CONDUCTIVE POLYETHYLENE AS SENSITIVE LAYER FOR GAS-DETECTION

Experimental results on the gas-sensing properties of composite polymer thin films are presented. This is the first study on such a composite in a sensor device application. Films are elaborated from a low-density polyethylene powder containing 1.5 wt.% of crystalline tetrathiofulvalinium-tetracyanoquinodimethane (TTF-TCNQ) organic salts as con ducting additives. Samples are cast onto ITO glass substrates at 80 degrees C using the so-called reticulate doping technique, and exhibit transversal conductivities of the order of 10(-9) Ohm(-1) cm(-1). D.c. measurements are performed to investigate the gas-detection properties of the film in the presence of CO2, NO2, O-2 and humidity species in an argon gas flow. Several interesting responses are observed at room temperature, such as reversible (CO2, O-2), non-reversible (NO2) or partially reversible (humidity). Response times from 5 min up to 1.5 h, and sensitivities from 15 up to 50% by absorption of 'polluting' gases in the concentrations usually encountered, are evaluated. Absorption results and the stability of the mechanical properties of the films are rather encouraging for the future of these composite polymer structures in the domain of gas detection.