Surface Modification Of Poly(Ethelene Terephthlate) By Radio Frequency Plasma

Poly(ethylene terephthalate) (PET) samples are modified by oxygen radio frequency (RF)capacitively coupled plasma, inductively coupled plasma, and inductively coupled plasmawith a RF bias, respectively. Surface morphology, functional groups, and wettability of theplasma modified PET samples are characterized by using atomic force microscopy (AFM),attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, anddynamic contact angle (DCA) measurement. Surface roughness (Ra) of the plasma modifiedPET samples increases from 0.443 nm for original surface to 2.779, 0.862, and 4.062 nm for300 s exposure by capacitively coupled plasma, inductively coupled plasma, and inductivelycoupled plasma with the biasing voltage, The-OH/C-H peak ratio in ATR-FTIR spectrarepresents that the content of the oxygen-containing polar functional groups on the surface ofthe plasma modified PET samples increases from 0.325 for original surface to 0.365, 0.343,and 0.351 for 40 s exposure by three coupled types of RF plasma, and changes to 0.340, 0.343,and 0.337 for 300 s exposure. The optimum wettability of the surface of the PET samplesmodified by three types of RF plasma is evaluated by dynamic contact angle, for advancingcontact angle (θ_A) of 53.4, 50.0, and 37.0°, and receding contact angle (θ_R) of 39.5, 37.2, and24.4°. At the storage temperatures of-10 and 25℃, theθ_A of the PET sample modified by RFcapacitively coupled plasma increases for 12 and 7°during 12 days storage, respectively. Forprolonged storage time up to 30 days, theθ_A keeps at constant. However, theθ_R isindependent on the storage temperature and storage time. It is found that content of theoxygen containing polar functional groups on the surface of the PET samples modified bythree types of RF plasma determines the hydrophilicity by a decrease of the advancing angle.Surface morphology mainly affects the receding angle of the modified surface.