The Relation between the Curing Conditions and Mechanical Properties of Polyimide Resin

Polyaminobismaleimide oligomer was cured at various curing temperatures from 210 to 290°C. The relation between the curing temperature and structural characteristics of the resulting polymers has been investigated by means of IR, DTA, TG, TMA, tensile properties and dynamic viscoelasticity measurments.The IR absorption peaks centered at 690 and 820cm-1 decreased in intensity with increasing curing temperature. Because the bands are assigned to the double bond of the maleimide ring, the curing extent may be estimated from the band intensities. As the curing extent increased, the thermal expansion decreased regularly. The temperature dependence of the dynamic viscoelasticity in the temperature range of 200-300°C varied with the curing temperature as well. The E′ value decreased considerably from 200°C and recovered up to 300°C. This variation in E′ decreased gradually at higher curing temperatures and disappeared at curing temperatures above 270°C. The α relaxation peak of slightly cured polymer seen in E″-and tan δ-temperature curves decreased in height and shifted to higher temperatures with increasing curing temperatures. It was found that the initial increase in the strength and elongation at break was followed by a decrease at curing temperatures higher than 280°C.