Study On Modified Starch Adhesive Prepared By Oxidation And Grafting

Starch adhesive is widely used in corrugated case manufacture, packaging, wood composite products and textiles industry because of its low price, numerous sources, green, biodegradable, etc. Gelatinized starch used as adhesive directly has several obvious disadvantages, such as high viscosity, low bond strength, poor liquidity and film forming ability. These shortcomings of starch adhesive lead to a limited range of application fields, which have relatively low requirements on the performance of the adhesive. This paper was mainly to improve the viscosity and bonding strength of starch adhesive. Firstly oxidation on starch led to degradation to reduce its viscosity and improve the flowability. And then grafting on oxidized starch was to improve bonding strength of starch adhesive.First of all, starch was oxidized through using sodium hypochlorite (NaClO) as oxidizing agent by two-step method which meant a process of semi-oxidized, gelatinization and deeply oxidized, preparing oxidized starch latex. And the oxidation experiment was carried out in the designed reaction conditions. The viscosity of oxidized starch was tested twice by NJD-1rotary viscometer, when the two-step oxidation reaction was finished and the solution was cooled to room temperature, then the second testing was24hours later. The ratio of the two viscosity data is defined as “stability”. Changing the dosage of oxidant, the reaction temperature and time, the optimum of oxidation was achieved when the dosage of oxidant was6mL, reaction time is3h, and reaction temperature is40oC. Through comparative analysis, the result showed that under the same condition of oxidation, potato starch has a lower viscosity and better stability than corn starch. And characterize the chemical structure, thermal properties and surface morphology of oxidized starch by FTIR, DSC, XRD, SEM.Then, graft butyl acrylate(BA) onto oxidized starch by the redox-induced graft polymerization of ammonium persulfate ((NH4)2S2O4) and sodium hydrogen sulfite (NaHSO3). And a kind of novel copolymer——oxidized starch graft BA(OS-g-PBA) was synthesized. In order to improve the dispersion of BA monomers in the starch system, we pre-emulsified monomers by sodium dodecyl sulfate before added. Explore the major factors influencing the performance of grafted starch adhesive, such as reaction time, reaction temperature, dosage of initiator, mole ratio of initiator, and dosage of monomer. Experiments proved that the optimum grafting condition was20g starch,4mL BA, reaction time2h, reaction temperature55oC, dosage of initiator0.6mmol, mole ratio of initiator1:1. The chemical structure of graft copolymer was characterized by FTIR. The viscosity and solid content of grafted starch was tested, and conversion rate of BA monomer was calculated. The properties of starch adhesive were studied, such as the peel strength, the tensile shear strength and the drying rates.