Study On The Method Of Microstructure Array To Adjust Wettability Of Polymer Surface

The hydrophobic surface in nature provides a template for the preparation of bionic hydrophobic surface.In practical applications,sometimes it is necessary to quickly roll off the liquid from the surface of the object,and the hydrophobic surface with the "Lotus leaf effect" has such characteristics,such as in the in the field of self-cleaning,drag reduction,anti fog,etc.But sometimes it also needs droplets to adhere to the solid surface,and the hydrophobic surface with "Petal effect" is just suitable for such occasions,such as in the in the field of micro-liquid nondestructive transportation,sample analysis,liquid collection,etc.According to actual needs,the construction of array microstructures with different shapes can realize the preparation of hydrophobic surfaces with different characteristics.In this paper,the method of forming hydrophobic units with different structure and size parameters on the surface of plastic parts by injection molding process is proposed to prepare hydrophobic surfaces with different hydrophobicity capacity.First of all,the microstructure array with different structural size parameters was processed on the surface of the mold insert by laser processing.The influence of different scanning path,laser power and scanning times on the microstructure processing effect of the insert surface was studied.It was found that the processing effect was more ideal when using concentric ring path and 20% power processing,and the microstructure profile was more uniform and smooth with the increase of the number of laser scans.Secondly,the influence of the injection molding process parameters on the warpage of the PP thin-walled parts was studied,and the using of annealing process was proposed to further reduce the warpage.The results showed that the amount of warpage increased with the increase of injection pressure,injection speed and mold temperature,but decreased with the increase of cooling time.When the melt temperature and holding pressure was increased,the amount of warpage decreased first and then increased.In addition,annealing process could reduce the warpage of thin-walled parts by 20 to 40%.Thirdly,by measuring the contact angle of 120 microstructural units on the surface of the plastic part,the effects of the spacing,height and bottom diameter of the microstructure on the size of the contact angle were explored respectively.The results showed that the existence of the array microstructure reduced the solid-liquid contact area to a certain extent,so that the original contact angle of the surface increased from 55.01° to 95.7~149.06°.And the size parameters of the corresponding maximum contact angle were: spacing 160?m,height 94.35?m,bottom diameter 150?m,which could reach the quasi superhydrophobic level.Within the set size parameter range,the contact angle decreased with the increase of the microstructure array spacing,but increased with the increase of the height and diameter.In other words,the relatively tall and compact structure was beneficial to increase the contact angle.Different microstructure sizes could adjust the degree of hydrophobicity on the surface of plastic partsFinally,by tilting the thin-walled plastic parts with static droplets at different angles,it was found that the surface of the plastic parts with microstructure had obvious contact angle hysteresis.And the droplets would not drip when the plastic part was turned 180°,which showed that the surface of plastic parts had strong adhesion and significant "Petal effect".For the rough surface without low surface energy modification,the existence of microstructure not only enhanced the solid-liquid interface force,but also increased the energy barrier when the droplets moved on the surface due to the pinning effect on the top of the microstructure.Both of these enhanced the adhesion of solid surfaces.The research content of this paper is of great research significance for improving the wettability of the polymer surface and the realizing controllable adjustment of its hydrophobic capacity.A method is provided to prepare polymer surfaces with different hydrophobic properties.