A nickel-fluoropolymer composite was produced by a technique using a Watts nickel bath containing PTFE in suspension. The effects of the PTFE concentration, the current density, the pH and the temperature on the volume percent of PTFE incorporation in the deposit were investigated. It was found that the PTFE content increased with PTFE concentration and current density. An optimum PTFE content (14.6 vol. percent) was possible by operating the bath at 6 A/dm 2 at pH 3.0 and 50 ° C. Fluoropolymers such as polytetrafluoroethylene (PTFE) and poly carbon monofluoride (CF) n have a unique repellent property for water and oils. These compounds are used for coatings with non-stick characteristics, low coefficient of friction and reduced wear as self-lubricants. 1,2 Low hardness of the PTFE compounds makes the coating wear rapidly. Ni- PTFE electrocomposites can overcome this problem and are attractive. PTFE-incorporated bronze bearings have been developed for many industrial applications and the compos- ite is being used in the preparation of molds for the release of plastics and rubber without release agents. 3 Recently, Ni- PTFE composites on a nickel substrate have been reported as a novel electrode for synthesis of organic compounds. 4-6 Despite the industrial importance of the composite, no sys- tematic study of its preparation has been attempted. In the current investigation, nickel-PTFE composite was prepared by electrodeposition from a Watts nickel bath containing PTFE in suspension. The effects of PTFE content in the bath, current density, bath pH and temperature on the volume percent of PTFE in the composite were studied and electroly- sis conditions optimized to get uniformly dispersed PTFE in the nickel matrix. Experimental Procedure The electrodeposition of nickel-PTFE composite was per- formed in a Watts nickel bath consisting of 250 g/L nickel sulfate, 45 g/L nickel chloride, 30 g/L boric acid and 0.1 g/L sodium lauryl sulfate. The PTFE polymer used for codeposition is in the form of a suspension containing 60 percent polymer by weight; the average size of the particles ranged from 1.5 to 2.0 μm. The same experimental set-up, as described elsewhere, was employed. 7 A known volume of 60-percent PTFE suspension was added to the Watts bath. By means of a mechanically controlled glass stirrer, the PTFE suspension was stirred in the bath for eight hr. Plating was carried out in a 1-L glass beaker. As anodes, two 5-mm-thick nickel pieces were used. Stainless steel specimens 7.5 x 5.0 x 0.1 cm size served as cathodes from which the coatings could be easily stripped for analysis. The extent of PTFE incorporation in the nickel coating was studied with respect to PTFE content of the bath. Current density ranged from 2 to 8 A/dm 2 , bath pH from 2 to 5, bath temperature from 30 to 60 ° C. The plated stainless steel samples with coating thickness of 50 μm were weighed (w 1 ) with an accuracy of 0.1 mg, then stripped in 50 mL of 20-percent warm nitric acid. The resulting solutions were made up to 100 mL in standard volumetric flasks. After stripping the deposits, the stainless steel substrates were again weighed (w 2 ). The difference (w 1 - w 2 ) gave the mass of the composite deposit. The nickel content of the composites was determined by analysis of the solutions, using atomic absorption spectrophotometry. 8 These steps determined the PTFE content. The volume percent of PTFE was evaluated as follows: Volume of nickel in composite (V 1 ) = Volume of PTFE in the composite (V 2 ) = Total volume, V = V 1 + V 2 Volume percent of PTFE = x 100 Triplicate analyses were performed in each case and the average values recorded. Results and Discussion Effect of PTFE Suspension On Volume Percent PTFE The extent of PTFE incorporation with 5 to 80 mL/L PTFE suspension in the bath over a wide current density range is shown in Fig. 1. Regardless of operating current density, PTFE incorporation increases sharply and attains an opti- Electrodeposition of Nickel-Polytetrafluoroethylene (PTFE) Polymer Composites By G.N.K. Ramesh Bapu and S. Mohan Mass of nickel Density of nickel Mass of PTFE Density of PTFE V 2 V Fig. 1—Effect of PTFE suspension on incorporation of PTFE in composite. Conc. PTFE, mL/L Vol. % PTFE in Composite 2 4 6 8 A/dm 2 86 PLATING & SURFACE FINISHING