OPTIMIZATION OF TRIBOLOGICAL PROPERTIES OF AN EPOXY HYBRID POLYMER COMPOSITE REINFORCED WITH ZrB2 AND PTFE PARTICLES USING RESPONSE SURFACE METHODOLOGY FOR HIGH-TEMPERATURE TRIBOLOGICAL APPLICATIONS

Hybrid PTFE/epoxy composites are widely used as materials for self-lubricating spherical bearing which are used in a high-temperature environment. In the present work, zirconium diboride (ZrB2) particles are incorporated to enhance high-temperature tribological properties of PTFE/epoxy composites. Pin on disc experiment is conducted with the aid of design of experiments (DOE) using central composite-response surface methodology (RSM). Under a load of 40 N and 1.25 m/s sliding speed, the optimum content 5.95 vol% of PTFE and 5.05 vol% of ZrB2, yields an ultralow coefficient of friction (COF) in conjunction with a low wear rate of the composite. The addition of ultra-high-temperature ceramic ZrB2 particles and solid lubricant PTFE is found to enhance the thermal conductivity and improve the heat transfer thereby reducing contact temperature. The use of optimum composition of the composite is capable of reducing the wear rate and high local temperature due to friction, implying its potential use as a self-lubricating spherical bearing liner material.

Wear characterization of basalt fiber reinforced polypropylene/polylactic acid hybrid polymer composite

In this work, the wear loss of basalt fiber reinforced polypropylene/polylactic acid polymer composite was analyzed using pin-on-disc under dry sliding conditions. The polypropylene, polylactic acid, and basalt fiber (chopped fiber) are melted and mixed homogeneously using a twin-screw extruder, which is followed by an injection molding technique for specimen preparation. The specimens are named as PPB1 (polypropylene, 50%; polylactic acid, 35%; basalt fiber, 15%), PPB2 (polypropylene, 55%; polylactic acid, 30%; basalt fiber, 15%), and PPB3 (polypropylene, 60%; polylactic acid, 25%; basalt fiber, 15%) based on their weight fraction. The wear rate and coefficient of friction are measured for each sample subjected to three different loads and sliding velocities. It is observed from the wear mapping that the wear loss of sample PPB3 is relatively less when compared with the other samples. The scanning electron microscope images of the worn-out region of the sample reveal the fracture and dislocation of fibers in the matrix. The sample PPB3 shows low wear loss. It is due to the better cohesion between the fiber and the matrixes when compared with the other samples.