| PTFE films usually are made by hot extrusion craft.This kind of PTFE film is a milky low-density film.The PTFE film of this research is a translucent high-density film.Its performance is significantly different from the low-density PTFE film.In order to understand the structure and properties of high-density PTFE films and find its potential applications,this research is focused on three aspects:(1)Structure and performance of PTFE films:infrared spectroscopy(ATR-FTIR),surface element analysis(EDS and XPS),surface Morphology(SEM and AFM),thermal analysis(TG/DTA and DSC),crystallinity(XRD)and other test methods were used to study the differences in structure and performance of low-density PTFE films and high-density PTFE films.(2)Plasma modification of high-density PTFE films:peel strength,wettability,photoelectron spectroscopy(XPS)and surface morphology(SEM and AFM)were used to study the effects of the gas types,discharge power,discharge time and gas flow rate on the adhesion and wettability of high-density PTFE films.(3)Dopamine modification of high-density PTFE film:Dopamine modification based on nitrogen plasma treatment and water-based PU coating was studied,and changes in surface properties,surface morphology,and wettability of the dopamine-modified PTFE film were investigated.Research results were as follows:(1)The high-density PTFE film has a higher crystallinity(89%),which is 10%higher than the low-density PTFE film;the crystal melting and recrystallization processes of the high-density PTFE film are very close,but the weight loss temperature at 2%weight loss rate of the high-density PTFE film is 500.9?,which is much higher than the low density PTFE film(weight loss temperature is 406.2?)(2)The surface roughness of the high-density PTFE film is lower than that of the low-density PTFE film.It has a lower surface energy,the surface energy decreases from 22.7 mN/m to 19.8 mN/m.The high-density PTFE film has a better mechanical property The breaking strength and elongation at break are respectively increased by 14.3%and 161.4%compared with the low-density PTFE film.(3)The optimized oxygen plasma treatment craft for high-density PTFE film is:300w power,5 cm3/min flow rate and 2 min time.The highest peel strength can be obtained under this craft.Nitrogen plasma-treated PTFE film has the highest peel strength and water contact angle,with a 539.8%increase in peel strength and a 11.4° increase in contact angle;Due to the contribution of the lotus leaf morphology with concave and convex grooves,the bonding strength and hydrophobicity of the plasma-treated PTFE film increased,and the original parallel cracks of the high-density PTFE film accelerate the formation of lotus leaf morphology.To Oxygen plasma-treated PTFE films,when the discharge volume is less than 36 kJ,the peeling strength have a nearly linear relationship with the discharge volume.which can be contributed to the combined effect of new functional groups and etching on the surface of the films.Continuing to increase the discharge volume,The peeling strength have a logical mathematical relationship with the discharge volume,which is mainly contributed to the steadiness of lotus leaf morphology of the film surface(4)Nitrogen plasma treatment of high-density PTFE film can enhance the surface activity and roughness of the film,and increase the adhesion between PTFE film and water-based PU because of the introduction of nitrogen-containing active groups and the increase of C/F ratio,which can enhance chemical crosslinking with water-based PU.The main reason that dopamine can be deposited on the surface of PU-PTFE film is that PU contains a large number of positively charged N-H groups,which can produce cation-?interaction with the aromatic in PDA.Dopamine-modified PDA-PTFE film has good hydrophilicity,antistatic,light-shielding and ultraviolet resistance.Its water contact angle is 65.5°,the electrostatic half-life is 3.4 s,the light transmittance is 2.99%,and UVA and UVB transmission all are 0.14%. |
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