Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2005
Publication Date: 4/1/2006
Citation: Liu, C., Latona, N.P. 2006. Lubrication of leather with mixtures of polyethlene glycol and oil. Journal of American Leather Chemists Association. 101(4):132-139. Interpretive Summary: Leather is commonly treated with lubricants called fatliquors to impart softness and flexibility. Traditional lubricants, however, are known to impair the mechanical strength of leather, sometimes as a cost for softer and more flexible leather. Fatliquors themselves also do not promote the retention of essential moisture, thus leaving the leather prone to over-drying. We have investigated the use of a polyethylene glycol (PEG)/oil mixture as a lubricant for leather. PEG is a humectant with the ability to retain moisture, thereby preventing the leather from over-drying due to environmental changes, such as low humidity and high temperature. This investigation has demonstrated that leather treated with a PEG/oil mixture is significantly increased in its moisture retention and heat resistance. These results suggest that adding humectants to traditional fatliquors helps prevent leather products from becoming brittle and fragile during transportation, storage and end use.
Technical Abstract: Moisture loss due to humidity decreases in the surrounding environment can result in area shrinkage, and therefore area yield. In addition, adequate moisture content is essential to the physical properties of leather, such as softness and mechanical strength. One of the problems, however, associated with leather quality is that traditional lubricants ("fatliquors," consisting of oils and surfactants) do not promote the retention of essential moisture, making the leather fibers prone to over-drying. We have recently developed a formulation of lubricants that consists of a mixture of oils and low molecular weight polyethylene glycol (PEG). Leather treated with PEG mixtures showed increased moisture retention due to the humectant effect of PEG on the leather fibers. We also characterized the lubrication of samples using an acoustic emission technique. The samples without any lubricants showed twin peaks on the plot of hits rate versus time. This implied that a non-uniform fracture occurred in a leather structure that was not lubricated. In contrast, leather lubricated with PEG and oil mixtures showed a steady increase in hits rate with time until it fractured after only one major peak of hits rate. Moreover, after the treated leather samples were heated at an elevated temperature, such as 90°C, observations showed that the tensile strength retention of treated leather increases with PEG concentration in the fatliquoring bath. This implies that PEG increases the heat resistance of leather.