Study On The Structures And Properties Of Down And Down Assemblies

As natural nonwoven and filler materials down fibers have characteristics of light,soft and warm, whose products in beddings and some outerwear for cold climates areirreplaceable all through. However, cognitions and studies on the structures andproperties of down fiber and down assemblies are both lacking badly at present.Especially it is not enough to realize the true mechanism of thermal insulation ofdown assembly.This paper studied amply the morphological structure, aggregating state structure,microfine structure and chemical structure of Taihu goose down of China for the firsttime. Using SEM observed the appearance morphological structure of down andobtained all levels length and fineness of down bifurcate structures. Expatiatedrespectively distributing rules and surface characteristics of all levels fibrils and nodeson down fibers. Achieved down ultrathin sections dyed very well and studied themicrofine structure of down inner through observing the TEM photographs. The basicdimension and composing of every part were introduced, and the first class fibrillarstructure was found. Making use of FTIR obtained infrared spectrum of down innerand down surface, and analyzed the basic absorbent apices characters. Throughamino-acid analyzer tested the basic ammo-acid composing of down. It was provedthat down inner bonding forms were almost the same with the wool fibers. Theamino-acid sorts of both fibers were uniform, but some contents were different. ByX-diffraction techniques studied down crystallization structure and by compensatingmechanism studied down orientation structure. The crystallinity of down was littlehigher than wool fiber, and the specific birefringence of down was much lower thanwool.This paper tested and analyzed quantificationally down thermal conductivity,bending properties, wetting and thermal properties for the first time. Making use ofresin embedding loose fibers, measured the basic physical indexes and thermal parameters of embedding block. Then calculated the thermal conductivity of down byweighted mean. The results indicated that the heat conductivity of down was lowerthan wool. Using the measuring device aiming at compression and bend of singlefiber tested and analyzed the bending indexes of down branch fiber. It had beenshowed that both the relative bending rigidity and bending modulus of down branchfiber were much lower than wool fiber. However, the bending recovery coefficient ofdown branch fiber was higher than wool. Measured contact angle and specific surfaceenergy of down branch fiber. It was proved that the wetting performance of downmuch lower than wool. Through DSC techniques measured the thermal properties ofdown.For the first time applied the fractal theories to characterize measurably themorphological structure of down, which also was one of the main innovation parts ofthis paper. The whole down possesses obvious self-similarity and scale-fixity, whichshowed that down fiber could be considered as a marked fractal; Utilizing computersimulation and practice calculation by Sandbox measurement calculated the fractaldimensions of down respectively as 1．66 and 1．678, which was provided with especialmeaning to fiber performances.This paper also measured and investigated the physical performances of downassemblies, and compared them with other fiber assemblies. Basing on the principiumof WRONZ bulkiness tester, a simple device was made to test the bulkiness of downassembly. The bulkiness of down assembly was 2～7 times better than otherassemblies. Using in-situ measurement devices to fiber assembly conductivity underfluctuant densities, measured dynamically the compressibility and permeability ofdown assembly. Along with the changing of assembly volume fractions thecompressibility of down assembly was much better than other assemblies. As initialvolume fraction was low, the change of assembly compression ratio with the pressureincreasing was evident, and the change followed typical compression characters.However, the compression-recoverability of down assembly was less than woolassembly. The permeability of down assembly reduced gradually as the increasing ofassembly volume fraction. Down assembly permeability is the least compared with other assemblies. By oven method tested respectively the hygroscopicity of downassemblies under various atmospheric states. So the hydroscopic isotherm andmoisture liberation isotherm could be gained. The absorbent qualities of down undervarious atmosphere states were lower than wool. On plate warmth retaining testertested and valued the heat insulating ability of down assembly. It was proved thatdown assembly possessed better heat retention than any other assembly under thesame volume fraction, and when the volume fraction retained between 0．002 and0．005 down had best thermal insulations.Colligating the characters and performances of both single down branch fiber andfiber assemblies, this paper valued the primary and secondary factors influencing fiberassembly thermal insulations. The fractal characteristic of down morphologicalstructure, which endowed down assembly with high bulkiness and plentiful still-air,was the most important factor leading to down assembly excellent thermal insulation.Besides, the lower thermal conductivity of down itself decreased the heat transferthrough fibers to some extent and was the assistant factor to thermal insulations ofassembly. The fractal structures and excellent bending recovery of down branch madedown assembly compressed puff out quickly under gently agitation, which providedthermal insulation of down assembly necessary condition. Because down had lesshygroscopic wetting property, down assembly could retain better heat insulting abilityas ambient humidity rising.This paper observed assembly inner fibers arrangement and distributing byMicro-CT techniques and calculated the fractal dimensions of assembly scan tierapplying fractal theory, so achieved the quantificationally characterizing to fibersarrangement in assembly. It had changed the thought and depiction of fiber assemblyhaving "even volume" and would approach the practice much more. It pioneered anew route to study the inner structures and mutual effects among fibers.