It is a hydrophilic modification method with simple process, good effect and cleaning resistance, which can effectively improve the hydrophilicity of the surface of the polyethylene glycol terephthalate (PET) film. Due to the defects of the existing PET hydrophilic modification methods, such as high equipment cost, complicated operation, this paper studies the use of polyvinyl pyrrolidone (PVP) as modifier and tert-butyl hydroperoxide (TBHP) as initiator for the shortcomings of the existing methods, the hydrophilicity of the PET film is significantly improved by grafting. Cut the PET film into a 1 cm×4 cm rectangle spline, put the spline into a centrifuge tube filled with absolute ethanol, clean it with an ultrasonic cleaner (SB-5200DTDN), and dry it in a vacuum drying oven (DHG-9075A). Put it into TBHP solution to initiate the reaction. The PET film strips that have been initiated are sequentially cleaned with absolute ethanol and water ultrasonically, and then put into PVP solution for modification. Finally, ultrasonically cleaned and dried for 24 hours using a contact angle measuring instrument (JC2000D1) and Fourier transform infrared spectrometer (TENSOR 27) to conduct contact angle test and infrared spectrum test to evaluate the hydrophilicity and surface composition changes of PET films respectively. First, the PET film is cut and pretreated with ultrasonic cleaning, followed by initiation and modification reactions; Second, during the initiation reaction, different amounts of TBHP (0%, 1%, 2%, 3%, 4%) were added, and the temperature-controlled magnetic stirrer (ZNCL-DB230) was used at 40 ℃ and the rotation speed was 450 r/min with heating and stirring; Third, after ultrasonic cleaning, change the type of PVP (PVP-K17, PVP-K30, PVP-K90) and dosage (0%, 2.5%, 5%, 7.5%, 10%), the modification reaction is carried out under the condition of rotating speed 600 r/min, 80 ℃, the final sample can be obtained by ultrasonic cleaning and drying and placing for 24 h. During the contact angle test of the sample, drop 2 μL of water droplets on the sample to be tested at least at 5 different positions, read the static contact angle measured by the water droplets at each position, and take the average value; in the infrared spectrum test, after PVP drying in a vacuum drying oven at 50 ℃ for 24 hours, the samples were prepared and tested by the tableting method. The PET and its hydrophilic modified samples were directly tested after being dried in a vacuum drying oven at 50 ℃ for 2 hours. The measurement range was 400-4 000 cm-1 and the resolution was 2 cm-1. PVP-K90 has the best modification effect on PET film, and the contact angle decreases most obviously, which is 21.3°. The effect of different concentrations of TBHP on the contact angle was studied. The contact angle decreased with the increase of TBHP concentration, and the contact angle was 28° when TBHP was 1%. The influence of different concentrations of PVP-K90 on the contact angle was investigated. With the increase of PVP-K90 concentration, the contact angle first decreased and then slightly increased, and reached the minimum value of 24.2° when PVP-K90 was 5%. The optimum formula and process were as follows: PVP-K90 5%, TBHP 1%, temperature 80 ℃, rotating speed 600 r/min and reaction time 1h. The contact angle of PET film decreased from 81.7° before modification to 29.5° after modification, and the hydrophilicity was significantly improved. The contact angle of the hydrophilic modified PET film remained unchanged after ultrasonic cleaning for more than 20 min. The characteristic peaks of the infrared spectra at 3 427 cm-1 and 1 608 cm-1 were significantly enhanced. PVP was grafted on the surface of PET in the form of chemical bonding. Therefore, using TBHP as initiator and PVP-K90 as modifier, the hydrophilicity of PET film can be improved by surface grafting. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.
