Xia Zhongfu

The excellent charge storage stability of porous polytetrafluoroethylene (PTFE) film electrets

The excellent charge storage stability both for negatively and positively corona charged porous polytetrafluoroethylene (PTFE) was studied by the isothermal surface potential decay measurements after constant voltage corona charging at room and elevated temperatures. The corona charged samples were aged at different temperatures and open-circuit Thermally Stimulated Discharge (TSD) experiments carried out. The comparison of the charge storage stability was investigated among porous PTFE, solid PTFE and Teflon FEP electrets. Their charge lifetimes were estimated by means of isothermal depolarization program in the several selected temperatures.

Charge storage and transport in polymethylmethacrylate (PMMA) film

Abstract In this paper, the PMMA films were prepared by spin-coating method. The films were charged by means of constant voltage corona charging. The charge storage stability and the transport of detrapping charges in the PMMA electrets were investigated by isothermal surface potential decay, open-circuit TSD current spectrum analysis. The shifts of mean charge depth for PMMA at different environment humidity and charging temperature were measured by heat pulse technique. The experimental results indicated that the charge storage stability of PMMA materials was significantly influenced by relative humidity. Charging at elevated temperature could improve charge storage stability in PMMA.

Electrochromic mechanism study of corona poled electro-optic polymer films

In the study of electro-optic polymers with nonlinear optical activity, the phenomena of electrochromic shifts and intensity decreases of charge-transfer absorption bands in the polymer film after corona poling have been used for real-time monitoring of the corona-poling process and poling stability. In this paper, the structure changes of the chromophore dipoles doped or chemically attached to polymer macromolecules before and after poling were investigated by measuring UV-VIS and IR spectra. The electrochromic mechanism was discussed. The results indicated that the main reason for the electrochromic shifts was the deformation of the conjugate /spl pi/ system in the chromophore dipole. The solvent used during specimen preparation affects the material structure.

Formation and Distribution of Space-Charge in Cross-Linked Polyethylene

The formation and distribution of space-charge in a cross-linked polyethylene (XLPE) sample are investigated by means of pressure wave propagation, infrared spectroscopy and electrostatic force microscopy (EFM). The related mechanism of space-charge distribution and the structure of XLPE are discussed. The EFM images show that quite large quantitative space-charges locate at the surface of spherulites.

Influence of environment humidity on properties of FEP, PTFE, PCTFE and PI film electrets

In this paper, the influence of environmental humidity on charge storage stability was investigated by means of isothermal surface potential decay and open-circuit TSD measurement. The shift of mean charge depth for these materials at different environmental humidities was studied by using the heat pulse technique.

Study of the inducement of PTFE electret on apoptosis of MKN tumor cell

By using the electrostatics field and microcurrent which was produced by an electret to induce the apoptosis process, we applied a /spl plusmn/300 V PTFE electret on the MKN tumor cell for 24, 48 and 72 h, respectively, to study the influence of electret on apoptosis by means of flow cytometry. It is shown that 1) compared with the control group, after 24 h action of -300 V PTFE on MKN tumor cell, the apoptosis amount of MKN tumor cell increased from 1% to 6% (some even to 15%) and intracellular calcium (Ca/sup +2/) concentration elevated, which indicated that the negative electret can enhance apoptosis;. 2) when +300 V PTFE was applied to MKN tumor cell for 24 h, it could restrain apoptosis; 3) with the increase of action time of electret on MKN tumor cell, the effect of induced apoptosis is proportional to the time.

Investigation of corona-charging of polypropylene at elevated temperatures

Stabilization of a negative charge in polypropylene (PP) corona charged at elevated temperatures is investigated. Measurements of corona current and TSC (thermally stimulated current) yield the charging efficiency and the structure of the trapping levels, respectively. With increasing charging temperatures, the TSC peaks shift to higher temperatures, while the charging efficiency drops. This can be made up partially by prolonging the charging time. A continuous distribution of trap levels has to be assumed, and a new phenomenological theory is suggested. To explain the shift of TSC peaks, trapping and detrapping are taken into account.<<ETX>>

The study of electret behaviour of rat skin with thermally stimulated discharge (TSD)

Thermally stimulated discharge (TSD) was used to study the changes of the dielectric properties of rat skin before and after charging, the properties of space charge and the dipole in the skin before and after charging. It was found that a) before charging, the current spectra appeared with several current peaks with different energy level distribution in the range RT-150/spl deg/C, which was related to the discharging of space charge and relaxation of the dipole during the transition of lamellar lipid and the denaturation of the protein of the stratum corneum (SC); b) positive charging caused a large increase of the intensity of TSD peak and a shift of the peak position to low temperature, due to the disordering of intercellular lipid bilayer and protein structure, and interaction between some dipole and space charges.

A study of the effect of PTFE electret on fibroblast cell cycle with flow cytometry (FCM)

In this paper, the PTFE films were respectively charged at /spl plusmn/300 V, /spl plusmn/500 V and /spl plusmn/1000 V by corona charge system. After applied on the cells for 24 h, 48 h and 72 h, the influence of electret on fibroblast (3T3 cell) cell cycle was studied with flow cytometry. The results indicated that 1) after action of negative PTFE electret field for 24 h, the cell number in G/sub 1/ phrase and G/sub 2/ phrase decreased, but increased in S phrase. It suggested that negative electret can improve cells growth. 2) negative electret can not only enhance the growth of cells, but also enhance the apoptosis of mutant cell. 3) after action of positive electret field on fibroblast for 24 h, the cell number in G/sub 1/ phrase increased, while the cell number decreased in S and G/sub 2/ phrase. Positive electret can block some cell in G/sub 1/ phrase. So it can restrain the growth of fibroblast cell. In short, electret has bilateral regulation effect on the enhancement and block of cell growth.

EFFECTS OF ELECTRET ON HYALURONIC ACID CONTENT AND VASCULAR PERMEABILITY OF SKIN OF SCALDED RATS

Abstract The changes in hyaluronic acid(HA) contents and skin vascular permeability of scalded rats were measured by FITC marked albumin and radioimmunoassay to study the influence of −100V, −250V, −500V, −750V and −1000V electret on the changes of HA contents and vascular permeability. The results showed that (1) 12h after scalding, the skin vascular permeability and serum HA contents increased markedly but a great decline of HA contents in skin tissue, and these changes can reflect the pathologic changes in inflammatory course. (2) 12h after treating with electret the skin vascular permeability and HA contents in serum decreased markedly and the reverse in skin tissue. The results suggested that electret is beneficial to retarding the decomposition of HA in tissue matrix produced by scalding and also is beneficial to the decrease of skin vascular permeability.