Synthesis Of Arylamine Modified Aqueous Polyurethane And Its Application To Aramid Fabric Bonding

Polyurethane have been widely used for its high strength and toughness.Through the macromolecule design of polyurethane,the preparation of highperformance waterborne polyurethane(WPU)dispersion is much highlighted as it would be both environmentally friendly and with excellent properties for application.The relevant research results are of great value to adhesives,coatings and other related fields.In this dissertation,aromatic diamine and para aromatic amide diamine was separately used as the chain extender for the copolymerization of WPU.Through the introduction of aromatic urea structures,the optimization on the the soft and hard segmental monomers and the design on the chain extension process,modified WPU was achieved which exhibited high strength as well as high toughness after film formation.The influences of preparation parameters and chain-extending monomers were systematically studied on the microstructure and performance of WPU films.The obtained WPU was used as the adhesive for aramid fabrics and aluminum alloy plates,and both showed good bonding performance.The main contents of the dissertation are as follows:1.WPU modified by the copolymerization of aromatic diamine.Diethyltoluenediamine(DETDA)was introduced into the WPU system as a chain-extender by a two-step chain-extending and post-dispersing method.The effects of the amount of hydrophilic monomer,R,the ratio of soft and hard segmental monomers on the dispersion and the films of WPU were investigated.The results showed that the dispersion could be stabilized and gave out uniform fine particle sizes when the DMBA dosage was 5-6%.Good dispersion stability and film mechanical properties were achieved when the R was 1.2.The ratio of soft and hard segmental monomers was also adjusted.When the ratio of isocyanate to polyol was in the range of 3.5/1?4.5/1,WPU film exhibited good mechanical properties.In this range,both the tensile strength and breaking energy reached their maximum,which were 51 MPa and 195.9 MJ·m-3,respectively.Meanwhile,the elongation at break was above 1000%,and the water absorption rate was reduced to below 10%.On this basis,the DETDA copolymerization structures were confirmed by FTIR,and the influence of DETDA dosage was systematically studied.It was found that stable WPU dispersion was obtained under the condition of DETDA dosage ?5%,and the storage stability at room temperature was more than one year.With the increase of DETDA content,the particle size increased from 57 nm to 86 nm.Dynamic mechanical analysis(DMA)results showed that the formation of aromatic urea bonds promoted the microphase separation in WPU films.Tensile test results showed that the tensile strength and modulus increased with the maximum strength of 59 MPa,which improved 300%in comparison with the films without DETDA incorporation.The fracture energy also increased correspondingly,and the maximum was 251.3 MJ·m-3.At the same time,the elongation at break remained above 1000%.The introduction of DETDA also enhanced the film compactness and light transmission,and when the amount of aromatic diamine was ?3%,the water absorption dropped to below 5%.The flexible aramid laminated fabric is widely used in the field of individual protective equipments.The WPU synthesized in this work was used for the binding resin for aramid fabric,and the adhesion process was optimized.Using the two-step dipping-scraping process and hot pressing at 120? for 60s under the pressure of 3 MPa,the peel strength reached the maximum of 7.64 N·cm-1 when the amount of DETDA was 2%.2.WPU modified by the copolymerization of para aromatic amide diamine.4,4'-Diaminobenzoylaniline(DABA)was used as the chain-extender before neutralization to introduce the para aromatic amide-urea structures into the hard segmental domains of WPU.The copolymerization structures were convinced by FTIR and 1H NMR.With the DABA dosage ?4%,the neutralized PU was transformed into a stable dispersion by forced dispersing in water.The dispersion was used for film formation.As the DABA dosage was increased,the results from FTIR analysis suggested the increase in hydrogen bonding degree.DMA characterization revealed that the increase of hydrogen bonding degree promoted the microphase separation of the hard segmental domains from the soft segmental matrix.The mechanical strength of WPU film was greatly enhanced,and the original characteristics of high toughness was maintained.The film with 4%DABA dosage showed the tensile strength of 73 MPa,elongation at break of?1250%and the fracture energy of 371.5 MJ-m-3.The water absorption in 24 h was suppressed to as low as 3%.In addition,bright blue fluorescence was observed on the film under the excitation of UV light.The WPU was also applied on aramid fabric,and exhibited the maximum peel strength of 3.53 N/cm-1.Moreover,the obtained WPU was used for surface bonding of aluminum alloy materials.The bonding part with a bonding area of 25 mm × 50 mm withstood a shearing force of 27.5 kg(about 269.5 N).