Research On The Lubricant Modification For Mrdical Polypropylene

Due to the excellent properties of polypropylene(PP),such as light weight,low price,health,thermostability,processed easily and so on,it has been one of the most important materials of medical products.It makes up approximately one in seven of the total and rank the second place.Unfortunately,the ordinary polypropylene has many drawbacks,including rough surface,unhydrophilic surface,which couldn't meet the demand of the medical plastic products and constrain its application.In order to overcome those shortcoming,the research on modifying polypropylene is necessary.In this paper two kinds of surface modification method of PP were presented.They were adding lubricants in polypropylene and surface coating.According to the selective standards of medical additives and the comprehensive performance of index of the additives,the two kind of lubricants were choosed which were stearic acid glyceride and zinc stearate.The crystallization behavior and rheological behavior of the blend of PP/lubricants were studied by DSC,XRD and dual capillary rheometry.The migration behavior of lubricant in PP were researched using UV spectrum and FTIR-ATR.Firstly the enrichment processing and plasma treatment for the blend of PP/lubricant were conducted and then PVP coating modification were employed.The surface properties and surface composition of the samples were characterized by contact Angle meter,friction coefficient apparatus and XPS.The results were as follows:1.The influence on polypropylene crystallization behavior of the two lubricants was different.The addition of GMS improved the crystallinity of PP,making the crystallization of PP more perfect.While the addition of zinc stearate reduced the crystallization temperature and the crystallinity of PP were also decreased.The research results of the kinetics crystallization indicated that glyceryl monostearate was mainly to promote the formation process of the crystal nuclei,while zinc stearate was to promote the crystal growth of PP2.The rheological behavior of polypropylene showed that PP was a pseudoplastic fluid,presenting obviously shear thinned phenomenon.Compared with pure PP,The viscosity and the flow activation energy reduced significantly for the blends of PP with an addition of lubricants(GMS,ZnSt2).The non-Newtonian index of PP/lubricants was less than virgin PP,which indicated that the blends were more sensitive to shear rate,which improved the performance of the polypropylene processing.3.The migration behavior of lubricants in polypropylene occurred and the migration amount was effected by its initial content,temperature and time parameters.The migrated mount of GMS from polypropylene to the surface increased with the increase of the initial content and treatment temperature.The migrated mount of the lubricants increased with the increase of processing time.The change of migration quantity was obvious in the early.The change of quantity was not apparent after 100 hours and the lubricant migration process achieved a state of balance at last.4.With an addition of lubricants,the surface hydrophilic of PP were improved..The water contact angle and friction coefficient were decreased.The migration process of the lubricant were further proceeded in the processing of high temperature enrichment treatment.As a result,the lubricity of the sample was further improved.After the plasma treatment,the surface of PP produced a large amounts of oxygen groups.As a result the water contact angle was dropped substantially and the hydrophilic proformance was improved largely.5.The characteristic peaks such as C = O,O-C = O,C-N,O-Zn2 +-O groups appeared on the surface of PP,which indicated zinc stearate in PP achieved a good surface enrichment effect and connected with PP surface through the adsorption or the surface grafted way.The surface friction and coefficient water contact angle were much less than pure polypropylene.