Acetylation of cotton knitted fabrics for improved quick drying after water absorption

Abstract Quick drying after water or sweat absorption is an important function of underwear. In this study, the hydroxy groups of cotton knitted fabrics (CFs) were partially acetylated, maintaining the original fabric structure. The following three heterogeneous acetylation processes were used: Ac-I (Ac 2 O/H 2 SO 4 /toluene), Ac-II (Ac 2 O/H 2 SO 4 /AcOH/water), and Ac-III (Ac 2 O/AcONa) systems (Ac 2 O, acetic anhydride; AcOH, acetic acid; AcONa, sodium acetate). Acetylated cotton knitted fabrics (AcCFs) with degree of substitution ( DS ) ≤ 0.5 and yields of > 80% were prepared. AcCFs prepared with the Ac-III system gave high degree of polymerization ( DP ) values of > 1500, whereas those prepared with the Ac-II system exhibited low DP values of ≤ 400. The moisture contents of AcCFs at 20 °C and 65% relative humidity decreased from 7.1 to 4.7% with increasing DS value up to 0.46; introducing hydrophobic acetyl groups into the CFs decreased their hydrophilic nature. Quick drying similar to that of a polyester fabric was achieved for some of the AcCFs with DS values of < 0.2. When the acetyl groups in the AcCFs were homogeneously distributed across each fiber width (achieved for AcCFs prepared with the Ac-II system), quick drying was evident in the AcCFs. The crystallinities and crystal widths of cellulose I for the AcCFs with DS values of ≤ 0.28 were almost unchanged compared with those of the original CFs. However, neither the crystallinities nor crystal widths of cellulose I were directly related to quick drying after water absorption. Thermal degradation of the AcCFs varied between the acetylation systems, and depended on the DP values and/or the presence of sulfate ester groups in the AcCFs. Graphical Abstract