Study on Viscoelastic Proerties of Rubbers(ゴムの粘弾性に関する研究)

氏名 Wu Junhao
学位の種類 博士(工学)
学位記番号 博甲第432号
学位授与の日付 平成19年8月31日
学位論文題目 Study on Viscoelastic Proerties of Rubbers (ゴムの粘弾性に関する研究)
 主査 教授 五十野善信
 副査 教授 西口 郁三
 副査 教授 塩見 友雄
 副査 准教授 竹中 克彦
 副査 准教授 河原 成元
 副査 准教授 前川 博史

平成19(2007)年度博士論文題名一覧] [博士論文題名一覧]に戻る.

Chapter 1. Introduction
 1.1 Rubber p.1
 1.2 Dynamic Mechanical Properties of Rubber Materials p.6
 1.3 Dynamic Mechanical Properties of Rienforced Rubber Materials p.9
 1.4 Linear Viscoelasticity and Nonlinear Viscoelasticity p.14
 1.5 Aim and Structure of Investigation p.17
Chapter 2. Temperature Dependence of Viscoelastic Properties of Carbon Black Filled Rubber
 2.1 Introduction p.24
 2.2 Experimental p.25
 2.3 Results p.28
 2.4 Discussion p.36
 2.5 Summary p.39
Chapter 3. Fill Effects on Temperature Dependence of Viscoelastic Properties of Filled Rubbers
 3.1 Introduction p.41
 3.2 Experimental p.43
 3.3 Results p.44
 3.4 Discussion p.53
 3.5 Summary p.57
Chapter 4. Chain Anisotropy Effect on Polymer Nonlinear Viscoelasticity
 4.1 Introduction p.59
 4.2 Experimental p.60
 4.3 Results p.62
 4.4 Discussion p.70
 4.5 Summary p.71
Chapter 5. Dymamic Properties of Unfilled SBR Vulcanized by Two-Step Cure Method
 5.1 Introduction p.73
 5.2 Experimental p.75
 5.3 Results p.76
 5.4 Discussion p.84
 5.5 Summary p.87
Chapter 6. Conclusion p.89
Publications p.94
Conferences p.95
Acknowledgement p.96

 This thesis focuses on the study on viscoelasticity of rubber materials in both linear and nonlinear regions.
 Organic softmaterials including rubber have been widely used. The biggest benefit of the soft materials can be found in good processability due to relatively low modulus and high deformability based on entropic elasticity. For industrial purpose, however, inorganic fillers are required to be mixed for reinforcement. In addition, polymeric materials have enormously wide distribution of relaxation time. The relaxation times vary too much depending on temperature. Therefore, one might consider that it is fairly difficult to treat viscoelasticity of filled rubbers in general fashion. For example, some investigators have reported shift factors in time-temperature superposition depend on kind of filler, but others have reported they do not depend on. However, it is well known that temperature dependence of polymer viscoelasticity is well expressed by simple WLF equation which does not depends on molecular weights, molecular weight distributions, and existence or nonexistence of entanglements, which suggests the temperature dependence of filled rubber viscoelasticity is fairly simple. The purpose of the thesis is to study the temperature dependence of viscoelasticity of filled-rubber by measuring dynamic modulus in wide range of temperature and frequency, and to make additional study on the origins of nonlinear viscoelasticity and its industrial application.
 In chapter 1, the background, the significance, and the purposes of the thesis have been described as the introduction. In addition, the points to be discussed on temperature dependent viscoelasticity of various filled rubbers, both cross-linked and uncross-linked, and on mechanisms of nonlinear viscoelasticity of polymers have been reviewed.
 In chapter 2, after the importance and the problems on time-temperature superposition procedures of filled rubbers are preliminarily discussed, the effects of existence or nonexistence of carbon black filler and cross-linking points on the glass transition temperature and shift factors have been discussed in terms of linear dynamic modulus measured in wide range of temperature and frequency. In addition, the results have been compared with the temperature dependence of the corresponding nonlinear viscoelasticity.
 In chapter 3, filler effects on temperature dependence of viscoelastic properties of filler rubbers have been discussed in a comprehensive way. The next two points have been found; a) the glass transition temperature increases with the introduction of cross-linking points, but does not depend on existence or nonexistence of filler and kinds of fillers, b) the temperature dependence of viscoelasticity of rubber materials can be expressed by a universal function of the difference between measured and reference temperatures irrespective of existence or nonexistence of cross-linking points, that of filler, and kinds of fillers, if we take the glass transition temperatures as the reference temperatures.
 In chapter 4, after change in entanglement density and anisotropic configuration of chain molecule are discussed preliminarily to be possible two origins of nonlinear viscoelasticity of well entangled polymers, the latter has been proved experimentally to be one of the corresponding origins.
 In chapter 5, it has been confirmed experimentally that process control of loss factor in rubber materials can be made by anisotropic chain configuration fixed on the basis of the new concept developed in the chapter 4.
 From the results above, it has been clarified that the temperature dependence of viscoelastic properties of filled rubber is determined by that of the matrix polymer, that is, filler does not change the time-scale but the magnitude of modulus. This means we are allowed to consider independently time-temperature correspondence effects and reinforcement effect in making simulation of processing by using viscoelasticity of filled rubber materials. The thesis has offered the novel guiding principle to be beneficial to industrial processing of rubber materials.