热历史对已固化环氧树脂松弛行为的影响

<正> 环氧树脂是一种性能优良且应用广泛的高分子材料,近年来,人们对已固化环氧试样在玻璃化温度(T_g)以下贮存时,物理性能随时间而变化的物理老化现象进行了广泛的研究.Ophir等发现已固化环氧试样经淬火处理后,其T_g随贮存时间升高,认为是由于自由体积随贮存时间减小所致.Mijovic用不同的方法进行过类似的研究,发现淬火环氧试样的T_g随贮存时间降低,认为是由于试样中的内应力松弛所致.本文试图进一步搞

THE RELAXATION BEHAVIOR OF EPOXY WITH DIFFERENT THERMAL HISTORY

The relaxation behavior of epoxy with different thermal history was studied by means of stress relaxation, DSC, dynamic mechanical measurement and thermo-mecha-nical analysis (TMA) methods.According to stress relaxation measurement, the internal stress of epoxy samples with different thermal history relaxed rapidly, when quenched samples were kept at room temperature.The phenomena of physical aging, i.e. enthalpy or volume relaxation of quenched and annealed samples, observed from DSC testing, are different. For quenched sample an additional physical aging peak shifted to higher temperature and the peak area increased with increasing storage time at room temperature. On the contrary for annealed samples, the additional peak shifted to lower temperature and the peak area decreased and disappeared gradually.The T9 of quenched samples, measured by TMA, decreased at first and then increased with increasing storage time at room temperature. It shows that there are at least two relaxation processes, internal stress and volume relaxation, which influence the mechanical properties, and the formerone changes faster than the later one.