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In this thesis, the formation and some properties of the loop
yarn by using a combined hollow-ring spinning system were
studied. There were five main subjects in this study:(1) to
evaluate the spinnability of this spinning system; (2) to
estimate twists in the loop yarn; (3) to establish a model of
the wrap thread length of the fixing thread in the loop yarn;
(4) to estimate the yarn appearance and the loop size; and (5)
to test the loop yarn's tensile properties. Several conclusion
from this study were as follows: The model of the wrap thread
length of the fixing thread in the loop yarn could be used to
reckon the amount of yarn materials. The geometrical models of
the loop yarn structure were able to predict the loop size.
Therefore, it was useful for the application of the computer-
aided loop yarn simulation. While the wrap twist(tpc) of the
fixing thread before being backtwisted increased, the loop
density(loops/100 cm) would increase, but the loop size would
decrease. The loop density and size all increased by
increasing the overfed speed ratio of the effect thread to the
core thread. The orifice of the core thread duct should be
positioned above the axis of the hollow-spindle. It was
advantageous to spin uniform loops while the duct closed to the
effect thread rollers. An attached fixing thread flyer would
increase the tension of the fixing thread and its stability.
For the selection of the core thread material, the untwisted
phenomenon of the OE yarn is less than that of the ring yarn.
The flexural rigidity of the effect thread would affect the
formation effect of the loop. When the loop yarn was extended，
the component thread would be broken respectively. Therefore,
it showed a peculiar morphology of failure. While the loop
yarn was knitted, the loop migration decreased by increasing
the tensile breaking strength of the loop yarn at the rupture
of the effect thread.
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