Structural relaxation processes in amorphous poly (ethylene terephthalate) (PET) and in amorphous lightly branched PET of ethylene terephthalate-trimellitic (TMA) copolyesters at temperatures below their glass transition temperatures (Tg) have been monitored by dilatometric volume measurements of the polymer glasses after they were subjected to several different thermal histories. Both of thermal annealing at temperatures above Tg and chain branching due to incorporation of TMA into PET were found to cause appreciable decreases in the effective volume relaxation time. A new molecular kinetics model of structural relaxation was presented to provide a unified interpretation of the experimental results.
The effects of additives in aqueous threadlike micellar systems formed with cetyltrimethylammonium bromide (CTAB) were studied by means of dynamic viscoelastic and 1H-NMR techniques. An additive used was an ionic aromatic compound, sodium p-toluenesulfonate (NapTS). Viscoelastic behaviors of an aqueous CTAB and NapTS system essentially agreed with those of an aqueous system sodium salicylate (NaSal). When a ratio of NapTS concentration (CS) to CTAB concentration (CD) was higher than unity, the CTAB:NapTS/W system possessed the single relaxation viscoelasticity. The longest relaxation times (τm) depended on the concentration (CS*) of NapTS in the bulk aqueous phase, whereas τm was independent of CD.
The effects of additives in aqueous threadlike micellar systems formed with cetyltrimethylammonium bromide (CTAB) were studied by means of dynamic viscoelastic and 1H-NMR techniques. Additives were ionic aromatic compound, sodium p-toluenesulfonate (NapTS), and noionic ones / styrene (St) , and toluene (Tol). When a ratio (CS/CD) of the concentration of NapTS (CS) to the concentration of CTAB (CD) was 0.3, 0.4, and 0.5, the longest relaxation time (τm) became longer with increasing St (or Tol) concentration [St] (or [Tol]). This suggests that St (or Tol) interacts with CTA+ at the micellar surface and a threadlike micelle grows longer as [St] (or [Tol]) increases. When CS/CD = 1, τm became shorter with increasing [St] (or [Tol]). This finding suggests that St (or Tol) is solubilized in the deep interior of threadlike micelles and the mechanical strength of threadlike micelles becomes weak with [St] (or [Tol]).
The effect of cetyl alcohol (C16OH)/cetyltrimethylammonium chloride (C16CA) molar ratio on the internal structure in the self-organized assembly (C16CA/C16OH/water) was discussed, based on the rheological properties, morphology and ESR spectra obtained with ESRspin probe method. When C16OH/C 16CA molar ratio exceeds 2, multilamellar vesicles form due to rigid association between surfactant molecules of the self-organized assembly. Rheological properties reasonably reflect these structure changes.
The rheological properties of synthetic hectorite/water suspensions have been measured by a cone-plate rheometer as a function of their pH values. Synthetic hectorite was dialyzed to remove electrolyte impurities involved, and then utilized for preparing suspensions. When HNO3 and NaOH were added to the aqueous suspensions to adjust pH values, the yield value and shear modulus of the suspensions decreased both in acidic and alkali regions. It was found by the use of a Cryo-SEM observation that different types of coagulated structures existed for different pH regions. These results were probably caused a change in the charge at the edge of hectorite particles as follows: (1) in the acid region, the electrostatic attraction between negatively charged faces and positively charged edges of the particle are dominant and a compact card-house structure is formed; (2) in the alkali regions, the edges of the particle are negatively charged and resulting electrostatic repulsion leads to dispersed state of the particle; (3) in the neutral region, around the isoelectric point of the particle's edge an extended network structure is formed due to edge-to-edge association.
Structure and dynamic viscoelasticity of pastes for screen-printing, which consist of fine polyimide-particles, polyimide-binder and solvent were investigated. The precipitation-temperature of the particles was found to be a definite factor determining crystallinity of the particles, which strongly affects viscoelastic properties of the paste. The degree of stirring of the paste had an influence upon particle size. The frequency dependence of G' and G''revealed not only the existence of usual interaction between particles but also the second interaction between particles and binder. The structure formed by the interaction was destroyed by the application of a strong stress but recovered in a short time. The rheological properties of the paste have been controlled by changing the precipitation-conditions and compositions of the pastes.