Research On The Preparation Of Amphiphilic Grafted Starch Sizing Agent And Its Application

Starch as an abundant glucose-based polymer with good reproducibility,biodegradability and low cost,has been widely used in warp sizing.However,the defects in the molecular structure of starch(many hydroxyl groups and cyclic structure)make it present insufficient adhesion to fibers and brittle film,which severely limits its application in the textile sizing.In order to improve the usability of starch size in warp sizing,this paper firstly prepared starch-g-poly(sodium allyl sulfonate-co-ethyl acrylate)(S-g-P(SAS-co-EA))with different grafting ratios by simultaneous graft polymerization of acid-thinned starch(ATS)with sodium allyl sulfonate(SAS)and ethyl acrylate(EA)as grafting monomers at a fixed molar ratio of 75:25 and a varied total amount,under the Fenton’s initiation system.The samples were characterized,and the effect of the graft polymerization on the sizing properties of starch was evaluated.It was found that,compared with ATS paste,S-g-P(SAS-co-EA)paste showed a lower surface tension,better adhesion to cotton and polyester fibers,higher viscosity stability,and greater film properties.With the increase in the grafting ratio,the adhesion,bending endurance and elongation at break of S-g-P(SAS-co-EA)film gradually increased,and the surface tension and tensile strength gradually decreased.These results indicated that the comprehensive performance of S-g-P(SAS-co-EA)obtained by grafting modification was improved compared with that of unmodified starch.Secondly,poly(allyl sulfonic acid)-g-starch-g-poly(ethyl acrylate)(PSAS-g-S-g-PEA)with different grafting ratios were prepared by a two-step grafting method under the same reaction conditions and monomer amount,and their structures were characterized.The different effects of the two-step graft polymerization and one-step graft polymerization on the sizing properties of starch were investigated by the S-g-P(SAS-co-EA)as a control sample.Under the similar grafting ratio,compared with S-g-P(SAS-co-EA),the adhesion of PSAS-g-S-g-PEA paste to cotton and polyester fibers,bending endurance and elongation at break of the PSAS-g-S-g-PEA film were higher,whereas the surface tension of PSAS-g-S-g-PEA paste and tensile strength of the PSAS-g-S-g-PEA film were lower.These results demonstrated the superiority of two-step grafting in these properties.With the increases in the total grafting ratios,the viscosity stabilities of PSAS-g-S-g-PEA pastes increased from 85.7% to 95.5%,their surface tensions decreased from 52.1 mN/m to 46.5 mN/m,and the film properties and adhesion-to-both fibers of PSAS-g-S-g-PEA samples were significantly improved.Thirdly,to further improve the sizing properties of starch,the anionic grafting monomer SAS was replaced with the cationic grafting monomer N,N-dimethylacrylamide(DMAA),and the PDMAA-g-S-g-PEA samples with a grafting ratio range from 2.63% to 10.80% were prepared by the above two-step method.The PSAS-g-S-g-PEA with a grafting ratio of 10.95% was used as the comparison sample for revealing if the PDMAA-g-S-g-PEA could further enhance the sizing properties of starch.And the influence of total grafting ratio on the sizing properties of PDMAA-g-S-g-PEA was investigated.The results showed that,under the similar grafting ratio,the PDMAA-g-S-g-PEA showed lower surface tension,improved viscosity stability,increased elongation at break and bending endurance of the film,smaller film strength and crystallinity,and enhanced desizability compared with PSAS-g-S-g-PEA(grafting ratio = 10.95%).In summary,the comprehensive properties of PDMAA-g-S-g-PEA were more excellent.As the total grafting ratios increased from 2.63% to 10.80%,the sizing properties of PDMAA-g-S-g-PEA samples were significantly improved.It is recommended to use the PDMAA-g-S-g-PEA with a total grafting ratio of 10.80% for the next research of warp sizing.Finally,based on the above study,PDMAA-g-S-g-PEA with a total grafting ratio of 10.8% was selected to blend with PVA1799 at the blending ratios of 0:100,50:50,60:40,70:30,80:20,90:10 and 100:0,respectively.Their sizing experiments to polyester/cotton warp yarns were conducted to investigate the differences in the sizing quality of polyester/cotton blended yarns affected by the blending ratios.The results showed that as the blending ratio of PVA1799 increased,the tensile strength,great elongation,high abrasion resistance,and lower hairiness.increased,and when the blending ratio was 70:30,the tensile strength,great elongation,high abrasion resistance,and lower hairiness rate of polyester/cotton warp yarn were close to those of pure PVA1799(0:100),Comprehensively considering the factors such as sizing properties and product cost,the size formula with a 70:30 blending ratio of PDMAA-g-S-g-PEA : PVA1799 was recommended for the sizing of polyester/cotton blended warps,fulfilling a good substitution to PVA1799.