Toshio Kunugi

A polypyrrole rotor driven by sorption of water vapour

Abstract The polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the film obtained have been investigated. The principle of motion was based on a reversible sorption of water vapour on one side of the film, causing an expansion of the film surface. On the basis of this phenomenon, we have devised a polypyrrole rotor driven by sorption of water vapour, producing a continuous rotation at a speed of 21 cm min −1 .

Mechanical properties and structure of the zone‐drawn poly(L‐lactic acid) fibers

The zone-drawing (ZD) method was applied three times to the melt-spun poly(L-lactic acid) (PLLA) fibers of low molecular weight (Mv = 13,100) at different temperatures under various tensions. The mechanical properties and superstructure of the ZD fibers were investigated. The resulting ZD-3 fiber had a draw ratio of 10.5, birefringence of 37.31 × 10−3, and crystallinity of 37%, while an orientation factor of crystallites remarkably increased to 0.985 by the ZD-1. The Youngs modulus and tensile strength of the ZD-3 fiber respectively attained 9.1 GPa and 275 MPa, and the dynamic storage modulus was 10.4 GPa at room temperature.

Adsorption-induced bending of polypyrrole films and its application to a chemomechanical rotor

We have discovered that polypyrrole films undergo rapid and intensive bending in the solid state. Bending was induced by the reversible and anisotropic adsorption of various substances in the vapor state. The speed and direction of bending largely depended on the adsorbate used. By using this phenomenon, we have devised an experimental “chemomechanical rotor” capable of transducing a chemical free energy change directly into a continuous rotation.

Preparation of ultra-high modulus polyethylene films by the zone-annealing method

Abstract The zone-annealing method has been used to prepare uniaxially oriented ultra-high modulus polyethylene films from single crystal mats of ultra-high molecular weight polyethylene. The maximum dynamic modulus and tensile strength at room temperature of superdrawn films were 232 and 6 GPa, respectively. The present paper discusses the advantages of the zone-annealing method, the determination of the optimum conditions for zone drawing and zone annealing, and the changes in superstructure and mechanical properties with processing.

Mechanical properties and superstructure of high-modulus and high-strength nylon-6 fibre prepared by the zone-annealing method

Abstract The relationships between mechanical properties and superstructure of nylon-6 fibre prepared by a new annealing method, called the zone-annealing method, were investigated in comparison with three other annealing methods, namely, annealing under release, annealing at constant length, and annealing under tension. It was found that the very high modulus and strength of the zone-annealed fibre were directly attributed to the large number of tie molecules connecting the crystallites and to the high orientation of the amorphous chains.

Application of a high-tension annealing method to nylon 66 fibres

A high-tension annealing (HTA) method has been applied to nylon 66 fibres to improve their mechanical properties. The HTA was carried out three times under high tension close to the tensile strength at break. The nylon 66 fibre used for the HTA treatment was previously zone-drawn twice at 210°C under applied tensions of 14.5 MPa and 182.2 MPa. To orient amorphous chains selectively, two HTA treatments were carried out; the first HTA (HTA1) at 100°C under an applied tension of 143.3 MPa, and the second (HTA2) treatment at 110°C under 142.0 MPa. The third (HTA3) treatment was carried out at 190°C under 75.1 MPa to crystallize the amorphous regions oriented by the HTA1 and HTA2 treatments. The resulting HTA3 fibre had a draw ratio of 7.3, a value of birefringence of 0.0761, and a degree of crystallinity of 40.4%. The orientation factor of crystallites almost approached unity in the first high-temperature zone-drawing (HT-ZDI) stage, but that of amorphous regions (ƒa) was 0.575 in the HT-ZD1 stage. The ƒa increased with the processing and finally reached a high value of 0.852 for the HTA3 fibre. Dynamic moduli increased with the processing, and the dynamic modulus of the HTA3 fibre was 21.7 GPa at 25°C and 15.0 GPa even at 200°C.

Preparation of ultra-high-strength nylon-6 fibre by a multi-step zone-annealing method

Abstract A multi-step procedure to improve the zone-annealing method was attempted to prepare a high-modulus and high-strength nylon-6 fibre. By the adoption of this procedure, the dynamic storage modulus at room temperature was markedly increased and reached 15.7 × 1010 dyne cm−2 which is 1.5 times that obtained by the previous zone-annealing method. Tensile properties, orientation, crystallinity and mechanical dispersion were also measured. Comparing the multi-step procedure with the previous one-step procedure, the excellent effects of the multi-step procedure on mechanical properties are discussed. Further, in order to prevent selective relaxation of amorphous molecular chains on removing the applied tension after zone-annealing, heat-setting at constant length was subsequently carried out on the as-zone-annealed fibre. The mechanical properties were further improved: for example, the dynamic storage modulus at room temperature of the resulting fibre was raised to 16.9 × 1010 dyne cm−2, which was well beyond the highest modulus available in the literature, 14 × 1010 dyne cm−2.

Preparation of high‐modulus nylon 6 fibers by vibrating hot drawing and zone annealing

To prepare high-modulus fibers, the vibrating hot-drawing and zone-annealing methods have been applied to nylon 6. The vibrating hot drawing was repeated two times, increasing the applied tension; further, the zone annealing was superposed on the vibrating hot-drawn fibers. The superstructure and mechanical properties of each step fiber were investigated. The vibration under a cooperation of heating and tension was very useful for increasing the draw ratio, birefringence, and orientation factor of the amorphous chains. Consequently, the obtained fiber indicated high moduli, namely, Youngs modulus of 23 GPa and the dynamic storage modulus at room temperature of 25.3 GPa.

Application of zone‐drawing and zone‐annealing method to poly(p‐phenylene sulfide) fibers

A zone-drawing and zone-annealing treatment was applied to poly(p-phenylene sulfide) fibers in order to improve their mechanical properties. The zone-drawing (ZD) was carried out at a drawing temperature of 90°C under an applied tension of 5.5 MPa, and the zone-annealing (ZA) was carried out at an annealing temperature of 220°C under 138.0 MPa. The differential scanning calorimetry (DSC) thermogram of the ZD fiber had a broad exothermic transition (Tc = 110°C) attributed to cold-crystallization and a melting endotherm peaking at 286°C. The Tc of the ZD fiber was lower than that (Tc = 128°C) of the undrawn fiber. In the temperature dependence of storage modulus (E′) for the ZD fiber, the E′ values decreased with increasing temperature, but increased slightly in the temperature range of 90–100°C, and decreased again. The slight increase in E′ was attributable to the additional increase in the crosslink density of the network, which was caused by strain-induced crystallization during measurement. The resulting ZA fiber had a draw ratio of 6.0, a degree of crystallinity of 38%, a tensile modulus of 8 GPa, and a tensile strength of 0.7 GPa.

Characteristics of water in polypyrrole films

Polypyrrole films containing different dopant ions were electrochemically synthesized and the interaction between polypyrrole and water was evaluated by means of sorption isotherm, cluster function and d.s.c. It was found that the water sorbed in the polypyrrole behaved as a non-freezing bound water which was rather isolated and prevented from clustering over the whole experimental range of the relative water vapour pressure from 0.1 to 0.95. This might be associated with the nature of the conductive polymers having a π-conjugated system where the delocalization of carbonium charges would lower the ionic polarity and hydrophilicity of the polymeric chains.