In false twist texturing processes, the yarn tension is very important factor affecting manufacturing process and characteristics of textured yarns. When a running yarn is twisted initially by a spinner, the yarn tension in the twisting zone is increased very rapidly to the maximum point-and then gradually decreased to the specified equilibrium level. This phenomenon is expressed by the following equation :
σL (t) = [1/ (1+kε₁) α {(1-e^-υ₂t/L) +e^-υ₂t/L·cosωLt} -1] ·E·cosωLt
where, σL : yarn tension in the zone L
E : elastic modulus of yarn
V₁ : surface velocity of 1st feed roller
V₂ : surface velocity of 2nd feed roller
α : V₁/V₂=feed ratio
L : distance between 1st roller and spinner
t : time elasped after the beginning of twisting ωL : twist angular velocity of running yarn in the zone L
k=ε₁"/ε₁
ε₁ : longitudinal strain due to the pre-tension
ε₁" : sectional strain due to the pre-tension
An investigation has been made of the yarn tension affected by the twist, heater temperature, feed ratio and the properties of untextured yarns. The equilibrium tension of running yarn decreases with increasing the twist and the heater temperature .
The coefficient of friction between the spinner and the processed yarn decreases with increasing the feed ratio and number of twists.

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The loop strength of a specified nylon gut or soft stainless steel filament was measured by hooking the specimens on the other single filament of different thicknesses. The relation between the loop strength of the specified samples and their load-elongation curves in normal tensile test was investigated, and the following assumption proposed in the previous paper was examined ; a fiber in loop test is broken at the region where the sum of bending and tensile strains has just reached the tensile breaking strain of the fiber. The results obtained are as follows :
1) The loop strength of the specified samples increases with increasing the opposite sample diameter. The degree of increase is dependent upon the tensile breaking strain of the specified samples.
2) The cross-sectlon of the specified nylon gut hooked on the steel filament is more depressed than that hooked on the nylon gut. The loop strength of the former specified nylon gut is larger than that of the latter at the same ratio of the opposite sample diameter to the specified sample diameter.
3) The following experimental equations are obtained for the specified nylon gut.
Δe=εe_m0… (a), e_m0=1/ (1+ε_rγ_d0… (b)
where, Δe is the decrease of strain which is defined as the difference between the tensile breaking strain of the specified sample and its tensile strain at the breaking point in the loop test, e_m0 geometric bending strain calculated from the micrographs of the hooked part of the specified nylon gut, γ_d0diameter ratio, and εand ε_r are constant being independent of the diameter ratio. Therefore, the loop strength of the specified samples for given diameter ratio can be estimated from both the above equation and their load-elongation curves of normal tensile tests.
The above equation (a) is also valid for the loop test of the specified single nylon gut hooked on a bundle composed of different numbers of the nylon gut.

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The acoustic behaviours…transmission loss…of flexible plastics sheet reinforced with plain woven fabrics, compounded with iron oxide powder have been investigated expermentally. The mechanism of sound transmission was analyzed by the resonance-curve method and the mass law. The calculated value were compared with experiments.
1) For single wall (double wall patched with the same material) of flexible plastics, the relation between the measured transmission loss and the value calculated by the mass law has shown that : (a) when mf (mass per unit area × frequency) <3 ×10³Kg/m²·Hz, measured transmission loss is larger than the value calculated by the mass law by several decibels, and (b) when mf>3×10³, however, transmission loss is smaller due to an internal friction and viscosity .
2) No coincidence effect has been found in the single wall of flexible plastics sheet.
3) If the mass per unit area is equal, the transmission loss of sandwich structure is better than single wall and double walls.
4) The resonance-curve method and the mass law are useful for evaluating the acoustic behaviours of flexible plastics sheet.

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Snag test methods were studied on woven and knitted fabrics for men's and women's outerwears made of textured polyester filament yarns, using the mace snag tester and the ICI pilling tester provided with built-in slate-sams. Also, the initial resistance force required to pull yarn out of the fabric was measured, and the relations between their results were investigated by comparing with each other.
The main test results are as follows :
(1) Although the action of the mace snag tester is rather severe for woven and warp knitted fabrics, the mace snag test is superior to the slate-saw test because of better reproducibility of the test results, and better distinguishability among samples.
(2) In testing woven and warp knitted fabrics by the mace snag tester, 1.7 minutes (100 revolutions) has been found to be recommendable as the testing time.
(3) A correlation has been found between the results of the mace snag test and those of the slate-saw test. However, a low correlation between the mace test results and the initial resistance forces has been found only for woven fabrics. Little correlation has been found if all the samples are taken into consideration.

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