Study On Preparation And Properites Of One-component Polyurethane Adhesives For Wood

Two kinds of one-component polyurethane wood adhesives were prepared by hydroxymethyl-cyclohexanone,cardol,polyaryl polyisocyanate?PAPI?,Polypropylene glycol?PPG,Mn=1000?and dibutyltin dilaurate?T12?in this paper.Among them,PMDI was partially blocked by hydroxymethyl-cyclohexanone and cardol respectively,and a blocked one-component polyurethane adhesive was prepared.The effects of blocked reaction temperature,blocked reaction time,T12 dosage during blocking,R value?molar ratio of-OH in the blocked agent and NCO in PMDI?on the blocked reaction were studied,the effects of hot pressing temperature,time and R value on the shear strength of the blocked-type adhesive during curing were investigated.In addition,the moisture-curing one-component polyurethane adhesive was modified by cardol.The effects of adding methods of cardol,R₁?molar ratio of-NCO in PMDI to-OH in polyols?,cardol dosage and T12 dosage on the properties of the moisture-curing adhesive were studied.At the same time,two kinds of one-component polyurethane adhesives were characterized by FT-IR,¹H-NMR,¹³C-NMR,TG,and DSC.The main research results of this dissertation are as follow:?1?The blocked-type one-component polyurethane adhesive was prepared by blocking PMDI with hydroxymethyl-cyclohexanone.The experimental results showed that when R=[n?-OH?:n?-NCO?]=1.1:1.0,the blocked temperature was 50?,the blocked reaction time was 4 hours,the amount of T12 was 0.1%t,the residual content of NCO in the system was 0.81%.Under this condition,the dry shear strength of the adhesive was 6.51 MPa,and the wet shear strength was 2.23 MPa.When used hydroxymethy-lcyclohexanone blocked the PMDI partially,and then reacted with PPG-1000 to prepare an adhesive.The experimental results showed that when blocked the PMDI to 70%?R=0.7?,the hot pressing temperature was 120?,the hot pressing time was 60 min,the dry shear strength of the adhesive was 11.23 MPa,and the wet shear strength was6.14MPa.?2?FT-IR,¹H-NMR and ¹³C-NMR analysis showed that PMDI could be blocked by hydroxymethyl-cyclohexanone,and-OH in hydroxymethyl-cyclohexanone reacted with-NCO to form-NH-CO-;DSC analysis showed that:the blocked product of PMDI could be deblocked in the range of 113.4?-144.6?.?3?The blocked-type one-component polyurethane adhesive was prepared by blocking PMDI with cardol.The experimental results showed that when R=[n?-OH?:n?-NCO?]=1.1:1.0,the blocked temperature was 70?.The blocked reaction time was 5 hours,the amount of T12 was 0.1%,the residual content of NCO in the system was1.33%.Under this condition,the dry shear strength of the adhesive was3.13 MPa,and the wet shear strength was 0.74 MPa.When used cardol blocked the PMDI partially,and then reacted with PPG-1000 to prepare an adhesive.The experimental results showed that when blocked the PMDI to 40%?R=0.4?,the hot pressing temperature was 140?,the hot pressing time was 75 min,the dry shear strength of the adhesive was 8.10MPa,and the wet shear strength was 3.26MPa.?4?FT-IR,¹H-NMR and ¹³C-NMR analysis showed that PMDI could be blocked by cardol,and-OH in cardol reacted with-NCO to form-NH-CO-;DSC analysis showed that the blocked product of PMDI could be deblocked in the range of 127.3?-143.3?.?5?The One-component moisture-curing polyurethane adhesives for wood was prepared by cardol,PAPI,PPG-1000 and T12,etc.The experimental results showed that When R₁=[n?-NCO?:n?-OH?]=6,the amount of cardol was 15%,the amount of T12 was 0.15%,and the pressure of the press was 1.5MP and cold pressed for 48hours,After72hours,the dry shear strength of the adhesive was 13.78MPa,and the wet shear strength was 6.56MPa.What's more,The tack free time of the modified adhesives was 25 minutes,which was 7 minutes longer than that of the unmodified adhesives and extended the application period of the adhesives;Used the blending method to prepared an One-component moisture-curing polyurethane adhesives for wood was prepared by cardol,When R₁=[n?-NCO?:n?-OH?]=6.5,the amount of cardol was 15%,the amount of T12 was 0.1%,and the pressure of the press was in the range of 1.0-1.5MPa and cold pressed for 48hours,After 72hours,the dry shear strength of the adhesive was 14.02MPa,and the wet shear strength was 6.29MPa.TG/DTG analysis showed that the thermal stability of modified adhesives could be increased possibly...