Preparation And Properties Of Itaconic Acid Based Polyester Crosslinking Network

Unsaturated polyester is a thermosetting resin material synthesized by condensation reaction of unsaturated dicarboxylic acid and diol.Because of its excellent mechanical properties,strong electrochemical properties and high corrosion resistance,it is widely used in military,coatings,conductive materials and anticorrosion materials.In this paper,a class of bio-based unsaturated polyester was synthesized.Itaconic acid based unsaturated polyester curing film without styrene crosslinking was prepared by light curing reaction.Functional unsaturated polyester material was obtained by adjusting its structure.Its application in self-healing and sensor was studied.Firstly,a kind of bio-based unsaturated polyester(PBIS)was synthesized from bio-based itaconic acid(IA),succinic acid(SA)and butanediol(BDO).Isocyanate groups were introduced at both ends of the molecular chain,and then crosslinked and cured by thiol-ene click reaction.The effects of synthesis conditions and molecular structure on the properties of the cured film(CPBIS)were discussed.The results showed that PBIS was esterified at 170 ? for 6 h and then polycondensated at 180 ? for 3 h.The acid value and intrinsic viscosity of PBIS were 17.65 mg KOH/g and 35.24 m L/g.When the molar ratio of IA to SA was 7:3 and the molar ratio of-SH to C=C was 3:5,the mechanical properties of CPBIS showed that the elongation at break and tensile strength of CPBIS were 41.55% and 7.77 MPa.It was discovered that the crystallinity and crystal orientation of itaconic acid based unsaturated polyester are closely related to its crosslinking density.With the increase of crosslinking density,the crystallinity and crystal orientation of itaconic acid based unsaturated polyester decrease and the glass transition temperature increases.The results showed that PBIS could be selectively degraded after crosslinking and curing.In the degradation solution of bovine pancreatic lipase and glutathione,the weight loss was 7.50% after 12 days of degradation.Secondly,a flexible self-healing polyester crosslinking network(CPUBT-UPy)was prepared by introducing 2-urea-4[1H] pyrimidinone(UPy)into PBIS chain through chain extension reaction and adjusting the structure and properties of unsaturated polyester with polyethylene glycol(PEG).The effects of crosslinking degree,PEG content and side chain upy content on the properties of(CPUBT-UPy)were studied.The results showed that the introduction of soft segment PEG increased the segment fluidity of unsaturated polyester crosslinking network and greatly improved the mechanical properties of unsaturated polyester.When the content of PEG was 80%,the elongation at break could reach 2020.94%.The results showed that the four hydrogen bonds between UPy groups could give excellent self repairing properties.When UPy content was 40%,the self repairing efficiency was91.33%,and the repair efficiency could reach 79.01% after 5 cycles.After doped 15%carbon nanotubes into CPUBT-UPy,the crosslinked network had sensitive signal sensing ability to finger bending,speaking and frowning,which provided a theoretical basis for the application of polyester in the field of flexible electronic skin.