| POLYMERS Vol.64 No.6 |
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COVER STORY
Why Not Re-Consider About Fracture of Polymeric Materials |
| COVER STORY: Highlight Reviews |
| Fracture of Plastics | Takashi KURIYAMA |
| <Abstract> Main fracture behaviors, such as brittle, ductile, fatigue and creep have been shown in article. Relation between plastic defamations of crazing and shear yielding and those fracture behaviors was discussed from the fracture mechanics approach in which handled a single crack. Keywords: Crazing / Shear Yielding / Crack / Brittle / Ductile / Fracture Toughness / Toughening |
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| Elastic-Viscous Transition in Tear Fracture of Rubbers | Yoshihide FUKAHORI |
| <Abstract> This report focuses on the elastic-viscous transition in tear fracture of cross-linked rubbers observed at around the glass transition temperature (velocity). It defines the discontinuous change of the rate of crack growth generated at the crack front depending strongly on the balance of elasticity and viscosity of the material. The elastic-viscous transition diagram is introduced to elucidate the mechanism of this transition, where the intermediate transition zone between elastic and viscous zones is characterized by stick-slip motion and velocity jump at a constant strain energy release rate. Keywords: Cross-Linked Rubber / Elastic-Viscous Transition / Brittle Fracture / Ductile Fracture / Stick-Slip Motion / Velocity Jump |
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| What are Characteristics of Gel Fracture | Yoshimi TANAKA, Takahiro MATSUDA |
| <Abstract> By observing how Lake-Thomas theory, proposed to explain fracture toughness of rubbers, should be modified for gels, we consider essential feature of gel fracture. Keywords: Gels / Fracture / Strength |
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| Dynamics of Adhesion and Debonding | Tetsuo YAMAGUCHI |
| <Abstract> Adhesion and debonding is one of the fracture phenomena occuring mainly at soft matter interfaces. In this paper, we will introduce the adhesion and debonding through the dynamics of giant and complex deformations of pressure sensitive adesives observed when they are detached from an adherend. Keywords: Adhesion / Debonding / Cavitation / Fibrillation / Dynamics / Pressure Sensitive Adhesives |
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| COVER STORY: Topics and Products |
| Mechanical Properties of Self-Recovery Tough Gels with Permanent and Reversible Crosslinks | Koichi MAYUMI, Tetsuharu NARITA, Costantino CRETON |
| <Abstract> We have studied the linear viscoelasticity, large deformation behaviours, and fracture properties of self-recovery dual crosslink gels having covalent crosslinks and reversible crosslinks. We have developed model dual cross-link gels with covalent and reversible bonds by the complexation of chemically cross-linked poly(vinyl alcohol) (PVA) gels with borate ions. The PVA dual crosslink gels are good model systems to investigate quantitatively the relationship between the breaking/healing dynamics of the breakable crosslinks and the macroscopic mechanical properties in large strain because they have a well-defined life time of the reversible bonds observed by liner rheology. We have proposed a physical model for the stress-strain relation of the dual crosslink gels considering the effect of the breaking/healing dynamics. The dynamic reforming of the reversible network structure during deformation improves the mechanical toughness and stretchability of the dual crosslink gels. Keywords: Polymer Gels / Reversible Crosslink / Rheology / Toghness |
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| Rubbers and Elastomers for High-pressure Hydrogen Seal | Shin NISHIMURA |
| <Abstract> High-pressure hydrogen gas seal is one of key technologies for materialization of hydrogen energy system. It is important to understand the durability of high-pressure gas seal. According to the results of O-ring fracture, we found the three fracture modes, internal fracture of rubbers originated from inflation of dissolved hydrogen, referred as “Blister Fracture”, external fracture in terms of volume inflation of rubber in the O-ring gland, referred as “Overflow Fracture” and “Buckling Fracture” Ethylene–propylene rubber (EPDM) and acrylonitrile–butadiene rubber (NBR) composites filled with carbon black, silica, and unfilled composites were exposed to high-pressure hydrogen gas. The blister fracture of composites with silica was less pronounced, irrespective of the hydrogen pressures. This can be attributed to their lower hydrogen content and higher strength than the others. Understanding the effect of decompression rate on the blister fracture is also important. The numerical analysis of blister fracture behavior during decompression process is undergoing. Keywords: Hydrogen / O-ring / Ethylene Propylene Rubber / Acrylonitrile Butadiene Rubber Carbon Black / Silica / Blister Fracture / Gas Seal |
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| Polymer Science and I: A Personal Account |
| Challenge for “Originality” | Hironori IZAWA |
| <Abstract> Originality is one of the important factors in my research. Although I have not achieved yet a confident “Izawa's model”, I would advance step by step to launch it. Some impressive stories, which were turning points for me, are described here. |
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| Front-Line Polymer Science |
| Polyelectrolyte Brush and Specific Ion Effect | Hideki MATSUOKA |
| <Abstract> Rescent research on polyelectrolyte brushes and thermosensitive poly(NIPAm) brushes is reviewed in this paper, especially regarding the specific ion effects on their nanostructure and responsitivity. They cannot simply be explained by the traditional Hofmeister concept, but require novel ideas on the characteristics of each cation and anion, especially on the spcific interaction between ions and polymers. Keywords: Polyelectrolyte Brush / Specific Ion Effect / Hofmeister Series / Poly(N-isopropylacrylamide) / Betaine Brush / Zwitterion / Polyampholytes / ζ-Potential |
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