Using the Lorenz-Park, Mooney-Rivlin, and dynamic mechanical analysis relationship on natural rubber/leather shavings composites

The tanning industry generates millions of tons of waste every year, which can cause environmental damage as well as problems to human health. In this article, we analyzed the use of leather shavings (20 to 80 parts per hundred rubber) as fillers in Natural Rubber (NR) composites. For this purpose, the interfacial interaction of the filler was quantitatively evaluated based on the cross-link density value calculated by the Flory-Rehner methodology using the Lorenz-Park equation (swelling). Then, the results of this evaluation were compared with those obtained by the Mooney-Rivlin method (by a stress-strain test). According to our findings, the tensile strength at rupture of the composites increased by 100%, that is, from 7.0 MPa (NR) to 14.0 MPa, when 80 phr of leather waste were incorporated. In addition, their final deformation decreased around 50% compared to pure gum (no filler). According to the Lorentz-Park equation, values over 0.7 indicate a strong interaction between the leather shavings and the NR matrix. Likewise, a dynamic mechanical analysis confirmed a strong interfacial interaction based on the B parameter. Scanning electron microscopy and Fourier transform infrared spectroscopy were employed to examine the morphology and chemical properties of the composites.