Study On The Gratfed Starch With Amphoteric Branch As Sizing Agents

In tradition, many studies had been done on the copolymerization of starch with acrylicacid, acrylamide, acrylonitrile and methyl acrylate etc, zeta potentials of these starch graftcopolymers were negative in water, the same as the fibers. The same charge resulted inrepulsion at adhesive layer-fiber interfaces, and might reduce the adhesion strength to fibers.When positively charged branches were attached onto backbones of starch, the branches werein favour of increasing the adhesion strength to fibers for strong electrostatic forces generatedat adhesive layer-fiber interfaces, but the existence of electrostatic forces were not beneficialto desizing in the textile printing pretreatment process. To solve the contradiction betweenfiber bonding and desizing when grafting branch introduced only containing positively ornegatively charged, amphoteric grafting branch with the positive and negative chargessimultaneously might be introduced onto backbones of starch. Therefore, the starch graftcopolymer with amphoteric branch starch-g-P(DMC/AA) could be prepared via the graftcopolymerization of corn starch with2-methacryloyloxyethyltrimethyl ammonium chloride(DMC) and acrylic acid (AA) in aqueous medium using Fe2+-H2O2initiator. Then, the starchgraft copolymer was characterized with infrared spectroscopy (FT-IR), thermogravimetricanalysis (TG), X-ray diffraction (XRD), and influence of amphoteric grafting branchP(DMC/AA) upon the properties of starch as warp sizing agents were studied in terms of thestarch paste viscosity, ζ potential, surface tension, adhesion to fibers, desizing, tensilemechanical properties of starch films, time required to break the film in water andbiodegradability etc. In addition, effect of amphoteric grafting branch P(ATAC/AA) on theproperties of starch as warp sizing agents also were studied.To evaluate the impact of amphoteric grafting branches preferably, acid-thinned cornstarch (ATS), the starch graft copolymer with anionic branch starch-g-PAA, the starch graftcopolymer with cationic branch starch-g-PDMC or starch-g-PATAC were prepared as controlsamples during this paper. The investigation results showed that: amphoteric graftingbranches introduced were able to improve the thermal stability of starch, reduce thecrystallinity of starch film and the surface tension of starch cooked paste, significantlyimprove the viscosity of starch cooked paste and viscosity stability, increase the adhesion ofstarch to cotton fiber and polyester fiber, and the bonding strengths of starch to fibersincreased as the mole percentage of DMC or ATAC units in grafting branches rose, improvebreaking elongation and work-to-break, but lower tensile strength, effectively relieve thebrittleness and stiffness of starch films for toughing starch film, when compared with graftedbranch PAA, PDMC or PATAC, amphoteric grafting branches on the improvement of sizefilm was quite alike, and water solubility of starch film got better. Besides, ζ potential ofstarch cooked paste as mole percentage of DMC or ATAC units in grafting branches increased, so that desizing efficiency of starch declined gradually, that was to say desizing got worse.Considering on various factors, amphoteric grafting branches not only improved the adhesionof starch to fibers, but also effectively improved the tensile mechanical properties of starchfilm, meanwhile solved the problem of grafted starch with positively charged branches weredifficult to desizing when the mole percentage of DMC or ATAC units in grafting brancheswas46.1%or46.8%.