Lei Qingquan

The role of water molecules in low density polyethylene

Experimental results show the water molecule, as a plasticizer, or via ohmic conduction and its strong poling field, to be able to accelerate the charge decay of the poled LDPE specimen; also, as an accepter, to assist charge injection during poling of specimens. A newly found humidity-induced TSC peak at medium temperature could be attributed to dissociated ions from trap in amorphous-crystalline interface.

Thermally stimulated current study of low-density polyethylene with and without inorganic filler

By measuring thermally stimulated current (TSC) spectra at various poling parameters in low-density polyethylene with and without filler (kaolin), (f-LDPE and LDPE), we show that the TSC spectra have a significant distinction. By analysing the change of peak current and temperature, and activation energy with poling field, we can see that TSC in f-LDPE comes from dipole relaxation due to polar groups in filler catching electrons injected at high field, rather than detrapping of captured electrons in interfacial trap between filler and polymer. So this filler, as a deeper trap stemming from its polar group or interface, plays the role of electron accepter. TSC spectra of LDPE possess the marked characteristic of electron release from traps in amorphous-crystalline interface or crystalline region.

Study of electroinjection of genes in cell under electrical fields

Electroinjection of foreign genes into freely suspended cells was based on the reversible electrical breakdown of the cell membrane under an electrical field. It leads to the controllable, reversible permeability of the normally almost impermeable cell membrane. Here, we have studied the effect of the electrical parameters, cell and DNA concentration transformation efficiency, by comparing the experimental results, and obtained a set of optimum parameters. We have also given a reasonable interpretation of these results.