Comparative investigation of the effect of selected natural polymers on the efficiency of load bearing Thread Lockers

Abstract

In this research, comparative investigation of the effect of selected natural polymers with the chemically synthesis imported polymer on threaded assemblies was carried out. The investigation involved the extraction of rubber and cashew resin using the continuous tapping method and ackee aril resin by the soxhlet extraction method, respectively. Stabilization of resin density, pH and viscosity was carried out by the addition of ZnO in different weight percentage of 3, 5, 7, and 10% wt. Sample with the best internal morphology, proximate and mineral composition were selected and used for the investigation. The research was carried out with the use of selected numbers of bolts and nuts (60 in total). Surface treatment was carried out on the bolts and nuts with dye penetrant inspection (DPI) standard method after which the resins (rubber, cashew and ackee) were applied on the bolts and nuts. The bolts and nuts were assembled and tightened with a torque wrench at under-loading, standard loading and over-loading conditions of 60, 80 and 100 Nm, respectively. The surface crack flaw free bolts and nuts were divided into five parts (for rubber, cashew, ackee, chemically synthesis resin and control). Each part contains 3 bolts and nuts for each loading conditions and were exposed to vibration test for 4 weeks within level 1 to 7 intensity scale. The samples were observed after 24 hrs and at the end of 164 hrs for subsequent periods and, the locking torque, break-loose torque and preload were recorded. It was observed from the results that the rubber resins performed the most among the selected natural polymer. From the locking torque results, rubber resin performed more than the imported thread locker with about 12% enhancement for under-loading, standard loading and over-loading, respectively. Likewise, about 7% enhancement was achieved for all the loading conditions for the break loose torque while 13% enhancement was achieved for all loading conditions for the pre-load as compared to the imported thread locker.