結晶性高分子の強伸度挙動 : 結晶性高分子の構造とレオロジー
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概要
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In general, fiber-forming substances are composed of long chain molecules linked together by bonds of secondary nature such as strong Van der Waal's and dipole-dipole bonds, etc. These cross linking bonds between polymer chains form an effective network structure. When these substances are deformed, the strong bonds act as junction points of the network, while the weak bonds will cause a viscous resistance to the relative motion of the segments. As a crystalline poltymer is cooled through its transition temperature region, certain degrees of freedom characteristic of rubbery solids are "frozen in" and at the same time the distribution of the cross bonds become dense, so the segmental motion (Brownian motion) of the molecular chain will be restricted. In fact, many of the crystalline polymers exhibit a sufficiently large elastic modulus in the lower temperature region, indication that only the energy component of force and not the entropy component is important in this region. To illustrate this mechanism the following model is adopted. Strong intermolecular bonds divide a molecular chain into a number of submolecules. Furthermore each submolecule is divided into two equal rodlike segments. As a result of the intermolecular interaction, the frictional force is applied to each molecule as it moves relative to the surroundings. For simplicity it is assumed that each submolecule interacts only through the linking point of the two-component segments. Based on this model the theoretical stress-strain cusves have been derived and compared with the observed stress-strain curves for the synthetic fibers subjected to a constant rate extension. It is found that a new yield point observed at low stress-strain region for shrinked synthetic fiber will be related to slackening of stretched molecular chain and regeneration of weak bonds on it. Some interesting informations are obtained upon the correlation between the characters of the stress-strain relation (stress, strain and magnitude of the viscous flow at the yield point) and the molecular constants (the rigidity of the molecular chain and strength of the intermolecular interaction ). It is obvious that this model should be improved by taking into account (1) the large deformation process for a folded molecular chain involving more than two rodlike segments, and (2) the entropy force caused by the thermal motion of the segments in the higher temperature region.
- 社団法人日本材料学会の論文
- 1959-04-15
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