Light Yellowness of Down Duvet

The yellowness of new processed down duvet after exposure to light irradiation seems very mysterious,degree of its yellowness sometimes minor,other times serious,seemingly erratic.So it is very essential for down duvet manufacturers to figure out the cause of this problem.The yellowed down duvet was split into two parts firstly,one was the external fabric which treated with antidrilling finish of polyurethane(PU) in advance,the other was filled down.Results showed that yellowing of external fabric was serious while the filled down yellowness was not obvious.However,when the external fabric and the filled down from the same batch of duvet were irradiated under the same condition respectively,the result indicated both the external fabric and the filled down had not yellowed as the above duvet.Therefore,it was inferred that the external fabric's yellowing was possibly induced by one property of the filled down.Then the key performance indicators of the filled down,such as cleanliness,oxygen consumption,and microorganisms,were measured and analyzed,and the extraction liquid of the down was also analyzed by the chromogenic reaction and UV-vis spectra.Results indicated the non-decomposed hydrogen peroxide residued in the filled down which would cause a higher oxygen consumption and induce photo oxidation yellowing of the PU film on external fabric,and the degree of its yellowing increased with the concentration of residual hydrogen peroxide increasing.Hydrogen peroxide composition would speed up the photo oxidation yellowing process and decrease the IR transmittance of PU film.Meanwhile its yellowed degree aggravating.

Tear Resistance of Orthogonal Kevlar-PWF-reinforced TPU Film

This work seeks to investigate the notch sensitivity and fracture behaviour of orthogonal Kevlar-plain woven fabric （PWF）-reinforced thermoplastic polyurethanes （TPU） film applied to high altitude balloon. Four types of specimens are implemented to measure notched strength and fracture toughness by conducting static tension and tear tests on an MTS system respectively. The damage and failure mechanisms are discussed and the results for notched strength and tear resistance are evaluated and compared with each other. From the experiments, it is found that the notch sensitivity of the film increases with the increase in the size of the hole, but the notch sensitivity and the stress concentration of the notch are insignificant and there is a decrease of only about 4%-10% in tensile strength for the notched specimens with different hole sizes in diameter compared with the unnotched specimen. In contrast, the tear resistance containing a central slit with only 1 mm length is about half of tensile strength of the unnotched film, which implies that the tear resistance exists an significant notch sensitivity. The results of this study provide an insight into notch sensitivity and fracture behaviour of the Kevlar-PWF-reinforced TPU film and constitute a fundamental basis for the design of high altitude balloon.