Mechanical And Optical Properties Of LLDPE/nano-silica Composites And Theory Simulation Of Relationship Between Modulus And Constituent

Polyolefih, whose output is the largest in polymer industry, has been widely used in many fields such as automatics, agriculture and package because of its low producing cost, good processibility and fine mechanical and optical properties of its products. However, this kind of resin also has some disadvantages such as low strength, bad heat resistance property and lacking of function, which limit its application to some extent. So the research of polyolefm composites with high performance and multiple functions is very important. In this paper, LLDPE/nano-silica composites have been prepared by melt-blending and the mechanical, optical and rheological properties were systemtically investigated. The effects of surface treatment methods of nano-silica on its dispersibility in LLDPE and on the optical performance of composites film have also been investigated detailedly Research in this paper laid a substantial theoretical foundation for the development and application of agricultural film that has high performance and multiple functions.The influence of the nano-silica content and its surface treatment methods on the microconfiguration of LLDPE/nano-silica composites was investigated using transmission electron microscope and particle size analysor. The result showed that the aggregate extent of nano-silica in LLDPE increased with an increase of nano-silica content. The dispersibility of nano-silica surface treated by silane coupling agent in an ultrasonic generator was better than that of nano-silica treated by silane coupling agent in a ballmill, for the former had a smaller particle size and more uniform distribution in LLDPE than the latter. The introduction of dispersant in the process of surface treatment using silane coupling agent in an ultrasonic generator further improved the dispersibility of nano-silica in LLDPE.The static and dynamic mechanical properties of LLDPE/nano-silica composites were investigated systematically. The result showed that the elastic modulus of the composites increased obviously with the increase of silica content and the elongation at break remained unchanged at lower content of silica. Both of the notch impact strength and tensile strength of the composites were improved with an increase of silica content and reached maximum when 3phr silica were introduced. As silica content increased, the storage modulus E' and loss modulus E" of LLDPE/nano-silica composites increased, at the same time the a transition peak of the composites shifted to lower temperature and its magnitude decreased.The elastic modulus of particle filled composites was investigated using three-phase model. The formative mechanism, thickness and modulus of mesophase were also investigated. The result showed that the volume fraction of mesophase increased but the thickness decreased with the increasing of filler content. The theoretical equation of composites modulus Ec with filler content f was consistent with the experimental result.The influence of silica content and surface treatment methods on the optical performance of LLDPE/nano-silica composites was investigated in detail. The result showed that the absorptivity of composites film for infrared ray ranging from 7um to Hum and ultraviolet ray below 300nm increased dramatically with the introduction of a small amount of nano-SiO2. Although the visible light transmittance of the film declined a little compared with pure LLDPE, the haze value increased much. It was also found that the surface-treatment methods of nano-SiO2 have great influence on the optical properties of the composites film. The IR and UV absorptivity as well as haze value of the composites filled with nano-SiO2 treated by silane coupling agent in an ultrasonic generator were superior to the composites filled withnano-SiO2 treated by silane coupling agent in a ball mill. This is because the former has smaller particle size and more uniform dispersion in matrix than the latter. The optical properties of composites film were further improved by the introduction of little amount d...