Preparation And Properties Of PLA/PCL Blends Filled With Kaolin And Boron Nitride Nanosheets

At present,the production of polymer materials mainly depends on primary energy fossil energy.It is difficult to recycle or completely degrade after being discarded,which brings serious harm to the ecological environment.At the same time,polymer materials have many problems,such as poor mechanical properties,low rigidity,poor heat resistance and so on.For the sustainable development of human economy and society,the development of high-performance environment-friendly polymer materials has become a research hotspot.In this project,polylactic acid(PLA),a widely used biodegradable material,was selected as the matrix material.In order to overcome the brittleness of PLA,polycaprolactone(PCL)and PLA were used to make polymer blends.PCL,which is a biodegradable material,has good toughness and it is usually used as plasticizer and lowtemperature impact modifier.In this project,they are combined by melt blending.When the mass ratio of PLA to PCL is 1:1,the blends show sea sea structure in microstructure.When the mass ratio of PLA to PCL is different,the blends show sea island structure in microstructure.Hexagonal boron nitride nanosheets(h-BNNS)were prepared by ultrasonic liquid phase exfoliation method and was added into PLA/PCL to improve the thermal conductivity of the composites.The results of tensile test show that the mechanical properties of PLA and PCL are better when the ratio of PLA and PCL is 70:30(wt%).The tensile strength reaches20.54 MPa and the elongation at break is 7.15%.On this basis,the mechanical properties of the composite were further improved by adding kaolin.The effects of different content of filler on the mechanical properties of composite were studied.Maleic anhydride(MA)was used as compatibilizer and BPO was used as initiator.The SEM results of the composites with kaolin showed that kaolin was dispersed in the interface between PLA and PCL or PCL phase.The kaolin was dispersed evenly after maleic anhydride was added.The results of mechanical properties test show that the tensile strength,elongation at break and bending properties of the composites are improved after adding kaolin and maleic anhydride.The tensile strength of 0.02MA-K/PLA/PCL is higher than other samples.Its tensile strength is 41.2MPa and elongation at break is 13.2%.The thermal conductivity of the composites with h-BNNS was tested by infrared temperature measurement imager.The results show that the thermal conductivity of the composites with h-BNNS is significantly improved.At the same time,the thermal conductivity of the composites can be significantly affected by changing the feeding order in the blending process.The thermal conductivity of the composites with PLA and PCL added first and hBNNS added later is better.Combined with SEM micrographs,we found that h-BNNS dispersed at the interface of the two phases.A continuous heat conduction network has formed,which significantly improved the thermal conductivity of the composites.