| Because of the excellent performance of Citric acid esters product in the world, it has been used in many fields.In China,its current application only restricted to the plasticized PVC products.And,the oversupply of citric acid in China is becoming increasingly serious.Therefore,vigorously develop the application of citric acid esters,is of practical significance.Firstly,the thesis summarize the biodegradable elastomer,world consumption, applications and stress introduce the research advance of polyurethane coatings,all of this also point out the future of polyurethane coatings.Secondly,A new type of biodegradable elastomer,poly citrate-ethylene glycol [poly(CA-co-EG),PCE],was synthesized through one-step polycondensation by citric acid(CA)with ethylene glycol(EG)and n-butanol(BA)as molecular weight regulator.A series of transparent and soft elastomer were prepared by changing the amount of n-butanol and post-polymerization time.PCE was characterized by Fourier transform infrared spectroscopy and gel permeation chromatography.It was found that the weight-average molecular weight of pre-polymers was from 800 to 1200.Measurements on the mechanical properties of PCE testified that the new polymers were elastomers with tensile intensity ranging from 0.5MPa to 1.5MPa, elongation at break ranging from 150%to 455%,Young's modulus ranging from 0.21MPa to 2.2MPa and cross-linked density ranging from 28.2mol.m-3to 303.9 mol.m-3.Hydrolytic degradation of the polymer films in a buffer of pH value 7.4 at 37℃showed that PCE had excellent degradability(all the films showed the weight losses more than 50%after 65 h incubation).At the same time,it was found that the different amount of n-butanol and different post-polymerization time had strong influence on the degradation,water uptake and mechanical properties.Thirdly,the high solid polyurethane coating has been prepared with citric acid polyester polyol as hydroxyl resin.The synthetical process of hydroxyl resin was optimized by orthogonal experiment:n(oleic acid):n(citric acid):n(1,4 butanediol) =1:1:3.5,150～160℃/3h,190～200℃/2～3h.This paper discusses the effects of hydroxyl value of polyester polyol and ratios of -NCO/-OH on the properties of polyurethane coatings.When the hydroxyl value of polyester polyol is 148 mgKOH·g-1,n(NCO):n(OH)=1.2:1,the synthetic properties of film would be optimum,could be accorded with S01-3 standard(the standard of polyurethane varnish).In addition,the study found that the mass concentration of drier was m(BTSL)/m(citric acid polyester polyol)=0.08%～0.1%,the dry time of superficial film could be reached 25 to 30 min.The innovations of article are:(1)A new high tensibility and low elastic modulus biodegradable elastomer,poly citrate-ethylene glycol[poly(CA-co-EG), PCE],was synthesized through one-step poly-condensation.Compared with others, the synthesize conditions of PCE were mild,Without any catalyst and crosslinker.At the same time,it was found that the different amount of n-butanol and different post-polymerization time had strong influence on the degradation,water uptake and mechanical properties.(2)The high solid polyurethane coating has been prepared with citric acid polyester polyol as hydroxyl resin,with well adhere,flexile, wearable,rigidity and Chemical resistance.Besides,the amount of VOC could be effectively reduced and the existing synthetical and applied equipment be utilized. The same type of article is not reported.
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