the volume and enthalpy relaxation in a-PMMA subjected to temperature jumps in tg region has been analysed. The measured H and V data were compared with respect to aging time and proportionality between them as a slope of (∂H/∂V)T dependencies has been found. According to previous works the slope was identified as an apparent bulk modulus, Ka. This method is applied to aging following temperature up-jumps after consolidation periods of varying lengths. the main
finding is a marked increase of Ka with consolidation time, approaching a limiting value in an asymptotic fashion.
Summary Volume and enthalpy relaxation in polycarbonate subjected to double temperature jumps in the Tg region has been analysed. It concerns both initial Tdown-jump from equilibrium above Tg to consolidation temperature below Tg and fina1 Tup-jump to relaxation temperature, also below Tg. The measured H and V data after Tup-jump were compared with respect to aging time calculating (dH/dV) ratio denoted as aging bulk modulus, Ka. According this new methodology H and V relaxation response after Tup-jump demonstrates differences in relaxation responses.
Authors:J. Grenet, J. M. Saiter, C. Vautier, and J. Bayard
The effect of ageing temperature (belowTg) on physical ageing of glassy PET has been investigated by differential scanning calorimetry. The position of the glass transition endotherm was found to be strongly dependent on the annealing conditions (time, annealing temperature). A single relaxation time model is proposed for the analysis of physical ageing.
Slow evaporation of toluene from poly(2,6-dimethyl-1,4-phenylene oxide), PPO, at 23°C produced crystals which melt between 185 and 265°C and have a crystallinityof 0.58. About 8 wt% of the crystals appear to melt temperatures below 220°C. The lattertemperature marks the end of the glass transition interval for this polymer.
Authors:S. Montserrat, P. Cortés, Y. Calventus, and J. Hutchinson
Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning
calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy
loss,δH, at an equivalent annealing temperatureTa=Tg-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofδH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent
activation energy,δh*. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length
of cross-link onrrpd and δh* was studied.
Authors:C. Bacharan, C. Dessaux, A. Bernès, and C. Lacabanne
Thermally Stimulated Current (TSC) spectrometry has been applied to the characterization of polymeric materials. The study
of a series of amorphous polymers having different physical structures has shown that the compensation parameters are independent
of physical aging; contrarily, the activation enthalpy distribution reflects the evolution of the heterogeneity of the amorphous
In copolymers, TSC allows us to identify segregated amorphous phases. In semi-crystalline polymers, with semi-rigid chains,
we have shown the existence of an amorphous crystalline interphase characterized by a plateau in the temperature distribution
of activation enthalpy.
This paper focusses on the conceptualising function of Scottish Gaelic preposed adjectives (i.e., AN vs. NA phrases). A combined analysis of a corpus study and interviews with native speakers was applied in the research which underlies the article. Preposed adjectives are often encountered with abstract concepts, verbal nouns, or with words with more complex semantics in general, while plain adjectives tend to qualify more tangible, countable nouns, such as people or objects, as well as pronouns. The plain adjective dona ‘bad’ often conveys criticism, and aosta/sean ‘old’ tend to refer to biological (or physical) age. The paper also addresses similarities with other languages.
This article addresses the potential effectiveness of blind review in selecting and funding research proposals in a “scientifically
small” country. By analyzing 474 responses of the blinded reviewers ever worked for Korea Science and Engineering Fund, it
was found that blind review is fairly effective. About two thirds of the blinded reviewers were unable to recognize the applicants
accurately. The applicant detection was affected by (1) physical age, (2) professional experience, and (3) geographical location
of doctoral education of the applicant, (4) review experience, (5) rank of employing universities of the reviewers, and (6)
similirity of research interest between an applicant and a reviewer. It was also found that blind review was more strongly
advocated by those who had made a wrong guess or who had given up guessing. Implications of the findings and future research
directions were discussed.
An intermediate range (50–1000°C) self-referencing differential scanning calorimeter (SR-DSC) has been built and its performance evaluated. The SR-DSC measures heat flow across a heat flow metal plate, and any changes to the heat flow caused by a thermal transition occurring in a centrally placed sample is monitored by a temperature difference across the plate. The criteria for high sensitivity are that the circular plate should be as thin as possible and have a low thermal conductivity. The best sensitivity conducive with robust behaviour was achieved with an inconel thermal plate of uniform thickness, 75 m, this gave reproducible results, and the enthalpy of the thermal transition was proportional to sample mass. Calorimeter sensitivity decreased with increasing temperature and a sloped baseline was observed. Both of these effects can be corrected mathematically. An example of the use of the SR-DSC in polymer characterisation was limited to a study of the physical ageing of PET.