Study On Preparation And Properties Of Gallic Acid Modified Waterborne Polyurethane

In order to alleviate the dependency of polyurethane finishing agent in leather industry to petroleum feedstocks and the difficult degradation of traditional water-based polyurethane,a bio-based polyester polyol(PPA)was prepared by using 1,3-propanediol(PDO)extracted from plant straw and adipic acid as raw materials.The waterborne polyurethane(WPU)was prepared via the reaction of PPA,isophorine diisocyanate(IPDI)and dimethylolpropionic acid(DMPA),and then WPU was modified by using gallic acid(GA)to obtain GA modified WPU(GWPUs).The emulsion properties,film performances and biodegradability of GWPUs were studied.AA and PDO were as raw material,p-toluene sulfonic acid(PTS)was as catalyst,two-step method was adopted to prepare PPA.The synthesis process was optimized by single-factor and orthogonal experiments.The results showed that the best experimental conditions were as follows.n(PDO):n(AA)was 1.25:1,the dosage of PTS was 1%(basing on the total weight of AA and PDO),the reaction time was 2.5 h,the reaction temperature was 125 ?.The acid value and the hydroxyl value of PPA prepared under the best experimental conditions were 2.17 mg KOH/g and 105.8 mg KOH/g,respectively.Fourier transform infrared spectrum(FT-IR),nuclear magnetic resonance hydrogen spectra(1H-NMR)nuclear magnetic resonance carbon spectra(13C-NMR)results showed that the reaction was carried out as expected route and the molecular structure of the products was consistent with that of the target product.Gel permeation chromatography(GPC)analysis showed that the number average relative molecular mass of PPA was 1019,polydispersity was 1.073.X-ray diffraction analysis(XRD)results showed that PPA had certain crystalline,its crystallinity was 25.92%,and there were multiple forms of crystal shape.The prepared PPA and commercial polyester diol were respectively used to synthesize WPU.The results showed that WPU prepared by using PPA had excellent flexibility,soft handle,less crystallinity and poor water resistance.A series of GWPUs were prepared by prepolymer method in which IPDI,PPA and DMPA were as raw materials,GA was as the modifier,respectively.The FT-IR spectrum proved that the reaction was carried out as expected route and the desired product was obtained.The mechanical properties testing result of GWPUs showed that when the dosage of GA increased to 3.3%from 0%,the tensile strength increased from 16.26 MPa to 41.57MPa,the elongation at break decreased from 519%to 279%,the water resistance of GWPUs film reduced to 31%from 156%.The DSC result showed that with the increase of GA dosage,the Tg of soft and hard segments of GWPUs film both shifted to high temperature direction at a certain degree.TG and DTG results indicated that the more the GA dosage,the better the thermal stability of GWPUs film was.When the heat loss rate of film was 50%,the degradation temperature of film increased to 385.2 ? at GA dosage 3.3%from 361.7 ? at GA dosage 0%.XRD result showed that when the dosage of GA increased to 3.3%from 0%,the crystallinity of GWPUs decreased from 6.79%to 0.35%.AFM result showed that when the dosage of GA increased,Ra value decreased to 2.69 nm at 3.3%GA dosage from 4.56 nm at 0%GA dosage.TEM and particle size testing results showed that when the dosage of GA increased,the emulsion particle was oval and the distribution was uniform.The particle size increased to 42.39 nm at 3.3%GA dosage from 20.65 nm at 0%GA dosage.The biodegradability analysis proved that the more the GA dosage,the more the weight loss of GWPUs film is.When the dosage of GA was 3.3%,the weight loss of GWPUs film after 25 d was 6.9%.This indicated that with the increase of GA dosage,biodegradability of GWPUs film became better.