Hirotaro Kambe

Determination of heat of mixing and heat of vaporization with a differential scanning calorimeter

Abstract A simple method is presented for measuring the heat of mixing and the heat of vaporization of volatile liquids at temperatures below their boiling point. It consists in introducing liquids by a microsyringe into a nearly closed cell of the DSC. The relative standard deviation for 4 to 5 runs is ca. 5% for heat of mixing and ca. 2% for heat of vaporization.

A Kinetic Investigation of Thermal Shrinkage of Aromatic Polymers by Thermomechanical Analysis

Abstract The kinetics of thermal shrinkage of the stretched polypyromellitimide (PI) films, Du Pont Kapton H, were investigated by thermomechanical analysis (TMA) at a constant rate of heating. The two-stage model of extended polymers has been applied to analyze the TMA data. The activation energy of the contraction reaction could be obtained from TMA curves at various heating rates. The one-step shrinkage of the 12.5% stretched PI film gives an activation energy of 10 kcal/mole for the first shrinking. From the 30% stretched sample, the second activation of contraction is 25 kcal/mole, and from 40% sample the third one is 33 kcal/mole. These three contraction reactions are observed successively for the TMA curves for highly stretched samples, and correspond to the various kinds of molecular motion of this special rigid polymer structure, which are also observed in the dynamic mechanical and dielectric properties of the same polymer. Polypyromellitimide (PI) is a typical thermally stable polymer due to th...

Thermomechanometry, a proposed nomenclature for thermoanalytical techniques based on changes in mechanical characteristics☆

Abstract A new term, thermomechanometry, has been proposed to the ICTA Nomenclature Committee as a group name for thermoanalytical techniques based on changes in mechanical characteristics. ICTA has adopted two terms: thermomechanical analysis and dynamic thermomechanometry as defined techniques in this group. A more general group name has not been defined in ICTA nomenclature. Dimensional changes caused by thermal and mechanical means are classified and the difference between thermodilatometry and thermomechanometry is shown. Viscoelastic deformations are classified according to the variation of the properties of a material with time. The effect of temperature on the static or quasi-static mechanical deformation and dynamic deformation are classified as the basis of thermomechanical analysis and dynamic thermomechanometry. Some references are given from recent publications by the authors laboratory on these techniques.

Degradation of poly (methyl methacrylate) by flash irradiation

Abstract Degradation of poly(methyl methacrylate) (PMMA) caused by irradiation of flash light from discharged xenon lamp was investigated in a vacuum and in the presence of nitrogen. Degradation products at a sequence of flashes were analysed by a gas chromatograph with hydrogen flame ionization detector after each flash. Among the degradation products of PMMA in vacuum by regular flash light, an amount of monomer was detected with the significant production of methanol and gaseous mixture. The molecular weight of the residual polymer decreased markedly by the first several flashes, showing that chain scission occurred. By filtering the u.v. component of flash light the monomer formation and molecular weight decrease were not observed. From these facts the flash degradation of PMMA in vacuum was concluded to be conducted by a photodegradation mechanism. The absorption of u.v. light by ester groups forms active radicals, which initiate chain scissions and depolymerization of main chains following methanol and monomer formation. At the flash degradation in nitrogen at atmospheric pressure PMMA degraded in the different manner. At the initial several flashes the photodegradation mechanism is also conducted in the polymer matrix and decomposed secondarily at the subsequent flashes to form a significant amount of carbon particles. Thereafter, carbon particles acted as a photoabsorber, and the thermal degradation of the polymer occurred predominantly around the heated carbon particles.

Differential thermal and infrared analyses of oxidized polyethylene

SummaryThe changes of crystalline and amorphous phases in a linear polyethylene by thermal oxidation were studied by differential thermal and infrared analyses. In the differential thermal analysis curve for polyethylene in a stream of oxygen an exothermic peak was obtained in the 180 °C region. It was confirmed by infrared method that the exothermic peak is due to oxidation of vinyl type double bond in the polymer molecule. This oxidation caused to decrease the crystallinity of polyethylene.The differential thermal and infrared analyses of polyethylenes oxidized in the solid state are compared with the above results. Further, it was observed that the differential thermal analyses for crystallization of unoxidized and oxidized polyethylenes show two peaks depending on the condition of melt annealing of the samples.ZusammenfassungDie Änderungen der kristallinen und amorphen Phasen in einem linearen Polyäthylen bei thermischer Oxydation wurden mit Thermodifferentialanalyse, mit Infrarot untersucht. In der DTA-Kurve für Polyäthylen in einem Strom von Sauerstoff wurde ein exothermer Pik bei etwa 180 °C erhalten. Es wurde durch Infrarot festgestellt, daß dies einer Oxydation von Vinyldoppelbindungen im Polymermolekül entspricht. Diese Oxydation verursacht die Verminderung der Kristallinität des Polyäthylens.Die differential-thermo-analytischen und Ultrarot-Werte von oxydiertem Polyäthylen in festem Zustand wurden mit den obigen Versuchen verglichen und so weiter beobachtet, daß die DTA-Kurven von unoxydierten und oxydierten Polyäthylenen 2 Piks zeigten, die von den Bedingungen der Schmelz-Temperung der Proben abhängen.

Melting Behavior of Some Oligomers of Heterocyclic Polymers by Differential Scanning Calorimetry

The softening point of polybenzimidazole involving aromatic ether linkage in the main chain is not measurable below degradation of the polymer. The various oligobenzimidazoles and benzothiazole and benzoxazole derivatives with analogous structures were synthesized and their melting point Tm and heat of fusion ΔH were measured by differential scanning calorimetry. The entropy of fusion ΔS was calculated by ΔS = ΔH/Tm. The accuracy of the method was examined and the effect of imidazole ring on the melting behavior was investigated.

Fatigue strength of aromatic polyamideimide-aromatic polyamide fiber composite films.

芳香族ポリアミドイミドを芳香族ポリアミド織維の平織布で強化することによって高強度, 高耐熱性の繊維強化フィルムを作成した. この繊維強化フィルムの疲労強度について検討した. 繊維強化フィルムの疲労挙動は強化繊維とマトリックスの挙動の特徴がそれが支える度合に応じて発現される. 疲労強度と静的強度の間には, ある種の相関がある. また, 面内には力学的性質と同様に異方性が存在する.

Dynamic Mechanical Properties of Aromatic Polyamideimide Degraded in NO2 Atmosphere

The degradation of aliphatic polyamide as nylon 66 in an NO2 atmosphere has been investigated by Jellinek,1 based on the mole-cular weight changes determined by the change of solution viscosity. The aromatic polyamideimides are also accessible to NO2, but are slightly soluble in polar solvents as N-methyl pyrrolidone(NMP) and the solutions obtained are not readily stable to estimate the degree of degradation from the usual viscosity measurements. Therefore, we investigated the degradation of aromatic polyamideimide by following the change of dynamic mechanical properties in an NO2 atmosphere.

Dynamic Thermomechanometry of Aromatic Polyamideimide

Temperature dependences of dynamic mechanical properties of commercial films of aromatic polyamideimide(PAI) were measured at uniform heating rates “by using modes of torsional, tensile, and flexural oscillations. Torsional oscillations of the film were measured with a home-made inverted torsional pendulum, tensile oscillations with a Rheovibron DDC IIC, and flexural oscillations with a du Pont 980 Dynamic Mechanical Analyzer. Corresponding molecular relaxations were found for each oscillation mode. Dynamic properties of composites of PAI reinforced with straight carbon fibers and with a glass cloth, and of PAI film sandwiched between two steel plates were measured for comparison. Similar results as obtained for film samples were found also for these composites. Degradation of PAI in an NO2 atmosphere could be followed by these techniques. A new molecular relaxation due to degraded surface layers was found below glass transition, and this relaxation was shifted to higher temperatures and shaded by glass transition after thermal treatments of degraded films.

Melting of some Aromatic and Heterocyclic Oligomers

The softening point of the aromatic or heterocyclic polymers is very high and usually undetected up to the decomposition point. The melting behavior of oligomers with the same basic structure of molecules as polymers has been measured by differential scanning calorimetry. The dependences of melting point, Tm and the enthalpy, Δntropy, Δlting on the degree of polymerization and the structure of molecules are discussed. The entropy of melting per ring for p-oligophenyl homologues decreases with the number of phenyl rings, n. For the longer p-phenyl chains, a sort of molecular arrangement would remain after melting; then, ΔS becomes low for the higher homologues, and Tm increases with n. A quite similar behavior was found for oligoacenes. On the other hand, Tm of m-oligophenyl homologues does not increase markedly with n. The asymmetric structure of the higher m-phenyls prevents the strong interactions between molecules in the crystalline state; therefore, AH becomes low for these molecules.