Low Temperature Activation And Induced Grafting On Surface Of Polypropylene By Argon And Oxygen Mixture Plasma

Because of its excellent comprehensive properties,polypropylene is widely used in machinery,automobiles,electrical appliances,construction,textiles,packaging,chemicals,medical equipment and other fields.However,the lack of polar groups in the molecular chain results in poor hydrophilicity,which greatly limits the application range of polypropylene products.In order to overcome the shortcomings of its poor hydrophilicity,this article chooses plasma surface treatment as the basis,adopts two methods,namely:plasma modification of polypropylene surface hydrophilicity,plasma-induced grafting of diethylenetriamine,using FTIR,AFM and contact angle testing to study the changes in the surface functional groups,micro-morphology,roughness and contact angle of the film during the modification process,and the effects of various process parameters on surface hydrophilicity of polypropylene,the results were shown below:It was found that the high-energy particles generated by the plasma break the C-C and C-H bonds on the surface of polypropylene,more polar-C=O and-OH groups were formed.With the increase of gas flow,processing time,power and pressure,the content of polar components gradually increases,the contact angle gradually decreases,and the surface roughness gradually increases.Through single factor experiments,the optimal process conditions for plasma treatment are obtained:treatment time is 5 min,power is 300 W,pressure is 80 Pa,and the optimal flow rates of Ar/O2 is 40/10 sccm,under optimal conditions,the surface contact angle of plasma treated polypropylene film can reaches 32°.When the film was placed in air for 30 days,the contact angle of the film to water recovered to about 90°,indicating that the plasma-treated polypropylene film has obvious timeliness.In order to improve the timeliness of plasma treatment of thin films,this paper used surface induced grafting method to treat the PP films.The effects of Soaking time,soaking temperature and soaking concentration on microstructure of film,group and contact angle were researched.After immersing in diethylenetriamine,the absorption peak of N-H bond appeared in the infrared spectrum,indicating that the double bond of diethylenetriamine had grafted reaction.As the immersion time increases,the contact angle of the film surface first increases and then decreases.When immersed for 30 s,the contact angle of the film to water increases from 35° to 72°.On the one hand,it is due to the relatively small amount of diethylenetriamine.The surface is arranged flat,with the hydrophobic C-C segments facing the outside.In addition,the surface of the sample after plasma activation is unstable.Cleaning causes some active groups to be inactivated,and the number of grafts of diethylenetriamine on the membrane surface is small,resulting in contact angle Elevated.As the immersion temperature increases,the contact angle of the film surface decreases first and then increases.When the grafting temperature exceeds 60?,the contact angle of the film increases from 35° to 42°.This is due to the increase in the kinetic energy of diethylenetriamine adsorbed on the film.The molecules on the surface can easily break away from the adsorption and leave the surface,causing the grafting rate to decrease instead.As the immersion concentration increases,the contact angle of the film surface also decreases first and then increases.When the monomer concentration exceeds 70%,the contact angle increases from 34°to 50°.This is due to the free radicals and monomers generated after plasma treatment.The binding reaction of diethylenetriamine is a chain reaction,and the mass fraction of diethylenetriamine is moderate,which is beneficial to the grafting reaction.Through single-factor experimental research,it was found that the optimal reaction conditions for surface-induced grafting were:grafting temperature of 60?,grafting time of 180s,and grafting monomer concentration of 70%.The timeliness of polypropylene film treated by surface grafting in air is significantly improved.As the storage time is extended to 30 days,the contact angle of grafted polypropylene hardly changes,just from 34 to 35°.