Study On Natural Leather’s Micro-structure And Its Permeability Of Air And Water Vapor

Air permeability and water vapor permeability are very important wearability of natural leather which are better than synthetic leather. Studies on the mechanism of natural leather’s excellent breathability performance, can effectively guide the production of higher levels of synthetic leather. The study of natural leather only stays in the level of macroscopic experiments, it is difficult to fundamentally explain the reasons of natural leather with excellent air and water vapor permeability performance. In this paper, we use molecular dynamics computer simulation methods to study and understand the mechanism of how temperature affects natural leather’s breathability performance from the microscopic structure.We use Tinker software to simulate the change process of a type III collagen’s (named lbkv collagen) micro-spatial structure, using molecular dynamics simulation to simulate the dynamic process of lbkv collagen under the environmental temperatures are respectively 300K,320K,340K and 360K. Then we analyse the trajectory and related physical quantities (radius of gyration Rg, contact number CN, interatomic distance Dis) with the simulated temperature trends, in order to get the mechanism how temperature affects breathability performance of natural leather whose major component is collagen. The paper only considers the internal voids (porosity) of leather components to analyse the breathability of natural leather, without other factors’changes, such as pressure, humidity and content of hydrophilic groups contained in the leather and intensity of its activites and so on.With simulation environment temperature increased from 300K to 360K, the simulation result shows that the radius of gyration gradually decreases from 24.9A to 24.5A which indicates all the atoms in the lbkv collagen molecules are combined with each other more closely, the molecular volume becomes much smaller. Also contact number value increases from 125 to 350 which indicates the binding of a-carbon atoms becomes more closely. From analysis of the interatomic distance, the number of relatively smaller atomic distance (4A to 12A) gradually increases when temperature increase, we get the following that the distance of atoms becomes smaller on entire, the inner collagen molecule voids become smaller. Given the analysis of the three physical quantities in the situation of the environment temperature increasing, we find that the spatial structure of lbkv collagen have changed, the distance of atoms gradually decreases and internal molecules voids become smaller, which will slow down the speed of air and water molecules through the leather without considering other factors changing, so the air and water vapor permeability performance of leather reduce.