| Plasma is a kind of substantial state which could be produced under high temperature or given conditions. Low temperature plasma is the ideal one among the technology of polymer surface modification. Many studies have been reported on the modification by low temperature plasma, but there are few reports on the density and change discipline of active radicals about the polymer surface after plasma treatment. So in this paper we focus on the research of a new method — the 2,2,6,6-Tetramethyl-1-piperidinyloxy radical (TEMPO)method to measure the radicals of PU and PE after plasma .First, we used low temperature plasma to radiate the surface of PU and measure the radicals concentration by TEMPO method, then under the conditions at which the radicals have optimal concentration, PU was treated by plasma to graft with Acrylic acid (AA) in order to testify the dependability of the TEMPO method. The effects of various conditions on radicals concentration were investigated. In addition, the influences of react conditions on grafting rate were discussed, the acrylic acid grafted on the surfaces was characterized by Scanning electron microscopy (SEM). The results suggest that the change of radicals created by plasma has a certain discipline, the TEMPO method can determine the concentration of radicals effectively.Second, we radiated the surface of PE by low temperature plasma and measured the radicals concentration by TEMPO method . The effects of various conditions on radicals concentration were investigated. Through the graft with acrylamide(AM), we found that there is favourable dovetail between change discipline of radicals and grafting rate. The results indicate that the TEMPO method is a reliable method to determine the concentration of radicals. Furthermore, the surface radicals were compared between PU and PE after plasma, preliminarily, the conclusion is that the radiation resistance of PE is better than that of PU, but its heat resistance is worse than that of PU.
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