Investigation On Chemical-enzyme Modification And Yarn Spinning Technology Of Jute Fibres For Textile Use

The fibrics made from natural cellulose fibre have good wearability and properties such as biodegradable,renewable,eco-friendly,and sustainable.The cellulose fibre will have a bright prospects in the future.The supply of the cotton fibre can not meet the needs of textile industry in China.The output of cotton fibre can not be increased largely due to the restriction of the plantation and planting condition.Therefore,more and more novel natural cellulose fibres have been developed.Jute fibre which occupies the second place to cotton in the output has many advantages such as high output,low price,good mechanical properties,excellent moisture absorption and antibacterial properties.However,it is difficult for the jute fibres to be spun into the finer yarns because the jute also has a few undesirable properties,such as stiffness, harshness and there are no turns on the fibre.Therefore,the jute fibre can not be used for clothes.Based on the investigations of the previous researchers,chemical and enzyme treatment was the most promising method for degumming the jute fibre.For the chemical treatment,the effect on jute fibre properties by sodium hydroxide concentration,sodium sulfite concentration,treatment time,treatment temperature and liquor ratio was studied in detail.For the enzyme treatment,the concentration of enzyme,treatment time and treatment temperature were optimized by using of an orthogonal experimental design.The chemical composition and crystallinity index of jute fibre were also investigated in this paper,the results show that most of the hemicellulose and part of lignin in jute fibre was removed by the chemical treatment. The lignin content was removed further after the laccase treatment.The crystallinity index of jute fibre was increased after chemical and enzyme treatment.After the chemical and enzyme treatment,jute fibres also show prominent stiffness and harshness properties,which offer hindrance to its smooth,truble-free spinning for web and yarn making.So,jute fibre is essentially conditioned for easy spinning modification by adding oil and water.The mechanism on softness of jute fibre by silicone oil treated at 300 g/L and 25 g/L was studied by using of SEM,FTIR and fibre friction coefficient testing.The results show that for the case of 25 g/L,the macromolecule of silicone oil was only on the surface of the fibre.For the case of 300 g/L,the surface of jute fibre was covered by the thick macromolecule of silicone oil and the macromolecule of silicone oil penetrated the inner structure of jute fibre. Therefore,the dynamic and static friction coefficient of jute fibre decreased after treatment at 300 g/L which results in increasing of the softness of jute fibreThe breaking strength of compact jute/cotton yarns was slightly higher than the corresponding traditional ring blended yarns.Whereas,the breaking strain of compact jute/cotton yarns was obviously higher than the corresponding traditional ring yarns. The compact blended yarns have lower irregularities,less thin places,and smaller the number of thick places than that of traditional ring blended yarns.When there were more than 50%jute fibres in the blend,the roving could not be spun into yarn on the compact spinning frame because the perforated lattice apron is not suitable for the jute fibre.Therefore,the blended yarns with jute proportion from 30%to 70%were spun by the traditional ring spinning technology and the relationship between breaking strength and gauge length was predicted by Weibull distribution.The results show that the J70/C30 yarn decreases more sharply than the other yarns because there are more weak points in J70/C30 yarn than of the others.The tensile behaviour of the yarn at different gauge lengths is very important for practices such as warping,sizing, beaming,and weaving.So it is crucial to reduce the number of thin places in the jute/cotton blended yarns.The two-parameter Weibull distribution does not always adequately describe the experimental bast fibre strength at different gauge lengths.For this reason,it was modified by incorporating the diameter variation(Weibull parameterγ) of jute fibres in this paper.The results show that the Weibull parameterγwas equal to 0.3474 according to the slope of liner regression between ln(Coefficient of variations of fibre diameter) and ln(gauge length).The modified Weibull distribution for jute fibre can be written as(?)=σ₀(L/L₀)^γ/mΓ(1+1/m),where m is Weibull modulus,σ₀ is the characteristic strength,L is gauge length,L₀=1 mm,Γis the gamma function.The breaking strength of jute fibre at 2 mm,3 mm,and 4 mm gauge lengths can be predicted by the modified Weibull distribution more accurately than that of two-parameter Weibull distribution.The investigation of scale effect on jute and cotton fibre indicated that both of the breaking strength and breaking strain of cotton fibre were fit to the two-parameter Weibull distribution.The cotton fibre is so-called classical Weibull fibre.Based on the modified Weibull distribution for jute fibre,the breaking strength of jute/cotton yarn can be given by:σ_y=(V_j+V_C(E_C/E_J))σ_0J(l_cJ^?m_J)^-1/mJ exp(-1/m_J)cos²Î¸' where V_J and V_C were fibre volume fraction for jute and cotton,E_J and E_C were fibre tensile modulus for jute and cotton,σ_0J and l_cJ were characteristic strength for jute and cotton,m_J was the Weibull modulus for jute fibre,andθ' was helix angle of the fibre at the time of yarn failure.The results show that the breaking strength of jute/cotton blended yarn is determined by the level of L_f/l_c ratio:the breaking strength of jute/cotton blended yarn increases with the increasing of the value of L_f/l_c.There is a good linearity between ln(breaking strain of jute fibre) and ln(gauge length),therefore the critical length(l_c) can be obtained byε_f =8.5634·l_c^-0.4343,where is the breaking strain of jute fibre in the blended yarn.The critical length of jute fibre increases as more jute fibres are added in the blended yarn and the critical length of jute fibre decreases with the increasing of gauge length.However,in practice,the value of L_f/l_c decreases because the increasing of thin places and CV value of the blended yarn when more jute fibre are added in the blended yarn.