Kan Shirakashi

Effect of Annealing the Polypropylene Spherulites

結晶性高分子は溶融状態から結晶化させると通常, 球晶構造ができる。いま, これがラメラからなりたっているものとすると厚さは小角X線散乱測定でおよその見当がつく。本研究においてはポリプロピレンの熱処理過程に見られる諸現象について, 特にラメラを単位とする微細構造の変化について検討した。実験に供した市販のポリプロピレン試料は結晶化温度をTx=126℃, 136℃, 146℃に選び, それぞれ十分な結晶化時間を与えた。これらの試料を結晶化温度と融点の間の温度域で熱処理した。このとき長周期の増加が認められ, その途中のプロセスでは部分融解に基く異常挙動が密度変化, 比容変化, X線の散乱強度変化によって観測できた。一方, 同一条件下で得られた薄いfilm試料について偏光顕微鏡下で二次元球晶の消光図形を観察したが, 最初不規則な消光図形を示す球晶でも熱処理時間の経過とともに明りょうなMaltese crossが現われてくる。この変化は電子顕微鏡による球晶表面観察で認められる規則性ある組織の出現と対応している。さらにマイクロビームX線による球晶のラウエ写真からも熱処理による微細組織の均一化が観測された。

レーヨンの引張強度について : 高分子のレオロジー : レオロジー特集号

Many studies on the breaking behaviour of high polymer has been done due to its large practical meaning. But the discussion concerning the internal structure is very little due its complexity. Although, the fringe micellar structure is not accepted for all polymers at present, it is proper to think of it for the internal structure of the fiber. According to this structure, there is a wide distribution of lateral order from perfectly ordered state in the crystalline region to random state in the amorahous region. The shape of this distribution differs according to the manufacturing process. The fiber possesses a net-work structure if both ends of the chain molecule are caught in the high lateral ordered region. If some proper swelling agent (NaOH so1. for rayon) is applied to such net-work structure, it relaxes and get freed from low lateral ordered region to high lateral ordered region gradually with the increase of the concentration of the solution, and there by the junction point of the net-work structure remains in more high lateral ordered region. The tensile strength of fiber in such condition is controlled mainly by the number of chain molecules caught by the junction point. The distribution of chain length of the chain molecule caught at both ends has much influence. The maximum valus of the number of molecules in the distribution of chain lengths of chain molecule is related to the tensile strength. The amount relating to the maximum value of the chain length of chain molecule caught at both ends in the high lateral ordered region can be determined from the difference of tensile strength when the concentration of the applying swelling agent is changed. The relation between the amount related to the maximum value of chain length in the high region and lateral order can be determined. In case of ordinary viscose rayon or bemberg, a large peak in the distribution occurs at the low lateral ordered region, which shows a discontinuous state of micelle. In case of all-skin type high tenacity rayon, there is no distribution at the low lateral ordered and the distribution in concentrated highly at the right peak region of high lateral ordered region. Fortisan shows a wide distribution and is distributed up to the very high lateral ordered region. The distribution at the low lateral ordered region increases gradually with the decrease of the thickness of skin layer for four types of rayon having different ratio of skin and core. When this behaviour is compared with that of ordinary viscose rayon, discussed before, the core part is related to the low ordered region and the skin part to the high lateral ordered region. In case of all-skin type high tenacity rayon, the chain molecule is quite similar in length and the mechanical properties of it is supposed to be good due to the equal distribution of forces to each molecule. The fatigue behaviour four types of high tenacity rayon has been examined as above. Although there were differences in the fatigue life of the four types of high tenacity rayon, on such large differences of tenacity could be seen in the dry state, but there were clear differences in the swelling tensile behaviour. When the distribution of tensile strength in respect to lateral order is determined, the fiber of short fatigue life shows a large distribution of chain molecule at the low lateral ordered region, and for that of long fatigue life the distribution is large at the high lateral ordered region. In case of repeating extension, it is necessary to distribute the forces to each chain molecule effectively, and in case of low ordered region the distribution is not sufficient, while the distribution is effective in the high region and the concentration of force is avoided.

The Effect of Moisture Sorption on the Dynamic Mechanical Properties of Textile Fibers

As the effect of moisture regain is very large on the mechanical properties of textile fibers containing hydrophilic groups, it is quite interesting to study on them. In this paper, the relations between the dynamic properties and regain of some textile fibers (Fortisan, high tenacity rayon, Bemberg, viscose rayon wool, nylon, acetate), which have got affinity to water absorption are studied. The stretched vibrometer system and the direct measuring method were combined as a measuring method, and a constant frequency 106cps is used. The humidity control was performed by mixing dry air with damped air and all the samples were tested at 20°C. The constant tension applied to the fiber is 0.2gr/denier. Until about 10% of regain the dynamic modulus of regenerated cellulose fiber decreased linearly with the increase of regain, but at higher regain region the decrease was rapid. Loss tangent, tan δ increased slowly in the region where the linearity of dynamic modulus exists and in the high regain region it increased rapidly. The difference of tan δ with the fine structure of various regenerated cellulose fiber is not much recognized and is of the same order. The change of dynamic modulus due to regain depends on the orientation and lateral order of cellulose fiber in the low order region. The dynamic properties of wool and acetate due to water adsorption showed gradual change in the low regain region, but in case of 6-nylon, the change of tan δ was large and could not be expressed by a linear relation. These difference were described by the flexibility of the chain molecule of the fiber and relaxation time of molecular segment of the large side groups. The region where the relation of the dynamic modulus and tan δ with the regain was linear has been determined and the experimental results are shown in Table 2. Some dynamic loss which is the product of tan δ and dynamic modulus showed maximum value and some did not. Bemberg, high tenacity rayon, viscose rayon, and nylon belong to the former case and Fortisan, acetate and wool belong to the latter. The result which was obtained by Quistwater for the dynamic properties of 6.6 nylon showed the same tendency of the effect of regain for 6-nylon. A double network structure can be conceived for cellulose fiber and it is thought that the main network structure is sustained in the wet state and the sub-network structure is broken by water adsorption. It is assumed that the stress is propagated in the sub-network structure mainly by hydrogen bond. The relation of modulus and hydrogen bond according to Nissans formula, n∝E3 (n is the number of hydrogen bond in unit volume and E is the modulus) was verified. With the elementary formula i.e., the breaking number of hydrogen bond with the addition of water is proportional to the number of unbroken bonds, the process of breaking of more than one hydrogen bond by one water molecule as an autocatalic effect was considered and the formula was calculated. In the low regain region the elementary relation was established in the case of cellophane, which possesses low orientation. But Fortisan, high tenacity rayon, viscose rayon and others possessing high orientation showed a deviation from this elementary relation in the low regain region. In the low regain region the breaking of two hydrogen bonds is done by one water molecule, and in the medium regain region, viscose rayon showed the maximum value, where 6 hydrogen bonds were broken. High tenacity rayon showed rapid increase of breaking number of about ten bonds in the high regain region. In the case of Bemberg the breaking was not so rapid as high tenacity rayon but was rather slow. The autocatalic effect was observed for cellophane in high regain region.

The Mechanical Behavior of Wool Fiber in Water

The mechanical behavior of wool fiber in water is studied by the free damped vibrational method at low frequency (period=4∼5sec) and large amplitude (maximum amplitude=2% extension) under various static strains and temperatures. In order to measure the stationary viscoelasticity, the logarithm of double amplitude must be decreased linearly with the vibration. In the case of wool in water, these straight lines (plots of logarithm of the double amplitudes (AN) against successive vibration numbers (N)) are concave or convex about the axis of the successive vibration number (N). There are three types of logAN∼N curves: Straight line and concave or convex against N-axis. The above three types are assumed as follows:(1) Straight line:The breaking and reformation of the secondary bonds are in equilibrium and a stationary state is attained.(2) Convex curve:The reformation of the secondary bonds exceeds the breaking during the vibration.(3) Concave curve:The breaking of the secondary bonds exceeds the reformation during the vibration.The above hypothesis may explain the mechanical behavior of wool in water at various conditions. This is shown as follows:1. The wool fiber is extended in the state where the breaking of the secondary bonds exceeds the reformation of the bonds, but during retraction the reformation exceeds. The change of the viscoelasticity under extension and retraction is reversible within 0∼30% extension region (Fig. 2∼3).2. During the stress relaxtation at 10% extension, the breaking of the secondary bonds exceeds and a stationary state is attained with the elapse of time (Fig. 4).3. When the vibration contains the yield point, the reformation of the bonds exceeds the breaking under large double amplitude, and the breaking exceeds the reformation under small double amplitude (Fig. 5).4. Under rising temperature at 10% extension, the breaking of the bonds exceeds and under falling temperature, the formation of the bonds exceeds (Fig. 6).The temperature dependency of the relative Youngs modulus is compared with the data of Meredith and Feughelman. The temperature coefficient of Youngs modulus at Hookean region derived by some workers are as follows:

Thermal Properties of Polyethylene Telephthalate Fibers

ポリエチレンテレフタレート繊維の温度上昇および下降時の力学的性質を動的および静的な方法を併用して検討した。未延伸試料では温度上昇たより静的な張力の急速な減少がみられ,70℃付近より動的弾性率の急激な低下,動的損失の増大がみられた。温度下降時には張力以外大きな履歴を示さなかった。3倍延伸繊維では熱処理の有無にかかわらず単調な張力低下を示した。温度下降時には120℃ 付近に変曲点が存在した。動的弾性率は延伸度,熱処理,温度の上昇,下降により若干差があるが110℃付近より減少が急激であった。動的損失も同様に130～140℃ 付近で極大値を示した。3.72倍延伸熱処理繊維では張力の極大,極小が動的損失の極大,極小温度に対応して現われた。未処理繊維では極大点が明確でなかった。温度下降時の張力は単調に減少し, エントロピー的寄与がある。高温分散のtanδの極大値は未延伸, 3 倍延伸未処理,熱処理,3.72倍延伸未処理,熱処理と順次減少を示した。3.72倍延伸,熱処理試料についての応力緩和挙動は前記の実験結果と対応した。また応力緩和とtanδの減少は類似の傾向を示したが,動的弾性率は徐々に増加した。これらの一連の現象を二重網状構造によって説明した。高度延伸, 熱処理は有効な二重組織を形成するものであることを認めた。

STUDY ON TIRE CORD

Tire cords, whose results are known through the vibrator and rotor tests, are investigated by following ordinary mechanical tests:For single fiber from the cord;1, tensile test (room temperature and 110°C) and Youngs modulus (static). For fatigued fiberafter vibrator test;1. tensile test and Youngs modulus (static). For cord;1. tensile test (room temperature and bone dry) and Youngs modulus.2, creep and recovery.3. repeated elongation tensile test (normal condition and bone dry).Good correlation for the fatigue tests is obtained in following tests:Tensile test for single fiber and cord at normal conditions, creep recovery for cord, and repeated elongation tensile test at normal condition.Recovery mechanism for mechanical deformation of fiber contribute to fatigue life of the rotor and vibrator tests.