Studies On Synthesis And Properties Of Polyurethane Medical Elastomers

Polyurethane material had excellent histocompatibility,hemocompatibility,and exceedingly good mechanical properties,which could be molded by pouring,mixing and other methods,additionally it was always under low prices.However,due to the traditional polyurethane material was non-degradable,its application limited in the medical field. Biodegradable polyurethane was synthesized by fully biodegradable polymer as the polyol component and diisocyanate,these polyurethanes were particularly suitable for the medical field.Polylactic acid was one of the fully degradable polymers,which was based on recyclable plant resources as raw materials,and it was a kind of biodegradable thermoplastic polyester could be obtained via biological fermentation or synthetic.Its characteristics of non-toxic,non-irritating,good biocompatibility,biodegradable,absorbable and high strength,which made it common medical material.Firstly,4,4’-diphenyl methane diisocyanate(MDI) or MDI/HDI mixture was used as hard segment,Polytetra methylene ether glycol(PTMG) was used as soft segment, 4,4’-methylenebis(2-chloroaniline)(MOCA) was used as chain extender,the raw materials above all was used to synthesize polyurethane medical elastomeric material. FTIR spectra characterized the structure, the result showed that the structure was in line with expectation.The influence of different MDI dosage,the amount of chain extender and MDI/HDI mixture on tensile strength properties,tear strength and hardness of medical polyurethane elastomer material were discussed and the result showed that the optimum formula was:isocyanate and polyol molar ratio of 3:1,chainextender in an amount of 3.7%.Compared to the HDI or MDI used alone,when HDI/MDI mixture was used as the isocyanate component,all aspects of performance were improved. MTT assay testing Cytotoxicity proved that toxicity of polyurethane elastomer extract liquor of all kinds were level l.The result corresponded to the cytotoxicity requirements of Class Ⅲmedical materials.Lactic acid impurity was removed,and discussed the effects of lactic acid impurity removal temperature and time on content of lactic acid.When impurity removal temperature was 90℃,impurity removal time was 40 min,the lactic acid content reached the maximum 98.93%.Purified lactic acid was used to synthesize polylactic acid by melt polycondensation. FTIR and 1H-NMR proved that hydroxyl-terminated polylactic acid was prepared and ethylene glycol used as blocking agent.Analyzed hydroxy-terminated polylactic acid synthesized at different temperatures by GPC.The result showed that when low synthesis temperature was 130℃ and high synthesis temperature was 160℃,the PLA-OH molecular weight was suitable molecular weight distribution was narrow.The self-made hydroxy-terminated polylactic acid(PLA-OH) and polytetra methylene ether glycol(PTMG) as mixed polyol component and hexamethylene diisocyanate(HDI) reacted to make prepolymer,and then added the catalyst and chain extender synthesized biodegradable polyurethane elastomer(PLA-PU).FTIR spectra characterized the structure,the result showed that the structure was in line with expectation.The mechanical properties,thermal stability,biodegradability of biodegradable polyurethane elastomer was analyzed.When the content of hydroxy-terminated polylactic acid(PLA-OH) was 20%,the degradable polyurethanes had appropriate hardness,tensile properties,tear resistance,which was suitable as medical material.TGA test showed that the larger PLA-OH content, made worse biodegradable polyurethane elastomer thermal stability and better biodegradable properties.Degradation result in 80℃ water and PBS buffer solution showed that the larger PLA-OH content made better degradation property.In conclusion,after adding PLA-OH,polyurethane had obvious biodegradablity.