Fluorescence Detection of Thin Film Electrical Contact Lubricants

A study to obtain a fluorescent dye suitable for use in detecting the presence of thin film electrical contact lubricants has been conducted, and it has been found that BBOT [2,5-bis (5-tert-butyl-2-benzoxazolyl) thiophene], a scintillation grade blue fluorescent dye, is a nuch improved replacement for the presently used proprietary green fluorescent organic dye. Using quantitative fluorometry, it was determined hat the fluorescence intensity from a lubricant film deposited from a solution containing 0.01 percent BBOT is about six times greater than hat from a film deposited from a solution containing 0.02 percent of the organic phosphor. The fluorescence intensity of the BBOT changes very ittle with time and exposure. With the organic phosphor, after seven lays the intensity decreases by about 90 percent, below that which can be visually detected using ordinary long-wave ultraviolet (UV) light. BBOT, n amounts twenty times (0.20 percent) the concentration required, apoears to have no detrimental effect on contact resistance, giving a maxihum shift in contact resistance distribution of about 200
\mu
\Omega
. BBOT is nontoxic and safe for use. On the basis of this, contact lubricant specifications are being revised to replace the organic phosphor with BBOT. These studies suggest that fluorescence techniques can also be used to neasure and monitor contact lubricant film thickness and distribution.