Study On The Structure And Properties Of Polyglycolide-based Polyurethane

Environmental pollution is a big problem that hinders national production and life.How to reduce white pollution through the development and use of biodegradable materials is an urgent problem to be solved in the 21 st century.Among them,bio-based polyurethanes have broad market prospects in the fields of biomedicine,packaging,automobiles,coatings,etc.,due to their advantages of micro-phase separation,excellent mechanical properties,and strong molecular structure design.However,currently,bio-based polyurethanes only pass through polydioxanone Ester(PCL),lactide(PLA),polyethylene oxide(PEO),castor oil,etc.copolymerize with each other to form polyester diols,the preparation method is complicated,the degradation rate is uncontrollable,the scope of application is limited,the mechanical properties are poor,and it is more difficult to use a single biodegradable polyester as the soft polyurethane segment to study its effect on polyurethane properties.Polyglycolide(PGA),also known as glycolic acid,has a chemical structure similar to PLA.As the simplest aliphatic polyester,it is also the earliest commercial surgical suture with good biocompatibility and biodegradability.However,there is little research on the influence of PGA as a polyester diol on polyurethane properties.Also,traditional diisocyanates generally use toluene 2,4-diisocyanate(TDI),diphenylmethane diisocyanate(MDI),and isoflurane aromatic isocyanates such as ketone diisocyanate(IPDI),aromatic polymers are more toxic and easily cause local inflammation of the body,so this article uses PGA as the soft segment,aliphatic hexamethylene diisocyanate(HDI)as the hard segment used as the raw material of polyurethane.The common method of preparing bio-based polyurethane is simple physical blending,the process is mature,and the feasibility is good,but the chemical structure of the polymer is difficult to accurately control,and small molecule residues,solvent residues,etc.easily cause side reactions that affect product performance,so here in the research,we tried to adopt the bulk/melt polymerization method.Not only can the polymer chemical structure be designed from the molecular level,but also the preparation process is simple and the experiment is highly repeatable.We designed and preliminary characterized the structure of PGA-based polyurethane(PGAU),compared the effects of different hard segment contents and different PGA molecular weights on PGAU performance at specific feed ratios,andstudied the degree of reaction of PGAU hydroxyl groups with isocyanate groups.The hydrogen bonds in the system were fitted with peaks to study the distribution of hydrogen bonds.Observe the changes of PGAU functional groups,crystallinity,thermal properties,and micromorphology during the hydrolysis of PBS buffer,and then analyze the mechanism of PGAU hydrolysis.FT-IR,1H-NMR,DSC,XRD,and other means to characterize the effect of soft segment content and hard segment content on PGAU performance.The hydroxyl-terminated PGA prepolymer is prepared by the ring-opening polymerization method,excess HDI is added to PGA by a two-step method to form PGA-based isocyanate,and then PGA-based isocyanate reacts with BDO to generate long-chain PGAU.By studying the effects of hard segment content and soft segment molecular weight on PGAU performance,the results prove that PGAU performance is mainly related to microphase separation and hydrogen bonding.PGAU obtained block PGAU by copolymerization of hydroxyl groups and isocyanate groups;however,when the content of the hard segment is higher than 28 wt% and the molecular weight of the soft segment PGA is higher than 20 k,PGAU undergoes microphase separation because of the self-polymerization between the HDI/BDO molecular chain The hydrogen bond content is as high as 60%.At the same time,the T_g of PGAU is lower than that of pure PGA.The higher the degree of microphase separation,the higher the T_g and Tm of PGAU.Also,the thermal stability of PGAU 18% and PGAU 2k is the worst because the thermal stability of the ester group is higher than that of urethane;the tensile strength of PGAU 38% is 1.97 times that of PGAU 18%,and the elongation at break of PGAU 20 k is 3.84 times of PGAU2k;PGAU 36% and PGAU 20 k had the fastest hydrolysis rate in the same time and hydrolysis increased the relative crystallinity of PGAU first and then decreased.The above work avoids the existing uncontrollable chemical structure of the existing physical blending to prepare bio-based polyurethane,which is easy to cause side reactions and may cause toxicity problems to the matrix and overcomes the difficulty of using pure bio-based polyester by copolymerization method to prepare polyurethane.The bulk/melt method using HDI/BDO as the polyurethane hard segment polymerization PGAU can also be conveniently used in existing bio-based polyurethane preparation processes.At the same time,the preparation of PGAU using ring-opening polymerization PGA and the two-step method will also provide new research clues and perspectives for the controllability,crystallinity,thermal properties,and mechanical properties of biodegradable polyurethane systems,and promote the related development of.Due to the limitation of time andexperimental conditions,the cytotoxicity test has not been carried out.In the future,based on the results of this experimental study,further research is needed on cytotoxicity,processing technology,and optimization of the reaction material ratio.