Application of a rate analysis to post-yield plastic flow in glassy polymers has been carried out through a novel approach. The rate analysis verified that during the yield process the structure of fully annealed glass initially in quasi-equilibrium was isothermally changed into various non-equilibrium melt-like structures depending on deformation rates and temperatures. It was shown that this was the case also for the polymer glass at temperatures far below the glass transition point. Structural relaxation in such mechanically induced non-equilibrium structures was illustrated using data of time-dependent mechanical property, differential scanning calorimetry and thermally stimulated deformation recovery. It was found that the strain energy given to glassy polymers during their yielding process was locked in tightly due to structural relaxation of the non-equilibrium structure. Applicability of the non-equilibrium structure to cold working of glassy polymers was discussed.
Composite particles consisting of polymer core and inorganic shell are formed by suspension polymerization. The ER behavior of suspensions is studied in relation to column structures in electric fields. It is demonstrated that the surface modification of particles is very useful to improve the ER performance of suspensions. The highly anisotropic structures are induced in electric fields and hence the ER suspensions show striking electrooptical effects. On the application of high electric fields to some insulating oils, a fluid jet with a velocity of about 1 ms−1 is generated from the electrode. New fluid devices such as liquid motors, inkjet nozzles, and ER elements are developed by active control of jetflow. Their performance will be discussed in relation to the rheological properties of electrosensitive liquids for future device technology.
Utilizing the thickening ability of threadlike micellar solution, which exhibits Maxwell-type viscoelastic behavior, we have developed a new thickening agent VISCOTOP for civil engineering usages. In contrast to usual thickening agent, VISCOTOP is able to increase viscosity of fresh concrete mixture without hardening retardation. In addition, we have found that VISCOTOP has various potential abilities in civil engineering usages because of its gel-like properties produced in the water. The cement slurry protected with VISCOTOP has unique properties; it can be poured into water without diffusion; it does not permeate into porous ground. The elastic property of VISCOTOP solution protects falling down of weak sand wall.
The three topics in our study are reviewed in the present paper: (1) molecular understandings of rubber elasticity of end-linked polymer networks and the dynamics of trapped guest chains; (2) elastomers with remarkable extensibility or high damping insensitive to both frequency and temperature via topology control of polymer networks; (3) phase transition in polymer network systems such as sol-gel transition and volume phase transition driven by nematic-isotroptic transition. On the basis of the biaxial elongation data of end-linked polydimethylsiloxane (PDMS) networks, the form of the strain energy density function is evaluated, and the five entanglement models of rubber elasticity are unambiguously assessed. It is shown that the dynamics of linear guest chains trapped in crosslinked networks obey the reptation concept. A dramatic slowing down of the reptation is observed in the host network whose mesh size is smaller than the entanglement spacing. The deswollen networks, prepared by end-linking long precursors in the diluted state and removing the solvent, exhibit a marked extensibility over 3000% as well as a very weak strain dependence of stress. These features stem from a small amount of trapped entanglement and a compact conformation of network chains. The damping of irregular networks containing many pendant chains increases with the amount of pendant chains. The damping is very weak dependent of temperature and frequency as a result of a slow viscoelastic relaxation of irregular network structures. The nematic networks swollen in nematic or isotropic solvents undergo a phase transition between the swollen isotropic and shrunken nematic states.
PDTS (1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol) is one of physical gelators and PDTS/Polystyrene (PS) system causes sol-gel transition. The viscoelasticity of the PDTS/PS system in the sol and gel states was investigated. In the sol state, the master curves of G' and G'' are identical with those of the matrix of PS melt, indicating that dissolved PDTS molecules in molten PS do not affect the viscoelasticity of the system. In the gel state, plateau region of G' due to the formation of PDTS network structures is observed. The values of G' in the gel state are well superposed in higher frequency region independent of the molecular weight of PS, indicating that the viscoelasticity of the gel network structures made of PDTS molecules predominates over that of matrices of PS melt in PDTS/PS systems. In lower frequency region, G' of the gel with the highest molecular weight of PS shows higher value than other gels. However, G' becomes close to that of other gels at the lowest frequencies where G' of the matrix PS is in the flow region.
This study is concerned with the relationship between wide angle X-ray scattering (WAXS) analysis and physical properties of amorphous polystyrene (PS)-silica (SiO2) composites. Nanoporous SiO2 for the fillers was prepared by the hydrothermal reaction and the structures of the composites were examined by WAXS. In their WAXS patterns, two characteristic peaks, inner peak and outer peak, were observed at q ≈ 7 nm−1 and 15 nm−1 corresponding to the intermolecular structure of PS chains and the intramolecular order of benzene rings, respectively. The ratio (Iin⁄Iout=P) in intensity of the inner peak (Iin) to outer peak (Iout) affords the structural parameter to well characterize the intermolecular and intramolecular structures of PS molecules and the P values are observed to change widely from 0.183 to 1.16 depending on the material compositions. The elongation at the break point increases monotonously with increasing P, whereas the yield strength and the Young's modulus decrease with P for P=0.497 or below but remain almost constant for larger P values. The elongation of 4.5% for (PS+MPS) / SiO2 is enormously larger than those for PS and the other composites, in contrast to a slight decrease of the other two properties relative to those for PS. It is also revealed that a strong interaction works between the COO or COOH groups of maleic anhydride modified polystyrene (MPS) and the OH groups of SiO2, which makes the PS polymer molecules to stack regularly on SiO2 nanofillers, leading to control the physical properties of the composites.
The structure of mono-modal spherical particle sols was controlled by changing the rotation rate of the spin coating. The number of cluster formed in the spin coated layer was counted. The apparent viscosity of particle (13 μm dia.) sols was measured, and the cluster size and number of primary particles contained in the cluster were predicted by the Usui's suspension model, which makes assumption that multi-breakup of inter-particle bonding occurs when a cluster breaks into two parts under a simple shear flow by spin coating. It was certified that the maximum packing volume fraction for particles can be successfully used to predict the slurry viscosity, and this means indirectly the maximum packing volume fraction determined in this study may be reasonable. Good agreement of the number of cluster between experimental data and the prediction was obtained. This means that the Usui's model can be used to predict the controlled structure of particles in spin coating technology.
Electrorheological response of barium strontium titanate (BST)/silicone oil suspension was experimentally studied with measurements of generated shear stress in a range of field frequency (200-4000 Hz) under steady shear. The BST particles were synthesized by the hydrolysis of complex alkoxide precursor that was prepared in a reflux of metallic barium, metallic and tetraethylorthotitanate in solvent. The hydrolysis was performed by the addition of water/ethanol solution to the precursor solution. Generated shear stress of as-prepared (unannealed) BST particles system decreased with an increase in frequency, while that for 1100 °C-annealed BST system increased with frequency. XPS measurements revealed that alkoxyl groups that were derived from unreacted alkoxide were on surface of the as-prepared BST particles, and the annealing at 1100 °C decomposed the alkoxyl groups to hydroxyl groups. Difference in electric conductivities of the surfaces is considered to be responsible for the different shear stress behaviors of the as-prepared and annealed particles.