Study On The Laser Surface Modification Of Inert Polymer Polyphenylene Sulfide

Compared with other engineering plastics,polyphenylene sulfide?PPS?has many outstanding properties.But its poor surface wettability and adhesion strength with other material layers have greatly limited the PPS's application in many areas.Therefore,there is an urgent need for the surface modification of PPS to improve its properties.In this study,the surface of PPS was modified by a 355nm-wavelength ultraviolet?UV?pulse laser and a 1064nm-wavelength infrared?IR?pulse fiber laser.The effects of laser fluence?LF?and spot overlap percentage?SOP?on the surface microstructure and chemical composition were studied by scanning electron microscopy?SEM?,x-ray photoelectron spectroscopy?XPS?,and contact angle measurement technology.The influence mechanism of the surface microstructure and chemical composition on the wettability and adhesion strength were discussed in detail.The experiments showed that,if the LF or SOP was high enough,the surface microstructure and roughness would change.At the same time,the chemical bonds in the PPS molecules would be broken,and then,reacted with oxygen-containing spcies in the air,to generate groups such as C=O,COO-,-SO,-SO₂,-SO₄,and so on.Thus,the surface chemical element content would change,in which the contents of elements C and O changed significantly,while element S content was only slightly reduced.It was thought that the interaction mechanism between the UV laser and PPS transferred from mainly photochemical effect?when the LF is low?to synergistic effect of photochemical and photothermal effects?when the LF is high?,and the surface microstructure of PPS changed from periodic pore structure to molten structure.At the same time,the surface roughness increased first,decreased subsequently,and then increased continuously.In the condition of the infrared?IR?pulse fiber laser,with the increase of the LF,the photothermal effect was thought to be dominant,and the surface had changed from periodic fluctuation structure to molten microstructure.Because the photothermal effect of IR laser was much stronger than that of UV laser,some melted and solidified glass micron and nanoparticles from the filled glass fibers in the PPS were found to distribute on the modified surface.At the same time,after a little change first,the surface roughness increased continuously.Although,the surface O/C element content ratio textured by the both lasers increased with the increase of the LF,the O/C ratio after the modification by the UV laser was higher.This was because there was a photochemical effect between the UV laser and PPS.On the other hand,when the SOP was higher than 0%,the increase of SOP could greatly enhance the heat effect of PPS surface.The both surface roughnesses of PPS textured by the two lasers changed little when the SOP was less than 0%,and then continued to increase with the SOP increasing.Especially,when the SOP reached 50%,both the molten structure and O/C ratio of PPS textured by the UV laser were greatly increased,while the surface O/C ratio textured by the IR laser reduced due to the carbonization.The surface microstructure and O/C ratio of PPS had an important effect on its wettability.When the LF was high enough,the PPS textured by the two lasers both could obtain a super-hydrophilic surface.While a near super-hydrophobic surface?the water contact angle was about 142°?could be obtained when changing the SOP at an IR laser LF of 15.70J/cm².The micro-pore structure was thought to be the main factor that ensured the good surface adhesion strength with an appropriate UV laser LF.