Evaluation of tribological properties of vegetable oil based formulations contained polyalkyleneglycols and ZDDP

Os lubrificantes a base de óleo vegetal surgem como uma alternativa ao uso de lubrificantes minerais, em virtude da crescente busca pela preservação do meio ambiente. O presente trabalho avaliou o desempenho tribológico de óleos vegetais misturados a Polialquilenoglicóis (PAG) e os comparou com óleos minerais, sendo ambos, as misturas e os óleos minerais, classificados nos graus ISO 150 e 220. Foram testadas formulações de óleo de mamona + PAG (ISO 68), óleo de mamona + PAG (ISO 150), óleo de soja + PAG (ISO 680) e óleo de soja + PAG (ISO 680), nas proporções 65/32, 80/17, 50/47, 38/59, respectivamente, aditivadas com 3% de ZDDP, aditivo Extrema Pressão. Tais formulações foram previamente determinadas com base na viscosidade das misturas a 40°C. Foi traçado o perfil de viscosidade de todas as misturas e foram feitas análises de Ressonância Magnética Nuclear (RMN) e Calorimetria Diferencial Exploratória (DSC), para caracterização das mesmas. Além destas formulações, para efeito de comparação, foram testados óleos minerais ISO 150 e ISO 220, óleo de mamona puro e óleo de soja puro. O desempenho das formulações em relação ao atrito e ao desgaste foi avaliado por meio de ensaios de HFRR (High Frequency Reciprocating Rig), com carga de 10 N, frequência de 20 Hz e 60 minutos de duração, todos em duplicata. A temperatura do banho de óleo foi mantida em 50 ± 5°C. Os corpos-de-prova, de aço AISI 52100, foram analisados em Microscopia Eletrônica de Varredura (MEV) após cada ensaio. A formulação de óleo de mamona + PAG (150) + ZDDP apresentou os melhores desempenhos em termos de atrito e desgaste quando comparadas com o óleo mineral 220.The biobased lubricants from vegetable oils arise as an alternative to the petroleum-based ones because of increasing search for the environment preservation. In this work, the tribological performance of vegetable oils with polyalkyleneglycols (PAG) was evaluated and compared with mineral oils. The vegetable oil and petroleum-based formulation are classified as ISO grades 150 and 220. Formulations were tested of castor oil + PAG (ISO 68), castor oil + PAG (ISO 150), soybean oils + PAG (ISO 680) and soybean oils + PAG (ISO 680), in the proportions 65/32/3, 80/17/3, 50 / 47/3, 38/59/3, respectively, and with 3% of ZDDP, an additive of extreme pressure. Such formulations were previously defined on the viscosity of the mixtures at 40° C. It was obtained the viscosity profile of the formulations and analysis were performed using 1H Nuclear Magnetic Resonance Spectroscopy (1H NMR) and Differential Scanning Calorimetry (DSC). Besides these formulations, petroleum-based formulations, ISO 150 and ISO 220, castor and soybean oil without any additive were analyzed to be compared with the biobased formulations. The performance of the formulations related to the friction and wear was evaluated through HFRR (High Frequency Reciprocating Rig) tests, with load of 10 N, frequency of 20 Hz and 60 minutes duration. Every test was made in duplicate. The oil bath temperature was maintained at 50 ± 5°C. The AISI 52100 steel specimens were analyzed by Scanning Electron Microscopy (SEM) after every test. The formulation of castor oil and PAG (150) + ZDDP showed the best performances in terms of friction and wear properties, when compared with the mineral oil ISO 220