Preparation And Barrier Properties Of Diamond-like Carbon Films On Polymer Substrates

Diamond-like carbon(DLC)films have been widly used in aerospace,automotive,optical and bio-medical fields,due to high hardness,high elastic modulus,low coefficient of friction,exceptional wear resistance,light transmittance,excellent chemical inertness and bio-compatibility,etc.In this paper,Plasma enhance chemical vapor deposition(PECVD)method were adopted to deposite Diamond-like carbon films on PET and OPP films,which could be used as packaging materials,and the barrier and recycling performance could be improved significantly.PECVD process parameters were investigated to explore the preparation of DLC films on flexible Poly(ethylene terephthalate)(PET)and oriented polypropylene(OPP)films,and the barrier properties of DLC films were tested to optimize the process parameters.The DLC films deposited on PET and OPP surface were prepared by PECVD,and acetylene and argon gas were used as working gases.Raman,SEM and AFM were used to study the surface morphology and the internal structure of DLC films,and the barrier properties of PET and OPP films with DLC films had been tested.The results show that nano-crystalline DLC films are mainly composed of sp2 and sp3 hybrid hydrocarbons,and the thicker DLC films lead to the better films barrier properties.The oxygen barrier property and water vapor barrier property have been increased by 11 times and nearly 12 times respectively with the 0.76 ID/Ig ratio.DLC films with smooth,compact and uniform microstructure were observed on the overall OPP surface.When the RF power was increased from 200W to 1000W,the RMS decreases from 2.149nm to 0.989nm and the Ra decreases from 1.622nm to 0.776nm.A small RMS roughness indicates a smooth surface of the DLC film.The ID/Ig ratio can be obtained from the Raman spectrum,and the ratio can indicate the content of sp3 bond indirect.The sp3 bond will affect the barrier property of DLC films.The oxygen and carbon dioxide barrier properties of OPP films are increased by 7 times and 4 times respectively when the DLC films deposited at the RF power 1000W,Ar:C2H2= 1:2,deposition time 60s and deposition pressure 15Pa,and the ID/IG ratio of the DLC film is nearly 0.396 with the 17.9nm thickness of DLC films.