Effects of chemical modifications such as mercerization (with and without stretch) and crosslinking (with HCHO and DMDHEU of various concentrations) on mechanical properties such as dynamic (sonic) modulus, immediate elastic recovery (IER), work recovery (WR), and crease recovery angle (CRA) of yam samples were studied. While slack mercerization reduced the dynamic modulus and the recovery parameters, stretch during mercerization brought about a profound increase in their values. The dynamic modulus and recovery parameters also increased progressively with the severity of crosslinking in HCHO and DMDHEU. A high degree of linear correlation existed between the dynamic modulus and IER, WR, and CRA for samples treated with a given reagent; however these relationships were specific to the reagent.Tensile recovery parameters such as immediate elastic recovery (IER), delayed recovery (DR), and work recovery (WR) of fibers are known to control the bending recovery of yams and the crease recovery of fabrics. Several papers [3,4,5,7,8,11 ] have discussed the relationship between tensile recovery and bending recovery of various textile materials. The dynamic modulus determined by the sonic technique is also known to be associated with immediate elastic deformation representing the recoverable component, while the static modulus is influenced by the plastic component involving the time-dependant recoverable deformation [ 16]. The sonic modulus could then be expected to show a relationship with the tensile recovery and bending recovery characteristics of yams. A recent study [10] has shown that considerable changes occur in the sonic modulus of cotton yams as a result of treatments like mercerization and crosslinking. In this study, we investigated the relationship of sonic modulus with tensile recovery parameters (IER and WR) and with crease recovery angle (CRA) for a sample of cotton yam subjected to mercerization, crosslinking in formaldehyde (HCHO), and crosslinking in dimethylol/ dihydroxyethyleneurea (DMDHEU), as well as for a set of yams spun-from different varieties of cotton.
Experimental Procedure
MERCERIZATIONThe study covered both raw and chemically modified cotton yam samples. The former comprised six yam samples covering a wide range of counts (from 6s to 120s). For chemical treatments, we chose one of these samples, 30s yam spun from L 147 cotton. Dewaxed and kier-boiled yam from this sample formed the control material for the treatments. For slack mercerization, the leas prepared from the control sample were immersed in NaOH 24% (w/w) for 30 minutes, washed with hot water, soured with 1 gb acetic acid, and finally thoroughly washed with water at room temperature and dried in room atmosphere. This sample is designated as DKMs. For stretch mercerization, leas already soaked in the alkali for 30 minutes were stretched to the desired level and washed in the stretched state.The sequence for washing was the same as for slack mercerization. Three different stretch levels were used: to 92% of the original length , to...