Preparation And Properities Of Nano Calcium Carbonate/Polylactic Acid Composites

Petroleum-based polymer materials have brought countless convenience to people,but also brought a lot of burden to the environment."White pollution"is becoming an increasingly serious problem.Polylactic acid(PLA)is a biodegradable material with excellent mechanical properties and has attracted more and more attention.However,PLA has disadvantages such as high cost and difficulty in coloring,which limit its application in more fields.Nano calcium carbonate(nano-CaCO₃)is one of the inorganic nanoparticles with the highest yield and lowest cost in the world,and is a environmentally friendly material,which is often used as the filler for PLA.The surface of the commercialized nano-CaCO₃ is generally modified by fatty acids,but the compatibility between modified nano-CaCO₃ and PLA is poor.In this paper,two methods were adopted to modify the surface of nano-CaCO₃.Nano-CaCO₃was modified by lactic acid oligomer to increase the compatibility between nano-CaCO₃ and PLA.Nano-CaCO₃ was modified by acid dye to explore the colouring method of PLA.Then modified nano-CaCO₃ were filled into PLA to prepare PLA matrix composites,and the properties of the composites were studied.Nano-CaCO₃ modified by lactic acid oligomer/Polylactic acid(g-CaCO₃/PLA)composite.Lactic acid oligomers were prepared by melting polycondensation and grafted onto the surface of nano-CaCO₃ to obtain modified CaCO(g-CaCO₃).Then g-CaCO₃/PLA composites were prepared by solution casting method.FTIR and oil absorption value were used to characterize g-CaCO₃.SEM,DSC,universal testing machine,rheometer,water vapor transmission tester and UV-Vis spectrophotometer were used to study the g-CaCO₃/PLA composites.The results showed that the modification of lactic acid oligomers reduced the oil absorption value of nano-CaCO₃,increased the compatibility of nano-CaCO₃ and PLA,and improved the dispersion of nano-CaCO₃ in PLA matrix.The g-CaCO₃ acted as nucleating agent,enhanced the crystallization ability of the PLA.The tensile strength and strain at break of the g-CaCO₃/PLA composites first rised and then fallen as the g-CaCO₃ content.When the g-CaCO₃ content was 5%,the tensile strength of g-CaCO₃/PLA composites reached 80 MPa,and was 50%higher than that of 5%CaCO₃/PLA composite(53.4MPa),and was 20%higher than that of pure PLA(67 MPa).When the g-CaCO₃ content was 10%,,the tensile strength(76.1 MPa)was still 13%higher than pure PLA.In addition,the addition of g-CaCO₃ improved the storage modulus and complex viscosity of PLA,and enhanced the barrier property of PLA to ultraviolet visible light and water vapor.Nano-CaCO₃ modified by acid dye/PLA(color nano-CaCO₃/PLA)composites.In the aqueous phase,the acid dye was deposited on thse surface of nano-CaCO₃ to obtain colored nano-CaCO₃,and then the color nano-CaCO₃/PLA composites were prepared by melt blending method.The results showed that by filling colored nano-CaCO₃ into PLA,a better colouring effect was obtained.The dye was fixed on the surface of nano-CaCO₃,which effectively enhanced the color fastness to washing.Compared with pure PLA,The mechanical properties of color nano-CaCO₃/PLA composites had been enhanced to a certain extent.In addition,colored nano-CaCO₃ improved the barrier property of PLA to ultraviolet and visible light.At the same time,the addition of colored nano-CaCO₃ reduced the cost of PLA and increased the cost performance of color PLA products,and provided a potential way for PLA coloring.