Glass Transition Temperature

The flame retardance and thermal stability of a methyl methacrylate (MMA) copolymer reactively modified by copolymerisation of the MMA with diethyl (methacryloyloxymethyl) phosphonate (DEMMP) have been compared with those of poly (methyl methacrylate)( ...

The accurate description of the relaxation phenomenon near the glass transition temperature allows a better interpretation of differential scanning calorimetry (DSC) curves, since it can be separated from other thermal effects such as crystallization, melting, and recrystallization. The structural relaxation model of Narayanaswamy and Moynihan for thermorheological simple glasses was numerically explored for obtaining a grasp of the functional influence of the different parameters: i.e. relaxation enthalpy Δh, non-linear parameter x, amplitude exponential distribution parameter b, and pre-exponential parameter A.It is known that when the relationship between the velocity of heat transfer in the cooling run (qc) and the velocity of heating in the heating run (qh) is equal to unity, the curves obtained in a DSC suffer only an horizontal translation for different absolute values of cooling and heating rates. It was found in this work that this criterion can be generalized, and curves also overlap by means of a horizontal translation when qc/qh is a constant different from one, whichever the particular values of qc or qh will be.Finally, changes in the shape of the curves when using different values of qh and qc with a fixed qc/qh relationship can be used as an indicator of the occurrence of other phenomena (i.e. recrystallization, melting, etc.) in addition to structural relaxation.

The aim of this study is to understand the effect of the glass frit chemistry used in thick-film Ag pastes on the electrical performance of the silicon solar cell. The study focuses on the physical behavior of the glass frit during heat treatment as well as the resulting Ag−Si contact interface structure. We observe that the glass frit transition temperature (Tg) and softening characteristics play a critical role in the contact interface structure. The glass transition temperature also significantly influences the contact ohmicity of the thick-film metal grid. A high glass frit transition temperature generally results in thinner glass regions between the Ag bulk of the grid and the Si emitter. It was found that a glass frit (with high Tg) that crystallizes fast during the firing cycle after etching the silicon nitride and Si emitter results in smaller Ag crystallite precipitation at the contact interface. This results in smaller junction leakage current density (Jo2) and higher open-circuit voltage (Voc). Using high Tg pastes (with the appropriate Ag powder size), greater than 0.78 fill factors and >17.4% efficiency were achieved on 4 cm2 untextured single crystal Si solar cells with 100 Ω/sq emitters.

Kinetics of the curic reaction and morphology of a diglycidyl ether of bisphenol-A based epoxy resin (DGEBA), using an anhydride hardener (nadic methyl anhydride) at different weight contents of carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) was ...