Effect of polyethylene glycol surface modified nanodiamond on properties of polylactic acid nanocomposite films

Nanodiamond (ND) was surface modified by polyethylene glycol (PEG) to improve the interfacial adhesion between ND and the polylactic acid (PLA) matrix and achieve uniform nanoparticle dispersion in the matrix. PEG functionalized ND (ND-PEG) was successfully prepared by a novel and scalable modification method. Firstly, the ND particles oxidized by air was treated with dopamine, and then the hydroxyl groups on PEG and polydopamine (PDA) were covalently linked by isocyanate groups. The Fourier Transform Infrared spectroscopy, Thermogravimetric analysis and X-ray photoelectron spectroscopy reveal that PEG has been covalently boned on the surface of ND. Compared with those of pure PLA film, the tensile strength, tensile modulus and elongation at break of the nanocomposite films with PEG modified ND increase by 66.64%, 37.6% and 187.43%, respectively. In the meantime, the degradation temperature at the initial stage and the temperature at the maximum weight loss rate of the nanocomposite films are significantly increased. It is suggested that the incorporation of ND-PEG into PLA matrix is an effective method to improve the mechanical properties and thermal stability of PLA.