パーオキサイド架橋ＥＰＤＭの構造と動的特性に関する研究 第１報 動的粘弾性とパルス法ＮＭＲによるＥＰＤＭのパーオキサイド架橋構造の考察

Abstract

The network structure of peroxide-crosslinked ethylene-propylene-diene rubber (EPDM) was examined by dynamic mechanical analysis and 1H pulsed NMR. The loss tangent (tanδ) hardly changed with the increase of the crosslinking density (νe) in the glass transition region (<0°C). However, in the higher temperature region, a broad tanδ peak was observed for less crosslinked systems. This relaxation was thought to be connected with the entanglement of long dangling chain ends. The tanδ values at 150°C decreased with the increase of νe. The signal of spin-spin relaxation time (T2) was resolved into three components. The three components respectively correspond to the molecules surrounding crosslinking points, molecules between crosslinking points, and non-network molecules such as dangling chains and end-chains. The increase of νe reduced the molecular mobility of each T2 component, and decreased the fraction of component with the longest T2 consisting of dangling chains. The fraction of each T2 component showed good correlation with tanδ values at 150°C independent of the kinds of fillers.