Studies on the water induced plasticization behavior of nylon 4. The influence of crystallinity and radiation crosslinking

Abstract

The influence of crystallinity and radiation crosslinking on the water induced depression of the glass transition temperature in Nylon 4 [poly(2-pyrrolidone)] has been investigated by differential scanning calorimetry. Radiation crosslinking was effective in preventing exothermic events associated with crystallization during the measurement of the incremental change in heat capacity (AC,); a parameter necessary for the theoretical evaluation of the depressed glass transition temperature. ACp , when normalized to account for fractional crystallinity, was found to deviate substantially from a linear two phase relation. A simple three phase representation of morphology is proposed to account for this deviation, and assumptions have been made regarding the distribution of plasticizer, leading to good agreement between the theoretical and experimentally observed depressions of the glass transition temperature. x, ACE' (X) Tg, ( X ) + ~2 ACp2 Tg, x, ACp";' (X) + 3 AC,, TP,, = Details concerning the origin of Eq.(1) may be found elsewhere*), but here 1 and 2 refer to polymer and diluent, respectively, Tg is the glass transition temperature of the pure component, AC,, is the incremental change in heat capacity at Tgz , xis the mole ' )

Band gap of β-PtO2 from first-principles

“…However, their calculated electronic density of states (DOS) indicates a metallic character of β-PtO 2 , which contradicts with the experimental measurement that β-PtO 2 is a semiconductor with a resistivity of ~ 10 6 Ω·cm [15]. Until now, no experimental data is available for the band 3 gap of β-PtO 2 , while the reported band gap of α-PtO 2 varies from ~ 1.3 eV [16] to 1.8 eV [17]. Our recent DFT-GGA calculation [18] with the PBE-type functional [19] gives a value of ~ 0.46 eV for β-PtO 2 band gap, which is further increased to be ~ 1.2 eV by using GGA+U scheme.…”

“…From the experimental side, the measured band gap of amorphous PtO 2 is ~ 1.2 eV [38], and that of α-PtO 2 ranges from ~ 1.3 eV [16] to 1.8 eV [17]. No experimental data is available for the band gap of β-PtO 2 yet.…”