Auxetic materials have negative Poisson ratio which has a multiple ranges of functional applications. The helical auxetic yarn was successfully developed through direct twist system by using core and wrap yarn or filament, which shows Auxeticity when the HAY is stretched in longitudinal direction in response it expand in transverse direction, Helical Auxetic Yarns were developed using various parameters of the core and warp filament, these parameters are wrapping angle (Twist per meter), diameter ratio, and modulus ratio. The strength of Helical yarn was characterized using single yarn strength and Image J software was used for the calculation of poisson’s ratio. According to test results, it is concluded that the core filament of helical auxetic yarn increased its thickness in transverse direction under stress, and a considerable negative poisson’s ratio was calculated. The values of negative poisson’s ratio described that the auxeticity had a direct relation with core filament thickness or diameter and inversely proportional to the linear density of wrap filament, in case of the wrap angle the auxeticity of HAY yarn had an inverse effect with wrap angle. Kevlar/polypropylene combination sample showed maximum auxeticity at a 15-degree angle while Kevlar/nylon combination sample showed minimum auxeticity at a 25-degree wrap angle.
Purpose
This study aims to evaluate the dyeing of the p-aramid fibre with cationic dyes and investigate the effect of dyeing in the protection of the fibre from ultraviolet (UV) light.
Design/methodology/approach
P-aramid fabric has been dyed with cationic dyes using benzyl alcohol as swelling agent to promote the penetration of dye molecules into the fibre. The fabrics were evaluated against colour strength (K/S) value and colour fastness properties after dyed with cationic dyes using full factorial design. This design was used to study the effect of factors that affect the response variables as well as to study the interactions among the factors on response variable. The bursting strength, scanning electron microscopy analysis and X-ray diffraction analysis of undyed and dyed p-aramid fabric were performed before and after exposure to UV light to investigate the changes in mechanical behaviour.
Findings
The results show that the p-aramid fabric dyed with cationic dyes has good K/S values and good fastness properties. The exposure of undyed p-aramid fabric to UV light causes serious loss in strength over short duration i.e. 40 h. Dyeing of p-aramid fabric enhances the resistance to UV light which reduces the loss in strength.
Originality/value
Most of the work is patented and no one has done the process optimization for the industry, so this study offers promising outcomes concerning the dyeing of p-aramid fabric with enhanced shade depth and good colour fastness characteristics.
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