Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/18/2002
Publication Date: 9/1/2002
Citation: LIU, C., LATONA, N.P., DIMAIO, G.L. LUBRICATION OF LEATHER WITH POLYETHYLENE GLYCOL. JOURNAL OF AMERICAN LEATHER CHEMISTS ASSOCIATION. 2002. V. 97. P. 329-338. Interpretive Summary: Leather is treated with lubricants called fatliquors to impart softness and flexibility. Traditional lubricants, however, are known to impair the mechanical strength of leather. They also do not promote the retention of essential moisture, thus leaving the leather prone to over-drying. The use of low molecular weight polyethylene glycol (PEG) may solve these problems. .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 PEG solutions is significantly reduced in stiffness, indicating the strong lubricity of PEG in leather. This research suggests that humectants are potential alternatives or additives to traditional fatliquors to help prevent aged leather products from becoming brittle and fragile.
Technical Abstract: One of the problems associated with leather quality is that traditional lubricants ("fatliquors" consisting of oils and surfactants) are known to destabilize collagen fibers. Moreover, because they do not promote the retention of essential moisture, they make the leather fibers prone to over-drying. We have recently applied an aqueous solution of low molecular rweight polyethylene glycol (PEG 400) to leather without using any surfactants. The resultant stiffness was characterized by Young's modulus, initial strain energy and acoustic emission methods. Results showed that leather treated with polyethylene glycol solutions showed a significant reduction in its stiffness, indicating that PEG has a lubricating effect in leather. Efforts were also made to understand how factors affect the absorption of PEG into leather. Observations showed that the rate of absorption is not constant; therefore Fick's second law of diffusion, dealing with unsteady state, was employed to derive a mathematical model for the absorption rate. The effect of temperature on the absorption rate was also included in the model by incorporating a linear equation into Fick's diffusion equation. The resultant model fits the experimental data very well. It not only depicts the mechanism of absorption, but also predicts the absorption rate as a function of key variables.