ェンタルピー緩和における記憶効果

摘要

ポリスチレンとPMMAについて，ァニール実験結果と 擬等温温度変調測定より求めたパラメータを用いた計算結 果の比較をもとに，ェンタルピー緩和における比熱極大の 履歴依存性を調べた。ポリスチレンにおいて，ァニール時 間にともなう比熱極大温度の変化は，平衡へ向けたェント 口ピーの減少と，ァニール中に緩和時間が長くなるという， 異なる2つの効果によって，それぞれ低温側，高温側に移 動するということを明らかにした。前者の効果は，ァニー ル初期において支配的で，後者の効果はァニール中の緩和 時間の増加が生じる，ァニール後期において支配的である。%The annealing effects are studied based on the comparison between the experimental results and the calculated ones by the phenomenological model equation with parameters obtained by the quasi-isothermal temperature modulated differential scanning calorimetry. We have clarified that the shift of the maximum temperature in specific heat toward low and high temperatures with annealing time originates from the two effects produced by the annealing; the decay of enthalpy toward the equilibrium and an increase in the relaxation time during annealing. We have also clarified the origin of two maxima in specific heat observed at high and low temperatures in the glass transition region in the annealing experiments in polymethyl methacrylate(PMMA). The higher maximum originates from the history of cooling and heating, and the lower one, from the annealing history. We have proposed that the apparently different behavior in enthalpy relaxation in polystyrene and PMMA is originated from the same mechanism.