Analysis And Characterization Of The Secondary Structure Of Slenderized Wool Fibers

Wool fiber is an excellent natural fiber, and its fineness is one of the key factors affecting selling price. The finer wool fiber is, the higher the price. So, there is much work on decreasing fineness of wool fiber, and the slenderization technology is developing technology during end of last century that is effective to contract fineness of wool fiber. There exist different points about the conformation transformation of secondary structure and major transformation period. Thereof, the paper is to use slenderization processing solution and technology to process wool fiber and to characterize and analyze secondary structure of stretched wool fiber.The paper is to investigate secondary structure, mechanical and surface properties of raw wool fiber and stretched wool fiber with stretching rated 30%, 50%, 70%, 90% and 110% by adopting Optical microscope(OM), Stress-strain Curve, DSC, FTIR and ATR and laser Raman technology. The investigating contents are as follows:1. To prepare stretched wool fiber with stretching rate 30%, 50%, 70%, 90% and 110% under low speed at 10mm/min and self-developed slenderization processing solution and technology.2. To measure surface shape and study the change of scale size of wool fiber under different stretching rate by OM.3. To characterize slenderization effects of fineness of wool fiber by OLYMPUS microscopic with CCD camera and comparing stress and strain curve transformed by load and extension curve.4. To analyze effect of slenderization on melting peak by DSC testing through comparisons between raw wool fiber and different stretching rate (30% and 110%).5. To analyze secondary structure of wool fiber by FTIR, ATR and laser Raman. Some researchers thought that structure of wool fiber changed mainly fromα-helixtoβ-pleated during slenderization process and the stretching rate is at most 70%～80% for current technology from foreign countries. Recently, Chinese experts present that there does not only exists conformation transformation fromα-helix toβ-pleated, but also slippage of microstructure and matrix during slenderization process. The paper aims to investigate the conformation transformation by adopting several characterization methods and corresponding conclusions are concluded as follows:1. With stretching rate increasing, fineness and breaking extension as well as yielding elongation of wool fiber all show decreasing trend, but specific stress increases. Moreover, fineness of wool fiber with stretching rate 110% decreased drastically with 6.4μm compared with that of raw wool fiber.,2. Based on DSC curve of wool fiber, melting peak drifts to low temperature region and the phenomenon mainly produces during initial period of slenderization.3. Based on ATR spectrum of wool fiber, it shows that there are all kinds of oxidation products of cystine. Slenderization will break S-S bonds of cystine and create cysteine-SO₃^-. By comparing peak areas of amide I based on FTIR and Raman spectrum, wool fiber exhibits conformation transformation fromα-helix toβ-pleated during slenderization process, andα-helix structure still exists in wool fiber structure under stretching rate 110% and is about half of content in raw wool fiber.4. Based on DSC, FTIR and Raman spectrum, during the slenderization process of wool fiber, there not only exists conformation transformation fromα-helix to B-pleated, also slippage of macromolecular structural block and matrix to some extent; meanwhile, fiber structure mainly changed during initial period of slenderization, and structure transformation of wool fiber with stretching rate 30% is more significant than that with stretching rate 110%.