Effects of Emulsifiers and Binary Grafting on the Properties and Applications of High Amylose Bio-based Wood Adhesive Derived from Corn Starch


Supervisor:xiong han guo


Degree Year:2018





Due to extensive utilization of fossil fuels,the energy demand of the growing population of the world is increasing day by day.The utilization of these fossil fuels also resulted in environmental pollution and energy crisis around the globe.As such,scientists and academics are trying to develop green materials which tend to reduce the impact of human on environment.These green materials are of great interest due to their characteristics such as biodegradable,easy to obtain and low cost.Starch as an agrosourced polymer has become much popular recently due to wide availability,low cost and total compostability without toxic residues.Starch is the most abundant organic compound found in nature after cellulose.Thus,starch is an attractive natural green material candidate for researchers to replace the petro-chemical-based ingredients in wood composite products.The concept of wood adhesive has led to the utilization of wood composite products which are promising source for construction,furniture and building industries.There is increasing demand for the wood adhesives in the recent years due to increasing applications of wood products.For many decades,the wood adhesive industry remained dependent on the petroleum resources due to the attributes such as high performance and low cost.However,these adhesives can create serious risks to human health and plummeting the indoor air quality by emitting these carcinogenic compounds into the environment during the production of wood composites.Additionally,the nonrenewability of these resources has induced the urge to prepare green,renewable and biobased adhesive which would be human and environment friendly.Therefore,there is a growing interest to replace the petro-chemical based ingredients in the adhesive formulation with green renewable material.During this research,the influence of different emulsifiers on the characteristics of wood adhesive and grafting of monomers were studied in order to prepare adhesive with a longer shelf life.Herein,this thesis carried out the following research contents and related results which are as follow:1.A facile approach was developed to dramatically boost the performance of high amylose starch-based wood adhesive(HASWA)by addition of sucrose fatty acid esters(SEs).The results showed that the addition of 6%(w/w,dry starch basis)SEs significantly improved the bonding strength in both dry and wet states as well as the mobility and storage stability of the adhesive.Fourier transform infrared(FT-IR)spectroscopy confirmed the occurrence of graft copolymerization reaction whereas X-rays diffraction(XRD)analysis verified the presence of amylose-SEs complexes.The formation of amylose-SEs complexes were proved by blue value or differential scanning calorimetry(DSC)analysis.The results also indicated that the incorporation of SEs into the HASWA hindered the aggregation of latex particles and enhanced the thermal stability of starch molecules.Furthermore,SEs addition in the adhesive system resulted in the inhibition of starch retrogradation as observed by time sweep and pulsed nuclear magnetic resonance(PNMR)analysis.The addition of SEs resulted in enhanced shearthinning and solid like-behaviors and anti-retrogradation properties of the adhesive with incorporation of SEs.These findings provide important information to prepare bio-based high performance wood adhesive by adding SEs to replace the traditional petro-chemical based stocks adhesives.2.High performance of starch-based wood adhesive is essentially important for its application in the versatile material science field.This study was carried out to evaluate the effect of different emulsifiers on the bonding performance,freeze-thaw(F/T)stability and retrogradation behavior of starch molecule in the adhesive system.The improved F/T stability and bonding performance was supported by the stability of viscosity after repeated F/T cycles and enhanced shear strength and grafting parameters.ζ-potential analysis revealed enhanced stability of the emulsion droplets through addition of emulsifiers.Furthermore,time sweep experiment,low-field nuclear magnetic resonance(LF-NMR),and x-ray diffraction(XRD)analysis showed that the retrogradation of starch molecule in the adhesive system was inhibited by addition of emulsifiers.Sodium dodecyl sulfate(SDS)showed the best improvement in the properties of high amylose starch-based wood adhesive(HASWA)among all the emulsifiers tested.These results offer a major step forward to prepare high performance bio-based wood adhesive in order to make them compete with less environment friendly wood adhesives.3.Enhancing the performance of wood adhesive is important for its industrial applications.Accordingly,we designed and demonstrated the use of two co-monomers vinyl acetate(VAc)and butyl acrylate(BA)for promoting the graft copolymerization while improving the bonding performance of wood adhesive.The results showed that the addition of comonomers in the ratio of VAc/BA 6:4(v/v,volume basis of VAc)could improve the shear strength and it reached to 6.68 MPa and 3.32 MPa in dry and wet states,respectively.Fourier transform infrared spectroscopy(FT-IR)analysis revealed successful graft copolymerization reaction while the morphologies were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Furthermore,the grafting reaction and thermal stabilities of wood adhesive were analyzed by x-ray photoelectron spectroscopy(XPS)and thermogravimetric analysis(TGA).The results showed that the properties of wood adhesive could improve dramatically by using two co-monomers VAc and BA during the graft copolymerization reaction.