The Structure And Properties Of Nano SiO₂and Re（I） Complex Doped Polyester Composites

In recent years，research of composite materials has focused on modifying the polymerwith inorganic particles to prepare material with excellent performance that generalengineering material fails to attain. Polystyrene （PS）, the traditional plastic, was widely used inpackaging material and sensing fields for its good transparency and permeability, but it is nondegradable. Among the broad biodegradable polymers family, poly （ε-caprolactone）（PCL）,Poly（Butylene Succinate Adipate）（PBSA）and polyhydroxyalkanoates （PHA） have received anuniversal attention for their good mechanical properties, biodegradability and biocompatibility.PBSA has the advantages of low cost, good processability. The application of PCL is restrictedby its low melting point, poor stability and deformation. The application range of PHA is alsolimited for its shortages such as high production costs, high fragility and narrow processingtemperature range.This paper summarizes the research progress and application situation of nano SiO₂andRe（I） in preparing composite. Doped with polymer respectively, they were used to preparematerials with good mechanical properties, processing properties and optical stability. First,with good biocompatibility and biodegradation, the PCL was blended with PBSA andPoly（3HB-co-4HB） to prepare polyester composites, which overcame weakness of singlepolyester. Second, PCL/PBSA and PCL/Poly（3HB-co-4HB） composites were modified bynano SiO₂so as to prepare a new biodegradable nano composite material with excellentperformance. Their mechanical properties, crystallization properties, rheological behavior anddegradation properties were analyzed. Finally, Re（I） with luminous groups were prepared andblended with PS and PS/PCL matrix to prepare composite nanofiber, and their photophysicalproperties were studied. The main contents and conclusions are as follows:Firstly, PCL/PBSA blends were prepared by mechanically melting mixing. Themicrostructure, crystallization, dynamic mechanical properties, and rheological behavior werestudied by DSC, the electronic universal tensile machine, SEM, rotary rheometer. When thequality of PCL/PBSA blend ratio was40/60, the tensile strength reached the maximum withrelatively high elongation and preferable mechanical properties. As the PBSA contentincreased, the initial temperature of the crystallization of PCL went up, the peak temperatureof the crystallization increased by2.5°C and the final crystallization temperature increasedfrom28.7°C to32.6°C. The rheological results showed that with angular frequency growing,storage modulus and loss modulus increased monotonically, PBSA content went up and thestorage modulus of the blend system decreased at first, then increased.Secondly, PCL/PBSA/nanoSiO₂blends were prepared with nano SiO₂content1,2,3,5wt%respectively. Microstructure, crystallization, dynamic mechanical properties, dispersion,degradation properties and rheological behavior were analyzed by FTIR, DSC, electronicuniversal tensile machine, SEM, rotary rheometer （AR-G2） The analysis of Infrared spectralshowed that coupling agent of organic titanate modified nano SiO₂and the modified SiO₂ nanoparticles dispersed well. Mechanical properties and SEM observation showed that whenthe content of nano SiO₂took up2wt%, nano SiO₂particles dispersed well with optimummechanical properties of the composite system. When the content was more than2%, thematrix particle agglomeration were prone to forming, leading to stress concentration andmechanical properties decreasing. Rheological behavior analysis indicated strong shearthinning behavior.Thirdly, PCL/Poly（3HB-co-4HB） composite was prepared, and the mechanical properties,thermal properties, degradation and rheological behavior of the composites were studied. Theresults showed that when PCL/Poly（3HB-co-4HB） mass ratio was60/40, elongation at breakreached the maximum. As the content of Poly （3HB-co-4HB） increased, the tensile strength,elongation at break and yield strength declined dramatically. Degradation analysis showedthat the weight loss rate was closely related to length of time and thickness of the sample. Asthe degradation time grew, the weight loss rate rise and the mechanical properties of thematerials declined. The thicker the sample was, the slower it degraded. Thermal analysisshowed that increase of Poly（3HB-co-4HB） also had a great effect on the crystallizationbehavior of PCL, leading to higher crystallization temperature and lower crystallinity. Studyon rheological behavior of polymer blends showed melt flow properties fluidity was sensitiveto temperature changes. As temperature increased, the storage modulus and loss modulusdecreased.Fourthly, PCL/Poly（3HB-co-4HB）/nanoSiO₂was prepared by melt blending. Theinfluence of coupling agent on the flow behavior of composite was studied. The resultsindicated that when the modified nano SiO₂content reaches4%, the notched impact strengthreached the maximum with tensile strength and toughness growing; The modified nano SiO₂facilitated the crystallization of PCL/Poly（3HB-co-4HB） matrix with the crystallization raterising dramatically; an excessive of modified nano SiO₂will block crystallization instead;Under a certain shear rate, as the content of coupling agent increased, shear viscosity of thesystem decreased. With a low shear rate, the shear viscosity decreased quickly and tended tobe shear-thinning, and at the same time, creep behavior of materials increased and stability ofthe material declined; the nano SiO₂accelerated the degradation of composites.Finally, A phosphorescent Re（I） was synthesized and compositiuie nanofiber wasprepared by doped PS and PS/PCL matrix. The optical stability, permeability and mechanicalproperties of the composite nanofiber material were studied. The results showed5.5%dopingconcentration was the optimum with sensitivity4.14, when light stability was best withoutbleaching phenomenon. The complex nanofiber with a small amount of PCL has bettermechanical properties of composite fiber, favorable luminescence property andbiodegradation, which can be applied in optical oxygen sensing field, packaging and anticounterfeit papermaking in the future.