高捩PVDF繊維の強度/変形特性及び熱アクチュエータへの応用

抄録

When Polyvinylidene Difluoride (PVDF) receives an external force, molecular structure will be changed. This PVDF has a unique entropic elasticity attributed to release and/or absorption of entropy when strain energy inside the polymer is introduced by loading a large torque. There is a possibility to develop an innovative thermal actuator, when the PVDF is highly twisted and fixed as a coiled shape after applying appropriate heat treatments. Mechanical properties of the PVDF polymer and the coiled shape PVDF were experimentally examined. Then, following results were obtained; (1) Tensile stress-strain curve of the PVDF polymer was independent on loading rate and the diameter of the polymer. However, the maximum temperature at annealing affected the strength at rupture and the stress-strain curve. (2) Spring constant of the coiled shape PVDF at lower temperatures was almost the same regardless of heating and cooling rates during forming process when the maximum temperature at annealing was controlled as the same. Minimum load where the coiled shape PVDF started to deform as the spring depended on both the maximum temperature at annealing and heating /cooling rates during the processing. (3) Although the spring constant rather decreased with increasing the testing temperature, the minimum load where the coiled shape PVDF started to behave as the spring greatly increased. (4) When both the heating and cooling rates at the forming process were set to be slow, the coiled shape PVDF showed the best performance as the thermal actuator.