Recent observations using fluorophore probes of local dynamics in polymer films have provided new insight into the glass transition. Using a percolation model, we predict the local Tg in a polymer film, as a function of distance from a substrate or a free surface. Our predictions are in good agreement with the observed elevation of Tg near a substrate, whereas the observed reduction of Tg near ...

High temperature shape memory polymers that can withstand the harsh temperatures for durable applications are synthesized, and the aromatic polyimide chains with flexible linkages within the backbone act as reversible phase. High molecular weight (Mn) is demanded to form physical crosslinks as fixed phase of thermoplastic shape memory polyimide, and the relationship between Mn and glass transit...

This study assessed methods for evaluation of glass transition temperature (Tg) of autopolymerized hard direct denture reline resins using dynamic mechanical analysis and differential scanning calorimetry in addition to the dynamic mechanical properties. The Tg values of 3 different reline resins were determined using a dynamic viscoelastometer and differential scanning calorimeter, and rheolog...

We have developed a sensitive experiment which allows the measurement of the growth of holes in thin freely standing polystyrene ~PS! films at elevated temperatures. In the experiment, a constant small pressure difference is applied and maintained across the freely standing film, and the formation and growth of holes is detected as a flow of air through the film. From measurements of freely sta...

The advent of chip calorimetry has enabled an unprecedented extension the capability differential scanning to explore new domains materials behavior. In this paper, we highlight some our recent work: application heating and cooling rates above 104 K/s allows for clear determination glass transition temperature, Tg, in systems where Tg onset temperature crystallization, Tx, overlap; evaluation d...

We studied the low-energy excitations in the meV region as well as the picosecond fast process in polystyrene thin supported films using inelastic and quasielastic neutron scattering in a temperature range from 11 to 430 K , covering the bulk glass transition temperature Tg. It was found that the mean square displacement u2 decreased with the film thickness below and above the glass transition ...

We have probed the whole chain mobility of polymer molecules confined to freely standing films by measuring the flow of gas through holes growing in the films at elevated temperatures using a differential pressure experiment. Freely standing polystyrene films were measured for the temperature range 92 degrees C<T<105 degrees C for films with two different molecular weights Mw=717 x 10(3) and 22...

The thermoplastic formability (TPF) of metallic glasses was found to be related to the calorimetrically measured crystallization temperature minus the glass transition temperature, Tg Tx = ΔT. Alloy development in the ZrTiBe system identified a composition with ΔT = 120 °C. Many alloys with ΔT > 150 °C and one alloy, Zr35Ti30Be27.5Cu7.5, with ΔT = 165 °C were discovered by substituting Be with ...

In order to develop the polymer materials having temperature-sensitive and high biological safety, Eudragit RS-PO and polyethylene glycol 400 (PEG 400) blend polymers (EPG) were prepared. The EPGs that have the glass transition temperature (Tg) at around the body temperature were prepared by the addition of 5--13% PEG 400 to Eudragit RS. As glassy polymers are not in thermodynamic equilibrium b...

The measurement of dc conductivity as a function of pressure in the range 0 P < 2:0 GPa for Se75In25ÿxPbx (x ˆ 0, 5, 10, 15) glasses are reported. n-type Se±In±Pb glasses show a maximum in the resistance versus pressure. Differential Scanning Calorimetric (DSC) studies have also been carried out for the measurement of the glass transition temperature …Tg†. The results have been explained in ter...