| Starch has been widely used in the field of warp sizing because of its good reproducibility,abundant resource and low price.However,the large number of cyclic structures and hydroxyl groups in the starch molecular chain make it have some inherent disadvantages,such as insufficient adhesion to fibers,strong film brittleness,easy rupture and detachment of the film from the yarn surface,which cannot meet the requirement of warp sizing well.Therefore,in order to improve the application of starch sizing agent in the field of textile warp sizing,the present work is designed to introduce hydrophilic 3-（trimethylammonium chloride）-2-hydroxypropyl（TMACHP）and butyrylate groups into the starch chain,and to prepare a series of quaternized-butyrylated starch（QBS）with a fixed quaternization level and increased butyrylation levels.The effects of amphiphilic modification on the starch paste properties,adhesion and film properties were investigated.The results showed that under the fixed mass（9.25g）of cationic reagent,the total degrees of substitution of the prepared QBS increased from 0.029 to 0.078 as the amounts of butyric anhydride gradually increased from 1g to 13g;with the increase in the total degree of substitution,the apparent viscosity and viscosity stability of QBS paste gradually decreased,but the viscosity stability was above 85%,which could meet the requirement of warp sizing and was higher than the acid-thinned starch（ATS）paste;compared with ATS,QBS had significantly improved adhesion to polyester and cotton fibers,as well as the elongation at break of the film.However,the tensile strength of the film was decreased,indicating that this amphiphilic modification could not only significantly improve the adhesion of starch to both fibers,but also reduce the brittleness of starch film;as the total degree of substitution increased,the adhesion and elongation at break gradually increased,while the tensile strength decreased.Secondly,the use of nano-SiO2 in the starch sizing agent can promote its sizing properties,but nano-SiO2 is prone to agglomeration and cannot better reflect its special properties.In this study,acrylic acid（AA）was used as the grafting monomer and butyric anhydride was used as the esterifying agent to chemically modify the nano-SiO2,and AA grafted SiO2（SiO2-g-PAA）and butyrylated SiO2 were prepared,which were then blended with QBS,respectively.The effects of different modification methods and different amounts of the modified nano-SiO2on the paste properties and film properties of the blends were explored to clarify the effects of different modification methods and amounts on the the above properties.It was found that the water-dispersibility of SiO2-g-PAA and butyrylated SiO2 were improved significantly;the viscosity stability of SiO2-g-PAA/QBS blended paste was maintained at a high level as the amounts of nano-SiO2,SiO2-g-PAA and butyrylated SiO2 were increased from 0%to 1%;as the amounts were increased from0%to 1%,the bonding strengths of three blended pastes to polyester and cotton fibers and the breaking elongations of the three blended films gradually increased and the film strengths were gradually decreased.And as the amount was continued to increase,the bonding strengths and film elongation decreased and the strength increased.In the terms of adhesion and elongation at break,SiO2-g-PAA/QBS was higher than the other two species,and the bonding strengths of SiO2-g-PAA/QBS to both fibers and its film elongation reached the maximum values as the amount was 1%.It was shown that the water-dispersibility of nano-SiO2 could be improved by chemical modification to further enhance the properties of QBS,and the most significant improvement in the sizing properties of the QBS was shown as the amount of SiO2-g-PAA was 1%.Thirdly,based on the above study,a series of SiO2-g-PAA samples with different grafting ratios were prepared by the graft polymerization between nano-SiO2 and AA monomer,and as its amount was 1%,the effect of grafting ratio of SiO2-g-PAA on the sizing performance of QBS paste was investigated.It was found that the apparent viscosity of the SiO2-g-PAA/QBS blended paste and its viscosity stability,bonding strengths to both fibers,and film elongation were gradually increased with the increase in the grafting ratio,whereas the tensile strength was gradually decreased,indicating that the increase of the grafting ratio was beneficial to enhance the bonding strengths to both fibers and reduce the brittleness of the blended film.Finally,based on the above study,SiO2-g-PAA with a grafting ratio of 14.3%and 1%dosage to the mass of QBS was chosen in this part to investigate the sizing quality of the blended paste on the cotton yarns and polyester/cotton blended yarns in comparison withthe ATS,QBS and nano-SiO2/QBS to reveal the enhancement of the combination between SiO2-g-PAA and quaternization-butyrylation on the sizing quality of the two warp yarns.It was found that compared with ATS,QBS and nano-SiO2/QBS,the sizing of SiO2-g-PAA/QBS paste had 28.6%increase in the tensile strength,21.4%loss in the elongation,82.5%abrasion resistance and 82.1%decrease in the hairiness for polyester/cotton blended warp,and 23.1%increase in the tensile strength,10.9%loss in the elongation,76.7%abrasion resistance and 86.7%decrease in the hairiness for cotton warp.The sizing properties of polyester/cotton blended warp and cotton warp were improved.It could be concluded that the combination of modified nano-SiO2 with quaternization-butyrylation was more favorable to promote the sizing properties of starch. |
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