Descrizione principale (Inglese)

Introduction Natural silk fabric is directly derived from insect produced cocoons containing large volumes of fibroin protein. The fibroin fibres secreted by the two silk glands of Bombyx mori are smooth and soft and form the structural center of silk. Sericin is a coating with an amorphous structure that bonds the two strands. It is the component hardening the raw thread. The fabric as we know it with low mass per unit area. The level of friction of textile materials depends on a number of test factors - normal load, contact surface area, friction speed, as well as the nature of the textile surface and the direction of friction - warp - warp, warp - weft. Experimental part In this study, four types of fabric made of 100% natural silk have been examined. They all have different characteristics for mass per unit area, weave, density and linear density of the warp and weft threads. The study makes use of appliance tribometer MXD -02, from Labthink, China to determine the values of static and dynamic friction coefficients. Friction is conducted in different directions and under different pressure. Three tests are performed for each studied fabric; all of them are conducted with low sliding speed and different directions and pressure levels are applied (pressure level is regulated by adding additional weights to the sled's own weight). First, normal compressive forces Ni and friction forces Fi are calculated; next friction factor and friction index are determined and lastly, Log (Fi / B) and log (Ni / B) are calculated. The following expression applies: y = a + x.b (where x = lg(Ni/B); y=lg(Fi/B); a = lgC; b=n) Results Frictional characteristics at rest and at sliding, namely friction index for friction at rest and at sliding, friction parameter, and friction coefficient, are determined and are displayed in a tabular form. Discussion This experimental study has clearly showed that silk fabrics with higher surface mass - display friction coefficient values (at rest and in sliding) greater than 1. Friction index and friction coefficient are influenced by the test direction where friction index in warp direction of one fabric with parallel arrangement of the threads is higher compared to threads in weft direction of another fabric. Conclusion Direction of friction which has been confirmed to have influence over frictional characteristics with other fabrics (fabrics with different composition and structure) has proven to have the same influence with silk. Keywords: Natiral Silk fabric, dynamic and static friction coefficient, friction index, surface textiles.