Preparation And Application Of Bio-based Polyester Underwater Adhesive

With the development of science and technology,the enhancement of people’s awareness of environmental protection and the increase of the demand for the development of new renewable resources,how to use bio-based renewable raw materials to prepare materials to reduce the dependence on petroleum and other fossil raw materials has attracted widespread attention,of course adhesive is no exception.Compared with petroleum-based adhesives,bio-based adhesives show renewable,bio-degradation and good compatibility,however,the poor wet adhesion performance limits the use of bio-based adhesives.It is found that water has corrosion and barrier effect on the adhesive,and the water resistance of the adhesive is able to be improved with the introduction of a large number of hydrophobic groups.But breaking the boiling water film to improve the effective contact area between the adhesive and the substrate is always the research focus in underwater adhesive field.The mussel shows excellent wet adhesion property,and the introduction of catechol-based adhesive can improve the wet adhesion property.Therefore,in this paper,bio-based underwater adhesive materials with good wet adhesion performance were prepared by co-polymerization of catechol-based monomer as the main adhesion unit and different functional monomers with adjusting monomer ratio and preparation process.The preparation of polyester was characterized,and the influence of bonding process of adhesive substrate was emphatically studied.A random copolymer P（DHHCA-GA）with branched structure was prepared by one-pot vacuum melt polycondensation using plant 3,4-dihydroxyphenylpropionic acid（DHHCA）as adhesion monomer and gluconic acid（GA）as absorbent monomer.P（DHHCA-GA）adhesives with different catechol content were prepared by adjusting monomer ratio and preparation process.The results showed that under simple bonding process（temperature 120°C,pre-loading 25 k Pa）,the adhesion strength of PGA adhesive on the glass,aluminum and steel substrates could reach 4.9 MPa,1.3 MPa and 1.4 MPa.After adding a large amount of DHHCA,the interfacial adhesion of P（DHHCA-GA）binder increased（2.9 MPa for aluminum,3.0 MPa for steel）,and the cohesion decreased（3.1 MPa for glass）due to the decrease of polymer molecular weight,but it was still higher than that of most existing bio-based adhesive.P（DHHCA-GA）shown good thermal stability and the mass loss occured after 170°C.Glass transition temperature was higher than 25°C,and P（DHHCA-GA）was able to be used at room temperature;With quickly bonding on aluminum,the wet adhesion strength could reach 2.5 MPa,which meant a potential application for P（DHHCA-GA）adhesive in the underwater adhesion field.In order to improve the adhesion property and reduce the effect of catechol group on the polymerization reaction,the PGA-g-DHHCA adhesive was prepared by introducing catechol group at the end of the PGA polymer chain.PGA-g-DHHCA adhesives with different catechol content were prepared by adjusting the ratio of DHHCA to PGA.In order to further improve the cohesion of the adhesive,PGA-g-DHHCA was crosslinked.The results showed that with the increase of the content of catechol group,the cohesion and interfacial adhesion of PGA-g-DHHCA adhesive increased,and the bonding strength of the glass,aluminum and iron reached 5.3 MPa,2.0 MPa,and 2.3 MPa.The addition of PEI could greatly improve the water resistance of the adhesive,and adhesive maintained enough cohesion strength after 96 h.PGA-g-DHHCA adhesive had a wide application prospect in the field of bonding underwater.And hyperbranched polyester P（DHHCA-LA）with long hydrophobic aliphatic chain and rich catechol terminal group was prepared by copolymerization with bio-based monomer lactic acid（LA）as hydrophobic functional monomer.P（DHHCA-LA）adhesives with different DHHCA contents were prepared by controlling formula and preparation technology.The results showed that P（DHHCA-LA）glue dry adhesion performance was good.With the increase of DHHCA content,the dry adhesion strength of P（DHHCA-LA）on the glass substrate increased to 3.5 MPa.The catechol group is an important adhesive group,and after being replaced by acetyl group the adhesive strength decreased to 1.6 MPa;LA helped to improve the wet adhesion performance of the adhesive,and the wet adhesion strength of P（DHHCA-LA）adhesive on the glass,aluminum and steel reached 2.7 MPa,0.9 MPa and0.8 MPa.After soaking in water for 1 month,the wet adhesion strength of P（DHHCA-LA）adhesive remained 81%,and the long-term stability was good.When the temperature was greater than 90°C and the shear rate was greater than 1 s^-1,the viscosity of the adhesive fluid was less than 10 Pa.s,which meant the flow property of adhesive was good.P（DHHCA-LA）had good thermal stability and mass loss occurred at 200°C.Glass transition temperature of P（DHHCA-LA）was higher than room temperature,and the adhesion strength still remained2.1 MPa at 30°C.MTT test showed that P（DHHCA-LA）adhesive had low cytotoxicity,and when the hot pressing temperature was 50°C,the adhesion strength was 0.5 MPa.P（DHHCA-LA）was able to be used for bone-repair,and there was a potential applications in bio-adhesive for P（DHHCA-LA）adhesive.