Study On Surface Structure Regulation Of Superhydrophobic Polylactic Acid Film Based On Yogurt Packaging

Leben is more and more favored by consumers because of its good health care effect on human body.However,as a viscous liquid food,there will always be a lot of yogurt adhered to the surface of packaging materials after eating,resulting in waste and confusion of consumers.In this thesis,the degradable polylactic acid(PLLA)was selected as the matrix from the point of view of environmental protection,and the hydrophobic flexible polydimethylsiloxane(PDMS)chain segment was introduced through chemical polymerization reaction to modify it.Furthermore,different proportions of nano-sized hydrophobic silica(Si O2)were added by physical blending method to improve the hydrophobic properties of the materials,and the blend hydrophobic materials were prepared.On this basis,the surface structures of different microarrays are obtained by hot pressing with different size templates.Finally,the milk was fermented by lactic acid bacteria,and the yoghurt with different viscosity was prepared by controlling the time of stirring yoghurt.The adhesion of yoghurt on the surface of the commercially available cup acid cover film and the film prepared in this thesis was analyzed.The results show that compared with pure PLLA,the introduction of PDMS increases the contact Angle of the material.With the addition of Si O2,the contact Angle of the material further increases.Then,the superhydrophobic films are prepared by hot pressing template.The contact Angle of the mixed film with 0.5% Si O2 is up to 122°,and the contact Angle of distilled water is up to 153° after hot pressing with 80?m convex template(?-80),which shows the superhydrophobic effect.The residual amount of adhesion to yoghurt with viscosity of 300 m Pa·s and 400 m Pa·s was only 17.9% and 9.4%.After hot pressing with ?-350 template,the residue was reduced by 20.9% compared with that of the commercially available cup acid cover film when adhened to yogurt with viscosity of 500 MPa ·s.This indicates that it is feasible to reduce the adhesion of yoghurt by increasing the contact Angle of the film surface.Meanwhile,it can be concluded that the yoghurt viscosity is matched with the convex diameter and concave-convex gap of the film surface structure,which can significantly reduce the residual amount of yoghurt.