Study On PHBH Packaging Film Modifidy By Nano-SiO₂

Poly-3-hydroxybutyrate-co-3-hydroxyhexanoate(PHBH)is a natural degradable plastic packaging material witch has good biodegradability and biocompatibility,and the physical properties are similar to the traditional plastic packaging materials.PHBH is one of the best choice to replace the traditional plastics.However,pure PHBH has many disadvantages,such as poor crystallinity,poor thermal stability,poor mechanical properties,and poor barrier properties,which limit its widespread use.In this paper,a nanocomposite packaging films was prepared by solution casting method modified by nanosilica,and in order to improve the dispersion of nanosilica,the nanosilica was modified by y-(methacryloyloxy)propyltrimethoxysilane(KH570).Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),polarimetric microscope(POM),thermal gravimetric analysis(TGA),differential scanning calorimetry(DSC),mechanical and barrier properties have been used to characterize nanocomposite packaging films to study the section morphology,thermal stability,crystallinity,mechanical properties and barrier properties.The results show that:The thermal stability and crystallinity of the nanocomposite packaging films were improved by adding unmodified nanosilica into the PHBH matrix,and the lager particles of aggregates appeared when the content of nanosilica exceeded 2wt%.At the same time,the elongation at break of the nanocomposite packaging films decreased gradually,but the tensile strength and the yong’s modulus increased by 40.1%and 60.6%respectively compared to pure PHBH,and the barrier of nanocomposite packaging films is much better.Using KH570 to modified nanosilica,TEM and FTIR indicated that KH570 was successfully grafted onto the surface of nanosilica.Nanosilica could be better dispersion at a content of 5 wt%.The dispersion of modified nanosilica in PHBH matrix is greatly improved,and a small amount of aggregates occurs when the nanosilica content is 9wt%.The thermal decomposition temperature range of the nanocomposite packaging films is increased by 13.5℃,the thermal stability and the crystallinity are both increased.The elongation at break decreases gradually,even from ductile fracture to brittle fracture,but the tensile strength and yong’s modulus increased by 70.8%and 75.4%respectively.When the nanosilica content is 5wt%,the oxygen transmission is reduced from pure PHBH 263cm3/cm2·d·Pa to 36.6cm3/cm2·d·Pa,the water vapor transmission was reduced from 63.3g/m2·24h to 43.3g/m2·24h...