Lieve Van Landuyt

Moisture sorption in developing cotton fibers

The moisture sorption behavior of developing cotton fibers is studied by dynamic vapor sorption. Mature fibers show a typical sigmoidal isotherm, IUPAC type II, describing the adsorption on macroporous and non-porous adsorbents with a typical hysteresis. This is different from the type III isotherms exhibited by elongating fibers explained by the weak adsorbate–adsorbent interactions. The maximum sorption capacity clearly decreases throughout the cotton fiber development. This decrease is very rapid during the elongation phase of the fibers, but declines beyond 25 days post anthesis (DPA). This transition corresponds to the time point where the secondary cell wall becomes dominant over the primary cell wall, as confirmed with FT-IR. Also only little moisture hysteresis appeared during the elongation phase whereas from 25 DPA onwards a distinct hysteresis is observed that remains almost constant until maturation of the fiber. The study clearly elucidates the sorption mechanism during the elongation phase of the fiber to be different from the one during the secondary cell wall synthesis. This improved understanding of the cotton sorption behavior is important for optimal application of cotton fiber in novel materials.

The effect of water immersion on the thermal degradation of cotton fibers

The decomposition behavior of cotton fibers is examined using thermogravimetric analysis. The effect of the test parameters on the thermal degradation of raw cotton fibers is determined. Focus is given to the influence of water immersion on the thermal behavior of cotton fibers. For less mature fibers a clear difference is noted between the degradation profiles of the water-immersed and untreated samples. On the contrary, only a small change is noted on the degradation profile for more mature fibers after water immersion. The maturity and variations in water-soluble content of the fiber are found to be important factors influencing the thermal behavior of raw cotton fibers. Inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to underpin the effect of water immersion on cotton fibers. This improved understanding for the role of maturity and water soluble constituents in thermal degradation of cotton fibers may lead to develop routes that improve thermal stability and smoldering characteristics of cotton fibers as relevant for future applications.