomass.

Unrefined cascara waste was investigated as a feedstock for dissolution in [DBUH][OAc] compared to cotton. Cascara is a high-volume agriculture waste that has heavy economic, environmental, and health burdens associated with disposal in producer countries. Unrefined cascara was partially soluble in [DBUH][OAc] (65% w/w), yielding a high viscosity, cellulose-rich solution that can be shaped and re-coagulated into fibers and films. Following, three pretreatments were assessed including ethanol extraction, dilute IL treatment (10% water), and an acid chlorite treatment. All pretreatments increased cascara solubility in [DBUH][OAc] (>75% w/w). 10% solutions of treated cascara were extruded into long fibers (>40 cm) with irregular, lobed cross-sections. Treated cascara fibers were qualitatively more robust than untreated cascara fibers. Ethanol treated fibers performed similarly to those treated with acid chlorite, showing promise that less harsh pretreatments of biomass may be sufficient for some applications. Overall, the cascara work suggests that complex biomass sources from agriculture waste may be viable for synthetic cellulose fibers.