| Porous ploytetrafluoroethylene films prepared in porous PTFE electret by means of unidirectional stretching at a suitably high temperature is widely used as biological electret for its outstanding charge storage stability at high temperature, good ventilation and excellent biological compatibility .The inherent opening porosity structure of porous PTFE composite films have larger interface to air than non-porous PTFE,which drop the charge storage stability of porous PTFE composite films in line with environmental humidity.In order to improve the charge storage stability of porous PTFE films,we prepared the porous PTFE/PE/PP composite electret by heat melting the porous PTFE as charge storage layer, polyethylene (PE) as conglutinated layer and PP as water resistant layer.The composite electret film was measured by using methods of isothermal surface potential decay, open-circuit thermally stimulated discharge current spectra and scanning electron microscope in order to study. l)the charge storage stability of porous PTFE/PE/PP composite electret films and its charge dynamics characteristic;2)the influence of environmental humidity to charge storage stability of porous PTFE/PE/PP composite elcetret;3)the fluctuation to charge storage stability with porous PTFE/PE/PP composite electret by different porous PTFE and the feasibility of porous PTFE/PE/PP drug transdermal delivery in searching for new drug transdermal delivery preparation.It was shown that: l)Charge storage stability for porous PTFE/PE/PP composite electret was almost the same as that of porous PTFE electret.2)The charge storage stability of porous PTFE/PE/PP electret was closely related to the thickness of porous PTFE, and the composite films made of porous PTFE with the thickness of 70μm have the most excellent charge storage stability.3)Under the high humidity circumstance, porous PTFE/PE/PP electret exhibited more excellent charge storage stability than porous PTFE electret with the same thickness.4)The porous PTFE/PE/PP electret prepared from thicker porous PTFE showed better charge storage stability. 5)Surface ultrastructure of porous PTFE /PE/PP electret filmsshowed good agglutination by their scanning electron micrograph. 6)The porous PTFE/PE/PP electret prepared from thicker porous PTFE showed better charge storage stability with same initial surface potentials.6)Porous PTFE/PE/PP prepared from thinner porous PTFE showed better charge storage stability due to its much more complicated porosity.7)Porous PTFE/PE/PP composite electret is used as a drive resource in drug transdermal delivery study for its excellent charge storage stability.The results show that porous PTFE/PE/PP composite electret films have excellent charge storage stability and hydrophobicity and can be used as a kind of physical means to increase the drug transdermal delivery. Further experiments concerning the comparative study of porous PTFE/PE/PP composite electret formulation to chemical enhancers in drug transdermal delivery enhancement,the influence study of electret and electret formulation on skin ultramicro structure,the mechanism study of drug skin permeation enhancement by electret are in progress.The prospective results could be reached in near future.
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