Investigation On The Synthesis And Performance Of Self-healing Colored Polyurethane

As a kind of advanced material with high performance,polyurethanes are widely used with the features of adjustable mechanical properties,good film-forming pproperty and easy processing.The traditional coloration method of polyurethanes is to mix colorants with them under mechanical effect.Due to the poor compatibility between colorants and polyurethanes,additives are often added to stabilize the dispersion system,resulting in a complicated application process.Meanwhile,cracks occur on the surface or interior of polyurethane under mechanical effect or ultraviolet irradiation,the service life of polyurethane is reduced.Therefore,the chromophore and reversible bond are covalently bonded into polyurethane chain to prepare self-healing colored polyurethane,which endowing polyurethane with bright colors,improved stability of the colored polyurethane and self-healing ability.The hydroxyl-terminatedcoloredpolyurethanes weresynthesized basedon1-amino-4-hydroxy-2-(6-hydroxy-hexyloxy)anthraquinone(AHHA)and dimethylolpropionic acid(DMPA)as chain extenders,isophorone diisocyanate(IPDI)as hard segment and polyethylene glycol 1000 as soft segment.The conjugated structure of AHHA was not affected after bonding into polyurethane chain.The rigidity of polyurethane chain is improved,resulting in an increased glass transition temperature(T_g)from-22.5°C to-10.5°C.The hydroxy-terminated colored polyurethanes exhibited good compatibility between soft and hard segments and no crystallization.The colored polyurethane films were obtained with the addition of IPDI trimers(tIPDI)into hydroxy-terminated colored polyurethane.The transmittances of colored polyurethanes films with 0.12%,0.89%,1.32%,2.13%AHHA were94.5%,87.9%,82.3%and 78.6%,respectively,revealing that colored polyurethane film possessed good transparency.The hydroxyl-terminated colored polyurethane can be used for the coating of cotton fabric with blocked isocyanate curing agent.The K/S value of cotton coating fabric was 5.20 under the condition of 2.13%AHHA acess ratio,20%curing agent,baking at 150°C for 5 min.The dry rubbing fastness and wet rubbing fastness were 4-5grades.The soaping fading fastness reached 3-4 grade and staining fastness was 4-5 grade.Di-(1-hydroxylundecyl)diselenide(DiSe)was synthesized using selenium powder,sodium borohydride and 11-bromoundercanol as raw materials.It was mixed with polytetrahydrofuranediol(PTMG)as soft segment,ethylenediamine(EDA)as chain extender to synthezise diselenide-containing polyurethane.The dynamic reversibility of diselenide bond remained unchanged when it was introduced into the polyurethane chain.The introduction of DiSe had no influence on the the degradation phase of polyurethane,but thermal stability of soft segment was reduced and it prevented orderly arrangement of PTMG,so that there was no crystallization in diselenide-containing polyurethane.The initial breaking strength of control polyurethane was 30.02 MPa,the healing efficiency was 21.29%and33.34%respectively after illumination at D65 for 24 h and 48 h at 25°C.When the DiSe content was 6.7,the initial breaking strength of polyurethane was 26.85 MPa,the healing efficiency was 46.44%and 77.03%after illumination for 24 h and 48 h,respectively,which possessed a less reduction of polyurethane strength and a better healing efficiency.In order to endow the hydroxyl-terminated colored polyurethane with self healing property,di-(1-hydroxylundecyl)diselenide was utilized to partly substituted DMPA as a chain extender to synthesize diselenide-containing colored polyurethane.Compared with hydroxyl-terminated colored polyurethane,the M_n and M_w of diselenide-containing colored polyurethane were increased.The introduction of di-(1-hydroxyundecyl)diselenide had no effect on its transparency,the transmittances of diselenide-containing colored polyurethane films were still above 80%and possessed high transparency.Due to the exchange reaction of diselenide bonds on the contact surface,diselenide-containing colored polyurethane films could hang 100 g weight after illuminating at 25°C at D65 for 12 h followed by illuminating at 20°C for 12 h while colored polyurethane film could not bear.