Properties of polymer-silver particles composites
Jerzy Myalski, Jakub Wieczorek
Quarterly No. 2, 2009 pages 175-180
DOI:
keywords: conductive composites, tribological properties, polymer matrix composites
abstract The paper presents the results of investigations of conductive polymer-matrix composites. As the matrix of the composites two most popular sliding polymer materials – polyamide and polytetrafluorethylene, were applied. Component providing electric conductivity were silver particles. Composites were manufactured by press moulding method and contained 30÷80% of silver by weight. Conducted investigations of electric properties have shown that good electric conductivity may be obtained after introducing about 50% of silver particles to the polymer matrix. It is caused by homogeneous spacing of silver particles, closing of the particles in polymer envelops of low thickness and increase in average number of contact points between individual silver particles. Such mass fraction of reinforcing component (silver particles) ensures also good mechanical properties of the composite. Taking into account a possibility of application of the composites as the elements periodically short-contacted (electric contactors) the tribological tests were also made. The tests let to determine an effect of the silver particles on friction coefficient and wear factor. The tribological tests were conducted on pin-on-disc system. As co-specimen in the friction-junction the pure silver pins and cast silver-glassy carbon particles composite pins were used. The results of the tests showed that value of friction coefficient is affected mainly by polymer matrix. The composites with polytetrafluorethylene show almost 2-times lower friction coefficient in comparison with the polyamide matrix composites. Such material may be used in friction-junctions as a sliding material. Change of content of silver particles in the composites only weakly affects a friction coefficient. Type of matrix decides also about wear processes and changes occurring in a surface area due to friction. Considerable decrease in wear was observed in the composites with polyamide matrix. The friction-junction containing glassy carbon composites show especially intensive wear and affect mechanisms of wear in surface area. Profilometric tests showed that in case of the silver-glassy carbon composite co-specimen, wear is of evidently abrasive character. Whereas in case of the pure silver pin occurred areas where adhesive wear was evident. Physico-mechanical and tribological properties determined within the investigations let to assume that composites containing silver may be used in the elements conducting electric cur-rent, short circuit and squib systems.