The hysteresis loops of several tire cord samples prepared under various spinning conditions and also various twisting conditions are measured by Instron Tester at cyclic elongation in the limit of 5, 10_??_15%. The results are discussed in connection with the internal structure of individual filament and also with the cord structures. The following observations are made:
(1) The cord structure was controlled by changing the procedure of twisting. In the previous results obtained in relatively low amplitude¹⁾, the dynamic viscoelastic properties were governed exclusively by cord structure, but in this high amplitude the cord structure had no effect on the hysteresis properties.
(2) The cord structure was controlled by changing the number of twists. Hysteresis properties were affected by the number of twists both in this high amplitude and low amplitude.
(3) Even if the same number of twists and identical procedure of twisting were applied, the cord structures were markedly different depending upon the properties of individual filaments used. As the results, in the low amplitude it was difficult to isolate the direct effects of internal structure of individual filaments on the final viscoelastic properties of cords. But, in this high amplitude in which the same number of twists were applied the cord structure had no effect on hysteresis properties. So, it was observed that the internal structures such as crystallinity, size of crystallite, degree of orientation have effects directly on the hysteresis properties of cord.

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Acetylated rayon of some 50% acetic acid content can be prepared within 10 minutes, by the action of acetic anhydride and kerosene at above 100°C, on the rayon impregnated with more than 40 % of its weight of potassium acetate from the aqueous solution and then dried. The acetylation reaction not only proceeds smoothly and uniformly, but the rayon suffers no loss of strength nor reduction of D. P. The drawing given to the rayon just after the acetylation improves its properties.
Acetic acid, the by-product of the esterification, retards the acetylation rate. Excess potassium acetate added in the acetylating liquid will produce a double salt, CH₃COOK•2CH₃COOH, and protect the reaotion rate from its lowering. When the acetylating liquid is cooled, the crystals of the double salt separate from the liquid. Thus acetic acid can be separated and the reactivity of the acetylating liquid is kept constant.
This acetylating process with the retention of fibrous form, the characteristics of which are short reaction time and easy recovery of the chemicals concerned as well as constant reactivity of the acetylating liquid, will make the continuous acetylation of rayon tow successful.

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Study of the fibrous acetylation of rayon has been carried on to find if rayon impregnated with potassium acetate can be acetylated very rapidly with acetic anhydride. For example, the rayon that is steeped in 40% potassium acetate aqeous solution, squeezed and then completely dried, may be acetylated in acetic anhydride and kerosene mixture at 135°C in 15 sec. to have 50% acetic acid content.
Observing the reaction rate closely, it was found that at the beginning the acetylation scarecely lakes place and this “Induction Period” lasted 2_??_5 sec. After the induction period, extraordinarily rapid reaction occurs until all the accessible part of the rayon is acetylated. Slow reaction follows this rapid one. Taking these facts into consideration, acetylation rate is formulated as follows: -log(A-x)=kt-(kZ+logA)
A: Accessibility
x: acetylated degree (mol %)
k: rate constant
Z: induction period
The activation energy was calculated to be 13.6 kcal/mol. which is rather lower than expected. This rapid acetylation will be useful for measurement of accessibility of various cellulose materials. Observation of the acetylated rayon through a microscope shows that the cross section is acetylated uniformly.

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The significance of the degree of swelling and dry-wet strength ratio (WS/DS) of rayons as a measure of structural and physical properties of rayons are discussed.
Once the concept of network structure that the crystallites are anchoring points of it is adopted for the fine structure of rayons, the degree of swelling depends on the intermicellar spaces and this is determined from the followings:
1. crystallinity, 2. molecular chain orientation in the amorphous region,
3. length of crystalline plus amorphous region. WS/DS depends on the degree of cellulose chain penetration through crystallites.
The degree of swelling of high tenacity rayon or Toramomen is lower than that of an ordinary rayon, and WS/DS of the former is higher than that of the latter. Therefore, high tenacity rayon or Toramomen have smaller intermicellar spaces and higher degree of chain penetration through crystallites.

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In order to ascertain how the structure and properties of recent high tenacity rayons had advanced, the change of the fine structure from super-2 type to super-3 type high tenacity rayon was examined based on the concept of the network structure.
The results obtained were as follows:
1. The crystallites, anchoring points of network structure, and the degree of crystallity became smaller, crystallite (plane) orientation became higher and the peaks of lateral order distribution curve shifted to lower order region for super-3 than those for super-2.
2. The molecular chain orientation in amorphous region became lower, and DP, degree of chain penetration through crystallites, and degree of uniformity of chainlengths between crystallites became higher, and network structure of super-3 became denser than that of super-2

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The film of fibrous cellulose triacetate which was made by the vapour phase acetylation, is brittle due to its molecular symmetry and crystallinity.
In order to improve this defect, its molecular symmetry must be broken, with this object in view, the properly pretreated cellulose was mix-acylated by the vapour of acetic and propionic or butyric anhydride mixtures of various mol ratios using ZnCl₂ catalyser and the reactions were investigated kinetically.
Given reaction extents (mol fraction) of the mixed acylation as x, y, the applied rate equation becomes:
In the acetylation-propionation or acetylation-butyration, the total rate constant k is the sum of the anhydride mol-fractional means of the respective independent rate constants, but acetylation rate tends to become smaller and propionation or butyration rate larger than the mol-fractional mean. This was worked out also from the activation energies.
The films of the soluble mixed triesters, containing more than 20 mol% of propionyl group or more than 10 mol% of butyryl group are not brittle.

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The absorption isotherms of Zambesi Black D (I) (C. I. No.27700) and Aniline→p-Cresidine→γ-Acid (II) were measured. From the results the heat of dyeing (-ΔH°) and the standard change in entropy (-ΔS°) of (I) and (II) were determined. For this purpose the value of -Δμ with a dyebath containing a salt conc. of 0.02mot/l and a dye conc. of 0.05×10^-3smol/l dyeing liquor have been taken at 90°, 80°, 70°, 60°C. The following results were obtained:
Such differences of dyeing properties can be explained on the following ground; (I) contains two groups at the ends of conjugated chain which probably favours the bond formation. (II) contains only one group at the one end.

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